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https://www.eevblog.com/forum/beginners/(temperature-sensor)-whos-industrys-default/
|
[Temperature Sensor] Who's industry's default? - Page 1
|
[
{
"post_id": "",
"author": "Mecanix",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "April 04, 2022, 11:54:30 am",
"content": "I understand everybody wants to be The Weatherman, and I have no problem with that! My problem is the countless sensors, ICs and other solutions that are available for measuring ambient temperature. And I don't plan on buying The Whole Internet to find a solution that actually works (done-that-been-there-before with other gizmos, no thank you very much). I need:1. 1dC accuracy max within a range of 0dC~50dCAnd that's it! Any proven 'solution & hardware' you care to share? Ideally one you've used and cross-tested against a calibrated/precision ref that is. That'd be extremely helpful. ThanksDisclosure: the temp sensor will be used inside a closed industrial enclosure (controlled environment, cooling)."
},
{
"post_id": "",
"author": "ataradov",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 04, 2022, 04:14:40 pm",
"content": "DS18B20 is as default as it gets. But also being the most used IC, it is faked like crazy. So, source it only from reliable distributors. Anything you see on eBay/Aliexpress - assume to be fake."
},
{
"post_id": "",
"author": "crgarcia",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 04, 2022, 05:33:25 pm",
"content": "Quote from: ataradov on April 04, 2022, 04:14:40 pmAre those factory calibrated? I have few and they are very inaccurate - but after reading your post, that might be because they are fake ones"
},
{
"post_id": "",
"author": "ataradov",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 04, 2022, 05:55:27 pm",
"content": "Yes, the original ones are factory calibrated and are accurate to +/- 0.5 °C in -10°C to +85°C range.But unless you've got them from Mouser or Digikey - consider them fakes. DS18B20 may be the the most faked device, it has to be in the top 10 for sure."
},
{
"post_id": "",
"author": "magic",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 04, 2022, 06:21:23 pm",
"content": "Make sure you are powering them right, too.That means providing permanent Vdd power or using fairly strong pullup for parasite power. Dallas made special bus drivers which can temporarily supply high power to the bus when nothing is expected to pull it down, or IIRC I calculated that 1kΩ pullup resistor to 5V should also provide enough current and still be within the permissible sink current limits. Or maybe I'm wrong, check the datasheetThat being said, I got them to work right with 1kΩ pullup on a short cable. Fakes are omnipresent on auction sites and there are even multiple kinds of them and they vary in quality from \"fairly decent at room temperature\" to \"absolute crap\" and you never know what you will get."
},
{
"post_id": "",
"author": "Mecanix",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "April 05, 2022, 09:29:59 am",
"content": "Appreciated, guys. I'll order a batch of DS18B20 and dev around that sensor. Feels good to be able to ignore the billion others...ps. not a financial issue, it's a logistic/sourcing/testing/time wasting issue. And so I appreciate the heads up on what works"
},
{
"post_id": "",
"author": "crgarcia",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 05, 2022, 10:07:30 am",
"content": "I just bought bunch of SHT41I, that are I2C temp sensors and they look very good on the specs. Hope they work well"
},
{
"post_id": "",
"author": "Mecanix",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "April 05, 2022, 07:02:10 pm",
"content": "I hope too!Side note; I remember toying with some so-called 'reputable' sop-6 ICs, some using k-type others p100, that was 3 or 4 years ago. I have no idea if the faults were caused by my circuits/parts or the ICs were completely out of specs, probably both. But anyway they were okay'ish for let's say 21dC to 25dC but below of higher they were off by 3+ dC. Some as much as 10dC within a miniscule range. Really had me losing hope in developing anything semi-precise temperature-wise so I just tossed the kits and moved on since - so that's why I'm interested to know what worked for you guys.Let us know how yours turns out!"
},
{
"post_id": "",
"author": "MikeK",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 05, 2022, 09:08:14 pm",
"content": "Quote from: crgarcia on April 04, 2022, 05:33:25 pmIf you have an Arduino there is a sketch to check for suspected fake ones."
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 07, 2022, 12:02:54 am",
"content": "I don't think you can get the DS18B20 from DigiKey, they show it as \"No longer manufactured\"Mouser shows a lot on order with one entry showing a delivery of mid April. This particular item comes in the giant economy package of 2,000 devices on a reel. Minimum quantity: 1 reel @ $5760I didn't explore all the entries, I just skimmed the headlines. Somebody else can do the real shopping."
},
{
"post_id": "",
"author": "MikeK",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 07, 2022, 12:08:00 am",
"content": "Quote from: rstofer on April 07, 2022, 12:02:54 amI wonder if that means that Maxim is abandoning it for a newer version. They probably lost a lot of money due to fakes.Just checked: Maxim's website says the DS18B20 is \"Active in Production\"."
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 07, 2022, 12:10:26 am",
"content": "Check AdaFruit, they have 70 in stock and they also have different sensor configurations. Just search for 'DS18B20'https://www.adafruit.com/product/374I'm going to go out on a limb and assume they aren't fake."
},
{
"post_id": "",
"author": "MikeK",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 07, 2022, 12:11:27 am",
"content": "Correction: Digi-Key does sell the DS18B20:https://www.digikey.com/en/products/detail/analog-devices-inc-maxim-integrated/DS18B20-T-R/3478852"
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 07, 2022, 12:13:38 am",
"content": "Quote from: MikeK on April 07, 2022, 12:11:27 amGood news! It sure didn't come up that way for me! I think my search revolved around Analog Devices and overlooked Maxim even though I didn't specify a manufacturer.Nevertheless, the AdaFruit offerings may be helpful."
},
{
"post_id": "",
"author": "MikeK",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 07, 2022, 12:17:35 am",
"content": "I'll admit that I have purchased some DS18B20's from Tayda for $1.75USD each, and the Arduino sketch told me they're probably legit. Maybe the fakes have gotten better or Tayda sells factory rejects. I should buy some legit ones to compare."
},
{
"post_id": "",
"author": "ejeffrey",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 07, 2022, 04:06:36 pm",
"content": "TMP102 is a decent option if you want I2C/SMBus instead of one-wire. Its SOT26 and requires more wires so it isn't really as suitable for remote sensing at the end of a cable as the DS18820 but it's good if you want a PCB mounted temperature sensor."
},
{
"post_id": "",
"author": "Terry Bites",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 07, 2022, 04:32:30 pm",
"content": "The NCT75 from Onsemi is a bargain 1'C I2C sensor- and they are available!"
}
] |
2025-10-17T17:12:29.562017
| 17
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/(time-nuts!!)-help-understanding-and-improving-on-gps-_assisted_-vfo/
|
[Time Nuts!!] Help Understanding and Improving on GPS 'assisted' VFO? - Page 1
|
[
{
"post_id": "",
"author": "rwgast_lowlevellogicdesin",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "September 09, 2017, 01:43:48 am",
"content": "Ok so I am working on building my own version ofthis project (a GPS 1PPS assited VFO using si5351)myself. I'm not using the project as is mostly because I want to learn and also I hope some of my ideas may improve on VFO. Most of the article is pretty basic and the only part that really matters to me is the part about \"disciplining the si5351 outputs\"QuoteSo im hoping someone can clear up a few things for me. So were counting 40 GPS pulses (this should equal 100mhz), Im guessing that 40 seconds was chosen to produce easy to work with numbers? Then were using the arduino counts over a 40 seconds to calibrate the si5351 clock? Well the arduino is using a 20ppm crystal, so how is that accurate?My Si5351 board has a 2.5ppm TCXO's on board and I'm looking to make it more accurate with parts I have on hand (e.g im not going to use a timing GPS and an OCXO etc etc, i want to make do with mostly what I have). So what is one were to use a 16mhz TCXO on the arduino, i don't understand how this project gets the accuracy it does using a 20ppm xtal on the chip that is doing the counting. Next what if instead of updating every 40s, we put a divide by 4 on the 1pps and then did the si5351's 25mhz clock calibration every 250ms?Ive been trying to dig through the code of the original project but im having a hard time dissecting it all, so for now im doing more research on the si5351 itself till things make more sense, but I feel like i am misunderstanding something maybe. I mean if the crystal is 20parts per million and a 100mhz is 100 million parts, doesn't that mean the arduino count can be up to 2000 counts off?"
},
{
"post_id": "",
"author": "jpb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 09, 2017, 01:23:41 pm",
"content": "Quote from: rwgast_lowlevellogicdesin on September 09, 2017, 01:43:48 amYour link didn't work for me but I think I found the right article by DuckDuckGoing (alternative to Google:)).I only skim read it but the impression I got is that the Arduino is only counting so its own clock accuracy doesn't matter - all that matters are the accurate (to plus or minus a few 10s of nanosecs) 40 seconds from the GPS 1PPS and the number of si5351 cycles it counts in that period so the Arduino's clock shouldn't come into it. I would guess 40 seconds was chosen as the GPS 1PPS jitter is of the order of a few 10s of nanosecs but this would be reduced by a factor of 40 giving close to nanosec accuracy for frequency measurement.There will be an uncertainty of 1 or 2 cycles which worse case is 1000 nsecs for the 1MHz output but this is measured over 40 seconds so should be reduced to more like 25 nanosecs to which a nanosecond or so for the GPS needs to be added. The whole thing would then be accurate to something under 50 nanosecs or 1/20 of a Hz at 1MHz which gives the claimed accuracy of less than 1 part in 10^7.At the high frequency end the 1 cycle will only be at 100MHz 10 nanosecs with the GPS jitter adding say 30 or so nanosecs so the total would be around 50 nanosecs over 40 seconds comming down to around 1 nanosec which is again around 1/10 of a Hz but would be much less than 1 part in 10^7EDIT:Looking at your quote, the frequency being measured is always 2.5MHz (presumably other frequencies are generated by the chips PLL) so the accuracy over 40 seconds is say 400 nanosecs (1 cycle, perhaps 800 nanosecs would be more accurate given uncertainty both ends) plus say 50 nanosecs or so for the jitter in the 1PPS so the accuracy would be aound 500 to 1000 nanosecs over 40 secs which is say 10^-6 over 40 or 2.5 x 10 ^-8."
},
{
"post_id": "",
"author": "StillTrying",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 09, 2017, 04:07:20 pm",
"content": "http://www.arrl.org/files/file/QEX_Next_Issue/2015/Jul-Aug_2015/Marcus.pdf\"Im guessing that 40 seconds was chosen to produce easy to work with numbers\"I think it's 40 seconds to give a total count of 100M to be able to detect changes of +/-0.01ppm - in theory.\"I mean if the crystal is 20parts per million and a 100mhz is 100 million parts, doesn't that mean the arduino count can be up to 2000 counts off?\"The timing of when the si5351's 2.5MHz / 100M count is captured is controlled by the GPS's 1PPS.As long as the arduino's clock is >2.5X faster than the 2.5MHz the 100M count will be captured within +/-1 count."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 09, 2017, 04:54:35 pm",
"content": "How accurate the frequency counting works, depends on the implementation on the Arduino. Normally connecting the 1 pps signal to the int0 input is not the best way to make a high resolution counter, though it is possible to get a good accuracy, if tricks like going to a sleep mode to avoid extra interrupt jitter are used. However there would be an additional error of up to +-1 clock cycle of the µC.The more logical way would be using a 10 to 20 MHz clock (e.g. 12.5 MHz) from the Si5351 to clock the µC and than route the 1PPS signal to the ICP input. This would give a slightly higher resolution due a higher count number, simpler software and no extra error from the extra µC clock. Ideally the software could use extrended resolution mode by looking at all the 1PPS pulses and not just the first and last in a 40 seconds window. This could give a little additional suppression of jitter of the 1 PPS pulses and maybe slightly better resolution (depending on the frequencies used - it won't help with exactly 12.5 MHz).PS. Even if counting over 40 seconds, 2,5 MHz are still 2,5 MHz it is just 100 million counts."
},
{
"post_id": "",
"author": "rwgast_lowlevellogicdesin",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "September 09, 2017, 07:09:26 pm",
"content": "@Kleinstien, your way does make much more sense, its how I originally envisioned this would work before reading this QEX article. Iv'e already decided if I use the interrupt technique described in the article I will probably dedicate an Attiny to doing nothing but setting up the si5351 and calibrating it against the 1pps signal. This way there is no interrupts or other code throwing off the timing, or I may just switch from AVR to a propeller chip and dedicate a full core to the task. The thing is I want to add a nicte 2.8inch TFT and two DDS chips locked to the clock, this way I can have quadrature squares or sign waves so I may just be moving it all to a cypress PSOC or something, in which case I can use the hardware blocks to separate any microcontroller issues from the timing.@Jpb, StillTrying thank you the paper makes much more sense now than it did before. But I am still hung up on the arduinos 20ppm crystal.. to me the logic is, yes all the arduino is there for is to count the 2.5mhz signal for 40 seconds, but wouldn't that be like using a frequency counter with 20ppm of accuracy, or am I confused and the counter peripherals are somehow not effected by system clock jitter?Code:As long as the arduino's clock is >2.5X faster than the 2.5MHz the 100M count will be captured within +/-1 count.Does this have something to do with NyQuist? I understand in order to recreate the original signal you have to sample that you have to same it at a clock rate at least 2x faster than itself, but I guess I am not seeing how that ties in to the accuracy of the count.Im sorry I keep pushing this 20ppm thing I am just not understanding why the micro that is counting the si5351 frequency wouldnt want a clock with less error, I am not arguing at this point that it needs a better clock only trying to understand why its accuracy is not important."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 09, 2017, 07:53:16 pm",
"content": "When using the method described in the article, the accuracy of the µCs clock does not matter (it could us the µC internal RC clock, that is something like +-1%). The µC is counting the 2.5 MHz clock, but sampled at the µCs clock.However the additional clock (even of stable) adds an additional jitter from the extra synchronization / sampling. So if clocked at 10 MHz, this would be another +-100 ns. It is only if the µC's clock is in sync with the signal to count that there would be no big additional jitter. Due to the synchronized input of the AVRs external counter input (for timer 1 - timer 2 can be async, but does not have a capture function) the µCs needs to be higher than 2 times the clock to count - this is the Nynqueist limit. A factor of 2.5 is more like a practical number to allow for uneven H/L.Using the interrupt method would essentially need a dedicated µC, or at least a way to have that µC not doing much else at the start and end of the gate time.When using the µC ICP function, the µC can do other things too, as the critical timing part is done in hardware. I have build a frequency counter that way, where is µC is also doing LED display multiplexing and checking keys. Especially with a 1PPS signal, the µC is essentially 99.9% free to to other things, maybe even relative time critical parts. So it seems reasonable to have the µC also program the clock generator or a DDS chip - however startup might be tricky as the clock is needed to start with. I don't think the AVRs allow to change the clock source on the fly - other µC might do."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 09, 2017, 07:55:55 pm",
"content": "Quote from: rwgast_lowlevellogicdesin on September 09, 2017, 07:09:26 pmNah. Use a £12 xCORE startKIT devboardStuff the XO output into a buffered input and use software to count edge transitions in a 62.5Mb/s input stream. Good to >15MHz, assuming a reasonable approximation to a 50% duty cycle."
},
{
"post_id": "",
"author": "StillTrying",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 09, 2017, 08:36:35 pm",
"content": "Quote from: rwgast_lowlevellogicdesin on September 09, 2017, 07:09:26 pmYep similar, assuming I am/was on the right page (I might not be!) ofAtmel-8271-8-bit-AVR-Microcontroller-ATmega48A-48PA-88A-88PA-168A-168PA-328-28P_datasheet_Complete.pdfPage 138/9(of 660) says:\"17.3 External Clock SourceAn external clock source applied to the T1/T0 pin can be used as Timer/Counter clock (clkT1/clkT0). The T1/T0 pin is sampled once every system clock cycle by the pin synchronization logic. The synchronized (sampled) signal is then passed through the edge detector....The registers are clocked at the positive edge of the internal system clock (clkI/O)....The synchronization and edge detector logic introduces a delay of 2.5 to 3.5 system clock cycles from an edge has been applied to the T1/T0 pin to the counter is updated....Each half period of the external clock applied must be longer than one system clock cycle to ensure correct sampling. The external clock must be guaranteed to have less than half the system clock frequency (fExtClk< fclk_I/O/2) given a 50/50% duty cycle. Since the edge detector uses sampling, the maximum frequency of an external clock it can detect is half the sampling frequency (Nyquist sampling theorem). However, due to variation of the system clock frequency and duty cycle caused by Oscillator source (crystal, resonator, and capacitors) tolerances, it is recommended that maximum frequency of an external clock source is less than fclk_I/O/2.5.\"I don't think the Marcus.pdf is using the hardware ICP1 capture pin, (I only had a quick-ish look) maybe just using every 40th GPS interrupt to capture the ~100M count value.EDITYRun the uP on its internal RC clock while it sets up the Si5351B to output 10MHz or 20MHz.Then switch the uP to use that as it's clock, the timer can then run/count at that frequency.I think you can use one of the analogue comparators on the 1PPS to capture the timer count every 1 second.That would then give you a 100M count for VCO adjustments every 5 or 10 seconds.Simples!EDITY2I think Kleinstein is correct above, I didn't see any way to swap to the internal RC osc even as a backup.And on the Si5351 data sheet I had only the Si5351Bversion had the VCO input."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 10, 2017, 09:34:50 am",
"content": "It looks like there are versions of the Si5351 that have pre-programmed settings to start with - so there would be a clock to start with, so the µC could run on this clock all the time.Another option would be using an external clock (e.g. 25 MHz oscillator, or if needed an VCXO) and use this to drive both the Si5351 and the AVR. Though only specified for 20 MHz (CPU clock) it should be OK, if the AVR internal divider is used to make the CPU run at half the speed.There is also the x-mega series that can directly run from 25 MHz - they may also switch the clock source while running, though might program there own clock source. At least some PICs and ARMs can do this.Though complicated in software to get it correct one could use a normal pin for the 1PPS signal. Using the ICP input is mainly avoiding the time critical program. The important step to avoid an extra error would be having the µC clock in sync. An alternative would be an external HW gate before the µCs counter input - sounds simple, but can be a little tricky with the sampling nature of the counter. A simple logic gate won't work, but a transparent latch would."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 10, 2017, 10:47:40 am",
"content": "Quote from: Kleinstein on September 10, 2017, 09:34:50 amMany processors have the ability to use either an internal clock multiplied from an external XO/resonator, or an external clock.One example is the XMOS xCORE devices, which can have clock-multiplied internal clocks up to 500MHz (=> 250Mb/s i/o per pin) derived from XOs up to 30MHz or external clocks up to 100MHz."
},
{
"post_id": "",
"author": "pigrew",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 10, 2017, 03:57:17 pm",
"content": "My understanding is that without DGPS, the GPS PPS signal will always have roughly sigma=15ns even with quantization error correction,See this ublox app-note.So, it's a good idea to have the phase measurement circuitry to have at least this accuracy (or else the system is limited by the phase measurement). >100 MHz clocks may be enough. I see a few options for doing this: using an external timing IC (such as the TDC7200), using a CPLD with a fast internal clock (>300 MHz or so, FPGAs are slower), or using a MCU timer (XMOS, PSoC, ESP32, whatever fast MCU you can find).I don't see any advantages to clocking the CPU with the reference clock, unless there are cross-talk/signal integrity concerns?"
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 10, 2017, 04:55:52 pm",
"content": "There is a definitive advantage in having the µC clocked from the reference clock (or one derived from it): most timers in the µCs are synchronized to the CPU clock (or maybe even a lower IO clock). If not in sync, this additional sampling would add an extra uncertainty of +-1 CPU clock. In addition there would be the +-1 clock from the reference that needs to be lower than the CPU clock. The problem gets smaller with a faster µC, but it is avoidable. Of cause it is not a problem with an extra TDC or similar to do the timing.One might avoid much of the extra error with a 2 step measurement:1. f(µC) relative to 1 PPS and 2. f(µC) relative to f(reference) using a higher frequency and this way less error. However this is still one extra step.There are also ARM based µCs with timer clocks up to the 100 MHz range. These usually allow to start from a different clock source. There are also some plans for a relatively simple analog timing interpolator based on a slow µC, with relatively little extra hardware.The 40 seconds timing is not a fixed value - usually it takes much longer to get a thermally stable value. Depending on the crystal oscillator, the optimum GPS to crystal cross over is at a longer time scale."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 10, 2017, 05:07:56 pm",
"content": "Quote from: Kleinstein on September 10, 2017, 04:55:52 pmOne justification for 40s might be that 100MHz and a 32-bit counter => rollover every 42.94s."
},
{
"post_id": "",
"author": "pigrew",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 10, 2017, 05:31:08 pm",
"content": "Quote from: Kleinstein on September 10, 2017, 04:55:52 pmExactly. I had been thinking about using a Tiva C at 80 MHz, clocking the counter with 10MHz reference, and triggering the count to be stored at the PPS edge."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 10, 2017, 08:38:48 pm",
"content": "Quote from: pigrew on September 10, 2017, 05:31:08 pmI think, you miss-understood me completely: This way would give you a 100 ns resolution from the 10 MHz clock plus likely an extra 12.5 ns extra jitter from synchronization to the µC clock (if the timer or 1 PPS capture is synchronous, as it is with nearly all µCs). So a total worst case error of +-112,5 ns plus analog uncertainties from slopes.The way I meant would be measuring the 80 MHz µC clock from the 1 PPS which would give an 12.5 ns uncertainty. Ideally this would be all it takes if the µC clock is accurately liked to the reference by an PLL. Otherwise one could divide down the Reference to a slower clock of maybe 10 kHz. This cold than be measured similar to the 1 PPS signal if done the simple way (start and stop only) the error for the whole step would be at 25 ns.When not just looking at the first and last pulse one can increase the resolution a little. This is kind of averaging all the 40 pulse instead of using only the first and last. The 1PPS measurement might get better by something like a factor of around 3. The gain in resolution also applies to some of the GPS uncertainties (especially jitter from quantization).Due to the larger number of pulses for a 10 kHz signal it might give an improvement by maybe an additional factor of up to 100. So the overall error could be reduced. Especially the second step from the reference to the 80 MHz clock can be very accurate this way and the two step process could be nearly as good as having a fixed (e.g. PLL) link. It is a kind of FLL link in software."
},
{
"post_id": "",
"author": "rwgast_lowlevellogicdesin",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "September 10, 2017, 08:48:18 pm",
"content": "So if I were to just clock the AVR from the same 2.5ppm 25mhz tcxo that is driving the si5351, I would virtually eliminate any short term jitter error, when counting the 2.5mhz output? What is the best way to do this, do I need an unity gain opamp between the tcxo and avr, or some extra hardware to make sure the tcxo can drive both systems?I have been reading up a lot on GPS 1pps jitter and made some most likely inaccurate measurements on my scope, so it seems reasonable to say a 1pps output suffers from 10 to 40ns jitter, what is the best way to handle this? The amount of jitter reduced from the 1pps measurement will greatly effect the very short term stability of si5351, right? I would assume over long periods of time the 1pps jitter will eventually equal itself out?Im sorry this is a real learning experience for me as far as timing and accuracy go. In the end I want to use the VFO a lot of things involving decently accurate quadrature clocking. But for now i'm really looking at using it to replace the 100mhz tcxo in my ADF4351 sig gen, this way I can accurately clock SDR applications for microwave satcom and radio astronomy. Is there any way this will ever be a better (i.e more accurate, phase noise is a whole other story) clock than the .5ppm tcxo on my airspy? The results the original author got look very promising, and i am assuming if slapping a .5ppm tcxo on the si5351 was more accurate that would have been the route he would have taken."
},
{
"post_id": "",
"author": "rwgast_lowlevellogicdesin",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "September 10, 2017, 09:00:53 pm",
"content": "Also what would be my best option of measuring accuracy if I don't have any frequency standard? ATM all I can think of is to experiment and measure any changes I make against the results before and when optimized just rely on the fact that GPS is a pretty stable reference."
},
{
"post_id": "",
"author": "jpb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 10, 2017, 09:13:31 pm",
"content": "Quote from: rwgast_lowlevellogicdesin on September 10, 2017, 08:48:18 pmThe GPS 1PPS is very accurate over 24 hours but suffers from short term jitter of the order of 10 to 50 nsecs, though with a good aerial and a timing receiver it should be nearer 10 nsecs than 50 nsecs. The longer the time interval the less important the jitter is but the more the drift in the crystal clock so a compromise is needed (as with a GPSDO). With a GPSDO the best compromise is taking a loop time constant that approximates where the Allan Deviation of the OCXO (or Rubidium) crosses over the Allan Deviation plot of the GPS receiver 1PPS. This can be anything from 100 secs to 10,000s of secs.The author of the article has selected 40 secs as a compromise which seems reasonable given that it makes the fractional error of the jitter only around 1E-9 but is not so long that temperature changes and so on mean that the characteristics of the crystal clock being calibrated are drifting significantly.You can't really do much about the jitter (other than installing a good outside antenna and say getting a cheap Lea-6T off ebay) but you can experiment with different time intervals for the measurement or improve the crystal clock (though I guess this is difficult if it is built-in to the circuit).I think worrying about the GPS 1PPS jitter is pointless as it is much less than the cycle time of the calibration clock (2.5MHz). A greater source of improvement would be to use some sort of interpolation scheme of calibrate at a higher frequency."
},
{
"post_id": "",
"author": "jpb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 10, 2017, 09:15:40 pm",
"content": "Quote from: rwgast_lowlevellogicdesin on September 10, 2017, 09:00:53 pmGPS is a pretty good reference if you take longer gate times. If you have a counter of some sort which measures down to 1Hz (I used a TI930) then taking a 100 second gate will give a very good measure of the accuracy of the counter."
},
{
"post_id": "",
"author": "StillTrying",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 10, 2017, 09:39:27 pm",
"content": "If I was using a 40 seconds count period, I'd create at least 8 40s counting periods all offset by 5 seconds to give a possible correction calculation every 5 seconds. Of course the counter is never stopped or reset because it helps to cancel some of the jitter, and detecting and fixing rollovers in the count-count periods is easy enough, well it is if you say it quick."
}
] |
2025-10-17T18:49:15.350178
| 20
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/(tina-ti)-trouble-with-lm5002-simulation/
|
[TINA-TI or LTspice] Trouble with LM5002 simulation - Page 1
|
[
{
"post_id": "",
"author": "bodzio_stawski",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "January 23, 2024, 10:49:18 am",
"content": "Hello,I wanted to recreate the LM5002 circuit in the TINA-TI program which seemed to me to fit the Texas chip like a glove.Unfortunately, the effects of this program quickly took their toll on me, and the circuit simply does not work properly, when it comes to output voltage.In fact, I could say that the output voltage is close to the set input voltage instead of being increased. A factor that may be crucial in this case is that I had to import the LM5002 chip into the TINA-TI program, which I did using the Tools-New Macro Wizard function.I downloaded this model of LM5002 from this manufacturer's link:Link to the LM5002 modelhttps://www.ti.com/product/LM5002?utm_source=google&utm_medium=cpc&utm_campaign=app-null-null-GPN_EN-cpc-pf-google-wwe&utm_content=LM5002&ds_k=LM5002&DCM=yes&gad_source=1&gclid=CjwKCAiAkp6tBhB5EiwANTCx1I02KymlWGVlOnDBXDaCyRaUBd2jIqiBK5bZqMnmFRwDUyP8UJMsixoCs_0QAvD_BwE&gclsrc=aw.dsIs it possible that I am making some mistake in running the circuit here?Link to my file: LM5002.TSChttps://easyupload.io/5u7xaw"
},
{
"post_id": "",
"author": "bodzio_stawski",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "January 25, 2024, 07:32:21 am",
"content": "Alternatively, do any of you have an LM5002 model that can run on LTSpice?I tried to use the same one (in .lib format) from the TI website, but it does not work the same as in TINA TI. When I prepared an alternative circuit with LT1371 in a similar configuration as boost converter, it worked (although it is, of course, an Analog IC, saved with the.subextension)."
}
] |
2025-10-17T16:41:37.130656
| 2
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/(tools)-battery-pack-calculator/
|
[Tools] Battery pack calculator. - Page 1
|
[
{
"post_id": "",
"author": "jekhatulan",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "November 12, 2017, 10:56:46 am",
"content": "Hi!I want to share this simple tool that I recently created for Beginners like me. It's a Battery pack calculator.It calculates the voltage, capacity and show your battery configuration ( ex. 4s 10p ) based on how many cell you have and how many S (serial connection you want).There's also a custom Calculator there if you want to design based on how much voltage, and parallel group you want it will give you the same output like the first one.If I have mistakes on my calculator just leave your comments or send me PM and If there's is a computations that I need to include and consider, just tell me.Thank you!"
}
] |
2025-10-17T18:45:07.857345
| 1
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/(tv)-capacitor-issue/
|
[TV] Capacitor issue? - Page 1
|
[
{
"post_id": "",
"author": "rthorntn",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "August 28, 2021, 09:33:42 am",
"content": "Hi,My 7.5yo LG 55EA9800 TV is playing up.Basically (as of yesterday) when I first turn it on from standby I get horizontal streaks and trails of pixels, flickering and blanking. After about 30 minutes it goes away.I think I remember reading that failing electrolytic capacitors have this \"once it warms up the problem goes away\", is that correct?I mean if its a simple repair then that would be great. I'd rather keep this set for another 2-3 years, it cost an absolute bloody fortune back in 2014.CheersRichard"
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 28, 2021, 09:50:01 am",
"content": "Hard to say, but yes, it might be bad capacitors.Might be something else too though.If it is just bad caps then yes, it is a simple repair for anyone who knows how to use a soldering iron and knows enough about capacitors to buy the correct replacement caps.You can also buy entire new boards for like US$60-100 on aliexpress. But the seller ratings look a bit low for me to want to take the risk on them."
}
] |
2025-10-17T17:23:39.577746
| 2
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/(type-of)-multimeter-advice/
|
(Type of) multimeter advice - Page 1
|
[
{
"post_id": "",
"author": "NrN86",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "October 13, 2025, 02:48:17 pm",
"content": "I’m looking to buy a multimeter that will be used for the following use cases:- Check the voltage of circuit breakers in a cabinet in residential installations (1-phase 230V and 3-phase 400V)- Diagnostics for Loxone installations (24V voltage measurements and especially testing voltage drops for 24V lightning)- I also occasionally install small solar panel installations (< 10kW)- Install and start up residential heat pump installations and airco installations (<10kW) (will start a course in November to become a certified refrigeration technician by the end of this year)I’m not sure what type of meter would best suit my needs and was hoping you could share your experiences so I can a make more advised choice.DMM- Brymen BM325 or BM257s- Fluke 115, 116 or 117Clamp meter- Fluke 323 or 325Electrical tester- Fluke T5 or T6 seriesIs there one device that can cover all my needs or would you go for a combo Fluke 116/323.Looking forward to your insights. Not only brand and model recommendations but also advice concerning the type of meter.Thanks a lot!"
},
{
"post_id": "",
"author": "BILLPOD",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "October 14, 2025, 01:50:04 pm",
"content": "Good Morning NrN86, The recommendations you will get, here on the Forum, will approach the number of members on this Forum, so I recommend you go to this site which will provide you with information on most, if not all, of the meters available on the marketplace, in spreadsheet format. Happy huntinghttps://www.eevblog.com/forum/testgear/multimeter-spreadsheet/"
},
{
"post_id": "",
"author": "themadhippy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 14, 2025, 02:22:46 pm",
"content": "personally id go for 3 meters,a good all round multi meter,a separate clamp meter and a simple voltage tester like the fluke T110. 99% of the time the voltage tester will be the one you grab as you just need to prove voltage or if theirs continuity"
},
{
"post_id": "",
"author": "NE666",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "October 14, 2025, 03:59:42 pm",
"content": "To add to the advice above, not only did I purchase a Fluke T110 for jobs like this (other models and brands are available), I got a proving unit to go with it. No point in realising that your voltage detector was defective, as you're being bitten.."
},
{
"post_id": "",
"author": "themadhippy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 14, 2025, 04:19:12 pm",
"content": "QuoteBack when i was an apprentice one of the biggest causes of failing the final practical exam was not proving the meter,not just before taking a reading,but afterwards also."
},
{
"post_id": "",
"author": "bdunham7",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 14, 2025, 04:44:37 pm",
"content": "Quote from: NrN86 on October 13, 2025, 02:48:17 pmI have this combination and it is pretty good setup for general household and light commercial electrical work. You don't want to be measuring current through your meter anyway in those situations so you need a current clamp. The 116 actually has a very nice feature set but without the current ranges.However, the 116 is a 600V CAT III meter, meaning according to the rules you shouldn't use it outdoors, on certain higher energy service panels or on HVDC solar. I have other meters for that, in my case a Fluke 289 (and 27, 189, etc) but in the EU you may find something like the Brymen 869S to be a good choice for much less money. If your solar systems approach or are over 1kV then you need a special meter for that. One thing to keep in mind is that any situation where the Fluke 116 is inappropriate is probably also a situation where PPE and specific precautions are also required."
},
{
"post_id": "",
"author": "free_electron",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 14, 2025, 04:54:32 pm",
"content": "Clamp meter. So you can measure current without having to interrupt the connection . No contact, no risk for overloads or popping fuses (or the meter ). clamps are the safest possible. Especially in residential."
},
{
"post_id": "",
"author": "BeBuLamar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 14, 2025, 05:38:40 pm",
"content": "I think the 116/323 combo is a good one. At work I used the 87V/374FC combo. I never have or use the tester."
},
{
"post_id": "",
"author": "Gyro",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 14, 2025, 06:23:51 pm",
"content": "When testing for dead, DMMs have too many opportunities for error - switch position, lead insertion etc.A proper appropriately Cat rated low-Z voltage tester has robust captive leads (including safety tips) and requires no switch setting, it also gives clear audible and visual indication and still operates even if the battery if the battery is flat or missing. Verified with a proving unit, before and after, as mentioned above is the only truly foolproof part of a safe isolation procedure. A DMM simply won't hack it. It's a relatively economical solution for achieving high Cat rating too.Of course DMMs, and especially clamp meters, have their place for diagnostic work too but ignore a proper safe isolation (ie. tester+proving unit) part of the job at your peril."
},
{
"post_id": "",
"author": "free_electron",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 14, 2025, 06:40:36 pm",
"content": "Fluke-T5-600"
}
] |
2025-10-17T16:13:13.908779
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/(uk)-free-pcb-designer-tutorial-and-british-manufacturer/
|
(UK) Free PCB designer + tutorial, and British manufacturer - Page 1
|
[
{
"post_id": "",
"author": "rhydiansion01",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 26, 2015, 10:38:46 pm",
"content": "Id like your thoughts about the best free PCB designer tool, along with good beginner tutorial. Also id like to know if there's a company that would produce a single PCB board for hobbyist in the UK?Im a bit of a novice, but im willing to learn, and hopefully will be getting the 3rd edition of the electronics bible soon for my 21st!"
},
{
"post_id": "",
"author": "ozwolf",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "March 27, 2015, 11:06:36 am",
"content": "Try AutoTrax Dex, free for non-commercial use, go tohttp://www.kov.com.Tons of videos on YouTube to help out.Ozwolf"
},
{
"post_id": "",
"author": "Sirius631",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "March 27, 2015, 11:14:27 am",
"content": "I've not heard of AutoTrax Dex.If you look in the PCB CAD section of the forum, the broadly used CAD packages with free variants are discussed widely. I've just downloaded Eagle and am generally happy with it, despite the lack of intuitive flow, which will be overcome with experience."
},
{
"post_id": "",
"author": "sleemanj",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 27, 2015, 11:40:39 am",
"content": "DipTrace is the most intuitive of the \"professional\" design packages IMHO (but I haven't tried AutoTrax), the free version will see you well into getting into some moderately big hobby stuff, and the paid versions are reasonably priced.As for board houses, don't know about in the UK, but there are plenty of cheap manufacturers in China for prototypes, usually in quantities of 10 boards for a buck of two each.For example, dirtypcbs.com protopack gets you \"around\" 10 5x5cm boards, sometimes as few as 8 sometimes as many as 12, with free shipping, for $14 USD, in a number of colours.Of course, you have to not mind waiting a few weeks for shipping, or pay extra for faster shipping :-)"
},
{
"post_id": "",
"author": "Wilksey",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 27, 2015, 12:12:46 pm",
"content": "DipTrace, EAGLE, KiCAD (completely free and open source).KiCAD's new windows builds are quite decent, you can do more advanced stuff like length matching and differential pairs, not that you \"need\" that yet, but can't hurt to have it if you are used to a package in a few years time!WRT Board houses, meh, PCBTrain, an offshoot of Newbury Electronics, it will cost you around £40 for one board, or, you can get 10 from China delivered for under £20."
},
{
"post_id": "",
"author": "rhydiansion01",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 27, 2015, 01:32:07 pm",
"content": "Awesome, I'll get to it now I think! Tbh I never thought a PCB would cost so much from UK, would you reckon it's possible to build your own PCB maker? but one that engraves out the tracks and stuff, like a CNC machine? Would make a decent project that."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 27, 2015, 03:06:02 pm",
"content": "Quote from: rhydiansion01 on March 27, 2015, 01:32:07 pmHave a look at my experiences onhttps://entertaininghacks.wordpress.com/tag/pcb/You can engrave PCBs, but the \"laser toner\" technique might be suitable for simple boards."
},
{
"post_id": "",
"author": "Wilksey",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 27, 2015, 10:16:10 pm",
"content": "Yes, it is possible, in fact, Maplin used to sell a starter kit for etching your own boards, you will need a laser printer for optimum results, for me, I prefer the £20 from china route, but you should at least have a go at making your own, just to experience the mess"
}
] |
2025-10-17T19:44:18.758400
| 8
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/(uk-specific)-soldering-stations/
|
(UK specific) Soldering Stations - Page 1
|
[
{
"post_id": "",
"author": "JonSick",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "October 05, 2015, 07:44:38 pm",
"content": "Hi allI want to invest in a decent soldering station, but having a bit of a tricky time. It's my first one, before I've just used and burned Homebase specials.I can't seem to find a decent station with easily replaceable solder tips. That is, easy to find and aren't £30 for a set of three, only one of which I'll ever use.So, can anyone in the UK point me in the right direction for a temperature controlled station with decently available chisel type tips?I mainly will use it for guitar electronics (potentiometers, jacks, etc) and putting effects pedals together using larger caps/resistors etc."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 05, 2015, 07:56:52 pm",
"content": "I spent several decades without a temperature controlled soldering iron. During that time I soldered many smaller, finer, more temperature sensitive components than you mention. However, they were all through hole components.The only reason I now have a temperature controlled iron is because I needed a small tip for surface mount devices which are thermally small and have small easily lifted pads on PCBsFor what you state you need, a traditional 25W iron is sufficient. Otherwise, have a look at something likehttp://www.maplin.co.uk/p/maplin-50w-solder-station-n78ar"
},
{
"post_id": "",
"author": "wraper",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "October 05, 2015, 08:25:14 pm",
"content": "Quote from: tggzzz on October 05, 2015, 07:56:52 pmIt is not temperature controlled, just a dimmer inside. Also it is ridiculous junk which is even worse than many uncontrolled irons."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 05, 2015, 08:36:21 pm",
"content": "Quote from: wraper on October 05, 2015, 08:25:14 pmThe temperature is controllable and it is more than sufficient for the stated requirements. You don't need a Rolls Royce or a Land Rover to go to the supermarket."
},
{
"post_id": "",
"author": "wraper",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "October 05, 2015, 08:44:08 pm",
"content": "Quote from: tggzzz on October 05, 2015, 08:36:21 pmNo, it's not controllable (unless +-100oC is considered to be controlled). Regulating power is not the same as controlling the temperature. I have used such soldering iron and it was almost the worst iron I held in my hands ever (worse than this were only $2 Chinese irons).Quote"
},
{
"post_id": "",
"author": "orbiter",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "October 05, 2015, 09:56:16 pm",
"content": "Check out Circuit Specialists.. They have some reasonable units (I used to have the BlackJack BK 2000 which was good.) Although don't expect an 8 second heat up time etc for these prices.They stock spares for most things too I believe..http://www.circuitspecialists.eu/soldering/soldering-stations/"
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 05, 2015, 09:58:50 pm",
"content": "Quote from: wraper on October 05, 2015, 08:44:08 pmI have one and the warm up time isfarless than that. I am entirely aware that heat != temperature. I am aware that there are far better irons than that. Indeed, I also have a temperature controlled iron and hot air gun. For the OP's stated requirements, I would probably use the cheap Maplin iron.I am also aware that the OP is sensitive to cost and that that iron is more than sufficentforhispurposes. I make no comment about your purposes nor your budget - they are irrelevant.Fitnessfor purposeis a very important engineering concern. \"An engineer is someone who can do for $1 what any fool can do for $10\"."
},
{
"post_id": "",
"author": "JonSick",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "October 05, 2015, 10:14:03 pm",
"content": "I should probably clarify a little more...AS for purposes, most of my work will be around larger components. But I do intend to get into PCB work later on, be it making up some effects or arduino-related projects.I'm not a complete newbie but I'm not a Professor of electronics either by a long shot. All of this is hobbyist.I'm not particularly after bargain basement as a lot of tools I've used in the cheaper price bracket tend to subscribe heavily to the buy cheap, buy twice mentality. I have had a Maplin solder station before which was around the £40 mark but I just could not find replacement tips for it and nothing else seemed to fit. At least properly anyway - using random bits of metal to wedge a solder tip in place is really not a safe solution.So as for budget, happy to spend about £100 on a decent station with the various paraphernalia (sponge, stand etc) that will last me. I just can't believe it's become so difficult to find something useful in the UK."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 05, 2015, 10:53:53 pm",
"content": "Quote from: JonSick on October 05, 2015, 10:14:03 pmDeisngning and making PCBs are much much easier than when I started!If you want fast turnaround then there's the homebrew \"laser toner\" techinque, which is just about good enough for double-sided 0.1\" boards.If you want several \"proper\" boards, then you can get 10off 5cm*5cm double sided PTH for £10 in 10 days.Don't be put off by surface mount - unless you expect to do a lot of reworking. You don't need a reflow oven; with care the skillet technique works remarkably well. Reworking really needs a hot air gun so as to heat up all contacts simultaneously; both temp and airflow mut be controllable.QuoteSometimes that's a good strategy, e.g. when learning or because you are going to damage it sometime so there's no point in spending more than necessary (think non-stick frying pans!)QuoteSounds dreadful! I'm surprised you got anything to work like that! The Maplin tips are easily available on ebay.QuoteI suspect that's the sour spot between \"disposable\" and \"good\". I found a £130 factory-return Tenma for half price, and had to repair a faulty joint in a connector. I haven't used it enough to have formed an opinion as to whether I would recommend it."
},
{
"post_id": "",
"author": "orbiter",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "October 05, 2015, 11:35:15 pm",
"content": "Perhaps you missed my post above?... Circuit Specialists are in Manchester UK"
},
{
"post_id": "",
"author": "JonSick",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "October 06, 2015, 06:48:11 am",
"content": "I did actually! Cheers for the tip."
},
{
"post_id": "",
"author": "GNU_Ninja",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "October 06, 2015, 07:15:08 am",
"content": "I recently bought this Atten 8586 rework station. Hot air gun and a 50W controlled iron for about £70 delivered. Quite happy with it, and it takes Hakko (or fake Hakko) tips wich are easily obtainable.Be aware, the iron comes fitted with one of those ludicrous conical/pointed tips, so you'll need to invest in a decent chisel tip too.Link here ==>http://www.amazon.co.uk/Atten-Digital-Rework-Station-solder/dp/B00D1V6TN2/ref=sr_1_1?ie=UTF8&qid=1444115383&sr=8-1&keywords=atten+reworkThis 75W job from Circuit Specialists was on my shortlist:http://www.amazon.co.uk/Station75-Temperature-Control-Soldering-Powerful/dp/B00SYLUXJK/ref=sr_1_34?ie=UTF8&qid=1444116288&sr=8-34-spons&keywords=soldering+iron&psc=1... But I finally went for the Atten rework station, as I want to get into the world of SMD.Hope you find something suitable"
},
{
"post_id": "",
"author": "Gyro",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 06, 2015, 08:50:51 am",
"content": "QuoteSo why not go for Maplin's slightly more expensive 48W properly temperature controlled one?http://www.maplin.co.uk/p/48w-professional-2-line-lcd-display-solder-station-n34fbIt still looks good value (my nephew recently got one for beginner's use). Tips are cheap (£7 for 3) as are replacement irons. The cords are burn proof silicone - I grabbed one off ebay to convert my weller TCP to zero voltage switching (and relieve the current on the thermostat contacts)."
}
] |
2025-10-17T19:32:32.023864
| 13
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/(very)-high-impedance-voltmeter-and-ads1115/
|
(Very) High Impedance Voltmeter and ADS1115 - Page 1
|
[
{
"post_id": "",
"author": "stcoso",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 24, 2019, 07:08:17 pm",
"content": "Hi to everyone... I'm trying to build a simple high impedance (TOhm range) voltmeter and use a ADS1115 as a ADC to convert the signal. The signal I need to measure is in the range of +- 0.5VI managed to get some results using the circuit that i attached but i would like to know how it can be improved. Because the ADS1115 is usable only down to GND-0.3V i thought that i could use a resistive divider to get a 2.5V voltage to use as reference attached to one of the probes. The trimmer in the schematic is set to get a reading of 0mV when the probes are short-circuited.Thank you, bye."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 24, 2019, 07:19:46 pm",
"content": "The pot is only setting the common mode voltage, so if would hardly effect the reading from the ADC. So no need to use a pot - just two fixed resistors are enough.The zero adjustment / compensation is better done digitally. So read zero with shorted inputs and subtract digitally.The TL082 is cheap, but not very good: it needs at least some 7-8 volts and does not work below some 3 V.A better cheap choice would be MCP6001 - it also works from the same 3-5 V supply as the ADC."
},
{
"post_id": "",
"author": "stcoso",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 24, 2019, 07:26:55 pm",
"content": "Ok, thanks! In which respect (besides the input voltage) the TL081 is not good for this application ?"
},
{
"post_id": "",
"author": "Gyro",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 24, 2019, 07:30:03 pm",
"content": "The LMC662 has averyhigh input impedance and typ. <5fA level input current. It's specified down to 5V and is cheap - it's a dual too, so you can play with the other half for mid rail buffering or whatever.EDIT: Do keep an eye on the datasheet input common mode range though."
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 24, 2019, 08:32:42 pm",
"content": "A TL081 can be made to work but there are better parts. The LMC6081 is my old favorite (and a good choice for this) but I know there are better parts now.A major improvement can be made with any part by bootstrapping the operational amplifier's power pins off of it output so they track the input signal and the common mode errors are reduced and the input impedance is increased significantly.This is commonly done in high impedance buffers to raise the input impedance. Ignoring AC effects, the input resistance is the change in current for a change in voltage. The input bias current depends on the common mode voltage so if the common mode voltage does not change because the power pins are bootstrapped to the output, then the input bias current also does not change."
},
{
"post_id": "",
"author": "not1xor1",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 25, 2019, 07:30:15 am",
"content": "Quote from: stcoso on March 24, 2019, 07:26:55 pmlimited input-output voltage range, high offset and offset drift...modern parts also feature less supply current which might be useful in some cases"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 25, 2019, 08:58:22 am",
"content": "FYI -https://www.eevblog.com/forum/projects/simple-dc-afe-for-adc-chips-with-unipolar-diff-inputs/msg2120179/#msg2120179That is a bootstrapped opamp.When you replace the input chopper opamp in my schematics with the above recommended opamps and remove the input protection transistors you may get a highR input."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 25, 2019, 09:24:03 am",
"content": "Below a simulation of a simple HighR AFE for ADS1115 (and others).Mind the serial resistance of the +/-1V input voltage source is 1T ohm.PS: the precise values or the tempco of the R6/R3 divider is not critical as the differential ADC input cancels the errors out.The R17=100Meg simulates the internal impedance of the ADC.Simulation only, use at your own risk"
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 25, 2019, 04:22:42 pm",
"content": "The 25 ohms resistors shown in the simulation from IMO are as shown not helping. If better tolerance to capacitive load is needed, it takes an additional resistor and capacitor as direct feedback. There may be no real need to buffer the virtual ground / negative ADC input.The choice of OPs depends on the needs, like cost, noise, bias, drift. Good choices are something like MCP6001 (low cost), LMC6482 (and a few similar ones) for low bias and OPA145 for low noise at still good bias.It may be a good idea to have a series resistor (e.g. > 100 K) at the input for protection - the OPs often include diodes by might need a current limit."
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 26, 2019, 01:33:31 am",
"content": "Quote from: Kleinstein on March 25, 2019, 04:22:42 pmYou have to be a little careful in applications where precision is important with MOSFET and JFET input parts which can have low open loop gain and low common mode and power supply rejection. The LMC6482 is far from \"precision\".Another thing to check if it is provided is the input bias current versus common mode voltage. In some parts, this curve is very flat while in others, the input bias current can vary considerably indicating low input resistance but such a part may still be suitable over part of its input common mode range."
},
{
"post_id": "",
"author": "stcoso",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 26, 2019, 06:38:05 pm",
"content": "Thank you all.I'm not an EE but you can surely inspire me to learn something new."
}
] |
2025-10-17T18:13:56.298149
| 11
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/(very)-small-current-ammeters-usage-of/
|
(very) small current ammeters - usage of? - Page 1
|
[
{
"post_id": "",
"author": "cspxo",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "October 10, 2013, 07:37:09 pm",
"content": "I have two meters that I am curious about. The first is a meter with a small (approx 3cm dia. bezel) round face, the needle at rest points vertically with a red sector to the left and a green sector to the right. It has the word NULL printed on it and +/- 500uA. I believe it may have come from a military field radio. The second is an old (1950s?) meter reading to 10 mA made by E.M.I. Service Ltd. of Hayes, Middlesex.My question is what are such meters used for? Apart from the obvious answer, measuring current! Can anyone give me specific information or examples please? I have googled but the interwebs greatest failing obstructs my quest for knowledge in this instance, all I get back are Chinese vendors of modern equivalents with specs but no useful information.I am self-taught/learning about electronics from books which is great for theory but apart from very simple example circuits I am finding real-world applications e.g. descriptions of actual products working circuits very hard to find.Thanks for reading.--Stephen"
},
{
"post_id": "",
"author": "niflheimer",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "October 10, 2013, 07:41:42 pm",
"content": "The first one is a null-current indicator used in things like resistance bridges and so on . It was a cheaper solution compared with the optical null detector ( which was flimsy as hell too ) . They both show when the current on one branch of the circuit is equal with that on the other branch.I dont know what it was used for in that application though - maybe some of the older guys around here can tell us."
},
{
"post_id": "",
"author": "Stonent",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 10, 2013, 07:52:31 pm",
"content": "I know 50uA ammeters are used as the displays for Geiger counters. The scale is changed to counts per minute but still current driven."
},
{
"post_id": "",
"author": "AG6QR",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "October 10, 2013, 08:15:17 pm",
"content": "Before the days of digital displays and ADCs, most meters were, at their heart, small-current DC ammeters. You can google \"D'Arsonval\", or \"D'Arsonval/Weston\" for details and an explanation of the theory of operation. They're still used for most moving-needle analog meters, but those are getting harder to find these days.Additional circuitry would be used to adapt these to measure voltage, resistance, different ranges of current, etc. In a radio, they might be used to measure signal strength, or maybe as an antenna tuning aid or SWR indicator (just a wild guess). Different scales would be added to the dials for various purposes."
},
{
"post_id": "",
"author": "cspxo",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "October 11, 2013, 11:16:16 am",
"content": "Thank you for your responses.AG6QR: I have previously come across information about D'Arsonval/Weston. When I look at 'vintage' or salvage parts, I suppose what really interests me is the history and detail of the kinds of machinery or equipment that preceding generations might have worked with.Stonent: That is an interesting example.niflheimer: I wonder if a null detector is the same thing as a 'magic eye' I have seen referred to in descriptions of old domestic radios?I am very interested in the 'history of electronics' as the appliances and devices we are all so familiar with form a sort of backdrop for the social history of the last century. Today's teenagers may not know what cassette tapes are, but my Grandfather was a boy in a world that didn't have broadcast radio for example."
},
{
"post_id": "",
"author": "dfmischler",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "October 11, 2013, 12:34:18 pm",
"content": "Quote from: cspxo on October 11, 2013, 11:16:16 amThis is what I know of as amagic eye tube. When I was a kid my Dad had a Stromberg Carlson radio that had a magic eye for accurate tuning."
},
{
"post_id": "",
"author": "vk6zgo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 11, 2013, 02:03:30 pm",
"content": "Quote from: cspxo on October 10, 2013, 07:37:09 pmThe number of devices which may have used a centre zero meter is almost countless.In this case,it may be an \"idiot meter\" to allow non-technical staff to tune a transmitter.It would have additional circuitry associated with it,so that it could indicate which direction you were off tune.The second meter was a pretty much \"run of the mill\"meter,probably used with a shunt to allow it to read higher currents.It is unlikely to have been part of a multimeter,as they used considerably more sensitive movements.Similar analog meters are still widely available."
},
{
"post_id": "",
"author": "rsjsouza",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 11, 2013, 02:59:20 pm",
"content": "Quote from: Stonent on October 10, 2013, 07:52:31 pm50uA was also widely used in several good quality analog meters.Professional wheatstone bridges used middle center galvanometers (that is how I called them) - one example ishere."
},
{
"post_id": "",
"author": "G7PSK",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 11, 2013, 03:20:42 pm",
"content": "Martin Lorton recently did a Video on a Heath voltage reference where he describes how a null meter might be used to find the voltage of a source using the reference."
}
] |
2025-10-17T20:15:32.621997
| 9
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/(vivado)-prevent-compiler-from-optimizing-logic-away/
|
[Vivado] Prevent compiler from optimizing logic away - Page 1
|
[
{
"post_id": "",
"author": "Digitalio",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "September 29, 2020, 08:59:04 pm",
"content": "I'm writing a test bench that generates the data for the code being tested (this part was easy), and I also need to write a module that takes the output from the code being tested and doesn't let the compiler to optimize it away. Any ideas how to do that?"
},
{
"post_id": "",
"author": "ledtester",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 29, 2020, 09:17:09 pm",
"content": "What compiler are you using?If it's a C compiler, how about compiling each module separately and then linking them?E.g.:Code:$ cc -c file1.c$ cc -c file2.c$ cc -o output file1.o file2.o"
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 29, 2020, 09:19:43 pm",
"content": "Generally, logic that doesn't ultimately lead to a pin (something in the port list of the top entity) will be optimized away. To look deep in the hierarchy with a logic analyzer, I have had to bring signals up through the various port lists. From the synthesizer's point of view. what good is logic that doesn't go anywhere?I don't do a lot of simulation but I think the issues are the same."
},
{
"post_id": "",
"author": "Digitalio",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "September 29, 2020, 09:30:28 pm",
"content": "Quote from: rstofer on September 29, 2020, 09:19:43 pmWell, it's only for simulation."
},
{
"post_id": "",
"author": "Digitalio",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "September 29, 2020, 09:31:25 pm",
"content": "Quote from: ledtester on September 29, 2020, 09:17:09 pmGiven that I mentioned Vivado, it's actually Verilog."
},
{
"post_id": "",
"author": "filssavi",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 29, 2020, 09:48:32 pm",
"content": "Unfortunately finding the root cause of why the logic has been optimised away in HDL can be extremely frustrating...There are few common problems that lead to it1) the logic does not exit the FPGA.The result of a chain of logic circuits/operations must always lead outside the chip itself, either through a Pin, or through the internal Busses on a SoC like the zynq, if everything stays inside the FPGA it will get optimised away2）the top outputs must not have a predefined value (otherwise the tool will just connect the pin directly to GND/VCC3) if you use AXI stream (or equivalent) channels make sure that the ready signals does go to 1 otherwise anything else is ignored3) if you have bus controlled peripherals (AXI, AXI lite, Avalon or whisk one) make extra sure that the bus interface part is connected and working correctly otherwise everything else gets thrown outThe tools output are unfortunately are quite bad, as they will not tell you clearly where is the root problem that caused the whole logic to be thrown out. However they usually tell you when something is removed so try looking for that in the synthesiser logAt the beginning my advice is also to Turn off the hierarchy flattening, as otherwise the synthesis result is quite far from your code, in terms of structure, even if it is functionally equivalent/better (don’t forget to turn it back on once done debugging though, as you are otherwise making timing closure much more difficult)Last but not least make shure that the testvench for simulation does test the top level module even if it is painful ( with SoCs for example it usually involves complex AXI bus functional models)All in all my general advice is to hang in there and not give up on FPGAs, past the initial learning curve you will start to get the hang of it and the disappearing logic will be mostly a problem of the past"
},
{
"post_id": "",
"author": "filssavi",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 29, 2020, 09:52:30 pm",
"content": "Quote from: Digitalio on September 29, 2020, 09:30:28 pmThan you should not be running synthesis (AKA compile) but only the behavioural simulation.Synthesis is only useful if you want to (sooner rather than later) actually run the code in hardware"
},
{
"post_id": "",
"author": "Cerebus",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 30, 2020, 02:32:17 am",
"content": "I've not used Vivado, but in all the other synthesis tools I've used a \"syn_keep\" directive ensures that something doesn't get optimised away. e.g.Code:wire iWantToSeeThis /* synthesis syn_keep */;If it's not exactly that in Vivado, I'm sure there's a functional equivalent under another name.A quick search seems to suggest (here) that in Vivado it's:Code:(* dont_touch = \"true\" *) <signal_name>;"
},
{
"post_id": "",
"author": "ejeffrey",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 30, 2020, 05:53:53 am",
"content": "Quote from: Digitalio on September 29, 2020, 08:59:04 pmBehavioral simulation should simulate all named internal signals. post-synthesis simulation won't but are you sure that is what you need?I'm not sure how to do do this in Vivado, but in Quartus you can assign something to be a \"virtual pin.\" This is treated like an external signal and will prevent logic from being optimized away but doesn't need to be assigned to a physical pin. The main purpose of this (at least for me) is to be able to synthesize and check timing on a module that can't be a top level module, particularly if it has more IO signals than the target FPGA has pins. That should do what you are looking for if you really need post synthesis simulation to work like this."
},
{
"post_id": "",
"author": "emece67",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 30, 2020, 07:39:27 am",
"content": "."
},
{
"post_id": "",
"author": "filssavi",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 30, 2020, 10:44:17 am",
"content": "In vivado you can use the (* keep=\"true\" *) directive on a signal (wire, reg, logic) etc to force vivado to keep the signal around even if it is useless.That said I would strongly suggest against using it unless it is really necessary, as that is only a band-aidas for simulating stuff with more IO than the whole fpga post synthesis it is really an exercise in futility, as the timing results you get form such a simulation are largely irrelevant once the module is instantiated inside a real design, since as opposed to software compilers, fpga toolchains do global optimization ( full program LTO in software term) by default, thus the results depend on the whole system not just the compilation unit."
}
] |
2025-10-17T17:41:35.335235
| 11
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/(wanted)-function-generator-and-laboratory-power-supply/
|
[Wanted] function generator and laboratory power supply - Page 1
|
[
{
"post_id": "",
"author": "fxr",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "December 10, 2019, 10:14:14 pm",
"content": "Hello everyone!I want to ask experienced people for advice about equipping for home lab.The main specialization of my projects is hardware design of digital audio devices.I need advice for acquiring a function generator and laboratory power supply.For this money I can buy Rigol DG4102 and Rigol DP832.For my opinion, this best price-quality ratio.How you thinks about my choice?Any advice and opinions..."
},
{
"post_id": "",
"author": "rapsforlife",
"author_rank": "Newbie",
"is_op": false,
"timestamp": "December 10, 2019, 11:08:33 pm",
"content": "Try posting in the Test Equipment subforum"
}
] |
2025-10-17T17:59:24.656718
| 2
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/(what-could-possibly-go-wrong)-transplanting-a-lithium-cell-protection-cirquit/
|
[What could possibly go wrong?] Transplanting a Lithium cell protection cirquit - Page 1
|
[
{
"post_id": "",
"author": "faekjarz",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "October 02, 2017, 07:04:55 pm",
"content": "Hey there, Enginerds!What could possibly go wrong?...when i transplant a (this) Lithum cell protection board onto a new, not bloated, cell?I'm asking for my alter ego, who bought a fairly grunty octa-core chinaphone, without double-checking availability of replacement batteries. My alter ego really wants to make that turd great again.Please throw your wisdom, explanations and sources at these questions:Of course, i'd choose a new donor cell with the same specs as the original; Good enough?What spec deviations could be considered, \"sufficiently same\" (as in safe)?What could possibly go wrong? (Do you have experiences, success or fail stories to share?)What does \"Execution Standard\" mean / what is being standardised?Are execution standards documented somewhere? (Where? Links?)"
},
{
"post_id": "",
"author": "Bicurico",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 02, 2017, 08:24:44 pm",
"content": "By no means am I an expert, but to the question \"what could go wrong\" I do have an answer:In worst case, the new cells will catch fire and/or explode. The fire will quickly reach such high temperatures, that you won't be able to extinguish the fire using normal processes like water.I am not sure how likely this is going to happen, but since the damage can be huge, even a small risk may void what you are planing to do.Regards,Vitor"
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 02, 2017, 10:04:49 pm",
"content": "The max charge/discharge rate (if it's even approached by the charging circuitry) should be fairly similar. This has fairly strong correlation to mAh capacity in practice (but in theory, not really. There's are high charge/discharge variations made for RC helicopters and whatnot).So in theory it might be possible you cause battery to pop. But IMO, the two things I'd worry most about are1. There a stupid chip on the circuit for protection to prevent you from reusing it. Once power is disconnected, it is dead, barring access to some factory reset protocol.2. You have zapped one of the FETS with ESD while transferring it due to careless handling.I wouldn't worry about it at all; I just wouldn't leave the phone charging unattended for the first score of cycles and observe that the battery is not overheating/bulging. Also, make sure you do your initial test runs with a HI output charger, with full 2+A output, to cover all your bases."
}
] |
2025-10-17T18:47:38.393805
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/(y-1)-dx-x(x1)-dy-0-stuck/
|
(y-1) dx + x(x+1) dy = 0 stuck - Page 1
|
[
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 08, 2015, 09:36:42 pm",
"content": "Hi,Is there someone to solve this?answer : xy+1 = C (x+1)my answer C(x+1) = x(y+1)(y-1) dx + x(x+1) dy = 0x(x+1) dy = - (y-1) dx = (1-y) dxExact? no pcq partial (y-1) dx/partial dy = 01/x(x+1) dx + 1/(y-1) dy = 01/x * 1/(x+1) dx + 1/(y-1) dy = 0Separable?1/x * 1/(x+1) dx = - 1/(y-1) dy1/(x+1) dx = - x * dy/(y-1)1/(x+1) dx = x * dy/(y+1)u1 = x+1du1 = 1 dxu2 = y+1du2 = 1 dydu1/u1 = x* du2/u2ln|u1| + ln|c| = x * ln|u2| + ln|c|ln|u1| + ln|c| = x * ln|u2|C(x+1) = x(y+1)Non separable?Thanks,JP"
},
{
"post_id": "",
"author": "SL4P",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 08, 2015, 09:54:35 pm",
"content": "Aren't you supposedto observe the (precedence) !?"
},
{
"post_id": "",
"author": "onlooker",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 08, 2015, 11:40:14 pm",
"content": "Your C(x+1) = x(y+1) should really be C(x+1) = x(y-1). Then, it is the same as xy+1 = C (x+1), except your C is not their C (differ by 1)."
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 09, 2015, 01:04:16 am",
"content": "answer : xy+1 = C (x+1)C(x+1) = x(y-1)C(x+1) = xy-yFor the minus signI thought- 1/(y-1) dy1/(y+1) dy"
},
{
"post_id": "",
"author": "JacquesBBB",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 09, 2015, 08:25:23 am",
"content": "Just separate the variablesdx/(x(x+1)) + dy/(y-1 ) = 0then 1/(x(x+1)) = 1/x-1/(x+1)thus by integratingLog(y-1) = C+Log(x+1) - Log(x)andy = C(1+1/x) +1"
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 09, 2015, 12:02:17 pm",
"content": "Quote from: JacquesBBB on July 09, 2015, 08:25:23 amI don't get that x-1Quote"
},
{
"post_id": "",
"author": "JacquesBBB",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 09, 2015, 12:32:32 pm",
"content": "Quote from: J4e8a16n on July 09, 2015, 12:02:17 pmI don't get that x-1QuoteYou have to integrate dx/(x(x+1))for this the classical way is to decompose in simple elements. Here it is easy as we have only simple poles.and1/(x*(x+1)) = 1/x - 1/(x+1)to verify it, just compute by reduction to the same denominator1/x - 1/(x+1) = (x+1 -x)/(x*(x+1))Is it more clear ?"
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 09, 2015, 12:58:48 pm",
"content": "1/(x*(x+1)) = 1/x - 1/(x+1)why is there a negative sign?1/x * 1 / x+1do you meanln|x| + ln|x+1| +Cln|x| = - ln|x+1| +C?"
},
{
"post_id": "",
"author": "Andy Watson",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 09, 2015, 01:27:13 pm",
"content": "Quote from: J4e8a16n on July 09, 2015, 12:58:48 pmIt's also know as partial fractions. Put 1/x and -1/(x+1) over a common denominator and add them together - you should arrive at the original equation 1/(x(x+1))."
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 09, 2015, 02:50:11 pm",
"content": "Quote from: J4e8a16n on July 09, 2015, 01:04:16 amYou really need to pay attention to details.x(y-1) = xy -xQuoteWhy would you think that?- (y-1) = -y - (-1) = -y + 1 = (1-y)Therefore:- 1/(y-1) = 1/(1-y)"
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 09, 2015, 07:25:03 pm",
"content": "Thanks. So we are there..answer : xy+1 = C (x+1)my answer:x(1-y) = C(x+1)The idea is to find wich one of the methods solves the equation:Linear, Exact, Separable, Integrating factor, Continuous, BernouilliI think we have taken of Exact and separable."
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 09, 2015, 07:56:45 pm",
"content": "Quote from: J4e8a16n on July 09, 2015, 07:25:03 pmYou need to show that \"xy + 1 = C(x+1)\" is the same as \"x(1-y) = C(x+1)\". Can you do that?"
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 09, 2015, 09:52:43 pm",
"content": "Well, both are equal to C(x+1), but I am not supposed to know the answer. ;o)Jean"
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 09, 2015, 09:59:58 pm",
"content": "If your answer is different from the correct answer, then your answer is not correct.If your answer is not correct then you have not solved the problem."
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 10, 2015, 12:42:59 am",
"content": "Right"
},
{
"post_id": "",
"author": "JacquesBBB",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 10, 2015, 08:44:19 am",
"content": "Quote from: J4e8a16n on July 09, 2015, 07:25:03 pmI gave you the proper answer above (y = C(1+1/x) +1) and the way to compute it.this is equivalent (for x non zero ) to(y-1)x = C(1+x)Now you can take any value of the constant C. If we use C=-C',we obtain(1-y)x = C'(1+x)which is one of the solution you find.If you take C=C''-1You obtainxy+1 = C''(x+1)which is the other solution you mention. They are all solutions, and just correspond to different values of the constant."
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 10, 2015, 01:10:40 pm",
"content": "thank you so much for your patience.I get it.partial fraction"
}
] |
2025-10-17T19:37:30.303836
| 17
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/(yet-another)-im-new-to-electronics-where-do-i-start/
|
(Yet another) I’m new to electronics, where do I start? - Page 1
|
[
{
"post_id": "",
"author": "rawrs",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "July 22, 2017, 04:18:59 pm",
"content": "Hey guys. I’ve thought about joining this forum for a very long time. I have always had an interest in electronics, but have never known where to start. Due to back damage forcing me back into the IT market at least, I’m looking to get into electronics, at last.But... where do I begin? I’ve done basic things like recap motherboards, but I don’t actually know anything. I don’t even know why a resistor is a thing, I just know that they are. That sort of thing.I’ve seen all the oscilloscope videos, and I’m very jealous. However my current situation might limit me to some less jealousy-inducing devices (like a DSO nano) or something). But I digress.My question is simple. I want to learn, but I don’t know where to start. I want to finally indulge in my hobby, learn with you guys and maybe even contribute when I reach a point where I might think I know what I’m talking about.I really look forward to contributing to this forum, though. I’ve been watching Dave for years and years, and I’ve been jealous of his gear all along. Someday I’ll own a scope... right now it’s a dream...Cheers guys!RorySent from my iPhone using Tapatalk Pro"
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 22, 2017, 04:32:17 pm",
"content": "Electronics is a VAST sandbox and few play in every corner. So, what do you want to do?Are you just interested in electronics as a study program? There are online programs including one from MIT. I think its nice to know about the physics behind electronics but it certainly isn't necessary.Circuit design? Well, again, everything is out there on the web. There is a really good Electronics 101 video series at Digilenthttps://learn.digilentinc.com/classroom/Microcontrollers? Everything that can be done with an Arduino has been done. There are literally thousands of projects out on the web. This might be a good place to start because it combines programming and interface electronics. Find something you want to build and get started. When you get stuck, ask!Art of Electronics and Learning The Art Of Electronics (lab manual) are a recommended place to start for both theory and practice. You will need a scope early on. It's too early to discuss all the reasons why but, were I just starting out, I would be all over the Digilent Analog Discovery 2 because it is a complete electronics lab in a little box.http://store.digilentinc.com/analog-discovery-2-pro-bundle/Yup, it's pricey! Not quite as much as a standalone scope but spendy nevertheless. OTOH, it has a dual channel scope, a dual channel arbitrary waveform generator (just call it a signal generator for now), plenty of digital IO that can also be used as a logic analyzer and a pair of adjustable power supplies (very current limited). You can go a very long way in electronics with this tool.Shorter answer: Figure out what you want to do and ask for specific suggestions. Electronics is too vast to describe in a forum post."
},
{
"post_id": "",
"author": "Teledog",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "July 23, 2017, 04:15:33 pm",
"content": "If you don't know anything, I might suggest taking a basic electronics course, part time - either through your local schools, online, self-study, etc.I built a Heathkit multi-meter -back in it's time - but didn't know my *ss from a hole in the ground then.Then decided to take a self-study Heathkit DC electronics course, via to local college back in the 80's..liked it so much I went to college full time (twice).Have fun!!! :-)"
},
{
"post_id": "",
"author": "boffin",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "July 23, 2017, 04:31:35 pm",
"content": "Quote from: rawrs on July 22, 2017, 04:18:59 pmI wouldn't get too excited about getting a scope until you really understand why you need one (which applies to all test equipment). My 1st recommendation is get two multimeters (mostly because very quickly you'll find you'll want to measure two things at once), along with a decentish bench power supply.Then, decide you want to build something small, and work your way through \"how does this work\". (and I mean start really simple, like blinking LEDs, or a simple switch for something)"
},
{
"post_id": "",
"author": "Vtile",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 23, 2017, 07:46:23 pm",
"content": "First thing you need to learn is so called ohms law voltage=current * resistance and how to solve each if you know two. This classic only applies in DC and need some more knowledge when AC is analysed.2nd thing you need to know is power and energy... Dave just put a short clip out. After watching that you need to get familiar with P=U*I (and the other forms ie. P=R*I^2, IIRC this is Joules law I could be wrong in this name though)3TH You need to get idea voltage and current dividers (fancy name is Kirchof voltage and current law)4th you need to get familiar how the coil and capacitors react with frequency (cap allows more current through when frequency go up. Coil acts another way around it allow less and less current)Build a really simple LM317 based power supply unit. For getting you started, you can use ie. batteries etc. to power it. If the smoke escapes from it you can always build a new.Get old analog or combiscope for starters (transistor not a tube amplified) with CRT (needs to be cheap to be justified). If you are only for digital stuff the 2nd hand DSO is far better option. I suggested analog since you don't have good understanding for basics and this would allow you to see what is happening.You can use 555-timer at the beginning as function gen. There is a million scematics around."
}
] |
2025-10-17T18:52:02.634905
| 5
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/(yet-another)-my-first-power-supply-question/
|
(Yet another) My First Power Supply Question - Page 1
|
[
{
"post_id": "",
"author": "paulca",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "November 02, 2017, 10:45:35 am",
"content": "I watched Dave's review of the cheap, cheerful DPS3003 style buck power supplies. He sold me on them, until I actually speced one out to buy.My use cases are basic electronics beginners stuff and Raspberry PI stuff were USB 3.3V/5V would be fine, but I also have ambitions for battery charger style circuits that would require 15V and the ability to test a 3A or 4A constant/limited current regulation circuit. So a 30V, 5A PSU sounded ideal.Buying for a UK seller the DP3003 30V 5A version are about £30. Great. However, the still require a DC power source. That's where it all falls apart. I simply cannot find a domestic wall-wart that will produce 30V and 5A. The best I can find is a laptop PSU that delivers 24V and 4A and it costs £35.Now on Farnell I can buy a professional single channel 30V 5A bench supply from Tenma for about £70. I can get a two channel PSU for £110.The only use case I can see for this cheap buck converter PSU is to run one or more of them in parallel off the bench supply. So I could power two or more of the cheap PSUs from the expensive one, rather than buying the more expensive 2 or 3 channel bench supply. Does that even work, considering impedance and what not?Thanks,Paul"
},
{
"post_id": "",
"author": "danadak",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 02, 2017, 10:57:02 am",
"content": "You can only parallel supplies if they have current sharing circuitsbuilt into their architecture. That architecture usually has anotherpin shared between them to effect the sharing control so that onesupply is not overloaded.Regards, Dana."
},
{
"post_id": "",
"author": "glarsson",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 02, 2017, 11:12:44 am",
"content": "You can't power two or more if these stupid modules from the same power supply. The reason us that they have their current sense on the low side and if you connect the low sides together (as we do when we for example need +5 and +12 for the same circuit) then the power senses will be shorted. You will still get your voltages but the current limiting will be disabled. Only use one power supply (isolated) for each module.Also, verify that the high ripple/noise of the modules are acceptable to you."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 02, 2017, 11:16:37 am",
"content": "http://www.google.co.uk/search?q=220V+36V+5A+PSU&tbm=shopThere's quite a few cheap options to power them, just not in a wallwart form factor."
},
{
"post_id": "",
"author": "StillTrying",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 02, 2017, 11:21:11 am",
"content": "\"Buying for a UK seller the DP3003 30V 5A version are about £30.\"You can get the DPS5005 50V 5A version for less than £30 from the UK.\"require 15V and the ability to test a 3A or 4A constant/limited current regulation circuit. So a 30V, 5A PSU sounded ideal.\"....\"24V and 4A\"24V @ 4A should easily give you 15V @ 5A, but as glarsson has just said, both sides +/- of the input supply has to be floating compared toeverythingelse."
},
{
"post_id": "",
"author": "paulca",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "November 02, 2017, 11:31:53 am",
"content": "I'm a little indecisive now. I can go for:Cheap Chinese DC/DC module + cheap chinese AC/DC PSU and hope it works, costing about £40-50.Or I can go for a proper supply like this:http://uk.farnell.com/tenma/72-10495/power-supply-2ch-30v-5a-adjustable/dp/2251947The indecision is that if I play about with things for a few weeks and then it all ends up on the shelf unused the £120 would be a waste. However the PSU would be a good investment if I carry on through the years with electronics.I did the same with the DMM I bought. Hmmm'd and Haa'd and watched reviews and show downs and tried to decide on a £120 Fluke or a cheapo (in the end I aimed in the middle with an Extech).Decisions decisions."
},
{
"post_id": "",
"author": "StillTrying",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 02, 2017, 12:18:53 pm",
"content": "If you need 2 voltages and it's always going to be mains powered anyway, I don't think the DPSs are going to be much use to you.I think that 2 channel tenma is going to be hard to beat.You could probably get a 30V 5A,anda 18V 2A for around £95 total.http://www.circuitspecialists.eu/power-supplies/bench-power-supplies/"
},
{
"post_id": "",
"author": "Terry01",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 02, 2017, 01:24:09 pm",
"content": "Get the Tenma from Farnells buddy. I got the 30v 5A one your thinking about. It's a great supply for hobby stuff. I also really like the UI too,easy to use and has all the safety stuff you could want.I have a boost/buck 35v 6A that I was sent as a mistake when I ordered a capacitor pack. It's I my desk drawer and I use it very occasionally,I use the Tenma nearly every day. Don't forget to order leads to connect to the supply.Hope you get what your after."
},
{
"post_id": "",
"author": "ManuelMcLure",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "November 02, 2017, 08:45:20 pm",
"content": "Another option is to get the boost/buck module (DPH3205) and use a 12V 15+A power supply for the input. I like old server power supplies - for example the HP DPS-600PB (12V 47A) are available for $20 shipped and can easily have their outputs floated if needed - RC enthusiasts commonly put a couple of these in series (after floating the second one) to get a 24V supply to power LiPo chargers."
},
{
"post_id": "",
"author": "paulca",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "November 02, 2017, 10:35:58 pm",
"content": "Quote from: ManuelMcLure on November 02, 2017, 08:45:20 pmI have a boost/buck (if that's the right term) LiPo (and most other battery types) charger for RC that I run off a single cheap chinese 12V 5A supply. It's amazing. It will happily charge a 15V lead acid to 15V CCCV at 4A. I did manage to charge two 3s LiPo in series requiring 25.2V using a balance splitter cable (monitors and balances the 6 individual cells), but it worked out due to not being about to charge them at 5A and only getting about ~1.8A that it was faster to charge them one at a time. It was $70 and the PSU about $10. An Accucell 60W. They do a bigger one, think it's 120W 10A, but I couldn't find a PSU for it. RC folks were (as you suggest) using old PC PSUs with the main 12V rails joined and stuff. Kinda scared me so stuck with my 60W.I'll mull over it a bit and decide on the chinese AC-DC power module + the cheap DC-DC one... or go for the Tenma.Thanks for all the replies."
}
] |
2025-10-17T18:45:49.068124
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/(your)-feedback-needed-on-mosfet-switch-design/
|
[Your] Feedback needed on mosfet switch design - Page 1
|
[
{
"post_id": "",
"author": "bryce1",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "May 05, 2015, 08:36:30 am",
"content": "Hi guys,I want to design an opto-isolated \"generic\" low side switch that can PWM (400-900Hz frequency) everything 12V from solenoids to motors with about 3A max current.TLP152 mosfet driver:http://toshiba.semicon-storage.com/info/lookup.jsp?pid=TLP152&lang=enCan you give me your two cents on the circuit?I'd be especially thankful for some hints on the voltage ratings of the diodes and caps.Thx!"
},
{
"post_id": "",
"author": "mzzj",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 05, 2015, 09:18:23 am",
"content": "Quote from: bryce1 on May 05, 2015, 08:36:30 amD6 most probably not needed.I would beef up the C20 from 100uF to 1000uF or morer10 10ohms sounds really low for 900Hz pwm frequency. Consider something like 20-1000ohms to reduce switching noise.C3 probably there for nothing.As for voltage ratings 16 volt electrolytic caps should be fine. Diodes 20 to 60 volt schotky diodes or just something general between 20 and 1000 volts."
},
{
"post_id": "",
"author": "PSR B1257",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 05, 2015, 03:19:17 pm",
"content": "QuoteThis is only usefull, if you know where to place it properly. Better is separate decoupling of the driver and the load terminal together with proper wiring.The best case scenario would look like this:"
},
{
"post_id": "",
"author": "free_electron",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 05, 2015, 04:01:14 pm",
"content": "why do you put feed-thru capacitors on the gate ? with 100uf ( i doubt you can even find em that high , a few hundred pf , yes. even 100nf i doubt .. ) . there is not going to be much pwm on the gate anymore ..."
},
{
"post_id": "",
"author": "tautech",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 05, 2015, 04:13:19 pm",
"content": "Quote from: free_electron on May 05, 2015, 04:01:14 pmI'd doubt they are feed through's, it was just a convenient place to put the wire."
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 05, 2015, 08:21:19 pm",
"content": "R16 might be a lot of sink current, check against the output rating of the opto. It might also not be needed (does the opto have a default-low state when, e.g., supply voltage is low?).Limited turn on/off speed, overheating and fault currents are other prime topics; if you are okay with having something that'll explode if misused, then it's fine as shown. If you'd like a more general purpose switch, you might look at some of those \"protected FET\" parts out there that provide current, temperature and voltage protection, or design your own.Tim"
},
{
"post_id": "",
"author": "bryce1",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "May 06, 2015, 05:40:52 am",
"content": "Quote from: mzzj on May 05, 2015, 09:18:23 amwhy?"
},
{
"post_id": "",
"author": "tautech",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 06, 2015, 06:04:29 am",
"content": "Quote from: bryce1 on May 06, 2015, 05:40:52 amWhen using a mosfet as a switch, you are always best to \"hammer\" the gate with plenty of current, increased bulk capacitance will allow that."
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 06, 2015, 06:47:40 am",
"content": "Quote from: tautech on May 06, 2015, 06:04:29 amNot as a general statement.When you can handle the large peak currents and high frequency content (with a suitably designed switching loop), and you have the EMI of that switching edge under control, then it's quite good -- less switching loss.For slower applications where low switching loss is not important, going slower helps. If you go slow enough, you don't even need the clamp diode! Of course, that's load dependent, so you're still better with it. You certainly don't want to go so slow that the transistor halfway burns out each time (>>100us??), but between \"as fast as possible\" (typically ~50ns for power switching grade FETs) and \"a relaxed pace\" (~1us), it's still quite fast for something that's switching only momentarily (>>10ms?).For a couple amps load, I would be more than happy with 100uF local. Don't even need that if there's another nearby in the project (say within 10cm or so?).Tim"
},
{
"post_id": "",
"author": "mzzj",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 06, 2015, 07:35:05 am",
"content": "Quote from: T3sl4co1l on May 06, 2015, 06:47:40 amYeah, it depends on wiring on the input side. OP was making something \"generic\" so I assumed that input wiring might be 10cm or 10 meters.100uF for that is a bit weeny with the typical 3ohm ESR. (supply voltage would drop to approx 7 volts at every turn-on and shoot up to 17v)Another issue would be insufficient ripple current rating."
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 06, 2015, 07:35:41 pm",
"content": "For single events, having the voltage bounded is better than unbounded; the ripple margin doesn't really matter. Ok, the opto might not be happy with a 17V excursion.Want to say I've seen much less than 3 ohms ESR for 100uF range capacitors. That's still possible under low temperatures or aged conditions (dried out cap) though. But such conditions don't really have an endpoint, so to address those failure modes, you'd have to use something other than electrolytic, entirely.Even against 10m of wire, you'll have maybe 6uH stray inductance, which will ring with 0.1uF at 200kHz (Zo = 7.7 ohm), and with 100uF at 6.5kHz (Zo = 0.25 ohm). Since ESR > 0.25 ohm, in series, the supply inrush/transient response will be well damped, so that's good. With ESR < 7.7 ohm, in parallel, inrush/transient to the small bypass cap will also be well damped. So at least there won't be ringing and squigglies due to that.Ripple current rating won't matter to non-repetitive events, of course. The supply becomes substantially resistive above 6kHz (where 10m of cable begins to act rather inductive), so any switching above 6kHz will be carried more and more by the cap, and the ripple rating will need to be observed.So, somewhere around the 1kHz-50kHz range, depending on cable length and attached capacitance, will be the crossover range where the local cap matters.Tim"
},
{
"post_id": "",
"author": "mzzj",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 07, 2015, 07:13:45 am",
"content": "Quote from: T3sl4co1l on May 06, 2015, 07:35:41 pmLooks like the \"Opto\" in this case is specified 10-30 volts so if there is a problem it would be the voltage droop.No arguing that its better have damped response, my recommendation wasn't 1000uF plastic cap there3 Ohm esr for 100uF cap seems like some brain-fart on my side, so lets just ignore that. 0,3Ohms looks more like it and should be fine."
},
{
"post_id": "",
"author": "bryce1",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 03, 2015, 09:04:00 am",
"content": "Quote from: T3sl4co1l on May 05, 2015, 08:21:19 pmAny recommendations?"
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 04, 2015, 06:27:21 pm",
"content": "Quote from: bryce1 on November 03, 2015, 09:04:00 amThis is the sort of thing,http://www.digikey.com/product-detail/en/VNS3NV04DPTR-E/497-13078-1-ND/3455768Mike (@mikeselectricstuff) might have a stronger opinion on these sorts of things, he seems to use them quite regularly (and with good reason).Tim"
}
] |
2025-10-17T19:30:55.371667
| 14
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/***-hooking-up-a-single-capacitor-so-confused-***/
|
*** Hooking up a single capacitor So COnFusEd *** - Page 1
|
[
{
"post_id": "",
"author": "jfiliaul",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "July 06, 2011, 12:40:17 am",
"content": "Ok, this maybe a very silly question but I cant find the answer. What is the difference between hooking up a capacitor inline (in series) with the positive line in a circuit and hooking it up in parallel (one side on negative line and one on positive)? It sounds like a real dumb question to me but I have seen it done both ways and Im sure there are reasons why to do it each way but can anyone help shed the light on this for me?Example: Here is an RC circuitNegative side --------------------------------\\| /| \\cap resistor| /Positive side --------------------------------\\VSNegative side --------------------------------\\/\\resistor/Positive side ----------|---cap----|---------\\THANKS FOR THE HELP !!!"
},
{
"post_id": "",
"author": "Ian",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "July 06, 2011, 01:07:42 am",
"content": "hithe first one looks correct to me. that is the way they are normally hooked up"
},
{
"post_id": "",
"author": "w2aew",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 06, 2011, 02:56:59 am",
"content": "It depends entirely on the application.The parallel combination can be considered a low-pass filter. It's a typical configuration for filtering a power supply for example. It allows DC to flow through the resistor, and shunts AC away from the resistor. The higher the frequency, the more that is shunted.The series combination can be considered a high-pass filter. It blocks DC from passing through the resistor. Thus, the impedance of the circuit is very high (infinite) at DC, and drops as the frequency increases.The answer is - both are correct. Each of these configurations are used for different purposes."
},
{
"post_id": "",
"author": "Tony R",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "July 08, 2011, 04:50:55 am",
"content": "Look at how they will act in DC conditions... if your application is DC...in parallel the cap will act as a open circuit (no current will go though it) so you basically just have a resistor.in series, the cap will still act as an open circuit, so what happens with the current?for AC condtions we can kind of think the same way, what is a DC condition, essentially a very slow AC signal (where the period extends to infinity.) so with them in parallel, the current will tend to go though the resistor, in high frequencys, they will tend to go though the cap (acting as a short)"
}
] |
2025-10-17T20:39:04.726971
| 4
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/***about-smps***/
|
***ABOUT SMPS*** - Page 1
|
[
{
"post_id": "",
"author": "MacIntoshCZ",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 27, 2024, 08:35:06 pm",
"content": "Hello,by time i will add here more questions. I dont have anyone to ask, so big thanks for reply!I dont understand how can one EA sink current at TL494. If you look in functional diagram there are diodes in the way.This is written in datasheet:https://www.ti.com/lit/ds/symlink/tl494.pdf\"Both high-gain error amplifiers receive their bias from the VI supply rail. This permits a common-mode inputvoltage range from –0.3 V to 2 V less than VI. Both amplifiers behave characteristically of a single-endedsingle-supply amplifier, in that each output is active high only. This allows each amplifier to pull up independentlyfor a decreasing output pulse-width demand.With both outputs ORed together at the inverting input node of thePWM comparator, the amplifier demanding the minimum pulse out dominates. The amplifier outputs are biasedlow by a current sink to provide maximum pulse width out when both amplifiers are biased off.\"#1 How can be \"ANALOG OR\" realized?Ive tried to measure compensator transfer function with added 47R before resistor divider and connected generator across this resistor, then take Vout as \"Vin\" and voltage at comparator input as \"Vout\". results on bode plots were unusable, to much distortion. Another problem is that EA does not have negative rail voltage so i cant measure response of EA alone with added DC offset it has no way how to bring this DC offset at negative EA input.#2 Is there way to bode plot compensator transfer function without getting SMPS turned on with load connected?#3 Is true that TL494 use OTAs instead of classic OAs?#4 Is possible to add external EA for PWM comparator within TL494? \"Analog or\" will be needed i guess =)#5 Does anyone here successfuly finish project with TL494 completely stable at DCM and CCM \"buck derivate topologies\"#6 Has anyone experience with bode plots on rigols MSO series usage on SMPS?Are results sufficient?I have problem with TL494 compensation at DCM. When i did control to output bodeplot i get about +90 degrees phase shift at low frequencies, type 3 noninverting compensator has -90 degrees at low frequencies. Well i calculated it with classic OA, if tl494 has OTA then my results are wrong becouse my aproach was to calculate voltage at nonivnerting input, then calculate current through resistor connected paralel at inverting input to ground and then multiply it with total impedance (EA output to ground). I will be thinking about forced CCM, if it does not add to much complexivity.#7 Since TL494 does not offer 180 phase shift, i though about SG3524, but i would like to has two EA to adjust voltage and current.So is possible to have external EAs at SG3524?, how can i do it?There will be something like \"inverted analog or i guess =)\".I am also thinking about average current mode control instead of voltage mode but CMC is more suscetible to noise and its not good at light loads.I am constructing high voltage, high power, high current, high everything... =D SMPS, i want voltage and current adjusting from zero to nominal value.#8 What do you think about CMC, is it preferable for regulated smps?https://www.allaboutcircuits.com/uploads/articles/Keim_10_13_Fig_3.jpgHere is schematic with average current mode control, to add current control i will need add another feedback loop for current and i need to \"OR\" output from voltage loop EA and current loop EA together at noninverting input of \"current error amplifier in the schematic\".#9 Am i right?I think its enough for now. Thaaanks"
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 27, 2024, 08:38:49 pm",
"content": "Always check the appnoteshttps://www.ti.com/lit/an/slva001e/slva001e.pdfUnusually, they actually go into near-complete detail, giving an at least representative transistor-level schematic for all blocks. A diode-OR is of course meaningless without some pull-down; the diodes are in fact emitter followers, and a 300uA sink provides pulldown (p.9, Fig. 9).Hah, typo, the inverting input shows an upside-down NPN. Clearly they meant a PNP there.Classic voltage-mode op-amp, no OTA here. Perhaps it can be abused as an OTA (e.g. compensation by R+C from COMP to GND), but this will depend on output current limits and likely give a nonlinear response (i.e. requiring low R and large C, just for, at best conditional effect, not general smooth and linear operation).The two internal op-amps are useless, one of them will be I mean, for current mode; you need them cascaded, not paralleled. Simply strap one off as disabled, and add an external op-amp. Usually this will be a TL431 ref, which is better described as an op-amp with open-collector output and conspicuous yet highly stable Vios.You might also want a more specific title for this thread...Tim"
},
{
"post_id": "",
"author": "MacIntoshCZ",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 28, 2024, 05:20:13 pm",
"content": "Quote from: T3sl4co1l on February 27, 2024, 08:38:49 pmAre you making reference to this image:https://www.allaboutcircuits.com/uploads/articles/Keim_10_13_Fig_3.jpg?There are OA cascaded. OA with inputs across rsense is just diferential one. Lower OA in the right is EA for voltage loop (lets call it EAV), then EA on the left is for current control (EAC).How this works? So EAV has its own reference on the noninverting input and want to has same amount of voltage on inverting pin, so it will adjust output voltage on noninverting pin of EAC. EAC has its inverting input connected to voltage equal rsense (probably multiply it with some factor, like 10 or so...). Every load has its own current which will flow when its connected on the output of PSU. EAV is trying to find current which will match output voltage and EAC is doing same job. EAC is trying to find voltage on its own output when both inputs match. Output voltages of EA are defined by A*(Vnon_inv-Vinverting) so it starts with max output and decreased it i guess? So it will overshoot current and then settle.But how is current adjusting added? Thanks"
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 28, 2024, 08:13:39 pm",
"content": "Yes, this diagram. Match up blocks. You already have part of the \"power stage\" in the TL494. You have the comparator and a ramp generator. You have a direct connection from a pair of op-amps to the comparator: this is your current error amp. The other one cannot be used (unless maybe as a U/OVLO, or some other process variable, temp limit, etc.) so probably just gets strapped off. Voltage error amp has to be a separate chip, and can be as simple as a BJT if you don't need much for regulation, but preferably is an op-amp proper.TL494 doesn't have a current sense amp so you need to add one externally; the diff amp in the diagram can be a current sense/shunt amplifier, Hall effect sensor, pair of current transformers in the power stage, etc.All the EAC is doing is comparing inductor current to the setpoint, and that setpoint comes from the EAV. Imagine you were controlling, by hand, a current source to regulate output voltage: you'd be adjusting this setpoint manually (pot from VREF to GND, say). But you're looking at VOUT in relation to VSET and adjusting it accordingly, which an EA can do automatically, and much faster than human reaction time.And we can limit the EAV's output range, so it only ever commands a current setting that is within nominal design range.We physically cannot overcurrent the power stagethis way, not under normal operation at least.Put another way: section off the power stage, PWM, EAC and sense amp. Wrap all of that into a block. What does it do? It takes in some power (how much, doesn't matter, other than for a buck, Vin > Vout), sends out a current, and that current is in proportional to the input voltage (current setpoint / EAV output). We have a transconductance amplifier.Which also means we can connectunlimited power stages in parallelif they are of this type: where the inductor current is controlled locally, in loop with its respective EAC. Such a circuit is highly scalable.Finally, for dynamics, notice the gm amp (the whole power stage + EAC block) has a dominant-pole response cutting at a well-defined frequency, given by inverter gain, inductance, and EA compensation. We put this inside the voltage loop, which has a dominant-pole response cutting at a somewhat lower frequency, given by gm amp response, the capacitor, and EA compensation.This pole can be higher than 1/sqrt(LC), thus we have better performance (lower output impedance, and to higher frequencies) than a voltage-mode control which has to have the compensation pole below the LC resonance.Overshoot is not at all assured: the EA can approach steady-state gradually and settle in, or too quickly and overshoot. There is no RHP zero as in a peak current mode control (although I don't actually know the details, and probably analysis is a bit worse in DCM; ACMC somewhat assumes CCM, or more to the point, is easiest to understand in CCM), so a simple 2nd or 3rd order overall response, of whatever desired prototype (i.e. Butterworth, etc.), is possible.PCMC tends to have overshoot, or a compromise in response (slower than might otherwise be expected), due to the RHP zero at Fsw/2, making it a non-minimum-phase system; the control pole is thus forced to be at least a bit lower than this (maybe Fsw/5 or something?). But this is fine, as using electrolytic capacitors for output filtering, they generally need to be more than large enough to meet this, and thus the voltage loop compensation pole is low enough to avoid the zero. A zero can also be added to the compensation (pole-zero or type 2 compensator) to win back further phase margin.Which, speaking of PCMC, almost every diagram you see of UC3842 has an R||C in the feedback network, which is... just bizarre. It's intentionally throwing away DC gain (and thus regulation and PSRR) just to make it a tiny bit easier to compensate (the limited gain at any frequency, means somewhat less chance for oscillation). Maybe not bizarre, being the best word for it, but definitely lazy. Lazy by both author and reader: another one of those oft-repeated errors that's just good enough to pass, and no one stops to question it. Well, I do, and I disagree.(The resolution is trivial: put the R+C in series instead of parallel, and adjust values until compensation is optimal.) (There is a further quirk of this, were the R||C sometimes is shown after an optoisolator, when compensation has already been realized on the secondary side around a TL431 or whatever. Which is just silly; the COMP pin can be driven by opto directly, or the error amp strapped as inverting-gain-of-1 with a pair of resistors, no compensation needed or desired. I think I've seen this a few times in TL494-related schematics too, additional compensation after the error amp proper. Go figure.)Tim"
},
{
"post_id": "",
"author": "MacIntoshCZ",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 02, 2024, 10:19:29 pm",
"content": "Thanks for detailed description!I'm a little confused about the behavior of error amplifiers.If you look at the block diagram of the TL494 (https://circuitdigest.com/sites/default/files/inlineimages/u2/TL494-Inverter-IC.png), you can see that when the OR after the PWM comparator is at HIGH logic level, output switching is disabled. If we look at the ACMC diagram againhttps://www.allaboutcircuits.com/uploads/articles/Keim_10_13_Fig_3.jpgwe see that the EAV will try to null the voltage difference at its inputs and thus increase the output voltage according to the equation gain*(NotInv-Inv). NotInv = Vref, Inv will be equal to 0V when the circuit starts. Same thing happened with the EAC. When we get to the PWM comparator, we see that its output is HIGH when the voltage at its non-inverting input is greater than the voltage at its inverting input, i.e. at the input to which the Vramp is connected. Vramp varies from 0V to 3V aprox. And at the non inverting input we have output of EAC which starts at higher voltage then peak voltage of Vramp i guess. I'm struggling a little with when the output of the operational amplifier changes the polarity of the voltage derivative, i.e. if the voltage will rise or fall. That is, when the circuit starts, the maximum voltage at the output of the error amplifiers corresponds to zero pulse width, i.e. the voltage at the output of the source cannot increase and the result of the equation Gain*(NotInv-Inv) of the operational amplifier will still be the same because the voltage at the inverting input will not change. This confuses me a bit. I though EA need some response when it sets its output high, by response i mean something that \"tells it\" that output voltage of power supply start to change, but in this circuit increasing voltage at EA output makes duty cycle actually smaller and when EA output start at its maximum voltage it cant has response then, so i am confused a bit with -> when EA decide to go down with its own voltage to trigger output response. I hope you can understand what I mean =)Thanks,"
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 03, 2024, 01:43:24 am",
"content": "Well if it's polarity you have a problem with, just swap it aroundTL494 is a bit weird in that its PWM variable (V(COMP)) is \"reversed\", but it can simply be whatever it needs to be, and you swap the op-amp inputs to close the loop with overall negative feedback.Helps to go around the loop, note each unit's sign/polarity, multiply them all together, and if after traversing the complete loop, you get negative, then it's negative feedback, and that's all you need.Tim"
},
{
"post_id": "",
"author": "MacIntoshCZ",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 03, 2024, 09:24:27 pm",
"content": "So i can disable op amps in tl494 by setting inverting input at higher voltage level than noninverting input, so letsay Inverting inputs is connected at Vref and noninverting ones are grounded, by doing so i have 5V feedback pin which is equal to 0% duty cycle. Someone mentioned through PM that i can use internal EA in inverting mode which i dont think so. I think there is way to add inverting EA by disabling internal op amps, add BJT NPN to the feedback pin and drive it with external EA configured as inverting amplifier. Am I right? Thinking about response of PSU, since BJT need small current to shut down feedback pin to ground level, so i am curious how EA will handle it =D"
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 03, 2024, 09:30:18 pm",
"content": "Just strap off one and use the other, no need to mess around with back-driving the pin."
},
{
"post_id": "",
"author": "MacIntoshCZ",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 03, 2024, 09:40:44 pm",
"content": "Using one internal op amp, and disabling second one for ACMC will be better aproach. I am just trying to understand how it will behave with BJT controling feedback pin =).(trying to convert tl494 for usage with external EAs connected in inverting mode)Edit:During night i have realized that its impossible to introduce negative feedback when ramop voltage is connected to inverting pin. BJT + inverting EA give positive feedback, and with negative, it will not work anymore."
}
] |
2025-10-17T16:39:34.246970
| 9
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-01uf-50v-zf-what-does-zf-mean/
|
0.01UF 50V ZF - What does ZF mean? - Page 1
|
[
{
"post_id": "",
"author": "requim",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 02, 2011, 05:18:51 am",
"content": "I need to replace a few caps on a receiver and the service manual species the following:0.01UF 50V ZF0.1UF 50V ZFWhat does the ZF stand for?"
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 02, 2011, 06:27:44 am",
"content": "I think it maybe another way of saying the temperature coefficient of Z5VThere are some graphs here which have Z5V(ZF) Y5E(YA) Y5P(YB) Z5U(ZE)http://www.docstoc.com/docs/68640250/ARITEC-Ceramic-Capacitor-TABLE-OF-CONTENTSAlso this table seems to back that up. It looks like there are three naming schemes EIA / JIS / GBIt does seem odd though because Z5V isn't a high spec cap, far from it. It's pretty bad in fact.So why anyone would label something as needing to be that type of cap is a bit weird.I'm sure someone will know for sure what it means"
},
{
"post_id": "",
"author": "hacklordsniper",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 02, 2011, 06:30:09 am",
"content": "It means it should be a 105 oC rated capacitor."
},
{
"post_id": "",
"author": "requim",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 02, 2011, 07:26:02 am",
"content": "So if I order a 5% part @ 125C then I should be fine, right?"
},
{
"post_id": "",
"author": "hacklordsniper",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 02, 2011, 08:01:05 am",
"content": "Quote from: requim on November 02, 2011, 07:26:02 amYes, even better than manufacturer reccomended specs"
},
{
"post_id": "",
"author": "Unknown",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "November 02, 2011, 01:34:12 pm",
"content": "Quote from: hacklordsniper on November 02, 2011, 06:30:09 amDo you have a source? The PDF version of the document Psi linked to claims 10 to 85°C. Choosing an NP0 cap should work fine, but is probably much larger and more expensive than required for this application if Z5V is called for."
},
{
"post_id": "",
"author": "requim",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 02, 2011, 01:52:18 pm",
"content": "I was just planning on buying the 3 caps and 2 fusible resistors through digikey. Total cost is < $5.00. Not a big deal."
},
{
"post_id": "",
"author": "hacklordsniper",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 02, 2011, 02:00:41 pm",
"content": "Quote from: alm on November 02, 2011, 01:34:12 pmYOu can find this data on Nichicon site"
},
{
"post_id": "",
"author": "Unknown",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "November 02, 2011, 02:12:27 pm",
"content": "Does Nichicon even make ceramic caps? How about a link?"
},
{
"post_id": "",
"author": "hacklordsniper",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 02, 2011, 03:13:31 pm",
"content": "Quote from: alm on November 02, 2011, 02:12:27 pmIm not sure how you know does authur means exactly ceramic capacitor, but if you checked their website you could see they dont make only electrolytic capacitors.Fell free to lookhttp://www.nichicon.co.jp/english/index.html"
},
{
"post_id": "",
"author": "Unknown",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "November 02, 2011, 05:44:32 pm",
"content": "Have you seen any 10nF/50V electrolytics (aluminum, tantalum or conductive polymer) lately? It could be film, but this would be indicated as such, and Nichicon doesn't make any film caps with ZF in the name. Part number search for ZF yields no results. Psi's answer looks plausible to me without any proof to the contrary."
},
{
"post_id": "",
"author": "hacklordsniper",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 03, 2011, 05:28:50 am",
"content": "Im not going to bother to prove anything to you"
}
] |
2025-10-17T20:37:57.037176
| 12
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-100v-variable-dc-power-supply/
|
0-100V variable DC power supply - Page 1
|
[
{
"post_id": "",
"author": "belzrebuth",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "June 13, 2020, 09:13:31 pm",
"content": "I've been messing quite a bit with transformers lately and now I've got a few laying around including a 2x48v 100VA toroidal.I also have a ton of heatsinks and spare cases etc..And I may have some analog voltmeters around.Okay you've guessed it..!I thought I could make a nice adjustable 0-100V power supply since my Rigol DP832 can only reach 60V with its main channels in series.There are times I've needed more than that so I thought why not roll my own since I've got most of the expensive parts at hand anyways.So..Is anybody aware of a solid design?Preferably regulated.I've came across a few dodgy ones on the net but I don't think I've seen anything regulated.Ideally I'd like to have half an amp or so of avalaible current.Maybe an amp tops, just what this 100VA transformer can output more or less.Current limit is not that important but welcome of course.Higher voltage is also fine with me.I mean I can adapt it for less I guess and my transformer is good for around 120V anyways."
},
{
"post_id": "",
"author": "Wolfgang",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 13, 2020, 10:48:41 pm",
"content": "maybe some of this:https://electronicprojectsforfun.wordpress.com/power-supplies/high-voltage-lab-power-supplies/"
},
{
"post_id": "",
"author": "belzrebuth",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "June 14, 2020, 10:04:33 am",
"content": "Plenty of info there! Thanks:)"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 14, 2020, 10:07:33 am",
"content": "Of course this is possible, but it's not a beginner friendly project.If you're talking about a linear supply, burning off 100W at a relatively high voltage in semiconductors is a bad idea. The safe operating area of BJTs is tiny, at high voltages. Look at the graphs on the data sheets.https://en.wikipedia.org/wiki/Safe_operating_areaA switched mode power supply makes more sense, but it's still non-trivial, especially over such a wide voltage range. You're better off building two fixed voltage, 60VDC power supplies and connecting them in series with your lab power supply, to get higher voltages. You'll need a reverse diode in parallel with the lab PSU, to protect it against damage from reverse voltage.Needless to say there's a risk of shock, from borderline deadly voltages."
},
{
"post_id": "",
"author": "belzrebuth",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "June 14, 2020, 10:17:11 am",
"content": "Yes I understand.I'm close to last year of my EE studies and I'm only starting getting familiar with higher voltages but one has to start somewhere I guess. Two 60V power supplies in series wouldn't be a bad idea I guess and I could probably have them regulated and current limited far easier too.I already have a Rigol DP832 and a Farnell LT-30 which could be wired in this fashion but I essentially use 4 power supplies for a 120V one and without independent control so it seems like like a hassle already.It's far tidier to have a single source independently controllable.I could use the dual 48V transformer to build two separate 60V supplies (one from each winding pair).I guess it will be easier to find a design for a 0-60 adjustable supply (maybe regulated too?)"
},
{
"post_id": "",
"author": "wizard69",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 16, 2020, 11:33:43 pm",
"content": "It might help to say what your intended usage is. A fixed voltage power supply is relatively easy but if you need multiple variable supplies it might not be too useful Given that I find fixed voltage supplies very useful if they come in the commonly used increments. That is a hefty 12 VDC (13.supply for Auto electronics, a 24 VDC supply for industrial circuits & etc.. If you have any desire to do automotive stuff a fixed voltage (battery eliminator as they are sometimes called) power supply is a very good option in my opinion. Your desire for much higher voltages though have me wondering if there is even a standard voltage for you to target.If you do have a good idea of what your usage might be you might want to consider a partially variable supply to avoid the high heat of a full range linear. I'm not sure if the approach would be worthwhile. Again it depends upon how you expect to use them.As others have indicated take care! High voltage DC can be lethal very quickly. At work I have to diagnose and repair servo drive systems from time to time with 500VDC bus voltages. Let me tell you it puts you in a different frame of mind, know your safety procedure for testing such hardware.Quote from: belzrebuth on June 14, 2020, 10:17:11 am"
},
{
"post_id": "",
"author": "Jwillis",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 17, 2020, 12:59:37 am",
"content": "Have you considered a Variac DC supply. A small 4 amp Variac with a rectifier and PI filter would work. The Variac would give you the isolation . Current control would be fairly easy if you drive a couple Mosfets with an Op amp powered by a separate small transformer. Your only dealing with at most a couple amps so Linear Mosfet 's like the IXTH30N60L2 would work."
},
{
"post_id": "",
"author": "bob91343",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 17, 2020, 02:49:07 am",
"content": "A variac does not give isolation."
},
{
"post_id": "",
"author": "xavier60",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 17, 2020, 05:08:14 am",
"content": "I would suggest a conventional transformer rectified and filtered to about 130Vdc followed by a MOSFET/diode Buck regulator.A half bridge comes with complications of needing to be able change to diode mode to prevent current flow back in some situations.A high-side driver would be used like the FAN73611.I'm hoping that a high value resistor from the 130Vdc to the Vb pin will keep the bootstrap capacitor charged during inactive periods.This will need to be confirmed at an early stage.A Zener diode would be needed to stop the capacitor from overcharging.With a UC3843, the slope compensation could be set to prevent the duty cycle from reaching 100%.EDIT: The TL494 could be better suited."
},
{
"post_id": "",
"author": "Jwillis",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 17, 2020, 07:12:45 am",
"content": "Quote from: bob91343 on June 17, 2020, 02:49:07 amYour right . I was thinking of the double wound variable transformer but the are very expensive."
}
] |
2025-10-17T17:47:58.387041
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-10v-calibrator-basics-idea-questions-target/
|
0-10v calibrator, basics, idea, questions, target - Page 1
|
[
{
"post_id": "",
"author": "sraken13",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "October 21, 2019, 07:01:04 pm",
"content": "Hello, I have nothing to with electronics but I have good electrical background. In my past Ive been programming atmega8 ~~I want to ask simple questions and I will appreciate any answer that can lead me in close future to creating my own regulated dc power source, 0-10V, mV steps, some % accuracy for calibrating purpose.on what components to base?I know about adjustable voltage regulators like LM317 for example, or precision voltage reference chips with ability to trim the output but not in such a range of 0 to 10I wish to know a bit more of basics and design of accurate voltage calibrator, lets assume; no display, no measure, output accuracy 1%, 0,5%, 0.2% or even less; 0,05 or 0,02 or 0,01. I have budget but absolutely no clue. Throw some ideas, datasheets, circuits or complex solutions for my better understanding, eventually I will grow up. Thank You."
},
{
"post_id": "",
"author": "MosherIV",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 21, 2019, 07:38:42 pm",
"content": "HiWelcome to the forum.So you are after something like this:https://www.rohde-schwarz.com/us/product/r6240a-productstartpage_63493-9189.htmlThey are not power supplies, they are a 'voltage source'You would be better posting in the metrology section.Have a look at what this guy has producedhttps://www.eevblog.com/forum/metrology/new-pdvs2mini-dc-voltage-reference-from-ian-johnston-reviewed/Basically, you need a high stability precision voltage reference.This then is the voltage reference for a high resolution DAC.The DAC then needs to drive a voltage buffer/amplifier (try a transistor in emitter follower mode).Once all this is working, you characterise the output for linearity and program the set point voltages into a look up table whuch is used to program setpoint voltage for the DAC."
},
{
"post_id": "",
"author": "sraken13",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "October 21, 2019, 08:37:10 pm",
"content": "ah so i need DACgonna study about them.I found forum index: Best out-of-the-box 10V reference, seems to be useful for me.https://www.eevblog.com/forum/metrology/best-out-of-the-box-10v-reference/that r&s 10 µV / 1 nA resolution ;DDD a bit too much for me and my needs.main purpose of mine is sourcing mV to simulate thermocouples and sourcing V to analog inputs of plc. I already own professional equipment to do that,but want to learn more in depth even if that thing will never get out of the breadboard."
},
{
"post_id": "",
"author": "Andreas",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 21, 2019, 09:13:41 pm",
"content": "a good entry would be Conrads article:http://conradhoffman.com/mini_metro_lab.htmlBuild or buy that is the question.Ian sells 0-10V calibrators at a very attractive price.Considering that you will probably need years until your first working sample is built.https://www.eevblog.com/forum/metrology/new-pdvs2mini-dc-voltage-reference-from-ian-johnston-reviewed/msg2647110/#msg2647110with best regardsAndreas"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 22, 2019, 06:20:12 pm",
"content": "If you want to learn something you may try the PWM source below (an example).The PWM 5V signal is generated by arduino (your atmega8 for example).At the output you will get around 1.3-10.00V with PWM duty 0-100%.In the simulation below the 1kHz 5V signal with 50% duty creates aprox 5.000V at the output.The real voltage will be +/- few mVolts off because of many factors.Mind the precision and stability and is not great. You may play with it and improve it with more skills.PS: add 100uF/25V capacitors at the input and output of the LM317."
},
{
"post_id": "",
"author": "ndzied1",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "December 02, 2019, 03:53:23 pm",
"content": "Attached is a circuit I found and breadboarded and it seems to work. Besides 0-10V output you can also get 4-20mA output. I'm actually trying to work on a small PCB version that can be powered from 24VDC or 3x9V Batteries."
},
{
"post_id": "",
"author": "fcb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 02, 2019, 04:13:51 pm",
"content": "The 317 output (OUT) is 1.25V higher than the adjust (ADJ) pin - if you set the ADJ pin to 0V, you will get +1.25V out of your circuit.So with a simple single rail 317 regulator circuit you can make a 1.25V to 10V voltage source.With a nice op-amp, voltage reference a few passives you could make an OK voltage source with PWM control.Don't forget that the accuracy of your PWM output will be related to your microcontroller voltage rail unless you use external switches for the PWM. There are some schematics of a Fluke calibrator reference generator somewhere out here, that makes fascinating reading if you want to build super-precise voltage source controlled via PWM."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 02, 2019, 04:15:54 pm",
"content": "A LM317 is not really suitable for a reference source, even at the lowest level. The TC is relatively poor, there are no separate sense pins (even if just inside the case) and the voltage reference and power stage are in the same case. So the temperature will change with loading.About the lowest level to consider would be an LM723 regulator with an external power transistor (even if small like BC548).A zener reference like LM329 (still relatively cheap) and OP (like OP07) should be more precise. For good accuracy without a good meter at hand, I would consider a ready build cheap ref circuit (e.g. from China) build around some AD58x chip supplied with measured actual value. With some luck the readings are really from that unit."
}
] |
2025-10-17T17:59:38.326113
| 8
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-10v-controlled-via-i2c/
|
0-10V controlled via I2C - Page 1
|
[
{
"post_id": "",
"author": "permal",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 20, 2018, 09:23:16 pm",
"content": "Hi,My kitchen LED lights are currently drivenby one of these DC Maxi Jolly, (English text starts at page 5). The current controller is in turn controlled via RF signal and very unreliable. To remedy that I want to build a new controller.Output: 0-10V, 35mAInterface: I2C - I'm going to use an ESP32 as the MCU.Powered by a single 12V supply (the AUX power from the Dolly driver)What I need guidance on is with the 0-10V output circuitry:- Would aDAC101C085 (0-5V DAC, I2C)with a single-supply OpAmp (LM2904?) (non-inverting with a gain of 2; negative voltages not needed) attached to the output do the trick?- How do I design the output to deliver, say 100mA to have some margin on the required 35mA?Thanks in advance!"
},
{
"post_id": "",
"author": "frozenfrogz",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 20, 2018, 11:35:41 pm",
"content": "How about using a DAC likethis oneand an op-amp with x2 gain setting?"
},
{
"post_id": "",
"author": "permal",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 21, 2018, 06:44:48 am",
"content": "Quote from: frozenfrogz on July 20, 2018, 11:35:41 pmYou're suggesting the same kind of setup as I did; so my thinking wasn't all wrong then. The MCP4725 and DAC101C085 seems pretty equal except that the former one is half the price.So what about the sourcing ability of this circuit? For example,LM2904can only source 30mA (Vcc at 15V), how do I increase that to the required >35mA? Are there any Single-supply OpAmps that are capable of sourcing ~100mA or more?"
},
{
"post_id": "",
"author": "HB9EVI",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 21, 2018, 07:54:20 am",
"content": "Controlling led brightness over the voltage is nonsense; what you need is a voltage controlled current source; so use a fet with a current sense resistor to build a variable current source"
},
{
"post_id": "",
"author": "permal",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 21, 2018, 08:12:30 am",
"content": "Quote from: HB9EVI on July 21, 2018, 07:54:20 amI already have the LED driver (linked above). It uses a0-10V control input signalto determine what current it should drive the LEDs with. I don't see how a variable current source would help in controlling it?"
},
{
"post_id": "",
"author": "tooki",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 21, 2018, 09:08:19 am",
"content": "I think they misunderstood, and thought the 0-10V was to drive the LEDs directly. Must not be familiar with the 0-10V control standard."
},
{
"post_id": "",
"author": "frozenfrogz",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 21, 2018, 10:01:49 am",
"content": "Quote from: permal on July 21, 2018, 06:44:48 amSorry, my bad. I read your post, then had it sit in my mind for some time and later hit reply without reading the post again :/One other thing that I thought about right now: A lot of the 0-10V signal inputs on dimmer circuits are built as constant current sources, so you can usually just connect a potentiometer and you’re good to go. Maybe try that as you can spare all the expense for a DAC + op-amp (feels like a bit of over-engineering - right?).If it works, you can simply use a digital potentiometer with I2C.Edit: The datasheet (p5 bottom left column) you posted confirms this, you simply need a 100kOhm pot.Hereis a selection of digital pots."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 21, 2018, 10:05:15 am",
"content": "There's no way you need 35mA for that. The LM358/LM2904 will be fine on its own. If you really want more current, two channels can be connected in parallel, using current sharing resistors.See the application note linked below:https://www.intersil.com/content/dam/Intersil/documents/an11/an1111.pdf"
},
{
"post_id": "",
"author": "permal",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 21, 2018, 12:00:04 pm",
"content": "Quote from: Hero999 on July 21, 2018, 10:05:15 amThe datasheet states \"Light regulation 0-100% by means of PUSH function, 1...10V interface (I=0.35mA) or 100 Kohm potentiometer.\", that's where I got the number from. Thanks for linking the AN, I learned something new.Quote from: frozenfrogz on July 21, 2018, 10:01:49 amIt does mention 100k pot - but not where to actually connect it, or have I missed it? If you're right it just goes on the input. I suppose I can simply give it a try.This'd be a much simpler solution if it works."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 21, 2018, 01:31:13 pm",
"content": "When using a digital pot, keep in mind the voltage at the pot must be inside the supply of the chip. So it would need a digital pot for at least 10 V - the normal ones are 5.x V max."
},
{
"post_id": "",
"author": "permal",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 21, 2018, 01:52:24 pm",
"content": "Quote from: Kleinstein on July 21, 2018, 01:31:13 pmYeah, I noticed that when reading a datasheet for one of the available ones.I connected a regular 100k pot, the result wasn't what I expected. Yes, the lights can be dimmed, but it all happens within the lower ~20% of the scale. Why specify 100k when the entire dimming happens within the lower ~20k?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 23, 2018, 04:39:54 pm",
"content": "Quote from: permal on July 21, 2018, 12:00:04 pmYou got the decimal point wrong. 35mA, is 100 times 0.35mA."
},
{
"post_id": "",
"author": "HB9EVI",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 23, 2018, 04:42:40 pm",
"content": "Quote from: permal on July 21, 2018, 01:52:24 pmcould have caught a logarithmic pot perhaps?"
},
{
"post_id": "",
"author": "james_s",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 23, 2018, 05:09:53 pm",
"content": "A DAC seems a bit extreme for this application. How about a PWM output from a microcontroller with a RC low pass filter? To get the voltage up to 10V you could either use an op-amp to amplify the resulting DC level, or buffer the PWM signal prior to the low pass filter."
}
] |
2025-10-17T18:28:34.056677
| 14
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-10v-or-10v-to-3-3v-adc/
|
0-10V or +-10V to 3.3V ADC - Page 1
|
[
{
"post_id": "",
"author": "PCBdesigner",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "February 28, 2022, 04:34:11 pm",
"content": "I need to interface some different signals into a 3V ADC, I will not have to monitor more than one signal at a time.Some input signals are 0-10V and others are -10 to +10v.I have one ADC and one input connector.I need to scale the input signals to 0-3V but to utilise the full scale resolution I would like to switch between the two, the switch can be a physical switch or something controlled with software (analog switch for example)Does anyone have any resources or examples for what I am after?"
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 28, 2022, 06:20:07 pm",
"content": "10 V ro 3 V is a divider by a factor of some 3.4.+-10 V needs even more divider and an offset. So this this could be the inital divider plus another resistor to 3 V at the ouput."
},
{
"post_id": "",
"author": "ledtester",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 28, 2022, 06:53:37 pm",
"content": "Here is a good video on how to condition a signal using an inverting opamp:#328: Circuit Fun: Op Amp Signal Conditioning - a Practical Example -- w2aewhttps://youtu.be/OlhN7ADpKdsUsing an inverting amplifier will invert the range -- so +12 will be mapped to 0 and -12 to 3.3V, for instance."
},
{
"post_id": "",
"author": "PCBdesigner",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "February 28, 2022, 08:58:38 pm",
"content": "Something like this, I will add a BAT54s on the output to protect the ADC if the analog switch is selected for bipolar but a unipolar signal is on the input."
},
{
"post_id": "",
"author": "ledtester",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 28, 2022, 11:13:22 pm",
"content": "What ADC are you planning to use? You might be able to remove the external multiplexer since the ADC pins of a microcontroller are already multiplexed and a lot of ADC chips have multiplexers built in."
},
{
"post_id": "",
"author": "PCBdesigner",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 01, 2022, 09:16:59 am",
"content": "I am using the internal ADC in a xmega256, I might omit the analog switch if I end up with enough adc pins as you suggest.I just want to make sure that my circuit is a good way a of doing it and I am not missing something obvious"
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2022, 01:34:01 pm",
"content": "There should be additional protection if the OPs get a supply higher than the supply of the µC.One does not really need the OPs and exra analog switch, though the OP can help with the protection in case there is a negative signal, but the input still in 0-10 V mode. It is enough to switch the resistor to the +3 V level with a switch that is low enough that the swtich resistance is not relevant. A low level P_channel MOSFET can be sufficient. After all the ADC in the µC is only a 12 bit one with more limited accuracy.A buffer OP (powered from the same supply as the µC) may still be usefull to limit the voltage. This way a ot of range voltage would not effect the µC.The protection diodes in the µC can withstand quite some current, but when there is current slow from an excessive input, adjacent pins (e.g. other ADC channels) on the µC may show odd behaviour."
},
{
"post_id": "",
"author": "RoGeorge",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2022, 02:02:12 pm",
"content": "Quote from: PCBdesigner on February 28, 2022, 04:34:11 pmI've seen a shift and scale level in the input stage of an ADC from a MAX10 FPGA, in a devboard called DECA, from Terasic. They usedINA159.See the capture for page 29 of 134 in the attachment, from the user manual of the devboard:https://www.terasic.com.tw/cgi-bin/page/archive_download.pl?Language=English&No=944&FID=3ac35e74e46b2fa89c4ee85345ff8df2"
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2022, 03:00:41 pm",
"content": "If the 3V range limit isn't critical, switching in a single pullup by changing an I/O pin from input to output high may be sufficient. Try a 6.98K:3.01K potential divider and a 2.26K switched pullup, which will give you about 3.15V on the high end for -10V to +10V in."
}
] |
2025-10-17T17:14:12.506754
| 9
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-10v-variable-output-power-supply/
|
0-10v Variable Output Power Supply - Page 1
|
[
{
"post_id": "",
"author": "Arzeo",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 12, 2020, 09:35:21 am",
"content": "I was wondering what would be the most simple way to get a 0-10v variable output power supply. I would be using this for a dimmer switch for this LED driverhttps://hubbellcdn.com/specsheet/LED-75W.pdfThere are so many light switches with a 0-10v dimmer built into them that are decently sized, it just seems almost ridiculous I can't find some simple plug with a potentiometer on it with 2 output wires. I have seen these little lm317 adjustable voltage regulators, but they seem to need a maximum window of ~3 volts above what your max output should be. I would want something I can just hook up to a 12v dc power adapter, or something more simple at a reasonable price."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 12, 2020, 09:46:21 am",
"content": "Why create a new thread? It's much easier if you keep everything related to a single thread.https://www.eevblog.com/forum/beginners/led-driver-0-10v-dimming/msg2957162/#msg2957162"
},
{
"post_id": "",
"author": "Arzeo",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 12, 2020, 09:54:16 am",
"content": "In my previous experiences with forums, it felt like older topics would end up getting lost. This new thread gets right to the point so that new people don't have to go through the other thread to get to the most recent question since it isn't too related. I guess I should have tried asking the other thread before creating this one though."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 12, 2020, 10:01:58 am",
"content": "Quote from: Arzeo on March 12, 2020, 09:54:16 amThe information in the other thread is relevant to the question. Bump the thread, with more information, if you've not got the answer you were looking for. Creating a new one will not help as people will quite likely suggest things which are completely irrelevant."
},
{
"post_id": "",
"author": "Arzeo",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 12, 2020, 10:08:55 am",
"content": "So are you suggesting I abandon this thread and bump my old one?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 12, 2020, 10:23:12 am",
"content": "Quote from: Arzeo on March 12, 2020, 10:08:55 amYes, please do that, so everyone can have all the background information. I have an idea of how this can be done, but it's not an off the shelf solution. I'll post it in the other thread."
},
{
"post_id": "",
"author": "Simon",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "March 12, 2020, 11:05:37 am",
"content": "https://www.eevblog.com/forum/beginners/led-driver-0-10v-dimming/"
}
] |
2025-10-17T17:54:16.725919
| 7
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-10vdc-signal-into-3-3v-mcu-adc/
|
0-10vdc signal into 3.3v MCU ADC - Page 1
|
[
{
"post_id": "",
"author": "StuntMonkeh",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "January 01, 2014, 02:58:07 pm",
"content": "I want to measure a dc signal from a device which outputs between 0 and 10v dc.I assume I need to somehow rescale the signal to between 0 and 3.3v dc for the MCU ADC input to read across the range.Ideally I need to protect the MCU from over voltage on the input also.I have read a couple of threads (see links below) but I can't seem to figure out what I need to do. Can someone point me in the right direction.https://www.eevblog.com/forum/projects/protecting-adc-input-with-diode-clamp/https://www.eevblog.com/forum/microcontrollers/robust-microcontroller-input-protection/"
},
{
"post_id": "",
"author": "gregallenwarner",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "January 01, 2014, 03:05:29 pm",
"content": "You need torescalethe signal using a voltage divider. Connect the 0-10v signal into the top of your voltage divider, and the center of your voltage divider into your MCU input. Choose resistance values in your divider such that 10v gets scaled down to 3.3v, for example, 6.8k for the top resistor, and 3.3k for the bottom."
},
{
"post_id": "",
"author": "StuntMonkeh",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "January 01, 2014, 03:12:17 pm",
"content": "I have figured that part out but how do I then protect the MCU if the voltage goes above 10v?"
},
{
"post_id": "",
"author": "Caca",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 01, 2014, 03:29:43 pm",
"content": "For that you can use diode clamp to 3V3"
},
{
"post_id": "",
"author": "DrLuke",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 01, 2014, 03:38:14 pm",
"content": "You could use a Zener diode to clamp the original Signal to 10V. Alternatively if your mcu has input protection and the original signal won't go into crazy high voltages, a high enough resistance in the voltage divider should do the trick aswell."
},
{
"post_id": "",
"author": "StuntMonkeh",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "January 01, 2014, 03:53:41 pm",
"content": "The diode clamp is this isn't it?I did find this PDFhttp://www.microrobotics.co.uk/doc/pdf/Sch-simple-analogue.pdfalthough I was rather confused what the two op-amps were doing exactlyOh and can someone explain this photo, I was trying to understand how this method worked but the schematic is difficult to decipher from the picture."
},
{
"post_id": "",
"author": "mariush",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 01, 2014, 04:52:38 pm",
"content": "You should read the documentation of the controller. Some pins may be 5v tolerant, but may be or not be in ADC mode.Next, you should think about how much accuracy you need. If you use a low voltage linear regulator to get 3.3v then I guess you could use the ADC with the Vin as voltage reference. But you may want to consider using the internal voltage reference configured to 2.048v or 2.5v. With 2.048v voltage reference, you'd basically have 50mV steps and a division by 5 using the voltage divider giving you 0-10.25v measurement ability, and you'd still have the range between 2.048 and 3.3v as over voltage protection ( 3.3v x 5 = 16.5v)Zener diodes would probably be the simplest method to add some protection. Something more complex I thought of would be using a schmitt trigger in combination with a p-channel mosfet. Give the schmitt trigger the voltage through a voltage divider and configure it in such a way as to go high when voltage goes over 10.5v and low when voltage goes below 10v (or something like that). When output is high , the p-channel mosfet breaks the connection to the adc.Something like this is used by various overvoltage/undervoltage controllers, just google for \"overvoltage p-channel mosfet\" and you'll see various integrated ICs using p-channel mosfets to protect stuff."
},
{
"post_id": "",
"author": "StuntMonkeh",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "January 01, 2014, 05:37:52 pm",
"content": "Obviously a number of ways this can be done. Each method with advantages and disadvantages I imagine.Thanks for pointing me in the general direction. I will have a look at that kind of method and see if I can't get some simulations to work."
}
] |
2025-10-17T20:10:55.531323
| 8
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-1_-pitch-pcb-header-options/
|
0.1" pitch PCB header options - Page 1
|
[
{
"post_id": "",
"author": "icon",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 08, 2015, 01:12:37 pm",
"content": "HiI'm putting together a simple RIAA phono widget plus preamp from PCBs supplied by Rod Elliott. Between the power supply board, the phono thing and the preamp, there's quite a few 2, 3 and 5 hole 0.1\" pitch connectors. I had thought of using screw connectors, but it'll be a tight squeeze, and I'm struggling to find a 5 hole one. Other thoughts are Molex headers and plugs or solder directly to the board (which could end up a proper cat's cradle).Molex connectors for mV signals? Any thoughts about that or otherwise?ThanksJohn"
},
{
"post_id": "",
"author": "cosmicray",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 08, 2015, 02:26:12 pm",
"content": "Even if you decide to use Molex type plugs (of which there are an extensive variety) be aware that the same style can be had in multiple contact finishes (tin, various thicknesses of gold, etc). Some of those are rather difficult to locate, so you may way to consider contact resistance in the selection."
},
{
"post_id": "",
"author": "PeterFW",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 08, 2015, 03:37:37 pm",
"content": "Quote from: icon on March 08, 2015, 01:12:37 pmI have seen so many of these connector over the years in all sort of audio related gear carrying everything from mic level to power:http://www.zeenic.com/c64psu/T07.jpgWith contact surfaces from ranging from gold, silver, tin to various types i could not identify with certainty.I have seen standard ribbon cable with your house hold crim press fit connector and so much more.Yamaha, Allen&Heath, Denon, Pioneer, high end, low end...What i am trying to say is, get a next best decent cable with a connector and youre good to go. If you solder cabled directly onto a board, only solder one side and use a connector on the other.That is way, way more service friendly"
},
{
"post_id": "",
"author": "icon",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 08, 2015, 09:28:54 pm",
"content": "OK, thanks. I think I'll go with service-ability and ease of assembly - Molex (or equivalent).John"
}
] |
2025-10-17T19:45:48.587219
| 4
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-1_-solid-conductor-ribbon-cable/
|
0.1" solid conductor ribbon cable - Page 1
|
[
{
"post_id": "",
"author": "djacobow",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "December 14, 2015, 10:08:04 pm",
"content": "I've built a few projects that used a standard cheapie 16x2 HD44780 and have been frustrated by my inability to find ribbon cable with 0.1\" spacing so that I can easily separate the LCD from my board.Note that I do /not/ want the more typical 0.050\" pitch IDC cable that crimps to 2xN 0.1\" headers connectors.I feel like this sort of 0.1\" spacing ribbon cable with solid conductors used to be quite common. You'd see it in consumer electronics and the like, where the cable would be stripped and soldered directly to a row of 0.1\" holes on both boards.Am I missing some magic keyword?Best,Dave J"
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 14, 2015, 10:22:32 pm",
"content": "http://www.digikey.com/short/t0799q?Not obvious if it's solid core (only 1 hit for full solid) or soldered stranded (which I recall being very common in your examples).You wouldn't really want solid for any kind of cable in the first place, so you might be better off using a connector or dealing with the loose strands (strip and insert carefully?).Tim"
},
{
"post_id": "",
"author": "djacobow",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "December 14, 2015, 10:38:56 pm",
"content": "Thanks! It's a bit disappointing that my only actual option for 16 conductor is 100' for $200. I guess that's a volume thing.I guess I could make do with the stranded stuff, particularly if I could figure out a way to very efficiency tin the ends so I can get them in PCB holes, but yeah, soldered stranded is probably what I'm thinking of."
},
{
"post_id": "",
"author": "mariush",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 14, 2015, 11:15:23 pm",
"content": "You could buy Dupont headers and female pins and crimp a couple of ribbon cables. You'd have two ribbon cables instead of a single wide one.Headers (you can find pins at the bottom at associated products):1x4 :http://www.digikey.com/product-detail/en/M20-1060400/952-2229-ND/3728193orhttp://www.digikey.com/product-detail/en/0050579304/WM2873-ND/24054021x8 :http://www.digikey.com/product-detail/en/M20-1060800/952-2234-ND/3728198orhttp://www.digikey.com/product-detail/en/0050579208/WM5347-ND/27314382x4 :http://www.digikey.com/product-detail/en/M20-1070400/952-2032-ND/3727996orhttp://www.digikey.com/product-detail/en/0901430008/WM8058-ND/760773orhttp://www.digikey.com/product-detail/en/A1-8D-2.54C/H123019-ND/39776052x8 :http://www.digikey.com/product-detail/en/M20-1070800/952-2037-ND/3728001orhttp://www.digikey.com/product-detail/en/90143-0016/WM8062-ND/760777or others...of course, this means you'd also need to invest in a crimping tool (like engineer pa-20 or pa-09 for example) and then you'd be able to use much cheaper ribbon cable (like the awg20-24 ones), and pitch wouldn't matter because you'd just crimp pins on both ends and plug the pins into sockets. And you could also get 32-40 wire ribbon cable if it's cheaper and just split it into strips of 8 wires or whatever configuration you'd like"
},
{
"post_id": "",
"author": "jwm_",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "December 14, 2015, 11:36:12 pm",
"content": "These pre crimped wires from pololu are great. After getting some and a variety of headers I find all sorts of uses for em.https://www.pololu.com/category/71/wires-with-pre-crimped-terminals"
},
{
"post_id": "",
"author": "djacobow",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "December 15, 2015, 12:37:10 am",
"content": "Quote from: mariush on December 14, 2015, 11:15:23 pmThis is precisely what I do now and am hoping to avoid!Using two 1x8 is not a problem, it's the dealing with each pin individually and having to split the cable that I want to avoid. Also, the connectors on both ends add considerable bulk in a small box. With mail pins and female connectors, we're often talking about almost 1 cm or more of dead, inflexible height.I should have mentioned that I want this because of the labor time. This is not a high volume project, but it's not a one-off. I'd be doing like 20 of these."
},
{
"post_id": "",
"author": "mariush",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 15, 2015, 01:05:29 am",
"content": "It's more expensive but you can buy ready made cables with one 2x8 connector on one end and loose ribbon cable on the other end (so you could solder directly in the 2x8 header or 1x16 on your LCD display) :1.http://uk.farnell.com/samtec/ffsd-08-s-02-00-01-n/lead-1-27mm-idc-2in-16way/dp/1932838(2\" of ribbon)2.http://uk.farnell.com/samtec/ffsd-08-s-02-50-01-n/lead-1-27mm-idc-2-5in-16way/dp/1932903(2.5\" of ribbon)For a 20 pcs run, it's kind of expensive, but it would save you a lot of time in crimping each cable individually"
},
{
"post_id": "",
"author": "sleemanj",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 15, 2015, 05:42:39 am",
"content": "LifeProTip: do not search for \"solid core ribbon\" on Aliexpress."
},
{
"post_id": "",
"author": "macboy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 15, 2015, 02:37:00 pm",
"content": "Search ebay or the other places for \"dupont\" wires. Typically you can get a 40 conductor ribbon with 40 individual female connectors on each end for about $2 or less (you can also get male-to-female, good for connecting things to breadboards, and male-to-male, good for basic breadboard interconnects). Youdon'tneed to buy ribbon, connectors, and housings separately and make your own. Peel off the number of wires you need, then individual pins can be arranged any way you want and super-glued together to form custom 0.1\" headers of any configuration. I don't know what I ever did before stocking up on these."
},
{
"post_id": "",
"author": "anachrocomputer",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "December 15, 2015, 04:44:42 pm",
"content": "I used something like this recently to link PCBs together in a chain, to make a big LED 7-segment display. I found ready-cut short lengths of ribbon cable at Farnell and RS Components, all 0.1-inch (2.54mm) spacing.http://uk.farnell.com/te-connectivity/fst-21a-10/ribbon-cable-ptfe-10way-25-4mm/dp/1310332http://uk.rs-online.com/web/p/flat-ribbon-cable/2992119/Looks like TE Connectivity have a range of the stuff, called FST."
},
{
"post_id": "",
"author": "djacobow",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "December 15, 2015, 06:58:59 pm",
"content": "Quote from: sleemanj on December 15, 2015, 05:42:39 amI did not know if you were making fun of me for not trying Aliexpress or if you were serious.Now I know."
},
{
"post_id": "",
"author": "djacobow",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "December 15, 2015, 06:59:48 pm",
"content": "Quote from: anachrocomputer on December 15, 2015, 04:44:42 pmYes!! This is the sort of thing I was after.Magic keywords are: FFC / FPC Jumper CablesHuzzah!"
},
{
"post_id": "",
"author": "rdl",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 15, 2015, 10:07:02 pm",
"content": "Flat flex cable is another name I've seen used.Those \"Dupont\" cables with the pre-crimped connectors almost invariably use 0.05\" pitch cable. That's okay if done well. DIY usually doesn't because it can be hard to get the wire length right so that the connectors end in a straight edge.Of course, some people don't care because it's mostly just a cosmetic flaw."
},
{
"post_id": "",
"author": "tszaboo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 16, 2015, 02:33:26 pm",
"content": "Quote from: sleemanj on December 15, 2015, 05:42:39 amAlso, the results for searching \"rubber feet\" are not workspace safe."
},
{
"post_id": "",
"author": "macboy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 16, 2015, 03:36:04 pm",
"content": "Quote from: rdl on December 15, 2015, 10:07:02 pmYes they are standard 0.05\" ribbon cable. They are so cheap you can snip off every-other end, and use alternating ones, or just separate the conductors enough to make it fit. It won't look great either way. I value function over form in these cases."
},
{
"post_id": "",
"author": "tooki",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 17, 2015, 02:33:57 pm",
"content": "Quote from: sleemanj on December 15, 2015, 05:42:39 amWhat the hell? I mean, I'm gay and I've never seen things quite like that..."
}
] |
2025-10-17T19:28:40.739934
| 16
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-1uf-esr/
|
0.1uF ESR ? - Page 1
|
[
{
"post_id": "",
"author": "Flump",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 27, 2014, 03:00:47 am",
"content": "I have a 0.1uF electrolytic cap whichmy tester measures as 107nFbut it cant get a ESR reading from the cap.Is this normal on caps this small ?"
},
{
"post_id": "",
"author": "c4757p",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 27, 2014, 03:02:44 am",
"content": "Very low-value electrolytics tend to have very high ESR. It's possible that it's overrange."
},
{
"post_id": "",
"author": "Flump",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 27, 2014, 03:21:59 am",
"content": "thanks very much"
},
{
"post_id": "",
"author": "PedroDaGr8",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 27, 2014, 03:24:48 am",
"content": "Quote from: Flump on July 27, 2014, 03:21:59 amI have a 0.1uF that I read an ESR of around 160. I think tan delta is a better indicator of health for these size caps (plus its in the datasheet)"
},
{
"post_id": "",
"author": "Flump",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 27, 2014, 09:22:52 am",
"content": "never heard of tan delta so will do some research on itthanks Pedro"
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 27, 2014, 09:27:20 am",
"content": "Tan delta is basically how lossy it is. Even on electrolytics it gives a good idea of the health of a capacitor. The smaller the number the closer it is to an ideal capacitor."
},
{
"post_id": "",
"author": "w2aew",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 27, 2014, 02:42:59 pm",
"content": "Quote from: Flump on July 27, 2014, 03:00:47 amThat's a pretty small value cap to measure ESR on. Many ESR meters use something on the order of 100kHz as a test frequency. This cap will have 16 ohms of capacitive reactance at that frequency, which many ESR meter designs will incorrectly interpret as ESR."
},
{
"post_id": "",
"author": "AQUAMAN",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "July 28, 2014, 12:37:14 pm",
"content": "U need to either buy a proper LCR meterOr u need a pulse generator and u can build a peak detector circuit to measure the peak current into the capacitor, from this u should be able to tell its ESR in some level roughlyI have built many circuits that approximately measure the ESR of gate capacitances in IGBTs or MOSFETs which are in the range of 50-100nF. They can be built very cheaply and easily.What I do is I measure the peak current flowing through the charging resistor.For my applications I only measure the CHANGE in the ESR during operation (and I measure this change in 1mOhm/C sensitivity), so actually I have no idea what the absolute value of it is and it does not matter to me either. But in theory you could probably work it out, even if I dont bother to do this.Using a pulsed ESR detection will never give u the true ESR as the peak current/instant voltage is dependent on the capacitor size, the inductance and also the resistance (search Peak Inflow Current into capacitors)"
},
{
"post_id": "",
"author": "Flump",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 29, 2014, 06:19:33 am",
"content": "Thanks AlanAquaman how will a LCR Meter helm me measure ESR ?"
},
{
"post_id": "",
"author": "AQUAMAN",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "July 29, 2014, 09:10:03 am",
"content": "Because thats what it measures?U can tell them to measure Cs-RsRseries is the ESR of the cap right?"
}
] |
2025-10-17T19:58:01.040225
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-1v-dc-dc-step-down-converter/
|
0-1V DC-DC Step down Converter? - Page 1
|
[
{
"post_id": "",
"author": "eevblognube",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 18, 2016, 06:57:29 pm",
"content": "Please let me know if I should post this is a different subforum.I am seeking an off-the-shelf, adjustable DC-DC Step down converter with the following specs.Input Voltage: 12-16VDCOutput current: 50mA minimumOutput Voltage: 0V-1VDCIdeally, the adjustable output voltage range would be 0mV-1000mV, although an acceptable range would likely be 500mV-1000mV.Most of the DC-DC converters I have found have a much greater output voltage. Exceeding 1000mV will likely damage the equipment connected to the converter's output.Alternatively, I could likely get away with having a fixed output voltage, but I'd have to experiment with voltages between 500mV to 1000mV in 100mV increments. An adjustable unit would be preferred for this reason.If anyone has seen a product like this, I'd sure like to check it out!*EDIT*It appears the B3603 unit on ebay would suffice. I would be worried that this thing would lose its memory and output some voltage greater than 1V that will damage the equipment on the output, though. This unit will be powered by an ignition wire on a car, so power will be completely cut every time the vehicle is shut off."
},
{
"post_id": "",
"author": "AmmoJammo",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 18, 2016, 07:07:14 pm",
"content": "You just need to have a voltage divider on the feedback line set up such that you can't adjust it above 1volt output."
},
{
"post_id": "",
"author": "eevblognube",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 18, 2016, 07:16:56 pm",
"content": "Quote from: AmmoJammo on February 18, 2016, 07:07:14 pmAgreed, although I don't actually have any electronics materials. I just have some basic tools and a multimeter. I figure a voltage divider will also sap energy and produce heat. I'm not opposed to purchasing a resistor kit and soldering iron, I was just hoping to find an off-the-shelf product first. I will likely need to fabricate an enclosure for the device, but I'm trying to stay away from protoboards at this time."
},
{
"post_id": "",
"author": "eevblognube",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 19, 2016, 05:20:01 pm",
"content": "Here is a unit that seems to fit the bill:http://www.ebay.com/itm/Digital-controlled-4-5-23V-to-0-20V-2A-Converter-Step-down-Power-Supply-Module-R-/330940929785?hash=item4d0d9dd6f9:g:X58AAOxyqOxRvbEeAlso this unit:http://www.amazon.com/5-32-0V-0-30-0V-Adjustable-Regulator-Converters/dp/B00ZF9ROKU/ref=sr_1_21?ie=UTF8&qid=1455899270&sr=8-21&keywords=smakn+converter+adjustableAnybody have experience with these converters?The unit must be able to store and restore the stored output voltage automatically after the input power is cycled off/on."
},
{
"post_id": "",
"author": "exe",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "February 19, 2016, 08:00:40 pm",
"content": "Quote from: eevblognube on February 19, 2016, 05:20:01 pmAsk sellers what IC they are based on. Then it's a matter of comparing claimed specs with datasheets. Do not take for granted that the devices can meet the claimed specs."
},
{
"post_id": "",
"author": "eevblognube",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 19, 2016, 08:05:25 pm",
"content": "Quote from: exe on February 19, 2016, 08:00:40 pmI think I'm going to go ahead and test out this unit:http://www.amazon.com/DROK-Regulator-Converter-Switching-Stabilizers/dp/B00Q48BRFO/ref=sr_1_38?ie=UTF8&qid=1455903164&sr=8-38&keywords=drok+converterMost of the units I've looked at use the LM2596. This unit seems to be able to power up when power is applied (ideal for my usage), since there does not seem to be an on/off button. Also, they claim that the issue where the voltage spiking at first power-up has been fixed. I'm willing to give this thing a try, since its under $10 and is available with free 2-day shipping with Amazon Prime."
},
{
"post_id": "",
"author": "exe",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "February 19, 2016, 09:20:20 pm",
"content": "Quote from: eevblognube on February 19, 2016, 08:05:25 pmYeah, and its clones. The problem is they cannot go below 1.2V (reference voltage). Anyway, good luck"
},
{
"post_id": "",
"author": "eevblognube",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 20, 2016, 06:58:03 am",
"content": "Quote from: exe on February 19, 2016, 09:20:20 pmCheck the link, it seems pretty convincing that they go to 0V. There are a lot of answered questions and reviews. Worth a shot.Sent from my HTC One_M8 using Tapatalk"
},
{
"post_id": "",
"author": "mariush",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 20, 2016, 07:42:13 am",
"content": "The problem with those switching dc-dc converters would be the noise on the output, it wouldn't suprise me to see +/- 10-40mV on the output, especially at the low currents the thread author mentions (50mA and up) ... some of those regulators even need a minimum of 1-5mA to function properly (and often those cheap eBay boards don't have \"built in\" minimum load)I can't think of anything off the shelf that would do your requirements (0..1v with a relatively decent amount of control, and at low currents like 50mA).Seems like small linear regulators with very low voltage drop would be ideal for this though and you could probably protect the output using some sort of zener diode or optionally disabling the regulator by setting the regulator's enable (if it has any) line high/low if the voltage goes above 1v.If you don't really need 0v but you could settle for a minimum of 0.25v or something like that, there are small linear regulators that have internal voltage references smaller than the typical 1.25vFor example a 3$LT3020has an internal voltage reference of 0.2v so you can output 0.2...1v but atmaximum 100mAand maximum 10v input voltage (you can just use a 2.5v or 3.3v fixed linear regulator in front of this chip or a cheap mc34063 solution or another dc-dc converter to make sure the voltage is always low enough for this chip)A 4.5$LT3021can do up to around 550mA and it's easier to solder (SOIC, 8 easy to solder leads) but otherwise has the same pros (0.2v minimum) but also same limitations.A <1$ Microchip (former Micrel)MIC47053will do 0.4..1v at up to 500mA but it's even pickier about the input voltage (shouldn't use more than 3.6v) and it would be somewhat difficult to solder. Maybe you can find it in other packages at other stores, I only checked Digikey.MIC59300is more expensive at around 3$ but it's quite easy to solder and would allow you to go for high currents (up to 3A) and has internal voltage reference of 0.5v so it gives you directly 0.5 .. 1v . It also works with low input voltages (up to 3.8v) so you'd have to use a regulator before it to give it the low voltage it needs.Digikey is quite good at this, you can go on the linear regulators page, filter by \"positive\" and \"adjustable\" and combinations of these words, then filter by minimum output voltage to see the regulators that can output much lower than 1v without messing around."
},
{
"post_id": "",
"author": "eevblognube",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 24, 2016, 07:07:46 am",
"content": "Quote from: mariush on February 20, 2016, 07:42:13 amExcellent info. I agree that linear converters are a good way to go. I did purchase that buck converter from Amazon because I need to do some testing to see what voltage range will work properly. I will use a 12V to 5V phone charger to supply 5V to the converter so the step down is less sharp.I think there is decent tolerance for ripple for my application, but I'm not really sure.Once I determine a proper range, I'll likely pursue a linear solution.Thanks!Sent from my HTC One_M8 using Tapatalk"
}
] |
2025-10-17T19:24:03.221270
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-20ma-current-loops-and-where-load-is/
|
0-20mA current loops and where load is? - Page 1
|
[
{
"post_id": "",
"author": "implor",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 01, 2025, 06:49:25 am",
"content": "Really noob question here. Mostly based on I have never designed a 0-20mA output stage before and I'm unsure what is \"standard\".I have looked at some reference designs based on a OPA + BJT transistor with current feedback resistor below emitter.(see image). This works fine as long as loop load is on high side. Due to voltage divider feedback to OPA is reference to GND this falls apart if loop load is on low side.You can make this agnostic with another OPA with differential connection over shunt resistor but I have seen many reference design with the setup above.So here is my question. Is there a convention that loop load will always be on high side (loop+, basically working as output impedance from voltage source)?Or can it be placed anywhere in the loop?"
},
{
"post_id": "",
"author": "Jeroen3",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 01, 2025, 07:25:01 am",
"content": "Most devices have multiple analog outputs on a power domain, so using the low side is complicated and there could be only one common wire.Outputs are not guaranteed to always be isolated either.High side is then the most suitable way. If yours is isolated, you can use low side.https://www.ti.com/tool/TIPD102Low side may also be subject to nonlinearities in the lower regions of the amplifiers.The 61131 standard deprecates 0-20mA in favor of 4-20mA, the maximum output impedance is 600 Ohm, and it of course should be able to withstand any overload."
},
{
"post_id": "",
"author": "Berni",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 01, 2025, 07:30:20 am",
"content": "Firstly the standard is 4-20mAHigh side or low side typically doesn't matter because these sensors are almost always just 2 pin devices, so it can be anywhere you like, it always passes current between its 2 pins and has no idea of its common mode voltage as it is floating with no reference to real ground.But what about the power input? That has ground!... Well you typically don't have one. The point of it being 4-20mA (and not 0-20mA) is that the 4mA down at the bottom can be used to power the sensor. At the same time it provides detection of broken wires if current falls below 4mA. This is why 4-20 current loop is so popular in industrial applications, it minimizes the number of wires, no need for a power supply, has fault detection built in, is not affected by long wires, immune to ground loops etc..The actual limit is the requirement of how much voltage a 4-20mA sensor needs between its two terminals in order to function correctly. Typically they work down to around 5 to 10 volts so that they can be used in a current loop with a 12V supply on the high side, but in industry supply is typically 24V so that allows for very long cables."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 01, 2025, 07:37:31 am",
"content": "Current loops normally don't go to zero, but 4mA. This is for error detection i.e. 0mA = open circuit which is a fault.Is this loop powered?Are the power supplies isolated?"
},
{
"post_id": "",
"author": "RoGeorge",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 01, 2025, 07:39:00 am",
"content": "Quote from: implor on July 01, 2025, 06:49:25 amThere is no rule about that, can be on either side, or on both sides at the same time, doesn't matter. The 4-20mA is supposed to be floating, isolated from earth/ground, and it usually powers itself from the 4-20mA loop/wires. The video linked in this reply happens to have some classic 4-20mA examples:https://www.eevblog.com/forum/projects/precision-current-sink-i-found-a-gem-of-a-circuit/msg5925196/#msg5925196"
},
{
"post_id": "",
"author": "implor",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 01, 2025, 07:56:41 am",
"content": "Quote from: Berni on July 01, 2025, 07:30:20 amYou are correct of course for 2 pin devices. This is for an HVAC and they are generally powered by 12-24VDC/VAC. in that case it may or may not be isolated ground references as both transmitter and receiver (Building BMS) may have the same power source in the setup (and common GND)."
},
{
"post_id": "",
"author": "implor",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 01, 2025, 08:09:07 am",
"content": "Maybe I have been mixing up 2 and 4 wire 4-20mA transmitters. What I have is a 4 Wire transmitter. Looking at this TI presentation then the sensor supply voltage to they loop and not the receiver in 4-wire designs.https://www.ti.com/content/dam/videos/external-videos/de-de/7/3816841626001/6213906106001.mp4/subassets/amplifiers-current-loop-transmitters-configurations-presentation-quiz.pdfIs it common knowledge among installers that 2-wire should be power and 4-wire should not?"
},
{
"post_id": "",
"author": "Berni",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 01, 2025, 09:49:50 am",
"content": "The 4-20mA current loop is mainly designed to be used for remote sensors that inherently float and scavenge power from the current loop itself, so it is a 2 wire sensor with no power supply needed, the floating 2 wire transmitter simply pulls the appropriate current from the loop by modulating its own power consumption. This hugely simplifies things.However when you want to use current loop to communicate between powered equipment then things get tricky and you basically need to generate an local isolated floating power rail inside your equipment to run the current loop (Like it is shown in that TI document). This is the only way to make sure there are no ground loop problems. Otherwise running a long cable on the other side of a large building could easily put an extra 10V of 50Hz AC onto your ground, this can cause all sorts of problems and completely mess up the signal.Robust long distance communication via copper is hard."
},
{
"post_id": "",
"author": "PGPG",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 01, 2025, 09:51:11 am",
"content": "Quote from: implor on July 01, 2025, 06:49:25 amIt is not clear for me if you are asking about analog current loop with all current values between 0 (or 4) and 20mA being possible or about digital communication 0-20mA current loop.In 90s we were using 0-20mA current loop to communicate by 2 wire between PC and our access controllers at the distance up to 1200m.AT PC side there was up to 64 current loops switch (with 4kV isolation of each loop) connected to COM port (and powered from its pins - 5mA was enough). The 20mA for current loops were supplied by controllers."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 01, 2025, 10:00:16 am",
"content": "It's not clear what the OP is trying to do.How about using a pre-built module?It will cost more in parts, but it saves in design hours and will be tested. If you choose a galvanically isolated module, then you don't have to worry about whether or not the output ground shares the input ground or not.https://www.phoenixcontact.com/en-gb/products/signal-conditioner-mini-mcr-2-u-i4-pt-2902030https://uk.rs-online.com/web/p/signal-conditioners/4662258https://www.prelectronics.com/filearkiv/pdf-ftp/3100_series/3105/manual/arkiv/3100v100_uk.pdf"
},
{
"post_id": "",
"author": "implor",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 01, 2025, 10:42:42 am",
"content": "Quote from: PGPG on July 01, 2025, 09:51:11 amQuote from: Zero999 on July 01, 2025, 10:00:16 amOriginal question was if loop load always was in series with Loop+ on collector side. Answer to that seems to be No.After a good lunch i figured out that you could get this isolated simply with an optocupler for the pwm signal and power the rest (opa, LDO, bjt) from the loop.I was stuck in my head with the problem to need a expensive isolation DC/DC to get the current loop power. But it's not needed."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 01, 2025, 11:52:49 am",
"content": "Yes, there's no standard.If the output shares the same positive, or negative rail as the input, then you could use an op-amp in Howland configuration to give a differential input and output.https://www.ti.com/lit/an/sboa436/sboa436.pdfU1 needs to be a single supply op-amp i.e. work when its input is near the negative rail.This circuit will work as either a current source or current sink. +out can be connected to +24V with the load connected between -out and 0V, or -out can be connected to 0V, with the load between +out and +24V. I've shown two load resistors, RL1 and RL2, for the purpose of the simulation.There obviously needs to be enough voltage headroom for the op-amp to drive the MOSFET.I've not done any transient/AC analysis. A compensation capacitor might be necessary. You'll probably get away without one, if you use a small, low power MOSFET and a slow op-amp."
},
{
"post_id": "",
"author": "Jeroen3",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 01, 2025, 12:56:00 pm",
"content": "Remember that this circuit also needs to survive at least 1kV fast transients according to IEC 61000-6-2."
},
{
"post_id": "",
"author": "BeBuLamar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 01, 2025, 02:43:57 pm",
"content": "There are devices that output 0-20mA as well as devices that take input of 0-20mA."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 01, 2025, 03:38:02 pm",
"content": "To be be pedantic the circuit I posted above is for 4mA to 20mA.If you want to convert 0 to 5V to 4mA to 20mA, then a voltage reference and biasing resistors are required. See the circuit linked below for an idea of how to implement this.https://www.eevblog.com/forum/projects/2-wire-and-3-wire-4-20ma-transmitter-designs/msg5923116/#msg5923116Here's another variation of the above circuit, but using an instrumentation amplifier. It has more voltage drop, as the minimum gain of the IA is 1, rather than the 0.1 I used before. It's much more accurate than the previous circuit and has a higher input impedance, but uses a more expensive instrumentation amplifier and a dual op-amp."
}
] |
2025-10-17T16:16:45.262635
| 15
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-2v-adc/
|
0-2v ADC - Page 1
|
[
{
"post_id": "",
"author": "KNSSoftware",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 13, 2017, 10:38:58 pm",
"content": "HiGot a nice little first project coming up, and I am going to need an ADC for a 0-2v input, with at least 14bit resolution (0->10,000). I have an ADS1115, but unless I am looking at the datasheet wrong, the min is 2v just to start, which is a deal breaker. If so, any recommendations? I am aiming for the same sort of price point? Can I even do any sort of simple (and i mean simple; this is my first outing) amplification/dc offset, and use what I have got?ThanksJohn"
},
{
"post_id": "",
"author": "danadak",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 13, 2017, 11:16:59 pm",
"content": "The ADC supply min is 2V, but characterized at 3.3V. At 3.3V Vdd itsinput range is 2.048 V full scale, differential (+/- 2.048V).Is this what you are asking about ?Regards, Dana."
},
{
"post_id": "",
"author": "KNSSoftware",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 13, 2017, 11:30:09 pm",
"content": "DanadakTo be honest, I am learning as I am going, so please bear with me. Is that part of the gain feature? Basically I can supply any VCC needed 3.3/5v, no prob, but my analogue output from the sensor will be 0-2v. Trying to work out if I have what I need, or a change of plan is needed. At first I though I could just use differential input mode, and put vIn- to gnd, Vref to 2, and vIn+ to sensor and sit back and enjoy, but now I am thinking I have made a mistake, and celebrating too soon..."
},
{
"post_id": "",
"author": "xani",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 14, 2017, 01:35:49 am",
"content": "Quote from: KNSSoftware on November 13, 2017, 11:30:09 pmSetting input mode to single ended and PGA to +- 2.048 V would be enough, altho it would probably be more accurate if you used differental one. Just take care about voltage limits of input pins. And read datasheet, there is really everything you need there"
}
] |
2025-10-17T18:45:03.544953
| 4
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-30v-0-3a-psu-audiogurus-version/
|
0-30V, 0-3A PSU - Audioguru's version - Page 1
|
[
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 01, 2019, 09:33:40 am",
"content": "This a followup tohttps://www.eevblog.com/forum/beginners/diy-0-30v-0-3a-again/It seems that project was not completed successfully.I am attaching from that thread what I believe is the final design.Is that considered to be the correct and final design and confirmed to work correctly?If so, is it possible to buy the PCB?In this thread I would like to come to a final, confirmed working, design, including specs, schematic, list of parts and PCB design.I am analyzing it. I see the op-amp on the right does the voltage regulation and it looks quite simple and straightforward.The op-amp and 5.6 volt zener in the center provide the voltage reference. I think it would be quite possible to simplify that and get rid of the op-amp and provide a simpler voltage reference. It might not be so exactly precise but I think it would be more than enough for most applications.The op-amp on the left does the current limitation control and Q3 lights the LED when current limit is active.I do not see why the 10V zener that lowers the supply voltage to U3 is needed. Maybe it can be omitted?Maybe I would add an \"ON\" LED, just to show voltage at the main capacitor."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 02:22:53 pm",
"content": "The circuit is an improved version from a rather common kit, that has quite some mistakes inside.It looks quite reasonable, though one might still want the transistor from the original to protect against an spike on turn on / turn off. With the auxiliary negative supply this may happen under some conditions during turn on.Another point might be a diode prevent to much reverse voltage to the output stage base / emitter current (add a diode like 1N4148 from output to right OP).The 10 V zener is there to reduce the supply to the first OPs. Depending on the OP used, this may not be needed or 10 V Zener could be still too little. To high a supply to the OPs was the main problem with the original circuit from the kit. A reduced voltage looks like a good idea.For the reference part there are a few options. The OP circuit can work in a way to keep the extra current through the shunt constant. So it's not such a bad solution. The OP could share the same reduced supply as the current regulator - so no special higher voltage OP needed here.By using only 1 raw voltage and with a relatively high drop, the circuit is not very suitable for high power. With some extra filtering one could at least improve a little on voltage lost: So something like 2 V lower AC could be sufficient. I am still not sure the circuit as shown would get to 30 V under all conditions (e.g. low mains and full load)."
},
{
"post_id": "",
"author": "kripton2035",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 02:30:28 pm",
"content": "seems you can buy this kit @ banggood and change the componentshttps://www.banggood.com/0-30V-2mA-3A-Adjustable-DC-Regulated-Power-Supply-DIY-Kit-p-958308.html"
},
{
"post_id": "",
"author": "Kalvin",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 02:55:51 pm",
"content": "Probably one could increase the available power by using an optional tracking pre-regulator feeding the power stage. The tracking pre-regulator will increase the output noise somewhat, but one can get higher output current with less heat. If the pre-regulator would be bypassed by a switch when a lighter load is connected, one could achieve low noise output at lower currents. There should be some cheap and suitable dc-dc buck-converters available at eBay, which can be modified so that it will track the power supply output voltage by 2 - 3 Volts or so. This modification would extend the usability of this simple power supply without serious heat issues."
},
{
"post_id": "",
"author": "Kalvin",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 03:07:36 pm",
"content": "I would also consider adding a unidirectional 30V TVS diode across the output, which would protect the power transistors from typical voltage surges occurring with inductive loads and connecting/disconnecting the load. Adding a polymer fuse to output should not hurt either."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 04:20:07 pm",
"content": "Quote from: Kalvin on March 01, 2019, 03:07:36 pmA polymer fuse at the output ( between the emitter resistors and the feedback) does add some resistance and thus effect the response a little towards a little slower response.AFAIK the board from the kit does not include the 10 V zener to reduce the supply to the not so critical OPs. So it would need better OP for all 3. The difficulty here is getting DIP8 OPs that can stand a high voltage (e.g. 40..44 V), without paying a premium price (like for OP27). Plain old 741 could work - though a little slow (especially slew rate for current limit - so quite some delay before CC mode sets in).The board I know also includes a layout blunder, that causes quite some ripple from the rectifier when in the CC mode (poor sense point for the negative side of the shunt). This can be fixed with a cut trace and bodge wire."
},
{
"post_id": "",
"author": "Kalvin",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 04:32:02 pm",
"content": "Quote from: Kleinstein on March 01, 2019, 04:20:07 pmOne can use an op amp in SO-8 with suitable breakout PCB adapter board or a piece of a strip board. Of course the op amp will cost a few dollars, which will effectively double the original price of the kit"
},
{
"post_id": "",
"author": "kripton2035",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 04:58:11 pm",
"content": "LTC6090 @ around 8€ each ..."
},
{
"post_id": "",
"author": "perieanuo",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 05:16:57 pm",
"content": "Quote from: kripton2035 on March 01, 2019, 04:58:11 pmWhat's wrong with TL082 replacement?Envoyé de mon iPad en utilisant Tapatalk"
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 05:38:43 pm",
"content": "There are good replacements like the mentioned TLE2141 or MC34071 - though not that easy to get in DIP8 form. An OPA604 could also work - though a little on the fast side and high supply current which is not that attractive with the negative supply. Only for 40 V, but otherwise the TLE2021 could be an option too.The easy way is to just reduce the maximum voltage a little.Another option would be to add a resistor and zener to limit peak voltages on the OPs supply. So the OP would not see the peaks.Just changing the OPs on the kit board only fixes some of the weak points. There is still only 1 power transistor, too small a filter cap, the high supply to the other 2 OPs that don't need it, the poor shunt layout, a poor choice for the negative supply of the reference OP. One could directly support an OP is SO8 case that is easier to get.There is already at least 1 thread in this forum about this supply and suggested changes. So there might already be an improved layout around.So it might be worth to make a new, revised board and not use the kit.Currently PCBs seem to be not that expensive when ordered in China.This circuit should fit on an 8x10 cm² size - especially with the power transistors externally."
},
{
"post_id": "",
"author": "rdl",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 05:43:36 pm",
"content": "Why not just reduce the output to 20 volts? I doubt many people ever really need more than that."
},
{
"post_id": "",
"author": "Kalvin",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 05:47:25 pm",
"content": "Quote from: perieanuo on March 01, 2019, 05:16:57 pmCheck the maximum operating voltage seen by the op amp: For 28V AC RMS rectified voltage, the peak rectified voltage will be 28V * 1.4142 = 39.5V. In practice one needs to provide few volts more across the power transistor, so in order to get stable 30V output voltage the RMS voltage needs to be 35V or thereabouts. Now, the peak rectified voltage seen by the op amp will be 35V * 1.4142 = 49.5V. Add to this the -1.3V negative power supply voltage and you will get 50.8V across the op amp, which will exceed the maximum allowed power supply voltage of TL082.Like others have suggested, reducing the transformer voltage ie. reducing the rectified peak voltage ie. reducing the maximum output voltage, one can use those cheaper op amps."
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 06:41:01 pm",
"content": "The original Greek kit and the Chinese copies used TL081 opamps that have a maximum allowed total supply of 36V and need a negative supply that is at least 4V then its maximum allowed positive supply is only +32V. Its max output voltage would be +29V if the driver and output transistors have minimum hFE and the output current is 3A. I removed R15 in series with the output of the voltage regulating opamp and the driver transistor that reduced the voltage 2.5V max to +26.5V. The maximum worst case voltage loss of the driver and output transistors is 3V so the worst case maximum output voltage of this old circuit would be only +23.5V at 3A. You would want less supply voltage for reliability.To make the +32VDC supply plus including the 2V drop from the bridge rectifier you need 34V which is produced by a 24VAC transformer.Texas Instruments still make the 44V TLE2141 opamp in a DIL-8 package. Digikey and others have thousands in stock. I recommended it years ago, why use a tiny surface mount opamp that would probably get too hot? The new 140V tiny opamp does not spec its maximum output current when the supply is less than +/- 70V.Besides the Greek and Chinese kits not producing 30VDC at 3A and not being reliable, they might not be made anymore."
},
{
"post_id": "",
"author": "floobydust",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 06:43:56 pm",
"content": "The original 0-30V PSU schematic has D10 and R15 which are needed.You can put a 1N4004 diode across Q4 E-C to protect against output overvoltages (instead of TVS) and it also stops the PSU failing when charging batteries.Lately, the kits are coming with wrong resistor R7 as 47R not 0R47 5W."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 01, 2019, 07:02:14 pm",
"content": "Even though it is nominally 30 V I do not need it to go so high and I am happy to call it 24 or 25 volt PSU. I already have a 24 V transformer, rectifier bridge, filter cap, power transistors and some other components and I would only need to make the control circuit. I want to make it as simple as possible but also design something reliable that can be trusted to work. nothing fancy but definitely reliable and protected.Quote from: Kleinstein on March 01, 2019, 02:22:53 pmKleinstein, thanks for your input. Could you expand on this? I guess it is a matter of disabling the output for a second or two when first connecting the unit so that all voltages have time to settle? This sounds necessary.Quote from: Kleinstein on March 01, 2019, 02:22:53 pmGenerally I do not have the problem of connecting voltage sources to the output of the PSU and I would consider a reverse biased diode in parallel with the output to be sufficient protection. Again, can you expand on this?Quote from: Kleinstein on March 01, 2019, 02:22:53 pmWell, the specified op-amps have a max supply of 44 V and I am planning on using a 24 Vac transformer which would not produce anywhere near that so away goes that zener.Quote from: Kleinstein on March 01, 2019, 02:22:53 pmThis seems to me to be more than is really needed for this type os simple PSU. A simple zener or a zener and a transistor should be good enough. I will study this more carefully.Quote from: Kleinstein on March 01, 2019, 02:22:53 pmI agree. I am going to call it 25 volt and the power transistors and other heat-generating resistors will go on the back, outside the box. I'm thinking \"outside the box\" here."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 01, 2019, 07:08:28 pm",
"content": "Quote from: floobydust on March 01, 2019, 06:43:56 pmYes, easy enough. OTOH, putting that resistor there means a voltage drop so I would like to supply the op-amp with a couple extra volts supply. Maybe, do on the positive rail something similar to what is done on the negative rail to get a couple extra volts. I will think about this. It may be worth it. I'd like to read opinions on this."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 01, 2019, 07:11:29 pm",
"content": "Quote from: kripton2035 on March 01, 2019, 02:30:28 pmIt sounds like kits for sale are not to be trusted and I think by the time we are finished re-designing this it might look very different."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 01, 2019, 07:22:46 pm",
"content": "Quote from: Audioguru on March 01, 2019, 06:41:01 pmAudioguru, thanks for your input. What is your opinion on restoring R15 and getting a couple extra volts to supply the op-amp as I mentioned earlier?Quote from: Audioguru on March 01, 2019, 06:41:01 pmI am not too concerned with the final voltage I can get. If it goes up to 25 Volts I consider it enough. I am making this with used junk parts and I have a couple of 12 Vac transformers from halogen lights. Now they are being replaced with LED lights I have a whole pile of these transformers.I am not interested in buying the kits as they sound like crap but I would be happy to devote some time to finish with a good and reliable design which others can build. I do not want it to go to so many volts or amps. Foremost I want it to be simple and reliable."
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 07:26:42 pm",
"content": "How much does Q4 dissipate when Vout = 1V and Iout = 3A?"
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 01, 2019, 07:33:07 pm",
"content": "Quote from: Kleinstein on March 01, 2019, 05:38:43 pmOK, let us call this project a 25 V PSU. As I have mentioned I already have 24 V transformers so the voltage at the filter cap will not go above, say, 32 V. I realize that maybe with high current demand the output voltage may not be able to go all the way to the max, That is something I can live with. So something like 25 volts at 1 amp, 24 volts at 2 amps, 22 volts at 3 amps is something I can live with.It sounds like the suggested Op-amps go to 44 volts so that should be plenty.I'd like to come up with a totally revised design we can all agree is reliable and well done. If it can use cheap and easy to find components I would prefer that over getting a few more volts out."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 01, 2019, 07:37:58 pm",
"content": "Quote from: rstofer on March 01, 2019, 07:26:42 pmThe answer is \"it depends\". It depends on the collector voltage, which depends on transformer and filter cap. It depends on the output voltage being output. Since the current is divided between two transistors each one is dissipating half but the total still has to be dissipated.Very bad case: collector voltage 33 volts, output voltage 1 volt, current 3 Amp, total power dissipated: 96 W. better have some good heat-sinks!"
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 01, 2019, 07:41:16 pm",
"content": "Quote from: rdl on March 01, 2019, 05:43:36 pmWell, I would say 24 or 25 volts is good enough for general work.Really, going much above 20 volts would require switching input voltages or generating a ton of heat. I would say 25 volts is about the limit with a single supply voltage and is generally enough for everyday work."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 01, 2019, 07:43:15 pm",
"content": "Quote from: Kalvin on March 01, 2019, 02:55:51 pmNo, that is totally out of the question. I am going for \"really simple, cheap, straightforward and reliable\"."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 01, 2019, 07:59:44 pm",
"content": "Quote from: Kleinstein on March 01, 2019, 04:20:07 pmSo, assuming a 24 volt transformer, so about 35 volt max input voltage, what are the options for common, cheap, through-hole op-amps?"
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 08:22:02 pm",
"content": "Quote from: soldar on March 01, 2019, 07:37:58 pmI must have missed that, the schematic in Reply #13 seems to show just one pass transistor. The original schematic in the OP shows two pass transistors. Either way, it's a lot of heat and that's why these projects turn south.There is a reason why transformers for bench PSUs have multiple taps and relays."
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 08:27:14 pm",
"content": "Quote from: soldar on March 01, 2019, 07:59:44 pmGiven that you will be designing a new board, why limit things to through-hole? Assuming that SMD components can meet the output current and dissipation requirements.As to high dollar op amps, what difference does it make for a one-off power supply? $1 versus $10 is pretty insignificant when compared to the total project cost. OTOH, if the goal is to commercialize the design, BOM costs matter."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 01, 2019, 09:09:54 pm",
"content": "For a one off unit cheap OPs are not that important, but even if not looking for the price the choice of easily available DIP8 OPs with at least a 40-44 V supply is not that large. Ordering from Mouser or similar could be a hassle from some countries.Many audio OPs like NE5534, OPA604 would need more current from the negative supply. So possible but not not really attractive.The right version of the 741 would be an option - though slow. The OP27 could also work - though high in supply current. The mentioned MC34071 can be tricky to get in DIP. So an SO8 - DIP Adapter may be needed.The TLE2021 might also be an option - though also difficult to get in dip.Starting with 24 V AC, the positive supply may reach some 35 V worst case. In addition one needs a negative supply for many OPs - especially the TL081 in the kit really needs some -3 V headroom on the negative side for the input common mode. Even with an extra diode to limit it, this could need some -4 V. Single supply OPs could work with less negative supply. So if single supply one could get away with a slightly lower supply rating.With 24 V AC the circuit would likely not give up to 30 V out - worst case it's more like 26 V depending on the OP. So even with a 44 V rated OP one would be near the edge with 28 V AC that may be needed to really get 30 V out.With a slightly modified circuit one could a a few small improvements, already discussed in other threads:1) limit the worst case voltage with something like a Zener. So less headroom needed for high mains2) Add extra filtering for the OP, so that it would see less drop due to ripple. This can reduce the dropout voltage and thus alow a lower transformer voltage. It could also safe a little on the filter cap - which is still too small for 3 A.3) reduce the voltage for the other 2 OPs (they only need some 15 V)this can also speed up the onset of CC mode4) add back the protection against a peak on turn on / off5) maybe add some fixed fast current limit as a fallback for transients6) fix the shunt layout7) Limit on how far negative the set voltage can be drawn done by the CC mode regulator: just a diode to ground as a hard clamp.Even the modified circuit would like an OP that can stand some 35 or maybe 40 V depending on the common mode and output range."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 01, 2019, 09:37:40 pm",
"content": "Quote from: rstofer on March 01, 2019, 08:27:14 pmThrough-hole is much easier for beginners, repairs, etc.You are right that for a one-of build the cost of the op-amp is trivial but I am just thinking of making it a good design in every way and that is one aspect.I am looking at a commercially-bought bench PSU which I reverse engineered when it failed and it has a single LM723 which includes voltage reference, current limit, etc. This unit switches transformer windings to limit transistor dissipation but I am thinking I could copy the schematic removing the transformer switching part.Another thought is that secondary voltages which require very little current can be obtained using transformers from old wall warts. I have several crates of these."
},
{
"post_id": "",
"author": "floobydust",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2019, 04:33:48 am",
"content": "These 0-30V 0-3A PSU threads always seem to fizzle out because the requirements are never nailed down.People want it all - low cost, reliable, high performance, easy build.But this is unrealistic starting with a $5 kit that is based at the absolute max. ratings of many parts, as a chinese design prone to smoke.So right off the bat, people have to add parts and cost just to get the PSU reliable and meeting its original specs, capable of running more than a few seconds at rated output.Audioguru did fix things by adding an additional pass transistor and lowering Vcc for the op-amps.I would add power-up/down overshoot & backfeed protection and limit Q2's dissipation to make it dependable, like the odd Mastech and Manson models.For high performance I use an auxiliary transformer and regulated supply for the op-amps.To keep things cheap, change to rail-rail op-amps or one's with PNP diff amp. and consider a Sziklai NPN power transistor configuration."
},
{
"post_id": "",
"author": "not1xor1",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 02, 2019, 06:06:24 am",
"content": "Quote from: soldar on March 01, 2019, 09:33:40 amI think that the only possible comment for this PSU design is:I wonder how many ms can it survive Bob Pease's file test"
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 02, 2019, 08:47:43 am",
"content": "Quote from: floobydust on March 02, 2019, 04:33:48 amYes, I have come to realize it's the \"design by committee\" phenomenon. In the end each one has to take the initial design and tweak it for his own needs and desires.I am attaching the schematic as I was redoing it. No great changes, just re-organizing it to make it simpler to analyze and understand. The more I think about it the more I think I won't go ahead with the project. The center op-amp which provides the reference voltage can easily be eliminated and replaced with a few discrete components. The right hand op-amp which provides the voltage control can also very easily be replaced with a few discrete components. The current sensing resistor dissipates a bit too much heat when it can be replaced by a much lower value and sensing with a current mirror as I have done in the past. Still, it is fun analyzing how it works.Many people seem to build a circuit they do not understand, just to save some money, and then go crazy when it does not work, sometimes by bad design but most often by mistakes made when assembling it. For me most of the fun is analyzing and improving circuits."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 02, 2019, 04:00:20 pm",
"content": "I am looking at a bench adjustable power supply which I built some twenty years ago or more. It is very similar in concept but only uses discrete transistors. Three transistors and few other components do the voltage regulation and reference voltage which takes two op-amps in the circuit we are considering. Now, maybe some characteristics are better with op-amps but you cannot compete with the simplicity of the discrete transistor schematic."
},
{
"post_id": "",
"author": "floobydust",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2019, 07:30:23 pm",
"content": "It's a good building block for voltage control. The pass transistor config (double or triple Darlington/Sziklai) is what I think is best.But... discrete transistor solutions fizzle out doing the adjustable current-limit feature. It's always difficult to measure mV without drift and linearity problems, more so on the high side (if you use the sense (emitter) resistors). I haven't seen any good variable current-limit solutions with discretes or even the LM723 PSU's."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 02, 2019, 08:17:10 pm",
"content": "Quote from: floobydust on March 02, 2019, 07:30:23 pmhmmm... I have a commercially built 30V - 5 A variable power supply which uses LM723 and the current limiting works fine. I also have several self-designed and built units with discrete components and they also work fine. Where do you find the problem?"
},
{
"post_id": "",
"author": "floobydust",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2019, 10:06:04 pm",
"content": "LM723 has a current limiter for short-circuit protection, it's not adjustable with a potentiometer because it's a simple transistor E-B junction. Changing sense-resistors with a rotary switch is something my 1978 Radio Shack lab dual bench supply does lol.This is where the antiqueMC1466Ldoes better, but it needs a dedicated floating rail. It's almost discrete - two diff amps and some glue.If you have seen a way for PSU adjustable current-limiting without a negative rail or dedicated floating rail, let me know.On the chinese kit, I hate the -ve rail and the need for the V ctrl op-amp to run at the top rail while the I ctrl op-amp runs on the low-side. I can find away around it all, but haven't built it to prove it works.So far, the only low cost idea is a low-side sense resistor and op-amp with PNP diff amp inputs, like LM358 (too slow) or MC34071 looks ok, for inputs that can go to ground. This is staying with cheap op-amps, not the ones worth twice the entire kit price."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 02, 2019, 10:47:00 pm",
"content": "Quote from: floobydust on March 02, 2019, 10:06:04 pmI see what you mean. Well, yes, it is a limitation and I have used different work-arounds. As you say, a separate floating rail is one way. That is what commercial Chinese PS does.What I usually do is have a fixed resistor and a pot in parallel so it allows a certain range of adjustment but, yes, it is not the best. I have never thought of switching resistors but it is not a bad idea. The pot in parallel allows continuous adjustment.What I have used with good results is a current mirror configuration. That requires a very low resistor value to produce a significant signal so that the heat dissipation in the resistor is kept low."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 03, 2019, 08:00:04 am",
"content": "Quote from: floobydust on March 02, 2019, 10:06:04 pmCome to think about it, switching resistors seems like a very bad idea because you are left with no resistor while switching.Now that I think about it, many years ago I did something like this but it only had two ranges, high and low, so the switch only connected and disconnected a second resistor in parallel. The current indicating galvanometer instrument was connected to the same resistor and so the power supply had two ranges, 2A and 0.2A. In the low 200 mA range the instrument always indicated just under 10 mA, even with no load connected, because of some internal current in the PSU.So I am coming to the conclusion that the basic voltage regulation can be done with discrete components or with an LM723 or other op-amp and the current regulation can be done with discrete components but it means using several transistors and so this part may be done with an op-amp to make it with fewer parts. The op-amp for the reference voltage I think can be eliminated.The advantage of using an LM723 is that it includes the voltage reference.Regarding using secondary floating voltages, I understand the desire to avoid them in commercial products where cost is a consideration but for one-of home-brews I have several crates filled with wall warts that I would be happy to put to some use."
},
{
"post_id": "",
"author": "not1xor1",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 03, 2019, 08:26:15 am",
"content": "Quote from: soldar on March 03, 2019, 08:00:04 amis it so hard to conceive a resistor permanently connected and just switch other resistor in parallel to that?One might even use low Rdson MOSFETs for switching a binary network of resistors.In any case that kind of current limit depends both on Vbe drift, temperature and the output voltage so a few milliohms of drift would be the least of the problems."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 03, 2019, 10:34:43 am",
"content": "This is something which works nice at least in the simulation. Experienced users may try.The R5 is actually an 1k pot/trimmer where you can set the current limit from 20mA to full in pretty linear way.The zener and 1k resistor is not related to the current limit circuitry (you may remove it).The Q3 feeds a constant current (around 800uA) into the base of the internal CL transistor. That current is being \"balanced\" against the current set by the R5, sensing the 0.56ohm shunt resistor.The 1n4148 with its series resistor have been selected such the scale of the R5 pot is somehow \"linear\".EDIT: this is from my simulation in adifferent thread:Code:R5 (w/ 100ohm in series) I_shunt_CL (0.22ohm)1000 0.82mA900 22mA800 157mA700 315mA600 503mA500 732mA400 1.02A300 1.37A200 1.75A100 2.14A0 2.53A"
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 03, 2019, 10:43:08 am",
"content": "Switching the current limiting shunt is not that simple, but can be done. Just a 2 nd resistor in parallel would add the switch / MOSFET resistance to the lower shunt - this can be a problem with a 0.1 Ohms or similar shunt. Given that in a 723 type current limit the accuracy is poor anyway, a MOSFET would be acceptable.The better way would be to have the 2 shunts in series and have a fixed path to read the voltage. The switch would change the path of the current, going one way or the other. Ideally one would need a make before brake type switch. If not, a diode could help.In the original circuit the OP for the reference can be eliminated, but a cheap OP (LM358 class) is not a bad solution to keep the current through the reference constant. This can help as the current through the reference would also end up to go through the shunt. The OPs for the reference and current regulation don't need a high supply and can be relatively simple types - down to the LM358 level, though the current control may like a more precise and maybe slightly faster one. Its already way to much text about possibly saving a 20 cent OP."
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 03, 2019, 05:17:28 pm",
"content": "Quote from: not1xor1 on March 03, 2019, 08:26:15 amIt might be easier to use two or more very small resistors in series and then just short them out to change ranges. No make-before-break required. Of course, the switch will need an adequate current rating."
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 03, 2019, 05:59:45 pm",
"content": "I think if you are going to make the old Greek kit or a Chinese copy then the proper opamp that is still available should be used and its input offset adjustment should be correct like this:I also got it wrong, this correction is as per the datasheet:"
},
{
"post_id": "",
"author": "jaycee",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "March 03, 2019, 06:33:23 pm",
"content": "Having recently built a 0-18V 0-1A bench supply, and plans to build a 0-30V 0-3A, here's my five cents on the matter.First off, powering the opamps from the same supply as the raw supply voltage is fraught with issues. The best way to alleviate these problems is dont do that - most linear bench supplies have a separate supply voltages for the opamp, with the midpoint tap connected to the main regulator's output. This is a bit of a headf*** at first, but it works extremely well - i believe it was HP/Harrison Labs who came up with this \"Regulator within a regulator\" topology.This may sound complicated because you need the extra transformer tappings, but you can always use a second small transformer, it doesnt need to be powerful, so some tiny 5VA thing from an old digital bedside clock works very well. In fact that is exactly what I used when I was prototyping my supply... and I could have built the end unit like that too, I just happened to find a suitable transformer core that I could re-wind with custom secondary taps.Tap switching is well worthwhile doing to vastly cut regulator dissipation. Use a 2x18V transformer for 0-30V (remember it sags vastly under load so you need quite a bit of overhead), connect the windings so you have 0-18-36, and you can easily arrange a circuit which can switch between the 18V and 36V AC taps.I've attached the main schematic of my power supply. It works well, doesnt oscillate or do stupid things under load, and uses only bog standard TL082 opamps. I haven't shown the front panel board, but it is only metering and display. The controls are 10K linear pots wired to CN2 with their top wired to VREF, the bottom wired to AGND, and the wipers to V_FINE, V_COARSE, and I_CONT respectively."
},
{
"post_id": "",
"author": "jaycee",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "March 03, 2019, 06:41:23 pm",
"content": "Here's a few pictures I took during prototyping it. As you can see, there's a tiny transformer with 9-0-9 secondaries. This provides enough for +/- 5V rails, and the raw rectified voltage is good enough to switch a relay with."
},
{
"post_id": "",
"author": "floobydust",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 03, 2019, 08:56:53 pm",
"content": "Using separate (floating) rails for the op-amps is best, it gets rid of almost all of the problems but adds cost and parts: additional small power transformer, fuse, bridge, filter caps, voltage regulators etc. The extra $10 might not be desirable, on a $5 kit.It also makes new issues:When you switch power on/off, the op-amps' rails and reference may or may not collapse/rise before the main DC voltage. Power-off under a heavy load, the main DC falls before the opamps & reference, but under a light load the main DC can stay up after the op-amps' rails first dropped off. Power on, you have to scope the rails rise and make sure the op-amps' rails come up ahead of main DC.Either way, there is an unpredictable output overcurrent/overvoltage spike to look after.TL0xx series JFET input op-amps exhibit phase-reversal at low common-mode voltages, below 3-4V above the negative supply.These $0.10 op-amps do a \"surprise\" which can smoke your load with overvoltage or overcurrent when you weren't looking.So I'm not sure about the mod lowering the -ve rail from -5.1V to -1.4V and deleting the UVLO, not introducing a new problem.edit: not relevant with mod's different op-ampTLE2141"
},
{
"post_id": "",
"author": "jaycee",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "March 03, 2019, 09:11:53 pm",
"content": "I dont have any issues with undervoltage on my build, but... I do have the OUTPUT_ON connected to a microcontroller on the front panel, which will drive the output off when power sinks too low such that it's brownout detector puts the processor into reset. It would be trivial to make OUTPUT_ON controlled by an \"AC loss\" detect circuit too.Phase reversal also shouldnt be a problem here, as it's unlikely the opamps will ever see anything near their rails.. however I used TL082 because I had them... I suspect any opamp would work just fine, though the compensation might need adjustment. I think I actually prototyped it with a 4558 first as I had it to hand.The cost of the additional small power transformer (not a cost at all if you can wind your own transformer) + associated bridge diodes, filter caps and regulators are small when the end result is a much better power supply."
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 04, 2019, 12:11:02 am",
"content": "Quote from: floobydust on March 03, 2019, 08:56:53 pmThe datasheet for the TL081 with phase reversal shows its input common mode range is 5V above its negative supply, the newer TLE2141 without any phase reversal has its range all the way down to and including its negative supply.One TL081CP at Digikey costs $0.53US today but in China a copy or reject might cost $0.10US. The TLE2141CP must be ordered at a minimum of 400 at Digikey but they sell one TLE2141IP at $2.09US today.One TLE2141 opamp in the 0V-30V circuit needs a -1V negative supply only because its output must go a -0.7V doped voltage drop less than the circuit's 0V when current limiting a shorted circuit output. Then its positive supply is safe to +42.7V."
},
{
"post_id": "",
"author": "floobydust",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 04, 2019, 01:48:11 am",
"content": "fixed - I missed the change toTLE2141in OP for your mods.Trying to improve this $5 chinese kit- without doubling its costs, is a good challenge. There is no other kit out there for beginners, aside from LM317 kits but no adjustable current-limiting feature in them.This PSU kit uses no op-amp IC's, just four TL431'shttps://www.eevblog.com/forum/beginners/cheap-chinese-adjustable-lab-power-supply-kit-on-ebay-(-3ag1-xiaolin-)/msg1412511/#msg1412511Try to do adjustable current-limiting with a TL431, for fun as a design puzzle.Voltlog #155found it has stability problems, CC oscillates."
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 04, 2019, 01:53:56 am",
"content": "\"Cheap\" usually means \"poor quality\"."
},
{
"post_id": "",
"author": "floobydust",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 04, 2019, 08:28:20 am",
"content": "I didn't realize this chinese kit has been out there for 10 years!1000's of postings across the Internet trying to improve it, or suggest throwing it in the garbage. It's some form of turd that keeps on smelling.I find it sad one weak design can proliferate and the rest of the world cannot be organized well enough to fix it. Communism++For OP, perhaps check CC mode. It looks like the -1.4V rail adds hum to CC mode which brought about a change to LM337T:Paul's DIY electronics blogis at revision 6 but 5 looked more complete, sch attached.I found a higher rev (original mods) schematic with the shutdown transistor left in.late edit: I found theoriginal 0-30V 2mA-2A PSU circuit, Practical Electronics Nov. 1978.Project on pg. 41 but big 12MB pdf:https://americanradiohistory.com/Archive-Practical-Electronics/70s/Practical-Electronics-1978-10.pdf"
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 04, 2019, 09:29:38 am",
"content": "The OPs for the current regulation and reference do not need to be powered from a high supply - the modified versions often include the series zener or a 7824 regulator. So it is only the OP for the voltage control, that needs to have a high voltage swing (e.g. TLE2141,MC34081,OPA604,...).It is funny to have this old kit still around, with so many points that should be fixed or made better with not that much effort.Using a separate floating supply for the regulator changes the circuit completely, going from a classical regulator with a low output impedance power stage to a low drop type regulator with a current setting output stage. The floating regulators has advantages (less voltage lost, usually better current control and flexible in the voltage range), but it also has a more complicated compensation for the voltage control and still often slower, unless tuned very well."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 04, 2019, 12:32:32 pm",
"content": "Quote from: floobydust on March 02, 2019, 10:06:04 pmA negative supply isn't needed, if single supply op-amps are used. Here's a proof of concept, based on a Howland current source, with voltage limiting. I haven't simulated the transient response, which is probably horrible. U1 is shorted by Q3 and current limits, when in voltage mode, which some may not like, but that can be avoided if necessary. The Darlington pair could be driven by a current mirror based source, with each op-amp diode AND'd pulling it down.I don't see the problem with the negative rail. I'd probably use the OP07 run off regulated +34V and -3V, derived from a 30V transformer."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 04, 2019, 01:23:05 pm",
"content": "Update: The stability analysis.."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 04, 2019, 02:24:52 pm",
"content": "And some minor resistor's values changes and notes..Update: Added V/A(out) as a function of R_Load."
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 04, 2019, 03:25:06 pm",
"content": "I first saw the original Greek kit 15 years ago at Eletronicslab.com where its problems were discussed in the forum there. Many parts were overloaded and failed.Paul's version will not produce 30V at 3A because his 24VAC transformer voltage is as low as the original Greek kit:1) 24VAC has a peak of +34VDC which is reduced to +32V at 3A by the bridge rectifier.2) Ripple from the small filter capacitors drops 2V to +30V.3) The voltage amplifier TLE2141 opamp maximum output drops 1.6V to +28.4V.4) R15 that is not needed drops 2V to +26.4V.5) The driver transistor drops 1V to +25.4V.6) The output transistors drop 0.5V plus 0.3V for their emitter resistors to +24.6V.7)At 3A the 0.47 ohms current sense resistor drops 1.4V to +23.2V.If the opamps and transistors have maximum spec's then the maximum regulated output might be +26V.The negative supply is not needed for the voltage amplifying opamp since its output can go down to 0.5V above its negative supply that can be the circuit's 0V."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 04, 2019, 03:31:08 pm",
"content": "And finally the stability with a capacitive load.15deg phase margin - it needs to play with compensation.."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 04, 2019, 03:55:27 pm",
"content": "One could reasonably simple modify the kit circuit to work essentially without a negative supply. The main point they use the negative supply is for the current control to pull down the set voltage alle the way to zero. So if one shifts the zero point for the set voltage to some +2 V there is no more need for the negative supply. So the feedback divider would go towards this auxiliary 2 V instead of GND and the set voltage too.There is a slight downside that the output would not drop all the way to zero without a minimum load - depending on the minimum load circuit there could be some 50 mV or so as a minimum. To really go to zero the minimum load would need the negative supply. So the need is back, but the regulator could still work without it, just not below some 100 mV with no load.The main limitation of the circuit is that the output OP needs to make the full voltage swing and a little more voltage lost. The good point is the the voltage compensation can be simple."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 04, 2019, 04:29:39 pm",
"content": "Quote from: imo on March 04, 2019, 03:31:08 pmThe first iteration had a gain of 10, but I changed it to 12V, because 2.5V is a common voltage reference: there was a reason for that seemingly odd number.You'll need a higher input voltage than 30V to get 30V out, probably at least 34V.Try simulating the transient response. Change the load current from 0A to 1A and 1A to 3A and back to zero again. If you use a current sink, then don't forget to click \"This is an active load\" in the parasitic properties section, otherwise it will try to force the output to sink current, when the output transistors are off.Another option is to use an if function with the load resistor.It works like the Excel.if(condition, value_if_true, value_if_false)Suppose you set the value of RL to:R=if(time>10m&time<20m,1,10)It would set the value of the load resistance to 10Ohm and change it to 1R between 10ms and 20ms.See example attached. Note the current and voltage spikes. I imagine the OP07 will be worse, then the ideal op-amp model I used with GBW=10Meg Slew=10Meg. You're right, adding a parallel capacitor would reduce the voltage spikes but make the current spikes worse. A series inductor would do the reverse: better current regulation at the expense of voltage. Care needs to be taken to avoid oscillation.I've noticed the current regulation is poor for lots of bench supplies, which are optimised for voltage. I've toyed with the idea of building my own, with a switch to select between better voltage or current regulation."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 04, 2019, 05:23:36 pm",
"content": "Current regulation is often not that good for different reasons:One is having a relatively large capacitor at the output. This limits voltage overshoot, but can add significant transient extra current.Another point is that a good shunt is expensive - so they tend to use a relatively low value shunt to limit the power dissipation and self heating. Still heating can be a problem in cheap supplies. Without range switching it get's tricky to measure small currents with a shunt made for 3 A.Also current regulation is often considered less important - more like a way to protect the supply and maybe circuit.Many commercial supplies use the floating regulators, that are in principle quite good in current regulation, except for the output capacitor.So there is not much option to switch the supply to a mode better for current regulation, as the output capacitor is required to get stability.In principle one could use a faster, tighter tuned controlled loop for the voltage control, so that less (and with well defined ESR) capacitance at the output is sufficient. So it would be more like improving voltage control to alow a smaller capacitor and this way faster current regulation. Adding range switching would be another step. I don't see much need to really switch the regulator to a separate mode - maybe add an optional addition capacitor to the output if needed to support the voltage regulation.The other point is a delay before the current liming sets in - this sometimes is desirable, but sometimes not. So this could be a switchable point.The circuit as shown, with an emitter follower at the output tends to produce current spikes from the regulator, as it takes some time for the CC regulator to kick in and the OP has to slew down - which essentially limits the rate on how fast the voltage can drop. It can work with less cap at the output, but there is a kind of simulated capacitance."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 04, 2019, 08:39:32 pm",
"content": "Quote from: Kleinstein on March 04, 2019, 05:23:36 pmYes a capacitor on the output doesn't help with current mode, but I think a glitch when switching back and fourth constant current and voltage is inevitable. When in CV mode, the CC amplifier will be trying to force it to limit the current and vice versa. Whether there's a voltage or current spike, depends on the design. Even if the rapid change on the output of either error amplifier can be greatly reduced, there's still the issue of the output having to rapidly change from a very low, to high impedance and back again.Yes, whether allowing current surges or not depends on the application. Recently I've being using a bench supply to power some LEDs and have had issues with huge current spikes at power up. Fortunately it didn't damage the LEDs, but it isn't good. It isn't the output capacitor because it should be discharged when the power is applied. I will try connecting a short circuit, in parallel with the LEDs, during power up."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 04, 2019, 10:27:14 pm",
"content": "The power up phase is a different issue from the normal regulation. In better supplies there is some extra circuit to keep the output off before the supply to the control is fully there and when the supply breaks down (turn off - which can be the more difficult case to detect). In the simple form this could be a way to disable the output if the raw voltage is below a certain level, needed to operate the OPs.The simple circuits have usually quite some glitch when switching between CC and CV mode, because the non active regulator will often run all the way to it's limits. In normal control theory this is call windup and in better regulators handled separately. This is not standard for lab supply circuits, but it is possible to add this to the circuit. With some extra circuitry the change over can be quite smooth.The circuit from the start of this thread uses a slightly unusual form, as the CC mode reduces the set voltage and thus works with both regulators in series. So there would be no (or only a small) spike when going from CC to CV mode as the voltage regulation is always active."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 04, 2019, 10:59:34 pm",
"content": "Quote from: Kleinstein on March 04, 2019, 10:27:14 pmI'm interested to see how the seamless switching between modes works.The original draft of my Howland current source based design did a similar thing to the circuit at the start of the thread, except it was the CV amplifier reducing the CC amplifier's set current. I only changed it to challenge the myth that a negative power supply is required, otherwise I probably wouldn't have posted it, since it was just a quick sketch, rather than a complete design."
},
{
"post_id": "",
"author": "not1xor1",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 09, 2019, 06:31:33 am",
"content": "Quote from: Zero999 on March 04, 2019, 12:32:32 pmI ran a few tests on variations of this circuit with LTspice.The circuit might work without negative supply with a LT1013. It has a better phase margin with low loads if you use 100k/470k resistors.The main drawback is the resistor tolerance. Even just 1% of umbalance would cause about 15% of current variation vs. load value (or output voltage if you prefer). 0.1% tolerance resistors would provide about 1.7% current variation which might be acceptable in a cheap DIY PSU provided that aging and temperature drift do not make it much worse.BTW the output current can be calculated like:I = (Vref * Rhot) / (Rsense *Rgnd)whereRhot is the resistor connected to the emitter/outputRhot are the 2 resistors connected betwen the BJT emitter/output and the opamp inputs, Rgnd are the resistors which connect the opamp inputs to ground... and Rsense... guess it."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 09, 2019, 09:34:20 am",
"content": "Quote from: Zero999 on March 04, 2019, 04:29:39 pmI think this is natural for starter, basic power supplies because they are used mainly in voltage mode and the current limiting is just a rough setting for protection and is not as critical as the voltage setting."
},
{
"post_id": "",
"author": "Tek Tech",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "April 24, 2019, 12:41:34 am",
"content": "Quote from: Kalvin on March 01, 2019, 02:55:51 pmThat's a brilliant suggestion! Do you have any idea how to make it relatively simply?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 24, 2019, 07:41:39 am",
"content": "Quote from: soldar on March 09, 2019, 09:34:20 amPerhaps in the past but nowadays lab PSUs are often used to power LEDs, in which case the constant current setting is more critical."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 24, 2019, 10:36:29 am",
"content": "A good current regulation is not often required and it also adds quite some costs for the shunt. To get good resolution at low currents the shunt can not be very small and with more drop the self heating of the shunt can limit the stability of the current regulation.Another point is that quite often the capacitance at the output is quite large and this makes the dynamics of the current regulation not that good."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 25, 2019, 10:39:38 am",
"content": "Quote from: Kleinstein on April 24, 2019, 10:36:29 amI would quite happily pay good money for a lab power supply with both decent voltage and current regulation. I don't demand anything fancy, just reasonable current regulation (5%) from 30mA to 3A, without high current pulses, more than double the setting.If it's well-designed, an output capacitor shouldn't be necessary. Any circuit which needs a power supply, with a low impedance at high frequencies, should have a decent decoupling: the transient voltage response, of a lab PSU, isn't as critical, as many believe it to be."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 25, 2019, 03:15:39 pm",
"content": "The output cap is there for 4 reasons:1) some capacitance could be needed for the stability of the CV loop (usually not very much though), especially if made to also tolerate a larger capacity.2) To avoid to much voltage drop on pulsed load the capacitor can reduce the drop, though making the time longer. Kind of having the cap to cover up a slow regulator and making it even slower3) To reduce possible voltage overshoot on transients (turn on, CC to CV transition)4) for the stability of the CC mode with inductive loads (this usually does not need much).Especially point 3 may need quite some capacitance.A very fast acting current limit can also be quite confusing as it may be too fast for some applications."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 25, 2019, 07:57:36 pm",
"content": "Oh I know why it's there. I just think it can be greatly reduced, if not eliminated.Local decoupling (which you should have anyway) will overcome the issues with pulsing and overshoot for sensitive loads. Seriously, who connects a microcontroller up with no decoupling? Even with the capacitor, inside the PSU, there can be spikes due to lead inductance.I think a switch to select between optimal current and voltage modes. One day I might get round to putting together a proper design."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 26, 2019, 06:08:17 am",
"content": "The usual circuits don't have much anti-windup for the regulators. This gives some extra current peak when going from CV to CC mode - this may be not that bad and even could be a good thing in some cases. However for the CC to CV transition this gives an extra charge pulse and thus possible voltage overshoot - a larger cap at the output is the easy way to limit this overshoot. Here one can not really rely on the cap at the circuit itself. In addition it does not look good if there is a 5 V overshoot without an extra cap at the output.Just for stability a capacitor in the 1 µF range could be sufficient for many circuits.I agree that the transients in CV mode are not that important, but a fast regulation is also the obvious way to reduce the capacitance at the output."
},
{
"post_id": "",
"author": "wandows",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "July 28, 2022, 05:56:56 pm",
"content": "Hello everybody! I would like to count on the help of friends!!!In the offset adjustment, my power supply has the output voltage >= 32.9V, and does not reduce to 30V.Any tips on what can be done to solve this problem?"
},
{
"post_id": "",
"author": "antoniodv",
"author_rank": "Newbie",
"is_op": false,
"timestamp": "September 07, 2023, 08:32:14 pm",
"content": "Hi everyone.Thank you all for the information you have shared.Inspired by the best electrical diagrams of linear power supplies made in the past and available online, I digitized them by adding a display microcontroller and DAC to have everything in a single PCB.As you can see in attached pdf , for the final stage I used the K7200 scheme.The firmware for ATtiny3216 is also ready.I'm waiting to complete the final PCB, all tests went well. I just doubt the voltage peak at shutdown I would like to remove it. Advises?"
},
{
"post_id": "",
"author": "MrAl",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 07, 2023, 11:59:38 pm",
"content": "Hello there,My question is mostly for the original circuit.Why use a circuit so complicated? What are the specs and do the specs warrant such a complex circuit design?If it was 30 amps I could see it, but 3 amps, that's nothing these days.As to the newer circuit, still a bit complex. What are the specs.Maybe a related question:What specs are you looking for."
},
{
"post_id": "",
"author": "xavier60",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 08, 2023, 12:05:05 am",
"content": "Maybe the -3.3V is discharging too quickly. Im curious about the CV loop's stability?The design that I like, doesn't need a negative control rail,https://www.eevblog.com/forum/beginners/lm324-power-supply-with-variable-voltage-and-current/msg3582664/#msg3582664"
},
{
"post_id": "",
"author": "MrAl",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 08, 2023, 08:13:47 am",
"content": "Quote from: xavier60 on September 08, 2023, 12:05:05 amHi,I've used the LM358 and LM324 variety of op amps for these things, but in one power supply I wanted faster response so I went with an IC that has a similar pinout but has a much faster slew rate."
},
{
"post_id": "",
"author": "xavier60",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 08, 2023, 08:49:22 am",
"content": "I used the TLC072 in my build of the deign I linked. It gave faster transition from CV to CC during abrupt overloads."
}
] |
2025-10-17T16:48:47.230295
| 77
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-30v-2ma-3a-dc-ps-kit-messed-up!/
|
0-30V 2mA-3A DC PS Kit - Messed Up! - Page 1
|
[
{
"post_id": "",
"author": "kiwizz",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 23, 2018, 11:19:20 am",
"content": "Hi All,My first post here so be niceplease.I spent an hour or so meticulously putting together this kit:https://www.aliexpress.com/item/0-30V-2mA-3A-Adjustable-DC-Regulated-Power-Supply-Diy-Kit-Short-Circuit-Current-Limiting-Protection/32814203124.html?spm=2114.search0204.8.24.77151dbKM88qE&priceBeautifyAB=4after which, I wanted to hook up a voltage meter and an ammeter (https://www.aliexpress.com/item/1pcs-Top-Quality-5-bit-DC-0-0000-3-0000A-Red-LED-Display-Digital-Ammeter-amperimetro/32640299154.html?spm=a2g0s.9042311.0.0.QEKCjh)Once I had connected these, and added a DC motor to the DC out - I powered the unit on and something or multiple somethings started smoking. Now the unit can no longer adjust the voltage - its 'stuck' at 30v DC out. I re-read the installation instructions for the ammeter and it said to connect after the DC load, whereas I connected it before the load. I'm not sure this would have caused the problem.I've attached the circuit diagram for the unit (does not include what I added). Here's how I connected things:24v 'fan' output (+) --> ammeter + (to power the unit, not the current measuring part)24v 'fan' output (-) --> ammeter - (to power the unit, not the current measuring part)PS DC OUT (+) --> ammeter (+) && PS DC OUT (+) --> voltage meterammeter (-) --> DC motor (+)DC motor (-) --> PS DC OUT (-)So essentially the voltage meter is connected in parallel across the (+) and (-) of the DC out, while the ammeter and DC motor are connected to the same output in series.I disconnected everything after it smoked a bit so I can't be 100% this is how it was connected, but I'm pretty sure it was. One thing I noticed is that the ammeter display started flickering and the DC motor didn't start moving when I increased the voltage (just before smoking). Any suggestions would be greatly appreciated. A friend of mine suggested buying a new kit (they are pretty cheap) but I am curious as to what went wrong and would like to repair if possible.Cheers!"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 23, 2018, 12:02:30 pm",
"content": "That kit is notoriously buggy.It's a classic, cheap Chinese kit. It won't meet its specifications and the op-amps are powered from too higher voltage. At worst it'll smoke, at best it'll just be unreliable. Here are some threads where this has been discussed previously.https://www.eevblog.com/forum/beginners/bangood-psu-enhancements/msg897523/#msg897523https://www.eevblog.com/forum/beginners/poorly-designed-kits/msg1314404/#msg1314404"
},
{
"post_id": "",
"author": "Microcheap",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 23, 2018, 01:51:16 pm",
"content": "Looks like that Q2 and/or Q4 are gone, check them and replace it if necessary. Both must be mounted on a good heat sink.I assembled my power supply based on this project more than 8 years ago when I started with electronics, and despite the well know e extensively discussed issues with the design, it has served me well that long. I had to change those transistors 2 or 3 times but apart from that it works well if you are aware of its limitations."
},
{
"post_id": "",
"author": "zvonex66x",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 23, 2018, 02:32:33 pm",
"content": "Think that U2 is blown... if u want i will upload schematics of my power supply... it's very simple and very good PSU, useing standard TIP3055 tranzistors as output regulation."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 23, 2018, 03:40:21 pm",
"content": "Quote from: Microcheap on January 23, 2018, 01:51:16 pmI'm glad you find it useful, but to me and perhaps, most people, replacing two transistors a few times in 8 years, would be unacceptable. What's worse is transistors have a nasty habit of failing short circuit from emitter to collector, which would result in the full voltage on the reservoir capacitors being applied to the load, causing destruction, if it can't handle 40V.Quote from: zvonex66x on January 23, 2018, 02:32:33 pmThat wouldn't be surprising, since the TL081 is only rated to 36V and this circuit can subject it to 40V or more. You could replace it with another op-amp, rated to 44V.Here's another thread, which discusses the shortcomings of this design.https://www.eevblog.com/forum/beginners/im-confused-about-power-supply-for-op-amps/msg932766/#msg932766"
},
{
"post_id": "",
"author": "Cliff Matthews",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "January 23, 2018, 04:31:01 pm",
"content": "Another threadhttps://www.eevblog.com/forum/beginners/bangood-psu-enhancements/"
},
{
"post_id": "",
"author": "abraxa",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 23, 2018, 04:58:18 pm",
"content": "A linear regulator being fed with 32V? That's gotta smell when using this to supply a 3.3V load - even at 1A, especially at 3A. ~70W of power dissipated in heat.Quote from: kiwizzWhat's that fan output, btw? Was it AC or DC?"
},
{
"post_id": "",
"author": "Calambres",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 23, 2018, 05:08:26 pm",
"content": "Quote from: Hero999 on January 23, 2018, 03:40:21 pmCan you be a little more specific?... what op-amp?"
},
{
"post_id": "",
"author": "Microcheap",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 23, 2018, 06:43:51 pm",
"content": "Quote from: Hero999 on January 23, 2018, 03:40:21 pmI totally agree with you, for me nothing is worse than not be able to trust your equipment while working in a project. But for the purpose that I built it, that was to start learning something, it was useful. And to be honest, I got to the conclusion that with the prices of a power supply today, I don´t think that even worth it to build your own. When you add the costs of components, transformer, enclosure, connectors, display and so on, you end up spending the same or more than a off the shelf PSU with better performance.Quote from: Calambres on January 23, 2018, 05:08:26 pmI think he refers to the TLE2141.Improvements to this project had been extensively discussed in this and other forums:http://electronics-lab.com/community/index.php?/topic/26825-0-30-vdc-stabilized-power-supply/http://electronics-lab.com/community/index.php?/topic/40835-0-30v-0-3a-latest-data/Quote from: abraxa on January 23, 2018, 04:58:18 pmI don´t own the Chinese version of this board, but as far as I understand, it has an auxiliary 24V DC output to connect a fan and the OP is using it to feed his meter."
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 23, 2018, 07:00:21 pm",
"content": "Oh, that circuit. I do not understand why it is so popular.Quote from: Calambres on January 23, 2018, 05:08:26 pm741, 741A, or 741M but *not* the 741C unless it is from TI because they like to confuse things. Check the manufacturer's datasheet to verify which suffixes are 44 volts.LF356B, but again check the manufacturer's datasheet to verify which suffixes are 44 volts."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 23, 2018, 07:04:29 pm",
"content": "Quote from: Microcheap on January 23, 2018, 06:43:51 pmHave you tried modifying it to make it more reliable? That would be a good learning exercise.Quote from: David Hess on January 23, 2018, 07:00:21 pmHow about the OP07? It should have a low enough offset to eliminate the trimming circuit.As to why it's popular: the PCB is available cheaply from many Chinese suppliers and it was featured on electronics-lab, a very popular site in the early 2000s, until a bad moderator caused all the nice and helpful people to leave."
},
{
"post_id": "",
"author": "Microcheap",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 23, 2018, 07:45:20 pm",
"content": "Quote from: Hero999 on January 23, 2018, 07:04:29 pmIn fact I did. I was working on this on the past few weeks and was thinking in make a post about it when I found this thread. I've been away from the electronics for quit some time and I had the opportunity to go back now so I thought that revive this project would be a good exercise to refresh things up.I'm not quite satisfied with the results yet, but if there is interest I would be happy to share it."
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 23, 2018, 08:02:28 pm",
"content": "Quote from: Hero999 on January 23, 2018, 07:04:29 pmNot all OP07s are 44 volts so check the datasheet for the specific part. Also the original OP07 has a very limited differential input voltage range which will require checking the circuit for proper operation.It looks like the inexpensive OP07s from TI will work but the functional schematic they show looks like a 741 so I am dubious about their claims. Having learned not to trust TI datasheets, I would want to test their part to verify it is what their datasheet says it is.QuoteEvery time I see its schematic, it prods me to design and release my own version. Then I consider the economics and lose interest."
},
{
"post_id": "",
"author": "Cliff Matthews",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "January 23, 2018, 08:38:18 pm",
"content": "FWIW, there's a lot of good historical (hysterical? to some here) reading posted by user liquibyte here:http://electronics-lab.com/community/index.php?/topic/40835-0-30v-0-3a-latest-data/On the second page he ends up using mc34071's and gives all files required (unfortunately I don't want to be a user there.. so I can't get them and this forum is enough for me). I pinched this though.."
},
{
"post_id": "",
"author": "zvonex66x",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 23, 2018, 09:27:07 pm",
"content": "This is simple circuit for psu 0-30v, 0-10a, i have made couple of adjustable psu, but tis is simple and best of all."
},
{
"post_id": "",
"author": "kiwizz",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 23, 2018, 10:40:37 pm",
"content": "Wow, so many replies - cheers!How can I check if Q2/Q4 are damaged (other than visual inspection)? I did stick a pretty big heatsink on Q4 with a fan - it was by far the hottest component on the board, even with the heatsink it was too hot to touch when the unit failed."
},
{
"post_id": "",
"author": "kiwizz",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 23, 2018, 10:43:42 pm",
"content": "U2 or Q2? I've ordered another kit as its cheaper than getting a single componentI am interested in building a more robust system after reading through the comments here - I don't really want to (at this stage) design and build my own PCB though - I have seen you can get them professionally made for a few bucks - do you have your design in a format where it can be sent to one of these companies to print? Also - is it adjustable etc?Cheers!"
},
{
"post_id": "",
"author": "kiwizz",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 23, 2018, 10:44:54 pm",
"content": "DC"
},
{
"post_id": "",
"author": "kiwizz",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 23, 2018, 10:46:54 pm",
"content": "Thanks for the reply - I don't see what you are referring to? previous schematic? forgot to add a link? Cheers!"
},
{
"post_id": "",
"author": "Cliff Matthews",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "January 23, 2018, 11:07:54 pm",
"content": "Quote from: kiwizz on January 23, 2018, 10:46:54 pmKiwizz, FWIW some users reply to specific messages by prefixing something like @username, but most just use theQuotefunction on the right side. BTW, welcome to the forum!"
},
{
"post_id": "",
"author": "zvonex66x",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 23, 2018, 11:36:51 pm",
"content": "Quote from: Cliff Matthews on January 23, 2018, 11:07:54 pm"
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 24, 2018, 04:38:47 am",
"content": "Quote from: Cliff Matthews on January 23, 2018, 08:38:18 pmThe MC34071 is not a bad choice but it is only available in surface mount. If you consider small outline parts then there are a lot more options.My personally preference would be to fix the design so a 44 volt part is not required. A simple zener shunt regulator for the positive supply to the operational amplifiers would help a lot but not really enough to support a 30 volt output without other changes."
},
{
"post_id": "",
"author": "Cliff Matthews",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "January 24, 2018, 11:38:23 am",
"content": "Quote from: David Hess on January 24, 2018, 04:38:47 amThat's why having a bunch of these is handy:http://www.dipmicro.ca/store/PCB-SOIC-SSOP16"
},
{
"post_id": "",
"author": "Hextejas",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 24, 2018, 04:05:32 pm",
"content": "So, is there a more gooder diy kit available that is similar ?"
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 24, 2018, 05:02:37 pm",
"content": "The Chinese kit for this defective old circuit has \"clearance pricing\" because it has been replaced by a much simpler power supply with poor spec's but with a V and A display."
},
{
"post_id": "",
"author": "kiwizz",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 24, 2018, 09:31:41 pm",
"content": "Quote from: zvonex66x on January 23, 2018, 11:36:51 pm"
},
{
"post_id": "",
"author": "zvonex66x",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 25, 2018, 12:05:45 am",
"content": "Quote from: kiwizz on January 24, 2018, 09:31:41 pm"
},
{
"post_id": "",
"author": "kiwizz",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 28, 2018, 03:59:23 am",
"content": "Quote from: zvonex66x on January 25, 2018, 12:05:45 am"
},
{
"post_id": "",
"author": "Cliff Matthews",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "January 28, 2018, 05:35:05 am",
"content": "@Simon, Why are the last 3 posts empty quoting without saying anything? Perhaps from the same IP?If the last two posters seriously want to gain a bad rap, you're getting successful at it"
},
{
"post_id": "",
"author": "zvonex66x",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 28, 2018, 08:26:20 am",
"content": "You have value of all component at this schematics"
},
{
"post_id": "",
"author": "kiwizz",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 28, 2018, 08:27:51 am",
"content": "Quote from: Cliff Matthews on January 28, 2018, 05:35:05 amHi Cliff - I'm not sure either. I'm replying after the 'quote' code block, so it should show up normally. Odd."
},
{
"post_id": "",
"author": "zvonex66x",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 28, 2018, 09:19:02 am",
"content": "And I have made this one... it's more complex and it's not cheap, but it's pcb and you only need to buy all of components and solder it... when all is done, you should go up to 100$ so it's not cheap, but is good PSU.. take a look...https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F192415947108"
},
{
"post_id": "",
"author": "kiwizz",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 28, 2018, 11:36:14 am",
"content": "Quote from: zvonex66x on January 28, 2018, 09:19:02 amThat looks pretty cool. What did you use for an enclosure?"
},
{
"post_id": "",
"author": "Cliff Matthews",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "January 28, 2018, 01:47:17 pm",
"content": "Quote from: zvonex66x on January 28, 2018, 09:19:02 amIf you don't link to, or post the schematic, one could think you are selling these.. please, open a new thread to discuss the merits perhaps.. (the current thread is getting stale))."
},
{
"post_id": "",
"author": "tooki",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 29, 2018, 06:59:53 pm",
"content": "Quote from: Cliff Matthews on January 28, 2018, 05:35:05 amzvonex66x screwed up while quoting several posts ago, leaving an unclosed quote tag, and that ripples through every time it’s quoted."
},
{
"post_id": "",
"author": "zvonex66x",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 29, 2018, 11:24:26 pm",
"content": "Quote from: tooki on January 29, 2018, 06:59:53 pmThen is better to not ppst anything here, becouse if you want to help someone like i did try it here, \"discuss the merits\"..."
},
{
"post_id": "",
"author": "Cliff Matthews",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "January 29, 2018, 11:51:40 pm",
"content": "Quote from: zvonex66x on January 29, 2018, 11:24:26 pmI'm sorry I rushed to conclusions there, but there is a reason why tens of thousands of electronics engineers and hobbyists use this forum ahead of any other on planet earth. Just be careful and stay outside those square brackets.. you'll be fine!"
},
{
"post_id": "",
"author": "mikerj",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 30, 2018, 04:03:06 pm",
"content": "Quote from: Cliff Matthews on January 28, 2018, 01:47:17 pmDropbox link.It's the Velleman K7200 PSU, I can remember wanting to build that back in my teens (but not being able to afford it!)."
},
{
"post_id": "",
"author": "tooki",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 31, 2018, 12:39:31 pm",
"content": "Quote from: zvonex66x on January 29, 2018, 11:24:26 pmMelodramatic much? LOLWhen people screw up with quoting, it makes it extremely difficult (or even impossible) to see the responses. This isn’t an attack on you, it was just a statement of how the problem happened."
}
] |
2025-10-17T18:39:25.399304
| 39
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-30vdc-variable-powersupply/
|
0-30vdc variable powersupply? - Page 1
|
[
{
"post_id": "",
"author": "Ian",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 22, 2011, 11:53:41 pm",
"content": "Hii would like to build a 0-30v DC variable power supply. it could be like 1.5v or 2.5v to 28v or 25v or 29v so basically what i am saying is that it does not have to go down to 0v and does not have to go all the way to 30v. I would also like it to have between 2.5a and 3.5a of of current. Also i would like it to have a maximum current output control so i can control the maximum current output. So i need a tutorial or a kit for this project."
},
{
"post_id": "",
"author": "Jon Chandler",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 23, 2011, 12:03:28 am",
"content": "Here's a way I made an adjustable power supply meeting some of your needs:Ten Buck Lab-Grade Variable Power SupplyIt uses an LM317 to regulate the output from a higher-voltage wall-wart switching power supply. It will handle up to about an amp depending on the voltage drop across it and has no current limiting but it's a easy starting point."
},
{
"post_id": "",
"author": "Ian",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 23, 2011, 12:30:24 am",
"content": "Thanks thats cool. Ya i have something like that"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 23, 2011, 07:11:43 pm",
"content": "Yes, the LM317 is good for this but it's only rated to 1.5A, if you want more you'll need additional components.To cut down on power dissipation I'd recommend using a centre tapped transformer and switching to the centre tap for lower voltages; this can be done automatically if needs be.The minimum output voltage from the LM317 is 1.25V, to go lower you need additional components."
},
{
"post_id": "",
"author": "Hypernova",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "March 24, 2011, 03:05:14 am",
"content": "Look up TI's OPA54x series opamps that can deliver up to 10A from up to 80V, TI actually include example on how to make pot or DAC programmable PSUs out of them."
},
{
"post_id": "",
"author": "grenert",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 24, 2011, 06:02:08 am",
"content": "For a beginner, the LM317 is nice in that it has built-in short-circuit protection."
},
{
"post_id": "",
"author": "Ian",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 24, 2011, 07:39:19 pm",
"content": "thanks so much"
}
] |
2025-10-17T20:40:23.272846
| 7
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-4mm-pitch-bga/
|
0.4mm pitch BGA - Page 1
|
[
{
"post_id": "",
"author": "ZeroResistance",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 02, 2020, 07:23:45 pm",
"content": "Hi,First time using a BGA, I have a 0.4mm pitch WLP package, 7 rows and 7 cols, The recommended pcb pad size for this is 0.25mm.Maxim has shown how to route this with 3 layers (image attached).My question is, this would require vias directly on the pads correct? so wouldn't the solder get sucked through the via hole during reflow causing a unreliable joint?Are these vias of a special kind?, I mean these don't seem to be the regular thru hole vias are there of the blind buried type?I was thinking of sending this to JLCPCB for board manufacture, but looks like their minimum via diameter is 0.45mm, so this seems to be beyond their capabilities, I have heard of Multech PCB too but never had any reviews of them, does anyone here gotten boards from Multech?"
},
{
"post_id": "",
"author": "dmills",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 02, 2020, 07:35:11 pm",
"content": "0.4mm is generally via in pad, filled and plated.EXPENSIVE in prototype quantities, and somewhat specialist, avoid if you can, otherwise someone like Wurths prototype shop can do this for you."
},
{
"post_id": "",
"author": "ZeroResistance",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 02, 2020, 08:15:10 pm",
"content": "Quote from: dmills on February 02, 2020, 07:35:11 pmThanks for your feedback, I'll stick to QFN for now.Are these the blind / buried kind of vias?I'd like to know what cost am I looking at for the 0.4mm via in pad PCB?"
},
{
"post_id": "",
"author": "aix",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "February 02, 2020, 08:36:18 pm",
"content": "I got curious and played with PCBWay's quotation system. It seems that four-layer boards with vias-in-pad start at around US$365 + postage.Also:https://www.pcbway.com/pcb_prototype/PCB_Via_in_Pad.html"
},
{
"post_id": "",
"author": "ZeroResistance",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 02, 2020, 08:45:25 pm",
"content": "Quote from: aix on February 02, 2020, 08:36:18 pmThanks for the info, that's indeed very expensive !"
}
] |
2025-10-17T17:56:33.403424
| 5
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-4mm-unplated-mounting-hole-for-kicad/
|
0.4mm unplated mounting hole for Kicad - Page 1
|
[
{
"post_id": "",
"author": "panocode",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "September 20, 2023, 07:31:39 pm",
"content": "Hello! I'm trying to make a 0.4mm unplated mounting hole for kicad, does someone know how I can make one/where I can find a footprint for one? I don't really know what other details to add, it's honestly just that, a small unplated mounting hole."
},
{
"post_id": "",
"author": "bill_c",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "September 20, 2023, 09:49:42 pm",
"content": "Are you sure abut that size? That's like human hair size in American units."
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 20, 2023, 10:16:10 pm",
"content": "Quote from: bill_c on September 20, 2023, 09:49:42 pmSize is OK. Your American hair would be 0.04 mm."
},
{
"post_id": "",
"author": "themadhippy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 20, 2023, 10:38:06 pm",
"content": "cant you just edit an existing hole from the library"
},
{
"post_id": "",
"author": "panocode",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "September 20, 2023, 11:40:25 pm",
"content": "Welp turns out you can just make an edge cut circle... and it works just as well... I wasted probably too much time on it."
},
{
"post_id": "",
"author": "ataradov",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 21, 2023, 12:19:52 am",
"content": "It may work for visuals, but your board manufacturer may not accept this.I don't think there is a way to make a hole like this from the PCB editor. The only way I know how to do that with no manufacturing issues is to make a footprint that is just an NPTH Pad with pad and hole diameter set to the same value. It would end up in a drill file, so it would be a real drilled hole."
},
{
"post_id": "",
"author": "sparkydog",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "September 21, 2023, 02:23:33 pm",
"content": "Place a footprint of an existing NPTH, e.g. MountingHole_2.1mm. Then either just edit the pad size, or edit the footprint if the margin is going to be a problem."
},
{
"post_id": "",
"author": "Doctorandus_P",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 21, 2023, 08:36:22 pm",
"content": "Indeed. KiCad has a \"MountingHole\" library, and it has some 100+ pre-defined mounting holes ranging from 2.1mm to 8.4mm and a good portion of them areNPTH(NonPlatedThroughHole).Apart from that, you can set any pad in a footprint toMechanical, NPTHand/or change it's diameter."
},
{
"post_id": "",
"author": "EPAIII",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2023, 07:48:34 am",
"content": "0.4mm translates to 0.0157\". The hair on my arm measures 0.1mm so 0.4mm is fairly large.0.4mm drills do exist and are fairly large as small bits go. 0.1mm ones are easily available. But will a fab house want to go that small without charging a large premium in the price? I don't know. I do machining work and I would be very nervous using such a small bit. Solid carbide would be necessary for PCBs and they are very brittle so breakage would be a big concern. And they should/must be run at high spindle speeds which a given fab house may or may not have available.Are you sure you need that dimension? Real sure?Quote from: panocode on September 20, 2023, 07:31:39 pm"
},
{
"post_id": "",
"author": "ataradov",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2023, 03:23:32 pm",
"content": "Why would they charge for 0.4 mm drill when they routinely drill 0.3 mm vias? Those vias before plating may even be 0.4 mm.But yes, as a mechanical hole, 0.4 mm does not make much sense. Still, it is very easy to do."
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2023, 07:07:42 pm",
"content": "Quote from: EPAIII on September 24, 2023, 07:48:34 am0.1 mm? Are you a wild boar?"
},
{
"post_id": "",
"author": "EPAIII",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 25, 2023, 03:25:55 am",
"content": "Well, bully for them. I am glad to hear that they can. But I did see that at least one source did charge extra for 0.15mm holes. That's a bit less than 0.006\".I have never even tried to order a hole that small, so I didn't know."
},
{
"post_id": "",
"author": "EPAIII",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 25, 2023, 03:29:43 am",
"content": "No, just boring.Quote from: Benta on September 24, 2023, 07:07:42 pm"
}
] |
2025-10-17T16:47:49.236765
| 13
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-5mm-part-solder-bridge/
|
0.5mm part, solder bridge - Page 1
|
[
{
"post_id": "",
"author": "Skippy",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "November 13, 2012, 12:58:16 am",
"content": "In attempting to add some solder to a dodgy connection on a 0.5mm SMD chip, I've made a massive solder bridge across 4 pins. Solder wick just isn't cutting it. Any suggestions, or have I had it? It was basically working before as well"
},
{
"post_id": "",
"author": "w2aew",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 13, 2012, 01:17:37 am",
"content": "Solderwick should work better if you add some flux. Even a vacuum desoldering tool (Solder Pull-it) may work well. Flux is your friend..."
},
{
"post_id": "",
"author": "George_Race",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "November 13, 2012, 01:18:51 am",
"content": "Melt the solder and use a small bristle brush to remove the solder. A solder sucker may also work as well.George"
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 13, 2012, 01:53:18 am",
"content": "Yeah solderwick works the best (good quality stuff)Alternatively you can try the following two methodsMethod 1- First make sure the pins are cold, if you're trying this method repeatedly wait 10 sec between attempts so the pins can cool down. It works because of the temperature difference between two adjacent pins.- Apply some flux- Clean the soldering iron so they're are no lumps of solder on the tip.- Apply the soldering iron tip to one pin only. Pick a pin that's 1pin in from either end of the bridged section.- As the pin gets hot and the flux activates it will often pull the excess solder from the other pins onto the iron. (Basically the solder likes to flow to the hottest point and nearby pins are colder.)- Wait a few seconds and repeat to remove all the solder bridges.Another trick you can try, and its a bit counter-intuitive, is to put more solder on.- Add some flux- Put a small blob of solder onto the iron tip.- Run the tip (and solder blob) down the pins of the IC from one end to the other.- The excess solder will ball up on the tip and pull solder away from pins.- Doing this you can often move all the solder bridges to one end of the IC. eg, 5 solder bridges become one big bridge on the last pin.- To remove the last bridge just keep cleaning the iron and heating the pin up so it pulls solder away the pin and onto the iron."
},
{
"post_id": "",
"author": "johnwa",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 13, 2012, 07:06:34 am",
"content": "One other technique (which may not necessarily be successful on something this small) is to apply a blob of solder, then rotate the board and iron together until the joint is vertical, and the solder runs down from the joint onto the tip of the iron. This is also good for things like tinning copper tracks without leaving big lumps of solder behind.I agree with the suggestions to use some extra flux."
}
] |
2025-10-17T20:29:05.664572
| 5
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-5v-or-0-12v-digital-input-to-3-3v-logic-levels/
|
0-5V or 0-12V digital input to 3.3V logic levels - Page 1
|
[
{
"post_id": "",
"author": "Macka",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 08, 2018, 11:22:39 am",
"content": "Hi,I'm working on a project where I have a square wave of either 0-5V or 0-12V as an input to a SAM3X microcontroller (3.3V logic). The signal(s) will be coming from automotive tachometers and other automotive pulse sources.Now obviously I can't input that directly and I'm not aware of any 5V tolerant inputs on this chip.A voltage divider that works for 12V is unlikely to yield good results with a 5V signal connected and vice versa. There is also a possibility that the source will not respond well to being loaded, so I believe a high impedance input may be required.I've seen suggestions to use a comparator such as an LM339 - it's my understanding that Vcc of the comparator will need to be Vmax (12V) to work, otherwise, if I use say, 3.3V as Vcc then a 12V input on the inverting/non-inverting pin will damage the IC - is this correct or can I actually run Vcc at 3.3V safely?If I put Vcc at 12V and put a 5V signal into the non-inverting pin, as I understand it I can get a 3.3V signal out due to the open collector output (pull up the output to 3.3V).What is the best way to convert this voltage range to something safe?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2018, 11:46:53 am",
"content": "What frequency is the square wave?The easiest method is to use a series resistor, say 10k to 1M, before the MCU input. The internal ESD protection diodes will clamp the input voltage at about 0.6V above the MCU's power supply."
},
{
"post_id": "",
"author": "Kalvin",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2018, 11:52:17 am",
"content": "Another alternative is to use a simple NPN transistor as a buffer:https://cdn.sparkfun.com/r/400-400/assets/learn_tutorials/1/9/3/logic-inverter-circuit.pngIf you need some more protection and ground loop isolation, you can use an opto-coupler with the NPN transistor."
},
{
"post_id": "",
"author": "danadak",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2018, 11:56:36 am",
"content": "You have to limit current so you do not trigger parasitic SCRpresent in CMOS devices. In increasingly numbers that currentspec is in MCU datasheets. Also known as latchup current, althoughthat can be the Idd once latchup occurs. Read datasheet carefully.https://en.wikipedia.org/wiki/Latch-upThe trade off is as R goes up, speed drops of this interface due toRC effects.Regards, Dana."
},
{
"post_id": "",
"author": "madires",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2018, 12:05:20 pm",
"content": "You can use a 74HC4050 or a more sophisticated level shifter."
},
{
"post_id": "",
"author": "tszaboo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2018, 12:21:55 pm",
"content": "Perhaps you can use a LIN transceiver in receive only mode for this. They are more expensive (while still very cheap) than similar circuit made from discretes, but they are fault protected and characterized. Made for automotive environment."
},
{
"post_id": "",
"author": "Tom45",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 08, 2018, 12:49:56 pm",
"content": "Use a series resistor that is connected to your input. Then at that input put a couple of diodes: one connected to 3.3V, and the other connected to ground."
},
{
"post_id": "",
"author": "Peabody",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2018, 01:01:16 pm",
"content": "The LM339 has an open-collector output, so I believe you can use that if you have a 12V supply available for its Vcc. Then on the output you would have a pullup resistor to the 3.3V rail."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2018, 01:03:52 pm",
"content": "You should consider whether galvanic isolation might be beneficial.If so, you could combine it with an optocoupler for level translation."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2018, 07:24:38 pm",
"content": "Quote from: Tom45 on February 08, 2018, 12:49:56 pmWhich will conduct first? Those diodes or the internal ESD protection didoes? They should be Schottky diodes to ensure they conduct and not the ones inside the IC."
},
{
"post_id": "",
"author": "phil from seattle",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2018, 07:30:59 pm",
"content": "BAT54S is a good one for that, SOT package, 2 diodes."
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2018, 07:31:31 pm",
"content": "Just use a discrete small-signal MOSFET with a drain resistor to +3.3 V. There are automotive types available with gate protection against transients.Don't forget it will invert the input, but your firmware should take care of that."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2018, 08:20:14 pm",
"content": "Quote from: Benta on February 08, 2018, 07:31:31 pmOr put the resistor between the source and 0V and connect the drain to +3.3V."
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2018, 08:36:54 pm",
"content": "Quote from: Hero999 on February 08, 2018, 08:20:14 pmThat would require a MOSFET that turns on at 1.7 V gate voltage, which is not easy to find."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2018, 11:21:23 pm",
"content": "Quote from: Benta on February 08, 2018, 08:36:54 pmNo it wouldn't. The logic input doesn't need the full 3.3V to work. The minimum high-level voltage will be something like 2V, so anything with a 3V threshold or less will do. The 2N7002 will do."
},
{
"post_id": "",
"author": "bson",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "February 09, 2018, 12:54:32 am",
"content": "If you don't mind signal inversion, with 5V you could just stick a 5V tolerant hex inverter in there."
},
{
"post_id": "",
"author": "ArdWar",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 09, 2018, 01:33:43 am",
"content": "It depends on how fast your signals are, what protection needed and how clean (signal integrity) you need the signal be.For automotive application interfacing into sensitive equipment, complete galvanic isolation using optocoupler is favored. Considering that automotive 13.8v line can surge to very high voltage at load dump, even peaking at 60V(!)Otherwise if the source is already surge-suppressed, you can use pretty much any logic level shifter. With comparator, the idea is to pull-up the comparator's open drain/open colector output into target voltage. Obviously the comparator itself is supplied from the (higher) source voltage. Unless specifically noted in the datasheet, never put voltages higher than supply voltage on any IC and expect it to work flawlessly.For simple shifter, you can also copy Sparkfun's level shifter. You also get bonus that it is bidirectional.About low voltage MOSFET. Almost all MOSFET Vgs(th) is pretty low in the ~2V area, and even lower for signal MOSFET. You don't need to get past Miller voltage just to conduct a few microamperes."
},
{
"post_id": "",
"author": "Macka",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 09, 2018, 02:36:21 am",
"content": "Wow, there've been a lot of responses on this so I'll try to address them all - thanks guys!Quote from: Hero999 on February 08, 2018, 11:46:53 amFrequency will be around the 0-1kHz range, duty cycle of at least one signal is fixed at 20%, the others I don't know the duty cycle of (the requirements I've been given are not super detailed).From what I've read, the ESD diodes aren't designed for this kind of service and could be damaged/do degrade when used in this manner. I had considered a zener diode in parallel with the input or 2 Schottky diodes as others have suggested, however I'm concerned about loading the transducer (at least one post I've come across was complaining of loading issues even with 10s of kOhms of input resistance).Quote from: Benta on February 08, 2018, 07:31:31 pmI'm currently looking at the FDN5632N-F085https://www.digikey.com.au/product-detail/en/on-semiconductor/FDN5632N-F085/FDN5632N-F085CT-ND/4562779, apparently it's an N-channel 'Automotive, AEC-Q101, PowerTrench®' MOSFET.VGS= +/-20VVGS(th)= 1 (min), 2 (typ), 3 (max) Is this a good value? I think it is, due to being low enough for 5V triggering and high enough for some noise immunityI believe, based on the on/off/delay and rise/fall times it should be good for ~15MHz (1/(30+15+1.7+5.2+1.3+12.9) = 1/66.1ns)Inversion of the signal shouldn't be an issue as I can set the capture to occur on falling edge (not that it makes a difference, when I think about it)Have I got everything here round the right way?The other possibility is the 2N7002BKV,115https://assets.nexperia.com/documents/data-sheet/2N7002BKV.pdf, which Hero999 has indicated would be sufficient (I have 4 pulse inputs, so 2 of these would see me right)Quote from: tggzzz on February 08, 2018, 01:03:52 pmI think to do this I'll need a transistor/FET input anyway, to avoid loading the transducer?Quote from: ArdWar on February 09, 2018, 01:33:43 amI believe there is already surge suppression on the signals, but I don't want to rely on that too heavily - does the above MOSFET satisfy the requirements or do I need further protection?Quote from: bson on February 09, 2018, 12:54:32 amI don't see signal inversion as a problem, but I think the issue will be when there's a 0-12V signal. I can't guarantee the person I'm designing this for will have all 5V or all 12V transducers; they have told me there's a mix and in the future the mix could change, so I'm trying to cover both cases."
},
{
"post_id": "",
"author": "max_torque",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 09, 2018, 12:39:47 pm",
"content": "As soon as a poster says \"automotive\" i know they are in a world of trouble!firstly, automotive isn't \"12v\"!! Typical \"normal\" signal voltages range from as little a 8v (most oems now protect down to 6 to support cold cranking requirements) up to around 15v (14.7v is a typical alternator output setpoint)However, abnormal events mean you need to be robust from -13vdc to around 90vdc (for 12v nominal systems)ime, you cannot have too much input protection!Assuming your device has a correctly specified and protected power supply architecture (if the micro itself goes bang because some one has just jump started their car and placed the jump leads the wrong way around then it's a bit late to be worrying about input protection for any logical input etc!) then you need to try to include as much resistance as possible, commensurate with providing a sensible noise rejection. As most vehicles have a common ground (the body shell) galvanic isolation is rarely required (it can be useful in certain circumstances, for example interfacing to devices with high di/dt or high dv/dt)For \"simple\" low frequency (<10khz) inputs i use a fixed resistive divider, followed by a voltage clamp (either diodes to Gnd / vcc, or a zener, depending on how near the rails i need the input signal to get), followed by more resistance, and then into the micro input pin. The second lot of R prevents excessive current flow through the micros internal clamping diodes and allows your out board clamps to shunt current away as necessary. I also add a select amount of capacitance to ground, a \"small amount\" directly on the input (needs a high enough voltage rating remember!) before the first resistive divider to provide a lower AC sink impedance (to try to shunt high frequency noise straight to ground) and then some more capacitance forming a low pass filter after the divider (frequency set to suit your input frequency range).You also may consider using a series diode or zener to prevent reverse current flow if the vehicle battery is connected backwards and to push up the minimum input voltage which is considered to be \"high\" to give yourself some head room from ground potential."
},
{
"post_id": "",
"author": "Macka",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 09, 2018, 08:51:25 pm",
"content": "Quote from: max_torque on February 09, 2018, 12:39:47 pmI should have mentioned in this case there's no alternator; the vehicle this is being designed for is not a standard street vehicle. It's my understanding that when the engine's not running the battery is isolated and when in the garage the battery is isolated and on charge.Does the lack of alternator change the load dump by much or any of the protection requirements? (I imagine starting the vehicle would still cause a significant load dump when the starter is disengaged).At the moment, the device is an Arduino Due + the shield I'm designing. I'm pushing for a single board (get rid of the Arduino and do a complete custom PCB) which would give me more control over the power supply and form factor - I'm not sure I'll get that though..I've already added an unpopulated capacitor across the input to the microcontroller, would it be better off having it on the gate? or maybe even both?I think I'd like to stick with the MOSFET inputs, but I'm wondering if maybe I should put a MOV or zener between the input resistor and the gate? VGSis +/- 20V continuous, so I'd only need to protect from transients above that. Would reverse current flow be an issue if there's a reverse polarity protection diode in the power supply (standard arduino) and a MOSFET on the input (no current from the gate?)"
},
{
"post_id": "",
"author": "max_torque",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 10, 2018, 01:20:37 pm",
"content": "No alternator helps from \"load being disconnected suddenly when it's sticking out 100A\" type surges, but obviously makes no difference to any other (common) automotive environment surge!Consider what does the additional mosfet bring you? You need to protect that Mosfets Gate, just like you need to protect the gate of the Mosfet (or similar device) in your microcontroller. In the event of a unprotectable surge (ie a surge that exceeds your protection system) that mosfet is dead, in the same way that the micro's input conditioning circuitry would be dead. End result is the same (there are some highly safety critical systems where you'd protect the micro at all costs because it's doing other stuff that is critical, but for your device, non functionality is non functionality is it not? Is there any other 'knock on' effect of possibly killing the micro itself?)If you can present a valid reason for having an \"active\" input buffer, and considering that you don't have any requirement for low current consumption, or a requirement (particularly) high input impedance or bandwidth. i'd consider using a Transistor and not a Mosfet to get away from the Vgs limitation and obvious failure mode inherent in that semiconductors architecture.But at just 1kHz, and with a (relatively speaking) massive input voltage range you can just install a huge series resistance into your input chain, and so effectively put in place a lot of over voltage protection easily. If you look up the voltage levels and hysteresis for your particular micro's input, you can easily work out a suitable voltage division and limitation mechanism to robustly protect that input.ime, keeping things simple, but robustly engineered and validated is the trick for automotive electronics (and i design these for a living)My principal \"Five Commandments\" are:1) Power supply to the logic must be BULLETPROOF2) Install the max impedance possible between the real world and your device, where ever signals cross the boundaries3) Use the least possible number of parts. 1 less part = 1 less thing to fail4) Protect ANY conductive path into your device from at least the following : 1) continuous connection to Vbatt+10% and continuous connection to -Vbatt5) if you can achieve 4) for what ever reason, document that fact to your clients in an obvious and EXPLICIT way."
},
{
"post_id": "",
"author": "Macka",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 10, 2018, 09:49:54 pm",
"content": "Quote from: max_torque onYesterdayat 11:20:37 PMI was thinking the MOSFET would give me a high impedance input with negligible change in rise/fall time, a large input range as VGS(th)is small, and it would be easier to protect the MOSFET, as I only have to worry about transients >20V as opposed to the MCU that needs protecting from anything above 3.6V.Having said all that, I posted in the beginner section because I don't know what I don't know and what I do know may be completely wrong.From the MCU datasheet:VIL: -0.3V min, 0.99V max (0.3 x VDDIO)VIH: 2.31V min (0.7 x VDDIO), 3.6V max (VDDIO+ 0.3)Vhys: 150mV min, 500mV maxVIL leakage current: 5nA typ @ TA= 25°C, 30nA max @ TA= 85°CVIH leakage current: 2nA typ @ TA= 25°C, 18nA max @ TA= 85°CThere's also an on-die series termination resistor of 36 ohms, but I think it can be ignored, as the ratings are at the pin, not after the resistor.So where do I go from here for the calculation?I tried following the example here:https://electronics.stackexchange.com/questions/124620/maximum-resistance-that-can-be-put-in-series-with-an-input-to-a-pic-microcontrI assumed assuming TTL noise immunity of 400mV (but maybe I should be using 500mV or 150mV from the MCU's hysteresis?).Max voltage across input resistor: 0.99V - 400mV = 0.59VMax current: 30mA @85°Max input resistor: 0.59V/30nA = 19.66 Mohms...Which seems very large, and I'd imagine would cause issues...So, would I take this (or perhaps a smaller value) and use that as the input resistor of a voltage divider and try to pick a ground resistor that would give VIH+ 400mV for a Vinof 12V?5V inputMin high input voltage = 2.31V + 400mV = 2.71VR1: 10Mohms (<19.6Mohms)R2: 12MohmVout: 5*12/22 = 2.72V12V inputVout = 12 * 12/(22) =6.54VI would need a clamping diode for this scenarioAm I on the right track here?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 11, 2018, 12:27:26 am",
"content": "Quote from: Macka on February 09, 2018, 02:36:21 amThat's a fairly low frequency, so the extra rise/fall time due to a resistor and get input capacitance won't matter.QuoteThe ESD won't be damaged, so long as the current is limited to a safe value. A 100k resistor will limit the current to 87?A.Quote from: Macka on February 10, 2018, 09:49:54 pmHow about using a potential divider and a clamping diode, such as the BAT54S, if you really want to avoid the ESD diode conducting, although it would be an issue at such low currents? Two 1M resistors would give the MCU, 2.5V with 5V in and it would be clamped to just over 3.3V, when the input voltage is above 6.6V. The current draw from the transducer will be negligible."
},
{
"post_id": "",
"author": "Macka",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 11, 2018, 07:17:24 am",
"content": "Quote from: Hero999 on February 11, 2018, 12:27:26 amI've run a sim on the voltage divider with a zener diode for overvoltage protection (see attached).It seems with a 1M/1M voltage divider, followed by a 1k resistor and a zener diode, with a pulse up to 87V, the most the MCU pin will see is 3.9V, then there's the internal 36R and the internal ESD diodes, would that be sufficient?Looking at the BAT54S, where would you place it? Before the VDiv or after it?If I understand the purpose correctly, if the signal is >=250mV above the rail, the diode will conduct and bleed the current into the 3.3V supply (hence the need for a \"robust supply\"?), resulting in the voltage dropping to a safe level.Would I be better off using the BAT54S in place of the Zener? or perhaps in addition to the Zener (attachment 2)? Are other resistors etc. required (e.g. Vdiv->1k->schottkys->1k->zener->MCU)?This article on digikey suggests a single Schottky, a low pass filter and a Zener for input protection and level shifting from 12V, however they are only worried about input line inductance over long distances, not load dump:https://www.digikey.com.au/en/articles/techzone/2012/apr/protecting-inputs-in-digital-electronicsThanks for your help so far, max_torque & Hero999, I'm sure it's frustrating trying to explain this."
},
{
"post_id": "",
"author": "Tom45",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 11, 2018, 09:44:18 am",
"content": "There is something wrong with your simulation. It would take well over 40000 volts to pump 39.5 ma through a 1 meg resistor and the zener diode.In any case, 1 meg for the voltage divider resistors seems way too high."
},
{
"post_id": "",
"author": "max_torque",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 11, 2018, 09:39:36 pm",
"content": "I typically use a 47k input resistor, with another resistor to ground, forming a voltage divider that produces a valid \"high\" state on the micro pin (if you want to go for the full automotive temp range (-45 to +125 degC!) then you need to ensure you get a \"High\" under all temperature conditions) at around 60% of the known voltage input value. I also then often use a zener to limit the voltage so i can have a voltage divider that uses the zener in normal operation, but should that zener fail, the increase in voltage is small enough. I include a small cap as a noise canceller / low pass filter. then i use something like a 10k resistor in series with the micro pin (to limit current into the micro's clamp diodes)ie say you have a nominal 12 Vin input, and you micro goes \"high\" at 2v (with a 3.3Vcc)i'd have a voltage divider (using the 47k input R) that exceeds 2v at around 8v (meaning the input stays high under most cold cranking conditions), which would in this case be a 15k to ground after the 47k inputR. i'd fit say a 3v zener (or use a diode clamp to Vcc), which would start conducting at around 12.5 Vin. With a typical automotive system voltage of 13.7v, without that zener, you'd still only get 3.31V after your divider which is still ok (won't start using the micro's internal diodes yet)Under typical surge voltage, lets say 48v, you'd get 11.6v after your divider (with the zener failed), so across the subsiquent 10k resistor you get 11.6 - 4 = 7.6v across the 10k and ~0.7mA flows into the internal protection diodes. which is ok. Normally of course, the upstream clamp zener or diode will prevent any significant current flow, but this way you have a 1 failure safe system. (i've assumed the internal diodes clamp about 0.7v above Vcc, hence the 4v value)"
}
] |
2025-10-17T18:38:33.908683
| 26
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-5vdc-to-2-2-2-8vdc/
|
0-5Vdc to 2.2-2,8Vdc - Page 1
|
[
{
"post_id": "",
"author": "aless2056",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "May 11, 2020, 09:58:57 pm",
"content": "Guys, how can I take a signal that varies from 0 to 5Vdc and convert it into a signal from 2.2 to 2.8Vdc.So, 0V will be 2.2V and 5V will be 2.8V."
},
{
"post_id": "",
"author": "Manul",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 12, 2020, 12:20:49 am",
"content": "This must be an exercise? Somehow it fits too nicely and practical use is hardly imaginable. Anyway, something like that (this not a complete practical schematic)."
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 12, 2020, 12:42:53 am",
"content": "See Chapter 4 of “Op Amps For Everyone”. Solve y=mx+b. Google for it...One op amp and 4 resistorsIt will have to be an inverting amplifier to get a gain less than 1. Use a second op amp to invert the result.So y=-(mx+b), I suppose."
},
{
"post_id": "",
"author": "Manul",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 12, 2020, 01:21:00 am",
"content": "Or it can be solved with a voltage reference and divider. But op amp with a reference solutions are more practical in my opinion, because things like DC shift and gain can be adjusted separately, more clearly and universally."
},
{
"post_id": "",
"author": "Manul",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 12, 2020, 01:29:36 am",
"content": "Quote from: rstofer on May 12, 2020, 12:42:53 amNice book, useful stuff"
}
] |
2025-10-17T17:50:15.429741
| 5
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-5x-auxiliary-barlow-lens/
|
0.5x auxiliary Barlow lens - Page 1
|
[
{
"post_id": "",
"author": "Slydder",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "September 23, 2017, 02:58:29 pm",
"content": "Hey all,I just bought a used Euromex scope (60 Euro). The following specs are all I know of atmWF10X S Oculars1x and 3x Objectives33mm diameter threaded auxiliary opening in the turretI am in need of a 0.5x Barlow that will fit the auxiliary opening and have absolutely NO idea what size I should buy.Does anyone have time to give a bit of info on this?Thanks folks,Chuck"
}
] |
2025-10-17T18:48:17.592044
| 1
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-60-vdc-power-supply-controlled-by-pic-0-5vdc/
|
0-60 VDC POWER SUPPLY CONTROLLED BY PIC 0-5VDC - Page 1
|
[
{
"post_id": "",
"author": "chuzkin",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "April 22, 2014, 10:18:59 pm",
"content": "Hi friends.I think i should give more detailed information.What I need is to uso a PIC microcontroller, so using 2 push-buttons, I can increase / decrease the voltage level from 0VDC to 60VDC. The PIC output range is 0-5VDC, so I need an interface to convert this signal to 0-60VDC.Current output needed 2.5 or 3A. Load is a magnet, with the following voltage/current measured:40V - 2.08A34.8V - 1.85A30.3V - 1.26A24.5V - 0.69A18.4V - 0.12A17V - 0.01AThe idea is to replace actual boards to get 50 or 60VDC in order to achieve a stronger magnetic force.Thanks!Best regards."
},
{
"post_id": "",
"author": "valentinc",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 22, 2014, 10:35:13 pm",
"content": "Hi,In order to produce an analog voltage output with a PIC microcontroller you need a digital to analog converter (or a microcontroller which has one integrated)... You also need an amplifier, a voltage reference and a power transistor...What is the input voltage of your system ?"
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 22, 2014, 10:38:24 pm",
"content": "If you're just controlling a magnet you can simply do PWM on the PIC from a 60VDC source.eg..75% duty cycle 60V pwm = power into magnet equivalent to a 45V DC source50% duty cycle 60V pwm = power into magnet equivalent to a 30V DC source25% duty cycle 60V pwm = power into magnet equivalent to a 15V DC source(Note this is not strictly true but close enough, if you're over-driving the magnet past its rated voltage the efficiency goes down)You just need- a N-channel logic level mosfet- 100R resistor between PIC output and mosfet GATE- Generic diode that can handle 2A placed across the magnet for backEMF protection (arrow pointing towards the 60V)Mosfet SOURCE to GND, mosfet DRAIN to magnet, other magnet terminal to 60VDC(Same circuit you will find everywhere for driving a relay from a 5V logic signal)"
}
] |
2025-10-17T20:03:36.395536
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-8mm-pitch-connector/
|
0.8mm Pitch connector - Page 1
|
[
{
"post_id": "",
"author": "e8ghtmileshigh",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "August 03, 2025, 11:24:55 pm",
"content": "Hello. I'm looking for a 1 to 2 female on all ends adaptor for this particular pin.Also where can I get more of these pins.They looks like this (pic 1)The housings look like this (pic 2)"
}
] |
2025-10-17T16:15:35.390587
| 1
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-8mm-pitch-hand-soldered/
|
0.8mm pitch hand soldered ? - Page 1
|
[
{
"post_id": "",
"author": "Simon",
"author_rank": "Unknown",
"is_op": true,
"timestamp": "July 14, 2013, 06:31:25 pm",
"content": "Is it worth considering hand soldering a 0.8mm pitch package ?"
},
{
"post_id": "",
"author": "Skimask",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 14, 2013, 06:40:41 pm",
"content": "Sure, easily done. Even down to .4mm isn't too bad with a steady hand and the right tip on the iron..."
},
{
"post_id": "",
"author": "c4757p",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 14, 2013, 06:44:09 pm",
"content": "A flux-drenched walk in the park."
},
{
"post_id": "",
"author": "Skimask",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 14, 2013, 06:44:46 pm",
"content": "Quote from: c4757p on July 14, 2013, 06:44:09 pmRoger that..."
},
{
"post_id": "",
"author": "Simon",
"author_rank": "Unknown",
"is_op": true,
"timestamp": "July 14, 2013, 06:45:41 pm",
"content": "ok i'm convinced, I may just put the dip away"
},
{
"post_id": "",
"author": "c4757p",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 14, 2013, 06:47:43 pm",
"content": "DIP sucks. You could park a truck on top of the chip..."
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 14, 2013, 06:48:46 pm",
"content": "I have soldered SMD parts with a soldering gun ( OK, they were resistors, capacitors and diodes with the odd transistor but still the tip was a lot bigger than the part) so you should have no problems provided you use enough flux, a good light source and a good magnifier to see what you are doing."
},
{
"post_id": "",
"author": "Kremmen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 14, 2013, 07:51:13 pm",
"content": "Down to .65 mm it is quite easy. That said and depending on the exact method you choose, a high magnification loupe would be a good idea. Sooner or later you are going to accomplish a solder bridge and they may be somewhat hard to spot with the naked eye..8 mm is a walk in the park."
},
{
"post_id": "",
"author": "hlavac",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 14, 2013, 08:05:13 pm",
"content": "My hands are shaking as hell but I still prefer SMD over through holeI want the small stuff...Just leave enough space around the pads to get there comfortably with soldering iron and solder wick without melting off the surrounding components should the things go south...And don't be afraid of solder paste and reflow, its even easier than hand soldering.Just get a suitable hot plate/ pancake maker.When doing manual solder paste with proper consistency you can even try to do it in reverse - dip the component legs in solder paste then place it on the pcbAuto solder pasting pick and place machine, anyone?"
},
{
"post_id": "",
"author": "lewis",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 14, 2013, 09:56:12 pm",
"content": "No probs. Plenty of flux and tin the pads, you'll be fine. Somegood tweezershelp too..."
},
{
"post_id": "",
"author": "poorchava",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 15, 2013, 11:56:53 am",
"content": "Quote from: Skimask on July 14, 2013, 06:40:41 pmRespect... for me there's a huge gap between 0.5 and 0.4. 0.5 is rather trivial for me, but 0.4mm is a total bitch to solder.0.8mm can be hand soldered even in volume production environment I guess."
},
{
"post_id": "",
"author": "EEVblog",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "July 15, 2013, 12:15:26 pm",
"content": "0.8mm is large enough to do each pin by hand with fine (<0.5mm) rosin core solder if you prefer.But of course you'd usually just drag solder.I assume you have solder mask between pins?"
},
{
"post_id": "",
"author": "Simon",
"author_rank": "Unknown",
"is_op": true,
"timestamp": "July 15, 2013, 12:25:40 pm",
"content": "On production yes, for prototypes probably not, I'll risk it when the time comes, at the moment it's functional prototyping versus finished product prototyping."
},
{
"post_id": "",
"author": "Zbig",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 15, 2013, 07:59:35 pm",
"content": "Go for it Simon, you won't regret it. I went straight from \"SMT by hand? You gotta be kidding!\" to hand soldering TQFP144 0.5 mm. The feeling of suddenly no longer being restricted to DIP stuff was one of the greatest moments I had with this hobby. And I only have freeware Eagle license so table-sized PCB was out of the question for meI use magnifying monocle (what is the proper English term for that?) - the kind of what old-school watchmakers used."
},
{
"post_id": "",
"author": "c4757p",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 15, 2013, 08:02:40 pm",
"content": "Loupe, if I understand you correctly. I'll assume you're not using a realmonocle.(Damn. Add \"loupe\" to the list of perfectly valid English words that Google Chrome's spell check doesn't recognize. What are they, illiterate?)"
},
{
"post_id": "",
"author": "Zbig",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 15, 2013, 08:18:49 pm",
"content": "Heh, that was too easyWe call this \"lupa\" as well yet somehow I was convinced you only call the hand-held type (like in search icon) that in English. Anyway, I found it works best for me even if you look a little weird wearing it (I got some funny looks at the fab when I was inspecting my first PCB). I wonder how would the USB microscope work out but I'm not sure about the eye-hand coordination while looking at the screen instead of the thing you're working on."
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 15, 2013, 08:29:16 pm",
"content": "Most loupes appear to be of the hand-held kind. But there is a kind that you hold in your eye socket like a monocle, leaving both hands free. My father used one when he was engraving. I've tried Googling, but I am unsure how to describe that particular device compared to the regular hand-held kind."
},
{
"post_id": "",
"author": "Zbig",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 15, 2013, 08:46:25 pm",
"content": "And this is exactly the thing I'm talking about, IanB. I find it perfect for SMD soldering. And I got it from my father, too."
},
{
"post_id": "",
"author": "Simon",
"author_rank": "Unknown",
"is_op": true,
"timestamp": "July 16, 2013, 05:21:21 am",
"content": "I just use reading glasses. refocusses my eyes closer so I can look closer at the board"
},
{
"post_id": "",
"author": "nukie",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 18, 2013, 12:17:52 am",
"content": "They are called eye loupes, used everyday by watchmakers. I drill holes on the side wall body of my loupe body for ventilation, it fog up after long hours of use.Some people might find eye loupes hard to fit in their sockets, you can buy head band for it.If you wear glasses, you can get clip on loupes.If possible, get stereo magnifier, mono vision is less 3D hard to work with 2D? vision and it can cause lazy eyes syndrome."
},
{
"post_id": "",
"author": "ptricks",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 18, 2013, 02:27:40 am",
"content": "I use a contraption I threw together with a usb camera and a 5\" LCD.usb camera is positioned close to work, found out you can adjust the lens on most of them to get very close, within 10mm of work easily.LCD is held in place above the work area so when I look down I see the image as though it were like a window to the work surface.Found that works best because it gets rid of the move hand up try to match the image issue that I had with the display in the normal vertical position."
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 18, 2013, 02:48:13 am",
"content": "I just use an illuminated magnification lens, the kind that mounts to the desk and can be moved around.My chin almost touches the lens (really close) i find that provides the most detail.It probably doesn't 'look' cool but it works really well for me.If your shortsighted it helps because you can focus on things closer than other people."
},
{
"post_id": "",
"author": "Zbig",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 20, 2013, 10:04:51 am",
"content": "Quote from: nukie on July 18, 2013, 12:17:52 amRight, that's exactly what's been done with mine on the photo as well."
}
] |
2025-10-17T20:19:16.953026
| 23
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-91__-oled-alternate-lcd-in-terms-of-size/
|
0.91'' OLED alternate LCD in terms of size - Page 1
|
[
{
"post_id": "",
"author": "RoadRunner",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 01, 2014, 05:45:48 am",
"content": "for little watch project am currently searching for small graphics display size about 35mm x 15 mm, first i was looking at those small 0.91'' OLED display as then are very small about 30mmX12mm and resolution is 128x32 pix, but power consumption of these display is very high for a coin cell battery operated always on watch.i am currently having a LCD which are consuming very less current but size of them is about 30mmX30mm , LCD or epaper any other low power display technology will suit my design .sharp is having such LCD but i couldn't find where they are available for buy.http://www.sharpmemorylcd.com/1-17-inch-memory-lcd.htmldoes any one know any such display which will fit into such size?"
},
{
"post_id": "",
"author": "hagster",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 01, 2014, 05:56:23 am",
"content": "http://uk.mouser.com/ProductDetail/Sharp-Microelectronics/LS013B4DN04/?qs=e9D5lEuj8rnQMFXjsqGSMA%3d%3dSharp 1.35\" MEMORY DISPLAY"
},
{
"post_id": "",
"author": "RoadRunner",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 01, 2014, 06:15:38 am",
"content": "Quote from: hagster on May 01, 2014, 05:56:23 amevery things looks very impressive about these display but size is a little bigger i am looking for about 35mm x 15 mm and that display is 32mm x 25mm ."
},
{
"post_id": "",
"author": "lpc32",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 01, 2014, 08:47:22 pm",
"content": "This EPD at 29x22 is also bigger, but closer than the Sharp:http://www.digikey.com/product-detail/en/EK014AS014/EK014AS014-ND/4437987"
},
{
"post_id": "",
"author": "RoadRunner",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 01, 2014, 09:01:47 pm",
"content": "Quote from: lpc32 on May 01, 2014, 08:47:22 pmyep it is a little bigger."
},
{
"post_id": "",
"author": "casinada",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 01, 2014, 09:10:30 pm",
"content": "For just one project is $10 nowhttp://43oh.com/2014/04/ti-e-store-430-day-deals-15-to-50-off/http://www.ti.com/tool/430boost-sharp96?DCMP=ep-mcu-msp-430day&HQS=ep-mcu-msp-430day-mspblog-142804-evm3-en50% off with code : 430DAYBP"
},
{
"post_id": "",
"author": "miguelvp",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 02, 2014, 02:51:53 am",
"content": "Quote from: casinada on May 01, 2014, 09:10:30 pmThank you! ordered"
},
{
"post_id": "",
"author": "RoadRunner",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 02, 2014, 06:25:46 am",
"content": "Quote from: casinada on May 01, 2014, 09:10:30 pmalready ordered. but they are also large.sharp is having exactly what i need but that specific is not in stock anywhere at all.http://www.sharpmemorylcd.com/1-17-inch-memory-lcd.html"
},
{
"post_id": "",
"author": "lpc32",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 02, 2014, 02:13:39 pm",
"content": "That 1.17\" is 29x6mm. Not much height."
},
{
"post_id": "",
"author": "RoadRunner",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 03, 2014, 07:58:35 am",
"content": "Quote from: lpc32 on May 02, 2014, 02:13:39 pmit not about the height(thickness) its about the width , it suppose to as narrow as 0.91'' OLED display."
},
{
"post_id": "",
"author": "miguelvp",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 10, 2014, 12:32:42 am",
"content": "Quote from: miguelvp on May 02, 2014, 02:51:53 amGot it today, took them a while to ship it but I have something to play with over the weekend.Up to 60Hz frame rate and only 6 uW while not refreshing the screen and just 12 uW while in dynamic mode!Also the board supports other Sharp screens driven by SPI, and provide a DC/DC converter for displays that require 5V.Gonna try to get the DE-0 Nano FPGA to drive it.Edit: site doesn't like the Mu symbol for micro"
}
] |
2025-10-17T20:02:32.829818
| 11
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-96-oled-display-i2c-config/
|
0.96 OLED display I2C config - Page 1
|
[
{
"post_id": "",
"author": "jvlobo",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "May 09, 2022, 08:28:47 pm",
"content": "Hello everyoneI got a new display but I'm struggling to use it over I2C. I've been investigating and there seems to be many different versions of these SSD1306 0.96 OLED displays... and sadly the one I got doesn't come with any information on how to configure it for using it with I2C.This is the one I have:So I just connected the jumper on the left and middle pad that says \"HC\" (which I supposed it is IIC).But then I'm not sure if I should populate or change the position of any of the resistors/capacitors.I haven't been able to get anything on the display using I2C. But I was able to use it with SPI.If anyone knows or have experience with this display I would highly appreciate the help.Thanks a lot."
},
{
"post_id": "",
"author": "MikeK",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 09, 2022, 08:53:19 pm",
"content": "That's the SPI version, not I2C. I don't think you can change it."
},
{
"post_id": "",
"author": "jvlobo",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "May 09, 2022, 09:33:10 pm",
"content": "Thanks for the reply.But are you sure about that?? I've seen many different 0.96 OLED displays that work both with SPI and I2C.And this one has the jumper to select I2C/SPI."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 09, 2022, 09:47:32 pm",
"content": "I2C on a SSD1306 OLED needs D2 broken out, (and ideally run through an open drain buffer as its weaker than allowed by the I2C spec) as it provides the ACK from the display slave back to the master MCU, and needs to be connected to D1, the display's input-only SDA pin. Also there are two other pins that need a different state to select I2C mode vs SPI mode. If those pins are on the flatflex, you can trace what components to hack on the PCB, but if they aren't, you are S.O.L."
},
{
"post_id": "",
"author": "jvlobo",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "May 09, 2022, 10:09:15 pm",
"content": "Thank you.I was taking a look a thisdocumentthat shows some examples of how to interface the SSD1306. On the I2C I saw the D0 and D1 connected to 10K resistors (something that is not done on the SPI one). And on my board, I can see those two 10K resistors. That is also why I believed I could achieve the I2C connection here.I'm also tried to figure out the other pins but I'm a bit lost as the flex cable has 30 pins and in those examples there are 24."
},
{
"post_id": "",
"author": "ledtester",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 09, 2022, 10:17:23 pm",
"content": "This looks like the official SD1306 datasheet:https://www.rhydolabz.com/documents/SSD1306.pdfStarting on page 18 it describes how to configure the I/O lines for I2C, 3-wire SPI and 4-wire SPI.I found the datasheet on this page:https://www.rhydolabz.com/displays-c-88/096-oled-display-module-spii2c-128x64-6-pin-white-p-2260.htmland that has some pics of a 6-pin module with some resistor config information silk-screened on the back of the PCB."
},
{
"post_id": "",
"author": "jvlobo",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "May 09, 2022, 10:20:22 pm",
"content": "Thanks for the info. I'll take look to that document.Indeed the board's pins are like mine, just with SCL and SDA instead of D0 and D1."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 09, 2022, 10:27:32 pm",
"content": "The problem is: You need the pinout of the actual display (not the assembled display + breakout) to tell you which pin of the flatflex goes to which bump of the SSD1306 die, mounted chip-on-flex. To determine this you usually need the display part number which is on the back of the display which has been bonded to the other side of the breakout PCB, and its very unlikely for the display or the number to survive being peeled off to read it.You may be lucky and be able to identify enough pins by tracing them from named pins/pads of the breakout to the flatflex and match them up to a similar enough display with the same flatflex pinout, but if you get it wrong, odds are you'll damage the display."
},
{
"post_id": "",
"author": "jvlobo",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "May 09, 2022, 10:32:14 pm",
"content": "UnderstoodI will try to trace the pins but honestly, I'm taking this as a learning exercise so I wouldn't really mind damaging the display. They are not expensive so I could get an already working I2C out of the box. But having this one and having the possibility to get t to work over I2C I'm up for the challenge heheThanks!"
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 10, 2022, 01:59:13 am",
"content": "I have a couple of incantations of the 0.96 OLED display for I2C and they vary in that the Vcc and Gnd pins are swapped. Both have only 4 pins. This is the one I use with the MicroPython version of the ssd1306 driverhttps://www.amazon.com/gp/product/B085WCRS7CI'm not sure which version you have but I would be very curious about it being I2C.I'm pretty sure this is the library I use:https://github.com/micropython/micropython/blob/master/drivers/display/ssd1306.pyIt looks like I pulled out the SPI specific code to save a little space."
},
{
"post_id": "",
"author": "jvlobo",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "May 10, 2022, 08:09:51 am",
"content": "Thank you.I'll check it out."
},
{
"post_id": "",
"author": "DavidAlfa",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 11, 2022, 07:17:16 pm",
"content": "That's exactly your screen? In every detail?S1 looks like the interface selector (IM1), switching between VCC and GND, in that picture it's already set in I2C Mode! Left=i2c, right=spi.And R2+R3 seems to be the i2c pullups.In I2C Mode, the signals are as follows:- RST still provides reset functionality, it can also be left unused, connected to VCC.- DC is unused and must be connected to gnd (There's R6 for that)- CS is the I2C lower address bit, but it's already connected to gnd in that display.- D0=SCL- D1=SDAAre you correctly sending the data, following the I2C format?You can't just send the bytes as-is like in spi, the oled i2c protocol is like this:Code: [Address (0x3C)] [mode(cmd=0x00,data=0x40)] Ex. To turn the screen on:Code: (display on CMD)To send data (Write to the display RAM):Code: [data 0]...[data n] Edit: Confirmed:https://forum.arduino.cc/t/ssd1306-oled-display-config/658283"
},
{
"post_id": "",
"author": "jvlobo",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "May 11, 2022, 08:02:01 pm",
"content": "Thanks David.That is exactly my screen, correct. I took that picture.I tried connecting the pins as you suggested. To see if the I2C is working I'm running an I2C Scanner on my Arduino UNO:https://playground.arduino.cc/Main/I2cScanner/But it never finds anything"
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 11, 2022, 09:47:36 pm",
"content": "Quote from: DavidAlfa on May 11, 2022, 07:17:16 pmI wouldn't call that 'confirmed' as it was a single reply noting that 'HC' might represent 'IIC' thus I2C to an uneducated Chinese eye, so making the 'HC' side of the solder jumper might put it in I2C mode. There was no followup giving the O.P's success or failure.Lets refer to theSSD1306(IC) datasheet.N.B. This is not the display datasheet, just the COG or chip-on-flex display controller datasheet so you wont find the ribbon connector pinout in it or details of the display size.From an interfacing point of view, the interesting stuff starts just before section 8, with 'Table 7-1 : MCU Bus Interface Pin Selection' There are THREE interface selection pins BS0-BS2, which select the interface mode.Taking BS2 as the MSB:BS2:0 Interface000 4 wire serial001 3 wire serial010 I2C100 6800 parallel110 8080 parallelAs you can see its possible to switch between I2C and 4 wire serial by a single solder jumper for SSD1306 pin BS1.However lets review the connections given in section 8:Quote from: datasheetandQuote from: datasheetIf D2 (SDA out) is not linked to D1 (SDA in), the SSD1306 cant ACK any data or address it receives on the I2C bus. The pullup will provide a NACK instead. This is non I2C standard compliant as ACK is usually used to indicate the receiver is present cant can accept more data. Therefore without the D1-D2 link, the SSD1306 cant be seen byi2cdetector other I2C scanners as they probe each address in turn looking for an ACK to map the connected devices. You'll also have to configure your I2C library to perform multi-byte writes ignoring the NACKs, rather than aborting on the first NACK.Note that D2 is only for ACKs, you cant read back any SSD1306 registers or display RAM.If your display is COG, due to the ITO track resistance, D2 needs buffering with an open drain non-inverting buffer, so it can properly drive SDA low against the pullup current. If its chip-on-flex the low resistance copper tracks mean you don't need a buffer and can simply link D2 and D1.TLDR: find D2 and link it to D1 for I2C mode to work properly!"
},
{
"post_id": "",
"author": "jvlobo",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "May 11, 2022, 10:02:27 pm",
"content": "Thanks for the detailed explanationSo, from my original picture. Knowing (or assuming) that those two 10k resistors are connected to D0 and D1 I could assume that the next pin is D2, and the ones following, D3 to D7 are connected together to ground.The thing is that D2 in this case is also connected to D3-D7, not sure why this is like that or if was a defect. I'll try to \"disconnect it\" and see what I get."
},
{
"post_id": "",
"author": "jvlobo",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "May 11, 2022, 10:22:26 pm",
"content": "WOW, some progress!!QuoteSo cool 👏🏽👏🏽I tried with an example sketch from the Adafruit library and it shows a lot of dots on the screen, so something must be wrong still. I'll keep investigating"
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 11, 2022, 10:25:18 pm",
"content": "Disconnect it and patch it to a length of 30 AWG Kynar wirewrap wire or magnet wire so you can connect stuff to it. Connect it to a 10K pullup to +3.3V, and scope the signal on it. You should see a low-going ACK pulse for the receipt of the I2C display address byte and every data byte after it in the same transfer. If so, you can safely connect it to D1. If not, you've got the wrong pin or it isn't in I2C mode or you aren't using the correct display address.Edit: So you went ahead and tied it to D1, and it worked? *GREAT* Ignore the paragraph above!"
},
{
"post_id": "",
"author": "DavidAlfa",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 11, 2022, 11:10:58 pm",
"content": "Ian, I said so because to date, all spi oleds I had could be configured to i2c just like that.I don't have exactly that model, but they're all very similar.Also, I thought the 0.96\" used the SH1106, and the 1.3\" the SSD1306, they're very similar but not identical, check the SH1106 attachment.Also attached the pinout."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 12, 2022, 12:10:00 am",
"content": "Yes, displays with aSH1106controller don't need D2 strapped to D1 for I2C mode, as you note above. Fortunately, D2 is Hi-Z in I2C mode so strapping it does no harm.Probably the best way forward for a display that refuses to ACK and doesn't appear to have D2 strapped to D1, is to investigate D2 as I suggested in reply #16. If you get ACK pulses on D2, it must have a SSD1306 controller, so will need them strapped. If it doesn't ACK on D2 but does on D1 (check this first before hacking the PCB) it must be a SH1106. If the PCB already has D1 strapped to D2 you should be getting ACKs on the combined SDA, and you'll have to distinguish between them by the display address mapping, or by attempting to read from it.Note that reading from a SH1106 over I2C has some quirks. See:https://arduino.stackexchange.com/questions/50640/reading-ram-from-sh1106-oled-controller-through-i2candhttps://picaxeforum.co.uk/threads/fyi-comparing-the-ssd1306-and-sh1106-oled-drivers.32387/which goes into more detail as the PICAXE doesn't have an OLED driver library so they are doing 'bare metal' register level access."
},
{
"post_id": "",
"author": "jvlobo",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "May 12, 2022, 10:41:17 am",
"content": "Thanks a lot guys. Got it 100% working nowAs a summary, these are the things I had to do:Connect D2 to D1 (by soldering a thin wire straight on the actual board)Connect the pins (in my case testing with an Arduino UNO):RST: connect to Arduino's Reset pin or VCCDC: connect to GNDD0: connect to pin A5 (19)D1: connect to pin A4 (18)To see if the display is found over I2C you can try with aI2C scanner.Then, to actually get something on the screen, I tried with the examplesimple_demofrom thess_oledlibrary, specifying the pins for SDA and SCLCode:#define SDA_PIN 19#define SCL_PIN 18And it works!Thanks again everyone. Hopefully this helps someone else out there"
}
] |
2025-10-17T17:10:50.184840
| 20
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0-ohm-resistors/
|
0 Ohm resistors - Page 1
|
[
{
"post_id": "",
"author": "madmaxbryan",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 08, 2011, 02:25:12 am",
"content": "What is the purpose of 0 ohm resistors? I have noticed a lot lately that most of the boards i assemble at work are using 0 ohm resistors rather then simply using jumper wires. For us the process is exactly the same for both jumper wire and resistors, same axial sequencer/inserter, same wave soldering process, same everything on our end. so wouldn't it be cheaper to use jumper wires rather then 0 ohm resistors?"
},
{
"post_id": "",
"author": "dmlandrum",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 08, 2011, 02:35:42 am",
"content": "I remember someone explaining on another board that pick and place machines have problems placing with little bits of wire, so they make the little bit of wire look just like a resistor and call it 0 ohms. Something like that, anyway."
},
{
"post_id": "",
"author": "DavidDLC",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "April 08, 2011, 03:03:05 am",
"content": "They could be also to make selections, like decimal places on Panel Meters.In the other hand 0 ohm resistor looks much better than wires."
},
{
"post_id": "",
"author": "madmaxbryan",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 08, 2011, 03:29:46 am",
"content": "as far as i know, pick and place machines cant be used at all for through hole parts, thats why we use an axial sequencer and axial loader. it bends and loads jumper wires just as good as it can for resistors or any other axial component"
},
{
"post_id": "",
"author": "PetrosA",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "April 08, 2011, 03:55:45 am",
"content": "0 Ohm resistor sounds like the kind of oxymoron Kurt Vonnegut or Joseph Heller would have thunk up"
},
{
"post_id": "",
"author": "Kiriakos-GR",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 08, 2011, 05:51:47 am",
"content": "Well for true low ohm bridges , only the silver wire can do the trick.But it costs a bit."
},
{
"post_id": "",
"author": "Simon",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "April 08, 2011, 06:37:35 am",
"content": "even silver wire will have an infinitesimal resistance. The term \"0\" ohm resistor really is just saying a jumper in the form of a resistor case"
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 08, 2011, 06:43:36 am",
"content": "0 ohms are quite handy when you want to make it easy for areas of your circuit to be disconnected from each other.For example, they quite often put one 0 ohm resistor in each power rail in cellphones (there are often 10 or so power rails for various things). It makes it easy to debug when you're trying to optimize power usage and reduce usage when in cpu sleep modes.You can unsolder a few 0 ohms and watch the overall current to see which area of the circuit is drawing power when it shouldn't be. You can also replace the resistor with some wires and measure the current directly."
},
{
"post_id": "",
"author": "mikeselectricstuff",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 08, 2011, 07:38:51 am",
"content": "Many years ago the Farnell catalogue had some 0R resistors listed with a 5% tolerance spec..."
},
{
"post_id": "",
"author": "madmaxbryan",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 08, 2011, 08:10:56 am",
"content": "so what is the point of using 0 ohm resistors over jumper wires? since a 0 ohm resistor is just a jumper wire with a resistor casing on it."
},
{
"post_id": "",
"author": "jahonen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 08, 2011, 08:54:40 am",
"content": "For SMD pick and place machines, chip 0R resistors are considerably more suitable than just a piece of wire. Most typical use for them here is to add possibility to easily cut signals when debugging designs if there are uncertainties involved, and they are usually removed at final stages of product development.0R resistors are something like 50 milliohms in reality. I had a case where I had to change 0R jumpers (used for prototype testing purposes) to 10 milliohm resistors (also used in the product), due to that the 0R resistors had inconveniently large voltage drop (three in parallel) for the current.Regards,Janne"
},
{
"post_id": "",
"author": "RayJones",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "April 08, 2011, 09:23:19 am",
"content": "Quote from: mikeselectricstuff on April 08, 2011, 07:38:51 amThey also list a power rating too! sort of crazy with \"0\" entered into the good ol I2R"
},
{
"post_id": "",
"author": "madmaxbryan",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 08, 2011, 09:27:24 am",
"content": "i can understand the usefulness of them in surface mount boards, but what about in through hole boards?"
},
{
"post_id": "",
"author": "Strube09",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 08, 2011, 12:18:01 pm",
"content": "I frequently use \"0\" Ohm resistors to allow for selecting options on my PCBAS.We have some boards at my work that are all the same layout and software but by populating the board with a 0Ohm in one slot or a 0Ohm in second slot activates powers different hardware or software options. Cheaper and smaller than dip switchesStrube"
},
{
"post_id": "",
"author": "madmaxbryan",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 08, 2011, 12:39:52 pm",
"content": "so heres a picture of what im talking about:I would think it would be cheaper to use the jumper wires they use in that picture rather then 0 ohm resistors."
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 08, 2011, 02:25:19 pm",
"content": "i think in through hole boards the zero ohm resistors (actual resistors with one black band) are mostly used as poor mans fuses. ie, intended to be a point of failure that is easy to detect/replace.Another reason maybe that, since the are the same size/shape as normal resistors, they can be used in whatever equipment or gear you might have in production/assembly that uses normal resistors.If you used wire instead you'd have to get it pre-bent to the right width or bend it yourself. Neither option would be as cost effective as a zero ohm resistor which can be produced in huge quantities easily with existing resistor manufacturing gear and meets specific standards on size/width etc.."
},
{
"post_id": "",
"author": "apex",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 08, 2011, 03:46:36 pm",
"content": "In a gadget I built about a year ago, I used zero ohm resistors as extremly low value shunt resistors.Their range is from 10 miliohm to about 100 miliohm.Since my device was self-calibrating, It could use about any resistor given...apex"
},
{
"post_id": "",
"author": "Simon",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "April 08, 2011, 07:11:30 pm",
"content": "what I don't understand is if there are under 10mOhm resistors why are \"0\" ohm resistors well over that in some cases ? I mean all you really need is a chuck of copper of the correct size possibly with a paint coating around the middle"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 08, 2011, 08:38:29 pm",
"content": "My guess is the 0 Ohm resistor manufacturers are just covering themselves for the worst case scenario. In real life, they're most likely to be much less than 0 Ohm. 10m Ohm resistors are also normally surface mount and physically larger than some 0 Ohm resistors."
},
{
"post_id": "",
"author": "Wim_L",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 08, 2011, 10:22:35 pm",
"content": "Quote from: Hero999 on April 08, 2011, 08:38:29 pmNeat! Cheapo two-wire amplifiers, no need to order tunnel diodes anymore"
},
{
"post_id": "",
"author": "RayJones",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "April 08, 2011, 11:47:11 pm",
"content": "Add a flux capacitor and the time machine is ready for action."
},
{
"post_id": "",
"author": "Wim_L",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 08, 2011, 11:56:45 pm",
"content": "They're great for charging batteries too!"
},
{
"post_id": "",
"author": "Simon",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "April 09, 2011, 06:49:45 am",
"content": "Quote from: Hero999 on April 08, 2011, 08:38:29 pmYou work for Farnell ? first they are 5% on 0 ohms now they are less than 0 ohms"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 09, 2011, 07:57:58 am",
"content": "Quote from: Wim_L on April 08, 2011, 10:22:35 pmLol, I think you probably know what I meant though."
},
{
"post_id": "",
"author": "Simon",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "April 09, 2011, 08:03:38 am",
"content": "err not really but I'll pretend i do"
},
{
"post_id": "",
"author": "gxti",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "April 12, 2011, 07:03:59 am",
"content": "Quote from: madmaxbryan on April 08, 2011, 12:39:52 pmYou're right, jumpers should cost less than jumpers with ceramic on them. It's possible that some machines can't handle bare jumpers, but if yours can then I've got no clue. You'll have to ask whomever is giving you these designs.Sort of funny how many people in this thread keep offering the same explanation about SMD pick-and-place because they aren't reading..."
},
{
"post_id": "",
"author": "tnt",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 12, 2011, 08:07:27 am",
"content": "Is it easy to find jumpers on reels ?"
},
{
"post_id": "",
"author": "metalphreak",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "April 12, 2011, 01:32:04 pm",
"content": "If anyone has ever seen the Atmel ButterFly developement boards, mine came with what was essentially a COM Port socket, with a 3pin header and some 0 Ohm resistors to connect to the board. Only thing I can think of, is that it stops solder from flowing from one side to the other, especially when the axial leads are cut short. It also provides some insulation, if the jumper is going across exposed tracks or other components."
},
{
"post_id": "",
"author": "madmaxbryan",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 13, 2011, 12:06:06 am",
"content": "Yes, you can find 0 ohm through hole resistors on a tape reel. any axial sequencer and inserter will cut and bend then the same way they would a regular resistor, it doesnt know the difference. if you take a 0 ohm through hole resistor and smash the ceramic off, you will see that its just a straight piece of wire (jumper wire) with the ceramic around it, theres really no resistance other then what little bit the wire itself might have."
},
{
"post_id": "",
"author": "tekfan",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "April 13, 2011, 03:51:47 pm",
"content": "Quote from: Wim_L on April 08, 2011, 10:22:35 pmAre tunnel diodes really unobtainable? I can't seem to find anyone that sells them. Can't even find the once popular 1N37xx series!"
},
{
"post_id": "",
"author": "Neilm",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 13, 2011, 07:50:06 pm",
"content": "The main reason for 0 ohm links is to give the designer some flexibilty on the board.If a designer thinks that a resistor might have to go there when the board is tested then the 0 ohm link puts pads where he wants. It can also be used to bypass bits of circuit. For example I have designed a widget that comes in several flavours. If you don't want all the bells - then the circuit is bypassed by fiting the link (and money is saved by not fitting the components. Alternativly, if you want the bell the 0 ohm link is not fitted and the other circuitry is. This will allow a designer to increase the volumes on the PCB and reduce the cost.YoursNeil"
},
{
"post_id": "",
"author": "Wim_L",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 13, 2011, 10:11:25 pm",
"content": "Quote from: tekfan on April 13, 2011, 03:51:47 pmI do think they're still around, but have mostly been replaced by fast IC amplifiers which are somewhat less tricky to use. There are also Gunn diodes which have similar characteristics, but they also seem unavailable through the usual big names. I suppose they're specialty devices mostly used by those with special high frequency needs."
},
{
"post_id": "",
"author": "ArtemisGoldfish",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 18, 2011, 06:13:54 am",
"content": "Just for kicks,http://farm6.static.flickr.com/5302/5614765792_bac140e704_b.jpgHere's a picture of a board with quite a few 0 Ohm resistors."
},
{
"post_id": "",
"author": "tekfan",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "April 18, 2011, 01:02:21 pm",
"content": "Quote from: ArtemisGoldfish on April 18, 2011, 06:13:54 amWow. That's some very high frequency design right there. You can see that the 0 ohm resistors are used as jumpers to go above the ground planes. Maybe they're even used as extremely low value capacitors. It doesn't take much capacitance to make a big difference in a >10GHz circuit like this."
},
{
"post_id": "",
"author": "Zad",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 18, 2011, 02:46:31 pm",
"content": "Quote from: ArtemisGoldfish on April 18, 2011, 06:13:54 amAs someone who does RF work, can I just say that board is pure pornographic FILTH!"
},
{
"post_id": "",
"author": "House91320",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 25, 2011, 01:04:21 am",
"content": "how would a zero ohm resistor be possible"
},
{
"post_id": "",
"author": "Joshua",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 25, 2011, 02:12:03 am",
"content": "In Dave's latest review of the hot air rework station (Atten?), On the pcb, you can see some 0 ohm resistors.Joshua"
},
{
"post_id": "",
"author": "ciccio",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "August 09, 2011, 08:23:14 pm",
"content": "Well, through-hole 0 ohm resistors are simply jumper wires with a plastic (or ceramic) coating in the middle.They are available in reel form, and can be prepared (bent and cut) and eventually inserted in the PCB with the same tools that are used for standard resistors.They were available also as simple pieces of wire, without the \"resistor like\" body, taped in reels.Many years ago I've seen a machine that, starting from a spool of solid wire, was capable of straightening it ,cutting it to length and bending it to U-shape, ready for insertion.I believe that these machines are still used for large productions, especially for single sided boards, but a simple piece of wire has some disadvantages:- it is difficult to handle (by hand): the \"resistor body\" type is larger, and is easier to pick-up and insert by hand- it is too lightweight, so it moves up during board manipulation and wave-soldering process (see photos in a previous post: the jumper wires don't look very professional...- for double-sided boards, it can short to top-side copper traces if the solder-resist is damaged.This is the reason that, for low production runs, they use the \"resistor-like\" type (the one with the single black band). For large production runs, I have no recent experience: nobody makes large production anymore, here in Italy....Regarding \"wattage\", obviously it has no meaning: it is a simple way to indicate size (yes, they have quarter an half watt types).Why are they used? There are multiple reasons:- on single sided boards, as jumpers to replace a track that should be on component side.Sometimes even in dual-side boards some reasons (difficult routing of tracks, track size, \"straighter\" way for signal, etc) suggest to use a jumper.- on both single and dual sided boards I've used (and seen other designers use) jumpers (made with wire or with \"zero ohm\") to leave the possibility of an afterthought, or to allow for different versions of the same boards, or whatever.I've not a great experience with the SMD version, but I believe they are used for the same reasons.Last point:ohm must be written with lower case letters. Upper case must be used for the unit's symbol (in this case a Greek omega, that I cannot write here).The same for volt, ampere, watt, meter, farad, henry, etc..."
},
{
"post_id": "",
"author": "gregariz",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "August 09, 2011, 08:54:04 pm",
"content": "Quote from: ciccio on August 09, 2011, 08:23:14 pmI used the old fashioned shorting pins and plugs several years ago. They are still available at places like keystone. But most people design them out these days by simply using multiple layer boards. The other reason would be in high power stuff. I'm working on a high power amplifier at the moment where 0 ohms are just not going to cut it so I've opted for shorting plugs instead.I almost always use 0 ohms on RF designs in order to debug a board during prototyping and usually keep them in during the manufacturing cycle (they cost almost nothing and will help in later debugging of any problems). The reason is that an RF design never comes up without a whole lot of bench work and you need to isolate it section by section until it all works together. Then put the 0's in (quite often I'll use a 1nF cap instead of a 0) and voila.."
},
{
"post_id": "",
"author": "ejeffrey",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 09, 2011, 09:06:31 pm",
"content": "One reason to use zero-ohm axial resistors over wire links is that they are insulated. This would be important if you were using them on a hand etched board with no solder mask. Even a commercial product with a nice mass produced PCB may have started out with a hand etched board. It also helps prevent contact with adjacent components, if only by forcing you to space your wire links to accommodate the resistor body.For mass production it helps that they come on reels with the same dimensions as a regular resistor.For hand assembly of manufactured PCBs with solder mask, I don't see a real advantage -- as long as the board actually has the space allocated as it would for a regular resistor."
},
{
"post_id": "",
"author": "metalphreak",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "August 10, 2011, 01:11:10 pm",
"content": "Most of the jumpers they use in single sided boards (the ones without any ceramic package) usually just come in a big bag, and are hand fitted.http://www.goodluckbuy.com/3-10mm-length-u-shaped-silver-tone-jumper-wire-cable-for-breadboard-thick-10000-pcs-.htmlI grabbed a bag of 8mm jumpersThey're perfect for bridging the centre gap on breadboards (2 pin gap between each end)"
},
{
"post_id": "",
"author": "AntiProtonBoy",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "August 10, 2011, 04:22:15 pm",
"content": "Quote from: ArtemisGoldfish on April 18, 2011, 06:13:54 amIt's witchcraft... all of it..."
}
] |
2025-10-17T20:38:39.070709
| 42
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/01r-vs-1r0/
|
01R vs 1R0 - Page 1
|
[
{
"post_id": "",
"author": "Rick Law",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "November 05, 2015, 10:10:02 pm",
"content": "Is there any difference between 01R vs 1R0 on the SMD? They are both 1ohm according to nomenclature.I see both on a PC server motherboard. That led me to think it may not be just different manufacturer as the server-board guy likely purchased the 01R and 1R0 from the same maker."
},
{
"post_id": "",
"author": "tron9000",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 05, 2015, 10:13:42 pm",
"content": "give it a test with the ol' DMM"
},
{
"post_id": "",
"author": "Monkeh",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 05, 2015, 10:44:12 pm",
"content": "Quote from: Rick Law on November 05, 2015, 10:10:02 pmI'd be willing to bet the P&P (or P&Ps) had multiple reels of 1R. They place A Lot™ of parts."
},
{
"post_id": "",
"author": "Maxlor",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 05, 2015, 10:49:21 pm",
"content": "There's a difference in the accuracy of the parts I'd guess?"
},
{
"post_id": "",
"author": "TimFox",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 05, 2015, 11:29:39 pm",
"content": "Leading zeros are not significant.Trailing zeros are significant."
},
{
"post_id": "",
"author": "Rick Law",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "November 06, 2015, 07:02:29 pm",
"content": "Quote from: tron9000 on November 05, 2015, 10:13:42 pmWith just it expected to be around 1ohm, testing in-circuit is likely not meaningful. This one looks like an 0603 or smaller on a still-in-used motherboard. It is easy to loose something that small when removed. I have yet to find a 0805 green LED that I knew for sure felt off the table and by now probably in LED heaven.These days, I scotch-tape SMDs down on the table top and only remove it from the scotch-tape covering when I am fully ready to solder that specific SMD.Quote from: TimFox on November 05, 2015, 11:29:39 pmThis is a good thought.* 01R is 1ohm with 1-digit accuracy.* 1R0 is 1.0 ohm with 2-digit accuracy.Unless/until another reason pops up, I will take it as 1 or 2 digit accuracy, I suppose. But I am still uncomfortable with that since accuracy is typically specified as 1% 5%... This is too esoteric even for my curiosity."
},
{
"post_id": "",
"author": "fivefish",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 06, 2015, 08:07:11 pm",
"content": "Who still uses 5% resistors? It's not the 80s anymore, 1% can be bought for $5.00 for 200pcs. They're so cheap nowadays.I only use 1% or better now in all my projects except if a value is OUT OF STOCK and I just want to get the project going, then I'll buy the 5%."
},
{
"post_id": "",
"author": "Rick Law",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "November 06, 2015, 08:46:09 pm",
"content": "Quote from: fivefish on November 06, 2015, 08:07:11 pmre: \"Who still uses 5% resistors?\"Yeah, I agree with what you said. Failing to find any difference between 1R0 vs 01R, I consider 1 ohm vs 1.0 ohm as aplausible explanationfor now.Quote from: Monkeh on November 05, 2015, 10:44:12 pmThis is also a very likely explaination in my mind. It could be just manufacturers labeling identical stuff differently. AsMonkehsuggested, it could be there was a wheel change between R5 and R36 (I am making the resister number up, I am not going to re-open the server just to re-read the resister number printed on the PCB)."
},
{
"post_id": "",
"author": "m98",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 06, 2015, 09:36:11 pm",
"content": "Quote from: fivefish on November 06, 2015, 08:07:11 pmEven in high-end products you won't waste money on not needed accuracy. Why would you waste more than one cent per resistor just to have for example an 1% accurate pull-up?"
},
{
"post_id": "",
"author": "fivefish",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 07, 2015, 02:12:32 am",
"content": "Quote from: m98 on November 06, 2015, 09:36:11 pmAnd I don't think manufacturers would waste an entire PNP feeder to load a 5% resistor just to save one cent for a pull-up resistor using your example, they'll just use other existing resistor values, even if it's 1%.In the same way that re-using resistor values rather than waste an entire feeder to load a different value... i.e. just load a single 10K reel on the feeder, and design the board to use (2) 10K resistors in parallel, rather than using a separate 10K and 5K reel of resistors."
},
{
"post_id": "",
"author": "logictom",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "November 07, 2015, 04:48:38 am",
"content": "Quote from: fivefish on November 07, 2015, 02:12:32 amSurely this is a toss up between how many reels are required for the run therefore how many runs through a pick'n'place vs the cost of adding two parts rather than one, board space taken up, number of boards run, etc, etc - it comes down to design/manufacturer specifics.I guess there's rules of thumb but how could you generalise it one way or the other?"
},
{
"post_id": "",
"author": "m98",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 07, 2015, 09:56:16 pm",
"content": "Quote from: fivefish on November 07, 2015, 02:12:32 amSure, that depends on the application. But often you won't need any 1% resistors in a (digital) circuit."
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 08, 2015, 02:48:50 pm",
"content": "Quote from: m98 on November 07, 2015, 09:56:16 pmTrue, but the manufacturer might already have the part in a feeder on the machine for another job, so it makes sense to simply use it as it meets the required spec. The particular board might only be a small run in amongst a larger run of boards, so minimising the number of feeder changes between jobs is a good thing to save wear on them, plus the cost difference between the parts might be zero. You often design a board and component layout based on a particular manufacturer's standard part feeder list, so that you do not pay a rereeling fee to have a part placed in a feeder just for you."
}
] |
2025-10-17T19:30:42.593260
| 13
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0603-package-used-instead-of-a-jumper-wire/
|
0603 package used instead of a jumper wire? - Page 1
|
[
{
"post_id": "",
"author": "Falcon69",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "September 16, 2014, 07:44:17 pm",
"content": "I am running into a problem with a circuit I am working on. Things are just way to tight on this board. Is it okay to use an 0603 instead of a jumper wire? I don't have space underneath to connect the ground plane of two connected vias that are connected to a component on the top layer. But, I may be able to run a 0603 across a trace on the top plane, then connect it to the ground of another component to connect that ground plane.I found some 0ohm resistors, would those work as a jumper?"
},
{
"post_id": "",
"author": "Pedram",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "September 16, 2014, 07:58:26 pm",
"content": "yes it works. but not for high frequency signals or very high impedance analog traces.also note that they cannot handle much current. ~1A typical."
},
{
"post_id": "",
"author": "Simon",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "September 16, 2014, 08:14:27 pm",
"content": "I believe that that is exactly what 0 ohm resistors are for and for what they will cost much cheaper to implement as they can be assembled with the rest of the board in a pick and place machine instead of being hand soldered jumpers later."
},
{
"post_id": "",
"author": "Falcon69",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "September 16, 2014, 08:31:20 pm",
"content": "OKay, sounds good.I have two more traces to do, and the might just be the fix!And yes, I know about the power rating. 0603 1/4 resistors should be fine.Are you saying, because they are 0 ohm, they can actually handle around 1A?"
},
{
"post_id": "",
"author": "Chris_PL",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "September 16, 2014, 08:58:27 pm",
"content": "Quote from: Falcon69 on September 16, 2014, 08:31:20 pmThey can handle *only* around 1A, because they *are not 0 ohm* in reality (in fact, nothing is, but this is a topic for a PhD thesis). In terms of current handling and so on, a jumper wire with 0603 diameter will do better of course."
},
{
"post_id": "",
"author": "Simon",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "September 16, 2014, 08:59:47 pm",
"content": "I don't know what they are made of but erm 0 ohm means no voltage drop so no power loss, of course they are not really 0 ohm and have a small resistance just like wire. 1A sounds right"
},
{
"post_id": "",
"author": "Falcon69",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "September 16, 2014, 09:10:09 pm",
"content": "cool, sounds easy enough.thanks guys"
},
{
"post_id": "",
"author": "Monkeh",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 16, 2014, 09:14:40 pm",
"content": "Quote from: Chris_PL on September 16, 2014, 08:58:27 pmDepends on the jumper. 'jumper' versions of standard resistors are a bit meh. Dedicated jumpers, well:http://rohmfs.rohm.com/en/products/databook/datasheet/passive/resistor/chip_resistor/pmr_jumper.pdf"
},
{
"post_id": "",
"author": "mikeselectricstuff",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 16, 2014, 09:40:41 pm",
"content": "Just make sure you use 1% ones"
},
{
"post_id": "",
"author": "Falcon69",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "September 16, 2014, 09:46:45 pm",
"content": "good point."
},
{
"post_id": "",
"author": "w2aew",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 16, 2014, 09:50:45 pm",
"content": "Quote from: mikeselectricstuff on September 16, 2014, 09:40:41 pmLOL!"
},
{
"post_id": "",
"author": "ConKbot",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 17, 2014, 01:46:51 am",
"content": "Quote from: mikeselectricstuff on September 16, 2014, 09:40:41 pm1%? Cheapskate!http://www.mouser.com/ProductDetail/Panasonic/ERJ-8GEY0R00V/?qs=sGAEpiMZZMvdGkrng054tw5%2fFYq5P%2fDo57ZeXVhw7gE%3d0.05% or bust!"
},
{
"post_id": "",
"author": "robrenz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 17, 2014, 02:15:17 am",
"content": "Mouser listing is wrong. The data sheet says 5% tolerance.But what is 5% of 0?A piece of 24ga solid copper .06 long is .000128 Ohms so 5% would be +/- .000006 Ohm"
},
{
"post_id": "",
"author": "Falcon69",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "September 17, 2014, 02:17:00 am",
"content": "Is that basically what is inside those zero ohm resistors? Just a piece of copper wire?"
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 17, 2014, 08:27:35 am",
"content": "No, they are manufactured with the same metallic paste as regular resistors, except it's put on thicker and, obviously, not laser trimmed to an exact value. You can use them for small resistances if you want, but don't expect great tolerance.Tim"
},
{
"post_id": "",
"author": "lilmantis",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "September 22, 2014, 02:36:50 pm",
"content": "I've seen these with up to 75-100 mOhms"
},
{
"post_id": "",
"author": "idpromnut",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "September 22, 2014, 03:00:00 pm",
"content": "If it's a layout issue (i.e. things are getting tight etc space-wise), this is typically a good time to stop and take a step back and ask yourself where the issue really is: perhaps the placement of your components on the board can be re-arranged to not have to use the jumpers (especially for a ground plane). If that doesn't work, go back and check your schematic for optimizations that you can make there which will help you lay out the board.I'm sure others here can throw out a few words of wisdom in terms of tricks to use to help ease the layout step of a new design. Try to lay out the board without jumpers!"
}
] |
2025-10-17T19:55:04.296265
| 17
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0603-resistor-pad-smaller-than-physical-resistor/
|
0603 resistor pad smaller than physical resistor - Page 1
|
[
{
"post_id": "",
"author": "DroneBuster",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "July 05, 2016, 07:41:52 pm",
"content": "Hi,Is it normal that high density pads are narrower than resistor (footprints generated with Altium IPC compliant footprint wizard)Pictures attached"
},
{
"post_id": "",
"author": "Christe4nM",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "July 06, 2016, 07:47:54 am",
"content": "No that seems wrong to me. The pad must be at least as wide as the terminal. If I remember correctly, a tiny bit wider even for IPC \"least\" (i.e. high density) footprints.A quick search gave me this IPC calculator at their official site, it might help:http://www.ipc.org/ContentPage.aspx?pageid=Land-Pattern-CalculatorBut do check if you entered the right dimensions into Altium's calculator. And also check if your 3D body has the right dimensions. Just to make sure you're not chasing the wrong error"
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 06, 2016, 09:36:18 am",
"content": "Side fillet can be -0.03mm.Tim"
}
] |
2025-10-17T19:15:42.649105
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0hz-600hz-5v-square-wave-doubler-circuit/
|
0Hz - 600Hz 5v Square Wave Doubler circuit? - Page 1
|
[
{
"post_id": "",
"author": "madhushankarox",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 30, 2015, 08:34:35 am",
"content": "I'm new to this forum and this is my 1st post to ask some help from electronic expertsFirst of all I'm not an Electronic expert or I don't have knowledge to design electronic circuits.Can some one help me to build a square wave doubler circuit to multiply the frequency of a variable square wave? I have an electronic speedometer to be calibrated, so the issue is my speedometer reads 50% off from the actual speed (due to a incompatible sensor).Sensor output is a 5v square wave.Frequency will be 0Hz to 600Hz (169.9Hz = 60Km/h)Here is the speedometer's PCB:(I have tried JayCar speedometer calibration unit too. It was failed to detect the input signal)"
},
{
"post_id": "",
"author": "Rerouter",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 30, 2015, 10:08:55 am",
"content": "your driving it with the wrong signal type... 5096 pulses per km (85Hz @ 60) is the norm, add a 10uF cap in series with your input signal and add a 1K resistor on the circuits side of the cap to ground,also for a yazaki pcb of this age replace all the electro's. when these caps leak and they will, they end up chewing that board to bits"
},
{
"post_id": "",
"author": "madhushankarox",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 30, 2015, 12:08:25 pm",
"content": "Quote from: Rerouter on March 30, 2015, 10:08:55 amHey, Thank you very much for the reply. Please see attached image. There is a 1uf cap in series with the signal input (see marked cap). Is it okay to leave it as it is and add an extra 10uf cap in series?(PS: This is not the original PCB. This is an extra one I used to test. I will change caps too.)"
},
{
"post_id": "",
"author": "madhushankarox",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 30, 2015, 01:00:19 pm",
"content": "Quote from: Rerouter on March 30, 2015, 10:08:55 amI've added a capacitor (c1) and a resistor (r1) as follows. c2 is the stock one I already had.I tried inputting a 169Hz wave and It still reads 60Km/h"
},
{
"post_id": "",
"author": "German_EE",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 30, 2015, 03:22:34 pm",
"content": "http://www.mikrocontroller.net/attachment/19388/clock_doubler.pngThe 74HC86 is a quad XOR gate."
},
{
"post_id": "",
"author": "PA0PBZ",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 30, 2015, 03:28:21 pm",
"content": "Quote from: German_EE on March 30, 2015, 03:22:34 pmQuote"
},
{
"post_id": "",
"author": "madhushankarox",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 30, 2015, 03:54:14 pm",
"content": "Quote from: German_EE on March 30, 2015, 03:22:34 pmIs there any way to mod above PCB? or do something as previous members idea"
},
{
"post_id": "",
"author": "grumpydoc",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 30, 2015, 10:40:44 pm",
"content": "Quote from: madhushankarox on March 30, 2015, 03:54:14 pmYou would need to change the values of R1and C1, however the circuit only works well for a single input frequency depending on the values of these two components. As you move away from that frequency the output will become progressively more asymmetric - at much lower frequencies than intended it will consist of a series of short pulses around the transitions in the input where the pulse duration is a function of the R1C1time constant. As you increase the input frequency the circuit will stop working properly at all once the input frequency is more than twice the set frequency.Your problem is that you actually have quite a wide frequency range to deal with - if you set the values to double the 600Hz output it probably isn't going to work as intended at 1Hz or 10Hz"
},
{
"post_id": "",
"author": "madhushankarox",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 31, 2015, 12:29:51 am",
"content": "Quote from: grumpydoc on March 30, 2015, 10:40:44 pmThank you very much for the reply.. Is there any way to make some changes to the original PCB?"
},
{
"post_id": "",
"author": "grumpydoc",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 31, 2015, 06:26:31 am",
"content": "QuoteJust to be clear I was talking about that little clock doubler circuit that was posted.As to the speedo PCB - sometimes there's a resistor which sets the scaling.How have you ended up with an incompatible sensor and speedometer PCB?"
},
{
"post_id": "",
"author": "Sirius631",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "March 31, 2015, 11:00:19 am",
"content": "Quote from: PA0PBZ on March 30, 2015, 03:28:21 pmI can't go into figures, but it might be possible to make the résistance frequency dependant so that the duty cycle of the output can be maintained at varying frequencies.Place a JFET, drain to source, in series with a smaller resistor, to replace the one currently shown. Take the original square wave, smooth it and apply resultant DC signal to gate of JFET. You'll probably need op-amp to invert or otherwise match JFET's RDS to required frequency response."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 31, 2015, 11:14:03 am",
"content": "The first thing I'd check is if the speedo actually needs a reasonably good squarewave, or whether its happy with a low duty cycle pulse as you *may* be over-complicating this."
},
{
"post_id": "",
"author": "dannyf",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 31, 2015, 11:23:09 am",
"content": "Use the frequency signal to drive a motor and on the motor mount a set of sensors, depending on how fast you want to the output signal to be."
},
{
"post_id": "",
"author": "PA0PBZ",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 31, 2015, 11:26:24 am",
"content": "It would be hard to do with discrete logic, but even the smallest pic processor should be good enough to measure the input frequency and output double that."
},
{
"post_id": "",
"author": "grumpydoc",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 31, 2015, 12:25:42 pm",
"content": "QuoteTo do it with a purely digital solution might be quite difficult - totally over-engineering the problem I though you could do it by counting a higher frequency using the input as a gate, then dividing the count by 2 and using that as the input to a programmable divide-by-n counter.Or, presumably, in the analogue doman a suitably configured LM331 acting as a frequency-t-voltage converter could then drive one configured as a voltage-to-frequency converterSledgehammer, nut"
}
] |
2025-10-17T19:44:15.511082
| 15
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0r-ferrite-beads-are-they-real/
|
0R ferrite beads ... are they real ?? - Page 1
|
[
{
"post_id": "",
"author": "softfoot",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "July 27, 2020, 07:33:54 am",
"content": "I've been in electronics for some years but I was looking at a design that called for a 0R ferrite bead in a power supply line.Zero ohm impeadanceYou can buy them on eBay for example but are they an inductor at all ??It strikes me that they are in essence a wire link rather like the 0R resistors you often find in a schematic to facilitate testing or controlling options.Have I got the wrong end of the stick hereTIA,Confused Dave"
},
{
"post_id": "",
"author": "Vovk_Z",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 27, 2020, 07:58:52 am",
"content": "They have some resistanse of cause. It can be about 5-20 mOhm (+-) depends on wire size, look at datasheet (I'm talking abou wired ferrite beards). They have inductance too - it is about 0.5-1.0 uH (at 100 kHz).And there is a type without wires - just small ferrite tubes."
},
{
"post_id": "",
"author": "Unixon",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 27, 2020, 07:59:51 am",
"content": "I guess something like a BL01/BL02/BL03 ferrite jumper (e.g. BL01RN1A1D2B) is implied."
},
{
"post_id": "",
"author": "brabus",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 27, 2020, 09:12:39 am",
"content": "They act as a short circuit in DC, but significantly increase their impedance in certain frequency bands, specified in the datasheet. Be careful though: they do not work as inductors, as they dissipate the energy rather than storing it.This exact behavior is desired in order to dampen any disturbance in the target band."
},
{
"post_id": "",
"author": "Siwastaja",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 27, 2020, 10:13:40 am",
"content": "It's a completely meaningless specification.The designer meant something, but wrote down something else. You can only ask the designer.Ferrite beads are different and they should be specified with part numbers, or at least with the basic stack of parameters like impedance @ 100MHz, DC resistance, and maximum current. Saturation current would be necessary as well but as the manufacturers fail to provide that, designers can't specify it either."
}
] |
2025-10-17T17:45:26.265932
| 5
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0v-15v-to-5v5v-question/
|
0V-15V to -5V|+5V question - Page 1
|
[
{
"post_id": "",
"author": "MegaWatt",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "August 11, 2013, 07:23:31 pm",
"content": "Hello everybody, I have designed a circuit to convert a 0-15V power supply to a -5V|+5V supply. You can see it on this picture:The voltages that I have written there are the voltages I measured when I built the circuit. Obviously this is not correct and I cannot find why, I would expect the inputs of the voltage regulators to be at +/-7.5V and the output at +/-5V, but that is not the case. I have already disconnected the diodes to check if they were causing problems but the result was the same. Can anybody see what I might be doing wrong? Thanks in advance!"
},
{
"post_id": "",
"author": "Dave",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 11, 2013, 07:48:04 pm",
"content": "The way I see it, you only have 2 input connections, right?You need to provide an unregulated positive supply rail, negative rail, AND ground. Just connecting 15V between positive and negative rail won't cut it.If your load doesn't require much power, you could try using asupply rail splitter. I said low power, because this circuit isn't too efficient."
},
{
"post_id": "",
"author": "MegaWatt",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "August 11, 2013, 08:00:40 pm",
"content": "Yes you are right, I see my mistake, very stupid. Thanks a lot!"
},
{
"post_id": "",
"author": "Dave",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 11, 2013, 08:29:27 pm",
"content": "Hey, you make mistakes and you learn from them. Don't worry about it.You are welcome."
},
{
"post_id": "",
"author": "hlavac",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "August 13, 2013, 05:18:12 pm",
"content": "As to why it does not work, see which way does the current have to go to charge each input cap,you will find it needs to go thru the opposite side regulator and load...Read up on the concept of \"virtual ground\". You need a way for current to bypass the side that requires less current.Fix could be as simple as putting two ~8V zeners across the input caps to bypass the other side unloaded regulator. Make sure that together the zener voltages are slightly higher than your supply voltage."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 13, 2013, 08:38:13 pm",
"content": "How much current do you need? 15V doesn't give you much headroom for the dropout voltage.The zeners are probably the simplest option but transistors would enable it to work from a wider voltage range.http://www.learningelectronics.net/circuits/discrete-virtual-ground-circuit.html"
}
] |
2025-10-17T20:18:22.058319
| 6
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/0v-on-a-bench-power-supply-common/
|
0V on a bench power supply = common?? - Page 1
|
[
{
"post_id": "",
"author": "jaunty",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "December 06, 2018, 04:36:58 pm",
"content": "here's a dumb 'beginner' question ... seems there are a lot of weird little things like this that eluded me over the decades.I'm building an amplifier circuit and the test instructions say emphatically to ensure that both this and that terminal have a solid connection to 0v on your power supply ... it's a complementary circuit requiring +/- voltages ... so i assume that would mean a floating 'ground'? someone else mentioned that i have to bridge the two sides of my power supply to get 0V - i think this would be the case for a dual rail supply that DIDN'T have a neg output (?) but my HP 6236B has a -20v output ...sooo ... it's basically a euphemism for 'floating ground' ?signed, slightly confused"
},
{
"post_id": "",
"author": "ogden",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 06, 2018, 04:46:10 pm",
"content": "Some supplies have two isolated/floating channels with both, '-' and '+' terminals available for each, so you have to connect '-' of one supply to '+' of another to get bipolar supply or just double the output voltage. Your supply is bipolar supply \"out of the box\" where this is done already, in \"common\" terminal which obviously is ground.Quote from: jaunty on December 06, 2018, 04:36:58 pmNo it's not. This ground we are talking about is as non-floating as you can get."
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 07, 2018, 02:42:55 am",
"content": "Think about 2 batteries stacked as they would be in a flashlight. The bottom battery (+) terminal butted against the top battery (-) terminal.Fine, the (+) of the top battery is the PS (+) output, the negative of the bottom battery is the (-) output of the PS and the junction of the two batteries is the 0V or 'common' output of the PS. Let's stay with 0V because a) the instructions say so and b) we have no idea whether that is 'ground'. Or even 'which' type of ground."
},
{
"post_id": "",
"author": "cdev",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 07, 2018, 02:49:56 am",
"content": "Think of it as the \"middle\" point of the (all voltages are relative to something) voltage range thats supplied.You can connect it to ground if you want to but its not the same thing as ground.You may have another terminal thats ground. (thatsalways connected to thecase)"
},
{
"post_id": "",
"author": "Brumby",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "December 07, 2018, 03:10:29 am",
"content": "0V is just a reference point. An ordinary single supply will have one terminal that is usually assigned this reference point - and, by convention, this is usually the \"negative\" terminal.With split supplies, the usual convention is to label the mid point as 0V.The following diagrams show the exact same circuit. The ONLY difference is where the 0V reference point is chosen."
},
{
"post_id": "",
"author": "jaunty",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "December 07, 2018, 05:07:45 pm",
"content": "Quote from: ogden on December 06, 2018, 04:46:10 pmwell 'about as non floating as you can get' to my mind - would be chassis or 'outlet' ground ... but this doesn't seem to be that at all ..."
},
{
"post_id": "",
"author": "ogden",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 07, 2018, 05:36:09 pm",
"content": "Quote from: jaunty on December 07, 2018, 05:07:45 pmRight. AFAIK there are many meanings for floating ground term. Few I know are: Mains equipment may have floating ground which means that it's case is not earthed which is earthing fault. Then two interconnected electronic devices may have floating grounds to each other, they may even have proper earthing each in it's own building but their ground potentials may differ, especially when lightning strikes nearby . Then there is improper use of \"floating ground\" term in devices/circuits when virtual ground term shall be used instead. Virtual ground means that \"ground\" have little or no current handling capacity, at least compared to specs of the power supply."
},
{
"post_id": "",
"author": "chris_leyson",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 07, 2018, 06:04:54 pm",
"content": "QuoteWell, not really. From the HP6236B manual \"The supply's three outputs share a common output terminal, which is isolated from chassis ground so that any one output terminal can be grounded\"0V or common is floating and ground means earth in the context of a power supply. Ground is a term that is used quite loosely, if there is an earth connection involved then ground = earth, if there is no earth connection and people use the term ground then they probably mean 0V. From Wikipedia \"Ground (electricity), the reference point in an electrical circuit from which voltages are measured\". Sometimes you have read between the lines to understand what the writer means when they say ground. I would go with the Wiki definition \"a reference point from which voltages are measured\". It could be floating or it could be earthed but in the context of a power supply ground would usually mean earth."
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 07, 2018, 07:56:54 pm",
"content": "Brumby did a much nicer job of showing the possible configurations than I did before him.Your situation is the leftmost sketch. 0V is in the middle.I don't want to talk about 'ground' for the various reasons given above. It turns into a huge mess unless you are looking at a specific circuit.I would expect modern multiple output power supplies to have each channel floating and not connected to the others. But even a supply like the Rigol DP832 has the 5V negative terminal connected internally to the output 2 negative terminal. There is no way to remove this connection and this has implications that are discussed in the User Manual. Basically, output 1 will be the -15V supply, output 2 will be the +15V supply and output 3 will be the +5V supply."
}
] |
2025-10-17T18:20:32.780799
| 9
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-0-mm-diameter-copper-(awg-18-)/
|
1.0 mm diameter copper (AWG 18 ?) - Page 1
|
[
{
"post_id": "",
"author": "made2hack",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 08, 2014, 01:03:26 pm",
"content": "Hello,I've got to put through around 2000mA (actually 1600mA) but, for argument's sake, 2000mA of 12VDC which is boosted to 40VDC. Final output is 39V @ 1.6A.Is 1.0mm diameter copper flexible (not solid core) wire sufficient? I think this is like AWG 18, but I'm not familiar with the AWG scale.Am I ok using this wire? The lengths is max 50 - 60 cm, no longer than 1m. I think the voltage drop will be ok, but I am concerned for the amperage going through."
},
{
"post_id": "",
"author": "Monkeh",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2014, 01:56:46 pm",
"content": "Quote from: trs80 on February 08, 2014, 01:03:26 pmNot with 12V 1.6A in, it's not."
},
{
"post_id": "",
"author": "denelec",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "February 08, 2014, 03:19:39 pm",
"content": "1mm diameter is indeed about 18AWG.The resistance will be around 20 ohms/km.It's going to be fine for 1.6A.But if you output 1.6A @ 39V, the current will be much higher at the 12V input.Since P=VI, 39V * 1.6A = 62.4WThe power at the input will be higher than 62.4W since the conversion is non 100% efficient.Assuming a 90% efficiency, the current at 12V will be: I = 62.4W / 12V * 110% = 5.7A.18AWG should also be fine for 5.7A."
},
{
"post_id": "",
"author": "mariush",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2014, 04:06:24 pm",
"content": "18 AWG is used by power supplies. A power supply sends 12v up to 150w to a video card through three yellow cables so each of those wires is meant to deliver 4A+ for long periods of time with no problems. 5-6A will be fine.However, follow denelec's post above me. 12v 1.6a in does not mean 39v 1.6a out .. can't raise voltage without lowering current, you can't have higher voltage without raising input current."
},
{
"post_id": "",
"author": "made2hack",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 08, 2014, 11:30:20 pm",
"content": "Thanks for the reply. I forgot that the 12V in doesn't provide 1.6A but moreSo, my project is essentially to 6 LEDs from a 650W PC PSU, like the one here:Now, mine is the 650W version but the power rail is the same, 12V / 18A / 450W. Does anyone know exactly what that means? I mean does it mean that every Molex connector can output 12V @ 18A? Because that would be 216W x 4 = 864W on the 12V Rail. Which doesn't make sense. Or is it that each rail can supply a maximum of 18A ? If I were to divide the 450W / 4, it would mean that max that each rail can give is 112W @ 12V (or about 9A)?Say that I want to drive 2 LEDs on 1 rail, so as per #denelec's efficiency of 90% I would use 12V @ 10.4. Can I then use another rail to do the same: another 10.4A? And finally a third?So 3 rails, using 10.4A each, for a total of 31.2A @ 12V or 374.4 W ?? Or is the PSU going to die after 18A? Or does my PSU reasoning not work? Is the current split some other way?"
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2014, 11:35:29 pm",
"content": "It means each rail can supply a max of 18A but the total power over all 4 outputs can't be higher than 450W.The 3 separate black lines you can see on the label show which outputs share their power and which are seporate.That psu likely has 3 separate transformers inside.Assuming the label isn't lying about the specs yes, drawing 9A from each of the 4x 12V rails at the same time would push the psu to its 450W limit. (You could still draw more from the 3.3V 5V -12V and +5VSB outputs though)In reality most computer powersupplys cannot handle what they say.If you try they protect themselves and switch off, then you have to unplug them from the wall and wait a few minutes for the caps inside to discharge so that the chip resets itself."
},
{
"post_id": "",
"author": "made2hack",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 08, 2014, 11:53:52 pm",
"content": "So if I'm drawing 31.2A (10.4) from 3 of the 4, I should be ok? Since 320W out of the 450 is good enough head room?I added a link to the manufacturer:http://www.inter-tech.de/index.php?option=com_content&view=article&id=615%3Aenergon-eps-650w&catid=125%3Aausland-atx-netzteile&Itemid=542&lang=en"
},
{
"post_id": "",
"author": "mariush",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2014, 11:54:21 pm",
"content": "The label is fake on that power supply.For continous use, I would give it maybe 12-14A at 3.3v (30-40w), 10-12A at 5v (50-70w) and maybe 350w at 12v (about 30a).The power supplysaysit has 3 rails, each can do up to 18a but can't all stay at 18a at same time. Ideally, one rail is dedicated to the ATX 24 pin connector + a 4-8 pin cpu power connector, one rail is dedicated to the PCI Express 6 pin or 8 pin connectors, and the third rail is dedicated to sata and molex connectors.In practice, it would be best to open the power supply and post some pictures here with the front and back of the pcb because a lot of such crappier power supplies aren't really split on 3 rails but rather have just one chunky rail capable of doing those 30 amps. They're just lying on the label about the rails being split.In this is the case, then you don't have to worry and you can just cut the connectors off and use the yellow wires to drive your leds."
},
{
"post_id": "",
"author": "made2hack",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 16, 2014, 03:01:08 pm",
"content": "I have uploaded pictures to this new thread:https://www.eevblog.com/forum/beginners/am-i-getting-18a-from-this-psu/if anyone has any ideas, can we move the conversation to that new thread?Thank you!!!"
}
] |
2025-10-17T20:08:01.477393
| 9
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-000-opinions-on-esd!!!!/
|
1,000 opinions on ESD!!!! - Page 1
|
[
{
"post_id": "",
"author": "bsahdy",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "May 18, 2016, 04:19:52 am",
"content": "helloi have been into DIY and electronics for sometime. i have gotten to the point where i am working on more advanced electronics consisting of MOSFETS and other (supposedly) ESD sensitive components.Untill now i have stored my parts in a regular plastic parts bin and i also made a small parts bin out of cardboard. I started to wonder was my parts ESD safe? i have the ESD strap and a small ESD mat but no ESD compartments.For the past day and a half i have looked up so much information on ESD that my brain will explode. However it seems like no one can actually make up there mind about how to actually protect your electronics from them or if you even need to!!!I think its safe to say that 50% say you dont need to worry about it just where a wrist strap when handeling them and you will be fine, and dont worry about the container you put them in there. The other 50% say that ESD is a big factor and it can damage your components really fast. Only use anti-static mats, wrist straps, and store them only in anti-static containers.this info i have got from both people that say they have worked in companies, regular engineers and hobbyist.i cant do anymore research im going crazy!i just have one question.if i was to make my own compartments what material should i use?a)cardboard (not conductive, and doesnt pick up much charge. right?)b)metal (very conductive but i will ground it with 1M resisitor so it will drain everything)c)regular plastic compartments are good.these are 3 materials that i have and can work with easily and cheaply.im sorry if this is annoying to ask . i honestly want to understand this stuff as i really do enjoy electronics. i think its time we get this finally straight."
},
{
"post_id": "",
"author": "mikeselectricstuff",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 04:34:33 am",
"content": "Metal is worse than nothing at all, or bare plastic.ESD is all about the \"D\" i.e. you need a low impedance discharge path.Loose components are hard to damage - assembled boards are much more at risk as they have enough capacitance, and potential low-impedance discharge paths to cause significant discharge current.In a hobbyist environment - forget about it, just not an issue as long as you don't have stupid carpet materials - if you never notice static, it's not going to be a problem.In a prototyping environment it's also rarely an issue as the people involved will be smart enough to know what is & isn't a problem, and also factor risk vs.consequnces- $1000 FPGA -take care. $1 MOSFET - meh.The only exception being particularly sensitive parts like laser diodesIn a produciton environment it makes a lot more sense to take more precautions, due to a combination of lower skilled staff, and worse potential consequences."
},
{
"post_id": "",
"author": "helius",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 04:37:07 am",
"content": "You seem to be under some misapprehensions about ESD. The overwhelming source of the high voltages that cause ESD are insulators. Insulators interact with other materials when they are rubbed or rolled, through the triboelectric effect, to create static charge. Only conductive materials like metals or graphite can protect against ESD, and they are the materials used to produce ESD safe boxes and bags. So, to correct your understanding, you must simply invert everything you believe about ESD: it should be very easy, since negation is such a trivial logical operation."
},
{
"post_id": "",
"author": "rs20",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 04:49:09 am",
"content": "Quote from: helius on May 18, 2016, 04:37:07 amAre you replying to the OP, or Mike? It's genuinely unclear to me."
},
{
"post_id": "",
"author": "zapta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 04:50:21 am",
"content": "Quote from: mikeselectricstuff on May 18, 2016, 04:34:33 amLike this?At my hobby lab I use a metal container for the components of each project and make sure to touch the metal container to equalize potentials before touching the component. Also a ESD mat and a wrist strap, that's it. So far I didn't have unexplained component failures."
},
{
"post_id": "",
"author": "bsahdy",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "May 18, 2016, 05:14:17 am",
"content": "like zapta said that he uses metal containers to store the parts. check this post as he says that the ESD compartts he got had a metal bottom plate that was connected to gound.https://www.eevblog.com/forum/beginners/yet-another-esd-storage-question/msg932981/#msg932981Quote from: mikeselectricstuff on May 18, 2016, 04:34:33 amif i ground the metal with a 1Mohm resistor wound that work like you suggested?Quote from: mikeselectricstuff on May 18, 2016, 04:34:33 ami have carpet floor but under my desk where i sit i put some shower pan liner. some type of rubber. i also always use a wrist strap as well.Quote from: helius on May 18, 2016, 04:37:07 amso your saying not like mike and saying that i should use metal containers?i dont mean any disrespect to anyone but as we can see there is different opinions on this matter and there has to be a way to prove one way or the other."
},
{
"post_id": "",
"author": "helius",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 05:21:09 am",
"content": "Quote from: rs20 on May 18, 2016, 04:49:09 amThe OP. I'm not so sanguine about ESD safety in a hobbyist environment, though."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 06:14:43 am",
"content": "I don't see what's so bad about metal. Unless it's shaped like a capacitor, it can't hold charge. The potential will be w/e it is touching. So as long as you store the container on a reasonably grounded bench/shelf, I don't foresee a huge concern.The only parts I take care to store in ESD safe way are FETs. I store them in brass containers. For larger through hole FETs, I have stored them wrapped in tin foil.I suppose it's possible that one pin is touching the metal and the other is floating, and when you pick up the container in your fuzzy robe and sandals, you can kill the part? I have never had that happen, storing smd fets in a brass tube.Non ESD safe plastics can build a surface charge. This can potentially cause damage to the FET. Much more of a concern, IMO, than a metal container. Bonus, a metal container is a faraday cage.IOW, I do not care about my hand damaging the part. I will touch my bench/ground/container before handling the part. The only worry that is big enough (in my mind) for me to care about is surface charge of the container. I.e. don't store fets in plastic container with a synthetic fur lining. Don't wear your fuzzy synthetic robe while handling parts. And you will usually be ok.OP, I would think cardboard is fine. Someone else will say it's a terrible idea."
},
{
"post_id": "",
"author": "sleemanj",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 06:33:21 am",
"content": "ESD bags are1. Cheap2. Easily available3. Heat sealable if you need to cut them down for space or economykeep your static sensitive things in an ESD bag, and put that bag and it's contents wherever you like, if it's in the (closed, folded over top is fine) bag, you can regard it as protected from ESD."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 06:38:31 am",
"content": "Yes, but ESD safe is a misnomer.Paper and carboard and metal and wood is ESD safe.ESD safe plastic is so labeled because some plastics/synthetics are the opposite of ESD safe.\"ESD safe\" is therefore almost always associated with plastics/synthetics. This is like \"low fat\" bacon.FWIW, I have been storing microcontrollers and any other ic's but FETs in regular polyethylene bags for years without the first problem. FETs are one of the only really sensitive components. And most IC's that include FETs have clamping diodes for ESD protection. If you're going to etch dozens or thousands of components on a wafer, might as well include a few clamping diodes.Also, FWIW, whenever you buy stuff from Digi/Mouser/Newark, you can hang onto the larger ESD safe bags. For w/e reason, they always ship stuff in these bags. Even switches or header pins. I'm sure its just cheaper for them to use one standardized roll of bag for everything, but it's still curious. These are the real deal, with faraday cage built inside the plastic as well as a surface coating to prevent surface charge. AND they are super tough. Add a heat sealer, and you will have bags for days. At some point in time, I bought a huge box of the pink bags. Ended up throwing them out. I never run out of Mouser bags."
},
{
"post_id": "",
"author": "wraper",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "May 18, 2016, 07:02:08 am",
"content": "Metal is completelynot ESD safeif surroundings get charged, or something can charge it. Example from the life, where you usually get worst ESD discharges which you can feel the most: car, door knob, kitchen sink, all metal. Metal itself don't need to get charged too, you can be charged yourself (by walking on the carpet, wearing sweater) but metal will provide the capacitance needed or low resistance path, so ESD discharge becomes \"successful\". Don't forget, in ESD discharge, capacitance is one of the most important things, because it provides the discharge with energy. Therefore the worst ESD discharge is between 2 metal objects, capacitance is high (provides energy) but resistance is low, therefore cannot limit the discharge current. If you check datasheets, there you can find ESD ratings for Human body model and Machine model, ESD voltage for latter is order of magnitude lower. The difference between them is capacitance.Example: you are walking on the carpet and get charged. You take plastic tweezers, touch the parts on the PCB which have high enough capacitance to the earth or is connected to it in some way - nothing happens. You take metal tweezers, move it towards to the part and spark happens - part is destroyed. ESD safe tweezers are covered with dissipative material BTW, not just bare metal, so there is no low resistance path from the hand to the metal part.If you have proper ESD safe area, where things cannot get charged, metal is fine and insulators should be removed, so no charge can occur in the area. But if the area is not ESD controlled, metal can be worse than insulators.EDIT: This is not to say you cannot use metal containers at all. This is mainly addressed for those who argued with what Mike said about metal."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 07:32:10 am",
"content": "But where/how are you normally storing and handling your metal container?Would you go out of your way to store your metal container on a shelf that is completely ungrounded and lined with fuzzy synthetic fibers? Or to set it on a BARE and freshly sanded steel shelf with a zero ohm connection to ground? (If the latter, and you touched the container to make a spark, would not the spark travel through the container like a faraday cage, and the container itself remain at ground? And contents touching the container still be at ground? In this case the metal will do you a favor of grounding you, since you forget to discharge yourself before handling your components.)Sitting on a wood shelf, it will be fine. I find it hard to imagine a scenario where it would not be fine, unless you go out of your way to create one. I'm only going to open the container and handle the contents when the box is on my bench.... ?And most common metals that one would use for a container, would be fine anyway, because they either naturally form a nonconductive oxide layer (that doesn't build surface charge), or they will be painted to prevent oxidation. The component leads themselves will form an oxide layer. A component resting on the surface will not form a good contact without a significant pressure.I store many of my components in painted steel boxes. Albeit sealed in bags, for more space/organization. Never had any issues, personally. I don't need an ESD safe label to know they're ESD safe."
},
{
"post_id": "",
"author": "wraper",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "May 18, 2016, 08:19:52 am",
"content": "Quote from: KL27x on May 18, 2016, 07:32:10 amThe problem is when you take or put he part. Spark goes through the part, not directly from you to the container. And why do you think that someone will always touch the container first? It's not rare that you open the drawer, take the parts, drawer stays open. You do the job, place remaining parts in the drawer. But you did not ground yourself to the container first. Or do youalwayskeep your parts far away from the container before touching it with a hand first?"
},
{
"post_id": "",
"author": "VK5RC",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "May 18, 2016, 08:24:29 am",
"content": "+1 re mikeselectricstuff, if in production you need to be obsessive; unless the part is crazy money or buried in a complex-to-trace device AND really ESD sensitive, an ESD mat and strap covers most hobbyists."
},
{
"post_id": "",
"author": "Rascal",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 10:23:15 am",
"content": "I think you will find 1000's of opinions on most subjects here. I guess that's the point to a certain extentMy opinion as a hobbyist - It does seem to me that many people spend so much time deliberating on various fairly petty issues, rather than 'getting on with it', and enjoying the hobby. Over the years I have stored sensitive and non sensitive components in whatever is available, plastic, cardboard, metal. Ive had very few problems.Does my hobby take place in a completely ESD safe environment? I very much doubt it.Paul"
},
{
"post_id": "",
"author": "sync",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 11:56:30 am",
"content": "I'm a hobbyist. I usually store the ESD sensitive components in the ESD safe bags in which they are delivered. I also use that black conductive foam. I not using an ESD mat (my bench is made from real wood) and I use my ESD strap only when I handling very sensitive stuff.In one case I suspect ESD damage. A bunch of TLC272 which where stored and moved for 20 years complete non ESD safe. They working fine except their input bias current is much higher than it should be.Maybe there are others small ESD damages which I didn't noticed. But I have destroyed much, much more components by mistakes which aren't related to ESD."
},
{
"post_id": "",
"author": "Marco",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 12:05:22 pm",
"content": "If we just stopped using old unprotected MOSFETs we could mostly stop worrying about ESD.Almost any modern IC is harder to destroy than a 2n700x.PS. TLC272 seems to have unprotected MOSFET inputs, showing its age."
},
{
"post_id": "",
"author": "Jay112",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 01:34:27 pm",
"content": "Is there any possibility of having such a noisy ground that keeping the metal box (with the components inside) connected to ground might cause some damage?"
},
{
"post_id": "",
"author": "CatalinaWOW",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 02:34:14 pm",
"content": "ESD is really simple in concept, but attempts to further simplify it with rules has caused endless confusion.Statements like \"can't hold a charge if not shaped like a capacitor\" indicate fundamental misunderstanding of a simple concept. I am in no way shaped like a capacitor, but if I walk across a rug in winter I can easily generate a spark when touching a grounded object.The simplest way (for me) to think about ESD is to look at the data sheets. All good ones have absolute max voltage ratings. Usually some number from a few volts for most signal processing parts up to a few hundred volts for power handling parts. Varies from terminal to terminal. Any time you expose a part to higher voltages the part is at risk. It may survive if the exposure is short enough (if the energy content is low enough). Now on to how those exposures occur. Any time different materials move relative to each other there is a possibility of electron transport. Those charges remain in place until they have a way to return home. How much charge is moved depends on so many factors that mere mortals can't calculate it, but can only observe situations that tend to favor it. All of the ESD rules are attempts to either reduce those charges, or reduce the rate that they can be applied to a part.So: Conductive surfaces, ESD sprays, ionizers, heel straps, and the like reduce the charge buildup. Resistors in the esd strap and between the esd mat and ground reduce the rate of discharge. Or thought of another way, create a voltage divider that uses a large resistor and the relatively low resistance of the part to create a voltage divider that brings the voltage within the parts capability.You can use these ideas to look at your practices. Cardboard parts bins for example. Conductivity will vary with humidity. In very dry environments there could be very low conductance and therefore hold a charge for a long time. Now, if you pick up a part by one lead, and another lead touches the charged region, and if you have a charge greatly different than the charge region some charge will flow. But the high resistance of the cardboard means that only a tiny region of charge will flow easily, and thus a tiny amount of energy. Not really much chance for damage, since many different things have to go wrong in just the right way."
},
{
"post_id": "",
"author": "zapta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 02:45:12 pm",
"content": "Quote from: KL27x on May 18, 2016, 07:32:10 amI am using covered metal containers and naively assume that they block any bad influence from the outside."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 10:44:14 pm",
"content": "QuoteBut how do you touch the part without touching the container, first? You have to open it?Let's examine this part, closer:QuoteHow is this any different than if the box where made of plastic. (Or ESD SAFE plastic). The difference is a non-ESD safe plastic that can build a surface charge might have charged the pin of a part to hundreds or thousands of volts. The metal cannot do that.And if the metal is grounded directly to ground (and why would it?) and you are charged (because you did not touch the container), and it is denuded so that it makes good contact with one of the pins... why is the spark going to travel through the part instead of sparking directly to the metal? The path of least resistance is through the metal, not the part.QuoteHow do you open the drawer without touching the drawer?QuoteYour body can hold a surface charge primarily for these basic reasons:You are wearing shoesYou are wearing clothesYou have hairThe shoes insulate you from ground. The hair and clothing increases your surface area by many fold, and the molecular structure of the surface of this hair and/or clothes is such that it can be ionized through friction against other objects. The charge isn't built/stored inside you. It's on you. This static charge is 100% due to the surface characteristics of your body and what you are wearing.A metal container does not normally have these features.The proof that metal does not hold/accept/give a charge is that to make the spark you have to touch a GROUNDED metal object.* The metal is just a conduit to ground, which is for practical purposes an infinite electron donor/acceptor.*Or a metal object in contact with something else that can act as a large enough donor/acceptor to allow ESD damage. In either case, the spark will travel through the metal, not the part."
},
{
"post_id": "",
"author": "Marco",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 11:15:31 pm",
"content": "So the bastards at the last air conditioned lab I worked in had grounded doors?I flinched every time I had to touch a door handle for a while."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 11:19:23 pm",
"content": "Hang a doorknob on a string. Rub your feet across the carpet and touch it. Let us know what happens!"
},
{
"post_id": "",
"author": "wraper",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "May 18, 2016, 11:21:48 pm",
"content": "Quote from: KL27x on May 18, 2016, 10:44:14 pm2 AM here, so won't answer to all of that nonsense but will write about this particular BS. Why are you so sure? I already mentioned the car and the door knob. They both are insulated from the ground and they both get large static charge on them. How do I know? Because I felt the static discharge many times just before touching them. And no, that wasn't I who was holding the charge. Because that freaking door knob was on the door to/from ESD safe area. So when I walked out of that ESD safe area, obviously not holding the charge on myself (dissipative floor, ESD boots, yada, yada), I often got a shock from that metal door knob. Usually that happened at the Spring, because of the air humidity change during the year."
},
{
"post_id": "",
"author": "sync",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 11:25:53 pm",
"content": "Of course a metal object can hold a charge. Electrostatics basics. In this video it is demonstrated (at 25s). The metal ball is used to transfer charge. That isn't possible when the metal ball can not hold the charge."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 11:47:23 pm",
"content": "Notice the metal ball is attached to something else. A glass rod. A glass rod can hold a significant surface charge.Even if it was a pure metal rod, he is holding it in his hand, and we have already determined the human body can carry a significant surface charge.This is also not showing any degree of significance. We do not know how much charge there is, other than not enough to make a spark.I have just a basic bog standard education. I'm not a professional scientist. All I have is a BA. I am frequently wrong. But I store FETs in bare brass containers. I put them in bare aluminum dishes. I have not had any problems, yet? (And I do take precautions with FETs because I do know how to kill them with inappropriate measures)."
},
{
"post_id": "",
"author": "zapta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 02:38:26 am",
"content": "If a metal container is a poor choice, ESD wise, this can be the subject of an interesting EEVBLOG myth busting episode."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 04:24:34 am",
"content": "https://en.wikipedia.org/wiki/Triboelectric_effectHere's what Wikipedia says. There's a list of some common materials, showing their propensity to develop surface charge. Along the right hand side.Maybe I'm not saying or understanding that correctly, so see for yourself.Steel is at zero. Wood very close second. Aluminum around same as paper. Brass goes the other way, but several materials closer to zero than polyethylene.Polystyrene is relatively non chargeable. Surprising, but I think Styrofoam is a special case because of the increased surface area.There's no scale for reference, but it gives some idea. Near the top of the positively chargeable materials is \"hair and oily skin.\""
},
{
"post_id": "",
"author": "mikeselectricstuff",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 07:17:15 am",
"content": "Quote from: bsahdy on May 18, 2016, 05:14:17 ampossibly not as the metal may have enough capacitance to ground to shunt the 1M to a muck lower impedance for fast discharges"
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 07:43:19 am",
"content": "Totally off base, I'm sure. But it seems to me that the surface of some metals can hold some amount of surface charge. Not quite sure how much, but not as much as a human being's skin, according to Wikipedia. Again, I'm totally wrong, I'm sure, but I was under the impression that it's not the interior of the metal that acts as a donor/acceptor, just the surface.I'm curious, how big is the surface area of the metal before this becomes a problem?If you took some copper clad and made a box out of it, you can no longer safely put a FET on it?Does a ground plane for a 12\" x 9\" pcb create a significant ESD hazard? Your PCB itself is a significant ESD hazard? And even if you ground it with a 1Mohm resistor, you can not assume to safely solder a FET to it?Does thick copper wire act as a capacitor? Say 20 feet of 6 AWG wire? Enough to create an ESD hazard?I would presume litz wire would have a lot more capacitance? How much litz wire of the same gauge before it can store a dangerous amount of charge (to a FET)?I must be totally off base. I can't figure out why this metal box is an ESD hazard.Thin metal foil can be made into a capacitor. Take two pieces of metal foil with a thin dielectric separating them. Roll them up tight. The close proximity of the metal plates is what allows one to store charge. If the plates were far apart, it would not work. The electrons would not want to be removed from their spot. The capacitance would be close to zero. It's only when you put them very close together that the one plate \"allows\" the other to borrow these surface electrons... as long as they are still within \"arm's reach.\" Try to charge it too high, like the 1KV of ESD range sparkies, and the electrons will want to return home so bad they will fry the dielectric.The metal box is not very much like a capacitor. A piece of copper clad is a lot more like a capacitor. A PCB with a top power and bottom ground plane is a lot more like a capacitor."
},
{
"post_id": "",
"author": "CatalinaWOW",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 02:28:18 pm",
"content": "The problem with metal boxes is that they are good conductors. They can provide a path for charge to go through a sensitive device. As you have pointed out, and observed in your experience, good practices make this a non-issue.It is kind of like belts and suspenders (or braces or galluses or whatever you want to call them). Either can keep pants up. And pants often stay up without either. But if you wear both belts and suspenders, pants are even more unlikely to fall. Some people will swear you need neither, and testify that their pants have never fallen. And if they have a large waistline and small pants they will be absolutely right. Others may have different experiences."
},
{
"post_id": "",
"author": "mikeselectricstuff",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 04:54:30 pm",
"content": "QuoteIt's not the box that's the hazard per se,it's the fact that it provides a low impedance discharge pathAgain, it's all about discharge impedance.Assuming you are not grounded and your body has a charge on it :You pick a part up off an insulated surface. The part now has the same charge as you do, and the part's capacitance to ground is low enough that the current flow transferring some of your charge to it to doesn't harm it.If you then bring the part near a grounded metal surface, the charge can discharge at a high current due to the low impedance of the discharge path. Even if the metal is not grounded, or grounded via 1M, if the metal is big enough, its capacitance to ground will provide a low impedance ground path.if you are wearing a ground strap it's not an issue, but who wants to dick about with those.Although using a raw plastic container has potential to produce some charge in the first place, and allow a board to sit there holding charge that can discharge when someone touches it, that risk is fairly minimal compared to the charge that a person can develop and hold due to size and the charging mechanisms available."
},
{
"post_id": "",
"author": "Raj",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 04:59:06 pm",
"content": "My dad collected lots of iron munition boxes while he was in the army, I use those to store components.while keeping them on a grounded aluminium plate.funny how the contents of those boxed, when burnt causes only red smoke to emerge while they are painted red and have \"danger, explosives\" written all over them"
},
{
"post_id": "",
"author": "Marco",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 05:28:25 pm",
"content": "The capacitance of a 100 mm sphere to ground at infinity is around 10 pF ... a 2n7002 has 30 pF gate-source capacitance.Do the math of what an ESD pulse will do across a capacitive divider with those two values."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 05:36:11 pm",
"content": "CatalinaWOW, it sounds like you are agreeing with me. Maybe I'm not a complete idiot.But as for the danger thru being conductive thing, I may be stupid. I will wear just the belt until my pants fall down. I see not too many men wearing suspenders, and yet I have to go to Youtube too see someone's pants spontaneously falling down.Also, I disagree with you.QuoteYou need suspenders when your waist is large. When larger than your hips, the belt don't work, anymore."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 05:42:00 pm",
"content": "QuoteWhat does infinity mean?"
},
{
"post_id": "",
"author": "Marco",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 05:51:40 pm",
"content": "Quote from: KL27x on May 19, 2016, 05:42:00 pmTo infinity and beyond ... as far away as possible and then some. Using infinity as the distance allows you to determine the minimum capacitance a sphere will have to ground, in practice it will always be higher.This free space capacitance of objects is part of why you spark to isolated metal objects when you are charged. The other part being the fact that both you and the metal object are relatively highly conductive, allowing the charge to distribute between you in a short time frame. Sometimes through the gate isolation of an unprotected MOSFET."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 06:23:54 pm",
"content": "Ahh, interesting. Yeah, it doesn't take much capacitance. I see.So let's see if I can piece this all together.A large enough piece of metal can be a donor/acceptor for an ESD. Because of it's surface area and its high conductivity.Let's say I'm positively charged. Because if you believe Wikipedia, I have positive triboelectric property.So now as long as I do not ground myself, by touching anything of significant size which has path to ground. And as long as I don't touch the container while picking up the part. And as long as I am picking the part directly out of the container with tweezers and I don't accidentally touch the tweezers to the container before touching the part. I can kill the FET? Is this correct? Is there some other way the metal container can aid in killing the FET?When I then take the FET to the PCB, same thing applies? This piece of metal in the PCB with enough surface area and conductivity is possibly large enough electron donor to zap the FET?So when handling FET, if I use an ESD safe (plastic) box. I will not have to take any precautions while handling the FET until I get to my bench? Or did I get it wrong? I will walk across the rug and pick up the part, and then ground myself when I get to the bench? (And why do I not take the whole box to my bench, I do not know...Instead, I must retain the capability of walking to another room in my bathrobe and slippers and pick up a single FET with tweezers in a fashion of playing a game of Operation, and walk back to my bench with it, and THEN take ESD precautions.)Or can I kill a FET by doing this even despite the fact it is labeled \"ESD safe?\" In which case the practical difference between the ESD safe box and the metal box is even less significant? What IS the remaining significance, in practical terms? What can I do with the ESD safe box that is going to affect the way I can work?What about non ESD safe plastics (nonconductive). In my experience FETs can be killed without even sparks occurring. Perhaps with small enough gate capacitance of tiny signal FET, they can die without a spark, due to triboelectric effect. Simply putting them in the box and shaking them around, generating surface charge between itself and the surface of a pin? Simply the triboelectric effect pushing gate beyond +-8V voltage limit? It is for this thing I am more concerned. I have only ever had FETs dead. And without spark. I suspect sparks are not needed to kill them. I am more concerned with non-conductor surface charge generator than high conductor tiny capacitance donor."
},
{
"post_id": "",
"author": "Gyro",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 06:26:46 pm",
"content": "I don't understand why there should be 1000, or even 10 opinions on ESD, it's really not a complicated enough subject to justify them!I'm not sure why there are so many spurious diversions of knobs, metal or otherwise.The fundamental requirements:1.You need to transfer the part from storage to the operator/workstation under equipotential conditions.2.You need to avoid damaging current discharges through the device terminals resulting from any remaining or accidental relative potentials.Meeting these requires:1.The operator needs to be grounded to (Edit: at) the same potential as the workstation, the most common solution would be antistatic mat and wrist strap.2.The antistatic mat should have a static dissipative surface to avoid any possibility of current spikes due to any accidental temporary potential differences between the operator and the workstation mat.3.A conductive storage container for the parts, could be metal, it could be something like a conductive plastic storage box, or it could be its original antistatic packaging / bag.4.This container needs to be either held at the same potential as the workstation or brought to the same potential while transferring the parts (this could be achieved by the operator holding it).5.The container should be lined with a static dissipative material to prevent any possibility of current spike due to temporary or accidental remaining potential differences (not bare metal!). This lining could be antistatic foam or even cardboard at a push (no one ever managed to significantly charge up a piece of cardboard by rubbing it with a cat!). You need something in the container anyway to prevent physical damage, bent pins etc.I realize that it's not as much fun, but that's all there is to it. You just need to ensure that your setup meets these requirements."
},
{
"post_id": "",
"author": "Marco",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 06:45:30 pm",
"content": "Procedures aren't always followed ... you can still reduce failures by reducing the impact of that.So semi-conductive materials instead of conductive materials, air ionizers etc."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 07:05:35 pm",
"content": "Human skin is a high impedance conductor, too.This why you can touch ground and discharge yourself. Or wear a doofy wrist strap if you somehow manage to work without touching your bench."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 07:08:57 pm",
"content": "If \"ESD safe\" is so simple and straightforward and well understood and I should always look for \"ESD safe\" label, and \"semi-conductor\" (by which I assume you mean high impedance conductor, not doped silicon, and with which I generally agree) is the best ESD safe material, maybe someone can explain why when I buy an \"ESD safe\" soldering iron and it has a 0.0R connection to earth?"
},
{
"post_id": "",
"author": "Gyro",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 07:25:12 pm",
"content": "I've wondered about that one, I'd prefer a resistively connected iron tip. I suspect the reasoning is that the danger of capacitively coupled spikes from the element supply switching etc. is higher than that of it being directly grounded. If everything else is resistively coupled then the risk is minimised as much as possible.QuoteThat's until you shuffle your feet or your a**! Stick with the doofy wrist strap. It's the temporary potential disturbances caused by these actions that are the main need for static dissipative (high resistance) linings / mats. A 1M resistor can't equalize your potential instantly when you shuffle about.P.S. Human skin isn't really a high impedance in ESD terms, hence the Human body model - 50pF1k5R(not significant at 2-8kV)"
},
{
"post_id": "",
"author": "CatalinaWOW",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 08:03:05 pm",
"content": "It really is fundamentally simple. You can go down many rat holes chasing details or formalizing a methodology that works for people with a wide variation in training, background and resources. The link at the bottom of this post from Maxim is a (to me) a clear, concise description of the problem, the impacts, and some strategies for resolution. There is no fixed answer on how to control ESD, just lots of things that help (or hurt). Doing a science based strategy for ESD control requires knowing things like acceptable failure rates, minimum life requirements, failure rates on ESD control devices, and things which are typically hand waved like degree of compliance with the ESD procedures at a given worksite.Keep in mind that the active pieces of our electronics goodies are really, really small so it doesn't take much energy to disrupt them. Also, when you are saying that you have never had ESD damage remember that many parts operate after ESD damage. They may meet all performance specs, as occurs when the first ESD contact vaporizes the ESD protection diodes which many ICs now incorporate. Of course the second ESD contact is likely to hurt something more important. The part may merely be degraded in some way, such as worse offsets, worse supply isolation or some other parameter which may not matter in the specific application. Or maybe just lost the top oxide layer so the chip is more susceptible to the environment.https://www.maximintegrated.com/en/app-notes/index.mvp/id/639"
},
{
"post_id": "",
"author": "Gyro",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 08:10:53 pm",
"content": "... and tracking down problems due to degraded parts is a hell of a lot more difficult that outright failed parts!"
},
{
"post_id": "",
"author": "tautech",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 19, 2016, 10:58:47 pm",
"content": "Quote from: bsahdy on May 18, 2016, 04:19:52 amMaybe but this is better and CHEAP:http://www.newark.com/multicomp/039-0050/low-density-conductive-foam-305x305x6mm/dp/87P0222Lines all my ESD sensitive parts boxes and drawers. ^^^"
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 20, 2016, 08:42:21 am",
"content": "You really can't be too safe.http://www.newark.com/ck-tools/z1123/esd-ball-pen/dp/64T4680"
},
{
"post_id": "",
"author": "CatalinaWOW",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 20, 2016, 01:42:25 pm",
"content": "When you are taking notes on assembly of a Jupiter orbiter that pen doesn't seem silly at all.When you are making something to make a toys eyes blink back and forth, meh!Before I retired, I worked with high value product where the consequence of failures was enormous. Just about every ESD precaution you can think of was employed. Because the product was high value and the consequence of failure was enormous full root cause diagnosis was done on failures and occasionally on random samples. And in spite of the precautions ESD damage was found in photomicrographs of the silicon die from time to time.But at home, working on my hobby projects I don't even bother with an ESD mat. I do the things I find appropriate to avoid pulsing a device with a static charge. I don't remember having a failure.Why the \"differences\" in results? At home I am doing far less volume of work than the team involved when I was working. That work is more varied and so I am more thoughtful and intentional than a person can usually be when working a more standardized job. I am in total control of everything that happens to everything from the time it is unpacked from the supplier until it is put into service. I am seldom under time pressure. And at home much of what I do is insensitive to minor ESD damage. So while damage may have occurred I am blissfully unaware.I am quite comfortable with the choices in both circumstances. These differences in circumstances and widely varying understanding of the mechanisms of ESD and the susceptibility of various devices to ESD are the reasons you find 1000s of opinions on ESD. Many of them are not wrong given their circumstances."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 20, 2016, 02:12:36 pm",
"content": "Any all-metal body, all-metal refill ballpoint will be ESD safe, if the user is properly grounded in an ESD safe environment, but is likely to be pricier than the CK tools ESD safe pen KL27x linked to. An all metal pen is riskier if the user is NOT properly grounded as if the object being labelled is a thin dissipative bag on a low impedance grounded surface, the pen could concentrate the discharge resulting in punchthrough and possible ESD damage to the bag contents.Me? well I wouldn't worry too much. I'm not building avionics or medical devices, and its ****ing awkward to write on a bag with parts in it under the label anyway so I tend to avoid that, either with a sticky label or simply shaking the parts to the end of the bag, + my preferred types of pen, (an ordinary 0.5mm fine line marker for paper labels or a Sharpie for direct writing on plastic bags), have insulating bodies so wont concentrate a discharge, and cant hold a lot of charge even if the workshop cat has been rolling on them!"
},
{
"post_id": "",
"author": "Gyro",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 20, 2016, 03:15:08 pm",
"content": "Of course the traditional wooden pencil could have beendesignedfor ESD safe environments - a resistive core and static dissipative outer.Just don't break the lead."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 20, 2016, 03:34:10 pm",
"content": "I fixed that for you:Quote from: Gyro on May 20, 2016, 03:15:08 pmOnce its coated with a manufacturer's lacquer or varnish finish you risk undesirable triboelectric effects."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 20, 2016, 07:18:06 pm",
"content": "Correction. After you paint it with the most tribolectric material possible, you spray it with conductive ESD-spray and sell it as ESD-pencil. Bare wood is natural, which you cannot call ESD-safe; that would just be a marketing ploy.QuoteYes, there is a time and place. I do not question all ESD safety practices. But I suspect some [products/practices/wisdom] are borderline questionable benefit, even where it does matter. General understanding maybe not 100% as straightforward to the general population or even to me. I just see some ideas out there and my own puny brain does not connect all the dots to know what the hell is the purpose. I suspect some of the generally accepted knowledge just might be misapplied or taken too far and/or used out of context. Since I don't have the tools to investigate, directly, I just speculate. When I find a dead FET taken from a metal container, I will be sure to make a post on this awesome forum.ESD mat to protect from a wood bench and metal containers are two of the things I am not particularly impressed about. Maybe I'm dumb and won't know the sky is falling until I can either understand why it is falling or when it hits me on the head."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 20, 2016, 08:07:13 pm",
"content": "Freshly oven dried wood is an insulator. Wood at a typical equilibrium moisture content to the air of 10% - 12% typically has a bulk resistivity of 10^10 Ohms/cm or less, which would put it at the upper end of the dissipative materials range. If your building is air conditioned or you are in a desert climate, you'd better soak your pencils in calcium chloride solution for a week then rinse and air dry to decrease their bulk resistivity."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 20, 2016, 08:17:19 pm",
"content": "Hehe.I just had a thought. Yeah, that is rare for me.Metal box has capacitance, and that is bad, right? If I solder a small value (smaller than gate capacitance) capacitor to one or other leg of a FET, is it more prone to ESD damage, now? The capacitance is in series with the gate. So the capacitance goes down, not up. And the voltage goes up? I mean, treating the FET gate as a capacitor.Now I'm just confusing myself more, lol. And now I wonder if I can increase the max voltage and/or reduce the total capacitance of a FET gate by adding a series capacitor.*Now I'm also wondering about what mike said. Grounded through 1megaohm resistor, the box can be dangerous through capacitance. The significant aside, I am now wondering if it deosn't makes a difference what metal. For instance, if human body has positive triboelectric effect, and aluminum has positive triboelectric effect, than aluminum cannot cause damage when it is so grounded. Or steel, which is close to zero. But maybe brass, going the other way (copper? who knows... it's a main alloying element in brass) can have some possible effect? Does any of this bare metal problem start sounding sorta trivial, to anyone else but me? (Of course when I saw trivial, this is assuming your bench is not made of bare metal, itself)."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 20, 2016, 08:41:44 pm",
"content": "Sounds like a good way of FUBARing it. Without a DC leakage path to the drain, any stray charge (e.g. from moving air) on the gate and your added cap will build up and shift the bias point. Whichever way it shifts, the result is likely to be silicon shrapnel as not turning fully on is just as bad as not turning fully off."
},
{
"post_id": "",
"author": "CatalinaWOW",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 20, 2016, 08:46:07 pm",
"content": "Quote from: KL27x on May 20, 2016, 07:18:06 pmI agree. The various practices don't all have equal value. And often the value lies more in the area of psychology than in physics. The ritual of daily checking continuity of wrist-straps (or checking the continuity indicator on a continuous monitoring wrist strap each time you touch hardware) is a continual reminder of what can go wrong. Even though in many cases years passed between an observed failure other than forgetting to put the wrist strap on. Same applies to other things like the anti-static ball point pen.The problems are real though. I used to plot product yield vs outdoor absolute humidity and see substantial correlation before appropriate indoor humidity control was installed. There are many other examples that I and others here could provide."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 21, 2016, 04:13:29 am",
"content": "^ no doubt, they are real. When you consider the number of active semiconductors in a modern computer, it makes me wonder how many failed boards go in the trash heap to produce 100 working units.QuoteThis reminds me of something I read about eastern pottery. Korean potters were at one time reknowned for a form of pottery that had a distinct greenish color. To produce this, the pottery had to be held to +- something like 15 degrees Celcius for a period of over 20 hours. Mind you this is somewhere in the 12th century AD, so this was something of a difficult feat. It was believed that this pottery could only be produced in times of peace and economic stability and spiritual harmony of the workers.The culture of ESD is undoubtedly important to manufacturers of complex devices. W/e it takes to improve the yield and bottom line. I think some hobbyists cross that bridge just for the sake of crossing it, without having a destination on the other side."
}
] |
2025-10-17T19:18:16.666635
| 57
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-15v-to-3-3-5v-converter-for-one-led/
|
1-15V to 3.3-5V converter for one LED - Page 1
|
[
{
"post_id": "",
"author": "symbianas",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 19, 2023, 10:26:16 am",
"content": "Hi, my car has factory ambient lighting which is very dim so I would like it to shine always at brightest setting, but I cant set it to brightest setting because it also changes instrument cluster brighness to max which I don't want to be at max.Current supply source changes depending on \"brightness setting/engine running\" from 1-15V. So I would like to convert 1-15V to 5V or 3.3V for one LED maybe 60mah max power, is there a simple board converter which I could buy for this purpose?"
},
{
"post_id": "",
"author": "tooki",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 19, 2023, 12:21:02 pm",
"content": "Converters that will start at 1V and still handle 15V is a tall order. Maybe it exists, but I wouldn’t count on it.Additionally, if the LED driver is a constant-current source (rather than a voltage source), then you have that layer of complexity to deal with, too.Wouldn’t it be easier to just use the fixed 12V supply and then a MOSFET or transistor to switch the enable pin of the DC-DC converter?Also, be aware that automotive electrical systems are extremely “dirty”, with lots of spikes and noise, so you need to provide robust input protection to everything."
},
{
"post_id": "",
"author": "HwAoRrDk",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 19, 2023, 02:27:43 pm",
"content": "How did you measure that 1-15V? I suspect the LED power is being pulse width modulated (where the voltage is always 15V, but pulsed on/off for a varying regular period depending on brightness desired), but when you're measuring it you're just seeing the average voltage level."
},
{
"post_id": "",
"author": "wasedadoc",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 19, 2023, 02:56:35 pm",
"content": "Quote from: HwAoRrDk on February 19, 2023, 02:27:43 pmIndeed that is a very reasonable suspicion given that LEDs that give useful light output from 1 Volt are as rare as rocking hor......."
},
{
"post_id": "",
"author": "symbianas",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 19, 2023, 05:44:45 pm",
"content": "Quote from: HwAoRrDk on February 19, 2023, 02:27:43 pmYes, I was using simple multimeter so it might be average voltage level. Do voltage regulators like \"step down\" work on this pulse width modulated power source?Quote from: tooki on February 19, 2023, 12:21:02 pmI might end up doing that..."
}
] |
2025-10-17T16:58:42.776901
| 5
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-2-volt-to-5-volt-boost-converter/
|
1.2 volt to 5 volt boost converter - Page 1
|
[
{
"post_id": "",
"author": "msuffidy",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 01, 2025, 12:45:54 am",
"content": "I got a solar light string from a store at a very low cost. I cut the line to the lights and measured the voltage, which was 1.2V. I am guessing it is more or less straight out of a nicd or some other chargeable AA battery inside the solar box. I was looking for a easy way to boost the 1.2V line to 5V to charge old power banks which then can charge more expensive devices. I found some videos describing crude converters that do not have regulator ICs. It seems like a lot of the stuff maybe can be found in a dead CFL bulb. I am not sure if these parts I found are adequate or not. This video wanted a BC547 transistor, but there are 2 4120PL transistors on this CFL as well as I have 2N222A here, which I think are all interchangeable? I was going to put that 200V 10uf capacitor across the output to try to reduce spikes."
},
{
"post_id": "",
"author": "msuffidy",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 01, 2025, 05:37:51 am",
"content": "I got these parts from the CFL bulb and I was kind of tempted to just use a 2 lead inductor controlled by a resistor capacitor oscillator. The inductors say 2.2? and 1mh. I guess I could install spice and simulate this and see what happens."
},
{
"post_id": "",
"author": "MrAl",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 01, 2025, 06:08:13 am",
"content": "Quote from: msuffidy on May 01, 2025, 12:45:54 amYou might check out converters like the Joule Thief. It works down to low voltage and provides higher output. You may need some other parts too though.That's if you don't want to use a chip made for this, of which there are many."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 01, 2025, 08:04:27 am",
"content": "It will take ages, days, possibly weeks, to fully charge a USB power bank from a solar light string. Heck, it might not even be able to provide enough power to make up for that lost in the charging circuitry."
},
{
"post_id": "",
"author": "jwet",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 01, 2025, 01:44:49 pm",
"content": "One of my favorite youtubers- \"Bigclive\" did a teardown and mini analysis for these circuits. Entertaining and knowledgeable- all you could want to know."
},
{
"post_id": "",
"author": "tunk",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 01, 2025, 01:59:36 pm",
"content": "Recently Diodegonewild had a video describing how they works:https://youtu.be/8JeSQ_8Ly5U"
},
{
"post_id": "",
"author": "xvr",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 01, 2025, 02:53:04 pm",
"content": "Quote from: msuffidy on May 01, 2025, 12:45:54 amThen connect LED USB lamp to power bank and light solar light string. Voilà, you have a perpetuum mobile."
},
{
"post_id": "",
"author": "msuffidy",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 01, 2025, 03:03:31 pm",
"content": "Quote from: Zero999 on May 01, 2025, 08:04:27 amWell I think the way it works is the nicd battery can supply a good amount of current granted there are no in line resistors. Mine does light up like 60 LEDs. So you may be able to generate an adequate 5V supply, just the battery will discharge pretty quickly and you would have to keep charging up the solar box so in that way you are correct. You can see from what this guy did that seems to be the case."
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 01, 2025, 03:10:44 pm",
"content": "Quote from: msuffidy on May 01, 2025, 12:45:54 amI have, from the days before lithium power banks, an \"emergency phone booster\". It takes two AA cells, and it outputs 5 V to charge a phone. It is, however, borderline functional. It only works in any kind of satisfactory way if you install two fresh Energizer Lithium cells into it, and even then, it struggles to produce much useful charging current, and this is with a professionally designed and engineered boost converter.In short, voltage is not the problem, but power and energy is. Small 1.2 V cells do not contain sufficient energy, and cannot produce sufficient power, to charge bigger devices.Your quest is hopeless and cannot succeed."
},
{
"post_id": "",
"author": "Andy Chee",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 01, 2025, 08:03:22 pm",
"content": "Co-incidentally, I was toying with a similar themed project made from junk parts I have lying around.In my case, I am building a 5V converter with 4-6V input. Haven’t decided on SEPIC topology or 4-switch boost (see p.18 Figure 17)https://www.onsemi.com/pub/Collateral/AN920-D.PDF"
},
{
"post_id": "",
"author": "Analog Kid",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 01, 2025, 08:20:03 pm",
"content": "Quote from: MrAl on May 01, 2025, 06:08:13 amYes, a Joule thief.I've built many of these to drive high-brightness LEDs, using this circuit:The transformer is a little hand-wound jobbie with the # of turns as indicated, wound on a little piece of ferrite (1/8\"/3mm) rod.Very easy to build and might just work for your application. It delivers pulses with ~7 volt peaks.I've run up t 4 LEDs in series/parallel with this, plenty bright: somewhere around 80 mA.I don't know what the limit is. Give it a try?"
},
{
"post_id": "",
"author": "msuffidy",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 01, 2025, 08:26:05 pm",
"content": "OH I more or less agreed it was going to be a problem. I was just out and shopping and I got another $4 solar thing. So I have a bunch of panels I got for around $10 Canadian now. I think I can just join them in series and parallel now and get a decent usb charger. I think I can mount the bigger panel on the back by drilling some holes and then it is some soldering and glue gunning. Ironically I suspect the bottom PCB has some of the guts of the Joule Thief and has an inductor to drive 2 bright LEDs. I measured like 1.2 volts across the LEDs so I don't really know why you need to boost it, but."
},
{
"post_id": "",
"author": "msuffidy",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 01, 2025, 10:50:45 pm",
"content": "OK Well I hope it is ok. I measured the solar cells under a fluorescent light and got 2, 1.5, 1.5. So I concluded 3.5 was not going to cut it and changed the wiring to full series. Problem is that it is cloudy here and I get 6V right now, so it could maybe go to 7.5 and this is to charge power banks. I used a breadboard end so I could maybe combine with another USB panel I have or use it for something else."
},
{
"post_id": "",
"author": "msuffidy",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 02, 2025, 12:46:43 am",
"content": "I fixed up some better USB breakout cables."
},
{
"post_id": "",
"author": "Gyro",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 02, 2025, 08:03:15 am",
"content": "Those solar cell leds almost certainly use the Chinese QX5252 IC. A single chip + inductor solution that works from 0.9 - 1.5V input...https://www.opengreenenergy.com/wp-content/uploads/2020/07/QX5252-Datasheet.pdfhttps://asset.conrad.com/media10/add/160267/c1/-/en/002268915DS01/datenblatt-2268915-tru-components-qx5252f-to-94-linear-ic-bulk.pdf"
},
{
"post_id": "",
"author": "tunk",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 02, 2025, 12:16:21 pm",
"content": "At least some cheap solar power banks use this setup:5-6V solar panel -> (Scottky) diode -> BMS -> battery/cell"
},
{
"post_id": "",
"author": "msuffidy",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 03, 2025, 03:11:40 am",
"content": "Quote from: Gyro on May 02, 2025, 08:03:15 amThey likely did before I just cut that part out. The weather has really sucked he in the last 2 days but I just want to see a basic bank charging application, which has not been realized yet."
},
{
"post_id": "",
"author": "Sacodepatatas",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "May 06, 2025, 12:50:16 am",
"content": "Quote from: Analog Kid on May 01, 2025, 08:20:03 pmThe topology is so simple that can be used to convert anything linear to switched mode... I succesfully used it to upgrade a linear DC motor speed controller by inserting a small toroid and a schottky diode into the BJT + potentiometer set. Torque was much better. Here i attach a picture of a similar circuit that converts a typical linear regulator in a mixed linear/switched one..."
},
{
"post_id": "",
"author": "Analog Kid",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 06, 2025, 07:40:40 pm",
"content": "That actually looks like the (sorta) classical boost converter topology, not a Joule Thief.A Joule Thief is a blocking oscillator. Similar but different."
},
{
"post_id": "",
"author": "Sacodepatatas",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "May 06, 2025, 11:52:17 pm",
"content": "Quote from: Analog Kid on May 06, 2025, 07:40:40 pmThe one in the picture is also a blocking oscillator. It's just a redrawn JT put in series with the load. A JT is a boost Converter but if you put It in series with a load (and you redraw it conveniently) then you substract the boost voltage, hence you create a buck converter. If you look carefully, this circuit is just the BJT hack for increasing the current of a linear regulator, but, the original BJT (a PNP here) acts as a current source of a very high output impedance when working in linear mode (and the voltage is commanded by the low output impedance of the linear regulator). Because you insert the transformer between the base and the collector of the transistor, then a positive feedback path is created (because the transformer shifts 180 degrees) and then the transistor begins to oscillate creating a pulsed waveform. The diode is there to give a path to the current stored in the collector's coil. Because once the transistor no longer works in linear mode, it doesn't act as a current source, then, for achieving the same effect, there is an extra inductance in series with the collector coil with a value >> 10 times the former, so it acts like a choke, that also, with the output capacitor in the linear regulator, then a LPF is formed."
}
] |
2025-10-17T16:19:03.103971
| 20
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-27mm-dupont-connectors/
|
1.27mm Dupont connectors ? - Page 1
|
[
{
"post_id": "",
"author": "michaeliv",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "September 21, 2015, 07:58:24 am",
"content": "Hi,Are there any Dupont connectors for 1.27mm pitch headers :http://www.aliexpress.com/item/200pcs-lot-1-27mm-1X40-Single-Row-Male-Pin-Header-Strip-Gold-plated-Connector-Plastic-in/1572815748.htmlIt's easy to find 2.54mm ones - here is what I mean:http://www.aliexpress.com/item/Free-Shipping-20cm-40P-1P-1P-Female-to-Male-DuPont-Line-Wire-Cable-for-Arduino-FZ0261/1542521528.htmlWhat solutions are there for connecting individual wires to 1.27mm pitch headers ?Thanks!"
},
{
"post_id": "",
"author": "mauroh",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 21, 2015, 10:10:49 am",
"content": "The pitch between the wires in the \"dupont\" connector you linked is already 1.27mm, you can easily cut the connectors and solder your own 1.27mm female strip to the wires.Or you can find a 1.27 connector like this:http://www.elechouse.com/elechouse/images/product/1.27mm10p.jpgMauro"
},
{
"post_id": "",
"author": "michaeliv",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "September 21, 2015, 10:33:51 pm",
"content": "I am looking for single-pin connectors, that can be connected individually on to the 1.27mm pin headers. I guess there may not be such a thing ... only full connectors."
},
{
"post_id": "",
"author": "mauroh",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 22, 2015, 08:05:30 am",
"content": "http://www.ebay.com/itm/10pcs-50-Pin-50P-1-27MM-Gold-Plated-Single-Row-Straight-Female-Pin-Header-Strip-/381374578531?hash=item58cbb23f63I meant: you can cut individual pins from strips ad solder your single wires.Mauro"
}
] |
2025-10-17T19:33:20.617690
| 4
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-2mh-20-30a-peak-inductor-how-would-you-make-that/
|
1-2mH 20-30A peak inductor - how would you make that? - Page 1
|
[
{
"post_id": "",
"author": "not1xor1",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 23, 2019, 08:09:55 am",
"content": "HiI'm playing with LTSPICE and simulating a linear PSU pre-regulator that approaches the efficiency of a switching one while keeping the noise at the level and frequency of an ordinary linear PSU.Unfortunately that would require an inductor in the range of the mH able to sustain tenths of Amps of peak current without saturating.Since I never saw such a beast I wonder if that would be just too expensive compared to other possible alternatives (ordinary switching preregulator or multitap transformer).Would a 50/60Hz toroidal transformer nucleus work for that? Any idea about size calculation?thanks"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 23, 2019, 08:39:39 am",
"content": "Presumably this is a low frequency switched mode?What about audible noise?Yes, I expect a toroidal mains transformer core will work quite well."
},
{
"post_id": "",
"author": "Berni",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 23, 2019, 08:46:09 am",
"content": "By itself 1mH is not that difficult, but yes doing that at 30A is going to require a very big inductor. Im guessing such a torodial core inductor would be about 5 to 10cm in diameter.This is a pretty useful calculator for designing inductors and transformers:http://dicks-website.eu/coilcalculator/index.html(Note that you will likely have to go find a core you want at a manufacturer and enter the data from its datasheet)The type of core also determines how well the inductor works at high frequency and the kind of losses it creates there. Cores such as silicon steel is only good for low frequency 50Hz operation. Ferrite cores handle higher frequencies and come in many blends that have different properties, some handle high fields (higher saturation current) some have high permeability (less turns needed), some operate well in >MHz ranges, some are very temperature stable etc. Typically a core optimized for one parameter is bad at all the other parameters."
},
{
"post_id": "",
"author": "not1xor1",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 23, 2019, 09:43:01 am",
"content": "Quote from: Zero999 on January 23, 2019, 08:39:39 amIt is a sort of hybrid between a classical SCR preregulator and a classical buck regulator.There is a MOSFET switch that goes on after 2-3ms from zero-cross and goes off as soon as the inductor has enough energy to re-charge the output capacitor for the worst case load. A 1000-2000µF capacitor, before the MOSFET, dumps the voltage spikes and store the energy released by the transformer secondary. Obviously on low current load it is the capacitor which provides most of the energy for the inductor, so in that case it is a real, albeit quite lazy, DCM buck converter.I've no idea about acoustical noise, in LTspice it is quite quiet. Anyway current value and frequency are about the same that go through an ordinary transformer secondary when charging the electrolytic capacitors, so I hope that would not be much more than usual."
},
{
"post_id": "",
"author": "not1xor1",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 23, 2019, 09:53:12 am",
"content": "Quote from: Berni on January 23, 2019, 08:46:09 amThanks for the link. I'll read carefully that page later.In the simulator there are current pulses ranging from fractions of ms to several ms (according to the voltage and load) at a frequency of 100Hz (120Hz). So I think that an AC mains transformer core would be more appropriate.I'm not an engineer and just studied electronics by myself on schoolbooks lot of years ago. My knowledge on electromagnetics is... just appropriately for an iron core... quite rustedI hope I'll be able to digest all that informations...thanks"
},
{
"post_id": "",
"author": "BravoV",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 23, 2019, 09:54:25 am",
"content": "I guess you should be looking for Siemens's stuff, as scored these recently at local junk yard (electronic recycler)Maybe in series ? If the biggest they've made isn't big enough.Measured details : DCR = 0.04 Ohm , inductance = 502uH@100Hz and 460uH@100KHz. A TO-220 body as reference size."
},
{
"post_id": "",
"author": "Berni",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 23, 2019, 10:31:39 am",
"content": "Yeah that does sound like low frequency operation so things designed for 50/60 Hz mains would likely work. Perhaps you can find a big enough balast inductor for a powerful mercury vapor lamp that would fit the specs. Perhaps stacking a few microwave oven transformer cores together would also get you there.But in terms of being a preregulator fed by mains its easier to get a transformer with secondary taps and then use relays(or tiacs if you prefer solid state) to switch those taps into the rectifier as needed. It requires no extra heavy iron core device , is run by very simple control electronics and adds no efficiency loss.The size of your required inductor is the very reason why switch mode supplies operate at higher frequencies, it makes there inductors and capacitors much smaller for the same power output."
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 23, 2019, 10:59:06 am",
"content": "How?Well, 2mH at 30A is 0.9J(!!), and assuming the frequency is low enough for laminated iron (mains frequency + harmonics?), that means Bmax ~ 1.2T is reasonable. 0.9J / (1.2T)^2 * 2*(1.26uH/m) = 1.57u m^3 or 1.57 cm^3 of air gap. At a typical aspect ratio of about 25:25:1, you'd need a core of 1.36mm gap and 34 x 34mm cross section. Which isn't terrifyingly big, about 200VA transformer size I think.That'll be a couple hundred bucks to get made custom, or maybe $50-100 if Hammond has one, stock?Whereas the filtering for a proper SMPS is just a couple bucks -- you can see clearly the economy heavily favors one over the other!Making a good SMPS is the hard part. Shielding and filtering one, easy!Tim"
},
{
"post_id": "",
"author": "Doctorandus_P",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 23, 2019, 04:10:07 pm",
"content": "Quote from: not1xor1 on January 23, 2019, 09:43:01 amIn what way would this be a lineair regulator instead of a switching one, as you suggested in your original postSize, wheight and costs go down with higher frequencies SMPS, and that is why higher frequencies are being used. Upper limit is mainly set by the quality of the semiconducter swich, because switching losses increase at higher frequencies, and switching frequencies for an SMPS of 1MHz or higher are no exception anymore.Several years ago I built an \"emcie\" / \"elmcie\" compatible LC meter with a LM393 comparator and a uC. primary coils of E-core transformers measured as a few Henries, and Toroidal transformers measured in the tens of Henries, but the measurement errors were probably very high.\"Wide bandwith\" is sometimes quoted as a disadvantage of toroidal transformers, but good for youSo if I assume a 10H primary inductance for a 230Vac toroidal transformer and you need 1mH then the secundary winding would be around 230/sqrt(10000:1) = 2,3Vac, and you want it to be able to handle 30A, so the size would be for a 70VA transformer.So if you have a 70VA or larger toroidal transformer in the closet and you put a handfull of windings from thick enough wire around it you have an inductor of the size you want.(I may have made some gross errors / assumptuions here, so check for yourself)If you want to do some measurements / experiments with power inductors, and if you have an scope, I can highly recommend:http://elm-chan.org/works/lchk/report.htmlhttp://www.pa4tim.nl/?p=1859With a pwm signal, and a handfull of cheap components you can easily measure inductances and saturation effects of inductors."
},
{
"post_id": "",
"author": "BravoV",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 23, 2019, 05:33:58 pm",
"content": "Quote from: Doctorandus_P on January 23, 2019, 04:10:07 pmIn this forum, we have similar inductor saturation tester circuit with \"energy recycling\", so the energy used to test the inductor will be recycle again rather than wasted, designed by respected member here Jay_Diddy_B ->Inductor Saturation TesterAnd successfully built by other member here too"
},
{
"post_id": "",
"author": "mvs",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 23, 2019, 06:04:27 pm",
"content": "Quote from: not1xor1 on January 23, 2019, 08:09:55 amAgilent U8002A power supply has preregulator with 900µH inductor. It is small \"transformer\" screwed to the case at photo below.http://caxapa.ru/thumbs/324496/TopView.JPG"
},
{
"post_id": "",
"author": "not1xor1",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 24, 2019, 06:36:25 am",
"content": "thanks everybody for all your repliesBravoV:QuoteProvided that it would work, that would make hard to replicate a possible project.BTW Yes, I already know (and will probably build) Jay_Diddy_B's Inductor Saturation Tester.Berni:QuoteI know about multitap transformer solution, but, apart the fact that they are more difficult to source (unless you stack multiple transformer with increase of cost and space), they are much less efficient when the output voltage is close to the lower limit before tap switch.T3sl4co1l:QuoteThe peak current would be inversely proportional to the inductance, so unless one needs 10A DC output, for 3-5A DC and 2mH 20A peak should be enough. Besides that we are not dealing with DC current, 20-30A would be the peak of few ms pulses...Anyway considering the energy of the load, e.g. 20V*3A*10ms = 0.6J, we are in that order of magnitude.Doctorandus_PQuoteYour calculations agree with what I got applying the formula in thepage linked by Berni:Imax =Φmax*N/Lto a 40VA transformerI got about 1.4mH from 26 turns and calculated 0.6mWb as Φ and so the result was about 11A of max current.BTW I already know about those inductor saturation tester projects and the advantages of a real switching PSU, but was just wondering about the feasibility of this different solution.mvs:QuoteI found the schematic in a Chinese forum, but I think it is likely wrong as there are many parts which do not make any sense."
},
{
"post_id": "",
"author": "not1xor1",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 24, 2019, 06:44:16 am",
"content": "I noticed there are various relatively cheap common mode choke rated for tenths of Amps.e.g.:on mouserHow can that be possible? Is that due to the fact that current flows in opposite directions and so the total magnetic flux is just the difference (i.e. close to null)?They also sell a 1mH 100A inductor. That is on E-I core and is really cheap... just about 264€BTW I have a few large common mode choke I probably salvaged from old broken ATX PSUs.Does anybody know if they can be re-winded and used for a switching PSU? Is the core suitable for that?"
},
{
"post_id": "",
"author": "Berni",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 24, 2019, 07:26:02 am",
"content": "Common mode chokes indeed use the opposing current trick to get to the impressive current ratings.They always have two identical coils around the same core, but when it is used as a common mode choke all the current flowing forwards trough one coil is returning in reverse on the other coil. This causes the coils to produce the same field strength but in opposite directions so they cancel out and create near zero field in the actual core. As a result the core can be smaller or made out of a high permeability material to get more inductance for a given form factor.The cores might also be a ferrite blend that is designed to have high core losses so that the differential mode current that it is meant to stop is swallowed by the losses rather than being fed back out from the stored energy in the core.Yeah ATX PSU power factor correction inductors are a common cheap way to improve the power factor of them. Id say go ahead and try measuring one to see what you get from it."
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 24, 2019, 07:34:03 am",
"content": "i made 6mH 10A dummy load for 12VDC so i could exactly simulate and test a product that was to drive a 10A automotive solenoid.Used four 'Apple' sized electromagnets wired in parallel. This came out to around 6.3mH total or something close enough to 6mH for my application.However i didn't need 10A continuous. Just short bursts of a minute or so.Even my large dummy load can't handle continuous use at 10A which is 120W of heat.I once left it on for 10min by accident and I started to smell burning enameled wireAfter that experience I thermal epoxied a 20A 60degC thermostat on to it for safety.It's been going good for 4 years now"
},
{
"post_id": "",
"author": "mvs",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 24, 2019, 08:24:29 am",
"content": "Quote from: not1xor1 on January 24, 2019, 06:36:25 amYes, it is wrong, since its not easy to reverse engineer multilayer board. Butlast versionis pretty decent result and might help to troubleshoot problems or get some ideas for your own design.PS They have placed inductor before bridge rectifier, so it will not saturate that much."
},
{
"post_id": "",
"author": "not1xor1",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 24, 2019, 08:28:01 am",
"content": "Quote from: Berni on January 24, 2019, 07:26:02 amI salvaged common mode choke.PFC correction inductors have usually higher inductance and are rated for much lower currents as they are connected to AC mains."
},
{
"post_id": "",
"author": "not1xor1",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 24, 2019, 08:52:30 am",
"content": "Quote from: Psi on January 24, 2019, 07:34:03 amyes, but in my case the pulses would last just fewsecondsmilliseconds.Anyway I think that at the end I'll build a switching preregulator.Probably it would still be useful to sync it to zero-cross so with low voltage and low current load I could use short pulse trains and so the low frequency noise would be synch-ed with AC mains."
},
{
"post_id": "",
"author": "Berni",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 24, 2019, 09:06:51 am",
"content": "Id just put plenty of passive filtering around it so that it doesn't make any high frequency noise, the low frequency stuff is hard to filter but any properly designed linear regulator should have >60dB of noise rejection at those so they wouldn't make it to the output. If that's not enough then add a capacitance multiplier circuit in front to pre-pre-regulate the noise out (They work up to 1 MHz with lots of noise rejection).Keep in mind that the mains has plenty of other noise than 50Hz. There are harmonics at multiples of 50 and there are other devices on the mains network spewing a broad range of noise into it. Anything with a brushed motor spews harmonics of its RPM back out and that can be in the KHz easily and none of it is in sync with the mains.We have a 4kW heat pump heating our house. It uses a 400 Hz three phase compressor that is driven by a single phase input VFD. Two levels up the building and all the outlets in that level running on a different mains phase i could tell if the RPM of the compressor is ramping up or down from the noise switching i was picking up from it"
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 24, 2019, 10:02:00 am",
"content": "Quote from: not1xor1 on January 24, 2019, 06:36:25 amYes, I took the worst case figures given. You certainly don't want it saturating around the peak, that would cause the current to increase suddenly.QuoteYes, that implies we are somewhere around continuous current mode.You might use even more then, to get more stable output voltage with respect to load current; or use less, so it's closer to a peak voltage switch thingy (that is, the output voltage is about equal to the peak voltage at the moment the switch turns on), with an inductor to help absorb the peak current surges (which would then be higher, maybe say 40A or something, but not unlimited destructive peaks; of course, at the expense of even worse power factor).What changes is how much capacitance you need for filtering, and the response rate of the control loop (gain and cutoff frequency).Incidentally, filter capacitance tends to rise with inductance, because the impedance of the filter Zo = sqrt(L/C) you don't want too high -- this is equivalent to the output impedance at its resonant frequency, when the resonance is critically damped. In other words, a step load change will see a peak voltage change of about Zo * delta I. In still other words: suppose the load suddenly stops drawing current, so the inductor was charged to some energy (say it's over 1J in this high-L case), and the load stops so that energy is discharged into the filter cap, so its voltage overshoots by that amount of energy.So, to put numbers to that, we can use an energy argument, and say the capacitor's voltage was 10V, and its value 20mF (just guesses). Its initial energy was E = 0.5 C V^2, or 1J also. Say we add 1J to it. Oh good, that's an easy ratio, it's doubled so it's obvious V has sqrt(2)'d, or 14.1V. A 40% overshoot is pretty generous, and probably not desirable, so you'd probably want a lot more capacitance.For the general case, invert the equation: Vfinal = sqrt(Etotal * 2 / C). If you continue substituting intermediate formulas until you get back to just the intial voltage and current, and inductance and capacitance, you'll have proven the same peak voltage change as calculated by Zo.This implies a smaller L is desirable, which is more or less true, until modulator nonlinearity causes instability, or PF gets so bad it's just a mess.In short, a middling value, where the inductor current goes nearly to zero every (half)cycle, at full load, is probably not horrible.The same mechanics apply to SMPS design -- you don't want to use too big of an inductor relative to the filter capacitors, or if you have to (usually because inductor losses are just too high to run at high ripple), you need to use more caps to keep the output impedance sensible. That's the gist of most ATX PSUs, and why they responded so damn slowly (cutoff frequency of just a few kHz!).QuoteIt's absolutely feasible, a whole generation of \"brick shithouse\" boat anchors were designed this way! But there's really only one reason why they were: they had to use SCRs to get the reliability and efficiency up, and the huge pile of iron is basically cleanup for that.Once good-enough transistors came along -- even just mere BJTs -- these designs were quickly migrated to more economical, and better performing, ones!Which, on a related note, generated more than a few tales of caution: the original RCA 2N3055 was a diffused mesa process or something like that I think -- almost as slow as a germanium power transistor, fT in the 10s kHz. Laughably useless for these sorts of things. When Motorola offered their epitaxial version (with fT ~ 2MHz, but they can't put that on the spec sheet because 2N3055 is a JEDEC spec -- not a description of the part you've ordered!), it was capable of switching comfortably in the ultrasonic range. Until a process change occurred, or someone in purchasing bought the wrong brand, or old stock or something, and KABOOM, product failures left and right... Fortunately, we don't have to worry about this much today (but it does remain a good reason to avoid overly general part numbers like those).Anyway, the phase controller -- it's still a neat design exercise, especially if you run across an occasion that really isperfectlysuited to phase control, or SCRs (or TRIACs) -- these are ever-fewer, but luck favors the prepared, as they say. But beyond a design exercise, actually building it -- if you learn better through doing, yeah, go ahead and do it.Here's a tangentially similar project I once did,Schematic:https://www.seventransistorlabs.com/Images/SCR_Inverter.pngOverview:https://www.seventransistorlabs.com/Images/SCR_Inv1.jpgUnloaded, low frequency waveform:https://www.seventransistorlabs.com/Images/SCR_Inv2.jpgLoaded, showing... commutation current I think? as well as supply voltage (fat trace is 120Hz supply ripple):https://www.seventransistorlabs.com/Images/SCR_Inv3.jpgZoom on commutation event, it's mostly smooth but notice the very slight, but very sharp, kinks at turn-on and snubber diode recovery:https://www.seventransistorlabs.com/Images/SCR_Inv4.jpgThose tiny (fractional volt) but fast (sub-microsecond edge) events are what you need to filter, to get a low noise output from an SCR inverter circuit. That can be difficult, too.And also, of course -- all of this notwithstanding the Agilent mentioned above. It's not clear to me that that's being used the same way. Similar applications include passive power factor correction (which you also see in later ATX PSUs from time to time, before active PFC and 80 Plus took over). But whatever it's doing, clearly that's how they chose to do it!Cheers,Tim"
},
{
"post_id": "",
"author": "not1xor1",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 25, 2019, 09:25:41 am",
"content": "Quote from: T3sl4co1l on January 24, 2019, 10:02:00 amAFAIK the old 2N30355 fTwas 800kHz.I have an old ST datasheet (1977 - it was SGS-Ates back then) listing both old mesa and new epitaxial models. The old (mesa) model is specified for a minimum fTof 0.8MHz while the new one is 2.5MHz.BTW I still have a few pieces from the early 70's ... SGS and Fairchild...QuoteThe circuit I'm simulating is not even a phase controller. The MOSFET is always switched on around pi/3, about the same time when a simple bridge+capacitor PSU would start charging the capacitor. I change just the on time according to the output voltage and load. There is a relatively small value cap after the bridge and before the MOSFET, just to dump the energy released by the transformer secondary when it is switched off.I do not think I'll go on with this project as I do not have a suitable core.I might rather change the phase of the switch-on (and remove the input capacitor). That might reduce the peak current (as there would be a much lower voltage delta when the inductor is switched-on), but would affect negatively the PF, the overall efficiency and stress more the transformer....or I might just check, before all that trouble, if I can get a reasonably low noise from a switching (pre)regulator."
},
{
"post_id": "",
"author": "Doctorandus_P",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 26, 2019, 08:23:33 am",
"content": "I do not understand why Jay_Diddy_B designed such a complicated inductor saturation tester.My saturation tester will be used for about 10 minutes each month on average, so no need to re-circulate the current into the Elco's.I just used some scrap elco's from the spare parts box and a 15ct HCPL3120 integrated gate driver from Ali instead of a bucket full of chicken fodder components."
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 26, 2019, 08:38:16 am",
"content": "You surely won't understand why I built this diode recovery tester either:Same basic idea, though in this case it's TVS clamped rather than recycled energy. (Schematic.)As you can guess from the large (air cored) inductor attached, it's quite sensitive to saturation and serves nicely for that purpose as well.Incidentally, I used to test saturation more frequently, but as my design knowledge has advanced, I've bothered less and less often. I suppose, take this as inspiration that it's a quite knowable process.Tim"
},
{
"post_id": "",
"author": "Doctorandus_P",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 26, 2019, 09:47:37 am",
"content": "That's right I do not understand.I do understand the learning experience in designing analog electronics, building it and the satisfaction of having a self designed circuit working.But why add a whole signal generator?Why go through the trouble of dropping a 9V supply to 5V and then pumping it up to 10V againI'm happy with a gate driver chip which receives it's input from my JDS6600, and my lab power supply for whatever voltage I fancy at that moment.Everybody his own I guess.I can understand the use of a discrete gate driver for the adjustment of the switching speed of the MOSfet in this case.This adjustment is also usefull for testing the MOSfet itself, and that is yet again one of the reasons that I've built my tester manhatten style.I can easily add / remove / adjust a series resistor between the driver and gate with a dab of heated liquid metal. Pot's don't work too wel here."
}
] |
2025-10-17T18:17:39.794988
| 24
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-2v-lvcmos-to-3-3v-lvttl-level-shifter/
|
1.2V LVCMOS to 3.3V LVTTL level shifter - Page 1
|
[
{
"post_id": "",
"author": "twitzelbos",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 07, 2023, 08:26:54 pm",
"content": "Hello all,I'm in need of an 8 Bit unidirectional level shifter that takes 1.2V LVCMOS input signals and turns them into 3.3V TTL output signals. There are a gazillion ICs out there, but I don't seem to be able to confidently select one with the search function in Digikey or on manufacturer websites. The data rate would be roughly 50 Mbps.Can someone please recommend an IC that will work for this application?Thank you,Thomas"
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 07, 2023, 09:11:20 pm",
"content": "LCMOS to TTL at 50 Mbps? Are you sure? Or do you mean LVCMOS?Ah! I see you fixed the OP. Gotcha."
},
{
"post_id": "",
"author": "twitzelbos",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 07, 2023, 09:14:26 pm",
"content": "Yep, we have this working at 3.3V routinely, but now we have a FPGA board that only outputs 1.2V on this port. We are operating SPI near its limits on this (actually mostly 39.5 Mbps, but occasionally higher).Thomas"
},
{
"post_id": "",
"author": "langwadt",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 07, 2023, 09:35:22 pm",
"content": "there's numerous dual supply 74xxx245 like;https://www.nexperia.com/products/analog-logic-ics/voltage-translators-level-shifters/74AVC8T245PW.htmlthat should work"
},
{
"post_id": "",
"author": "twitzelbos",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 07, 2023, 11:24:51 pm",
"content": "Thank you. Do I read the datasheet correctly, that I would then supply Vcc_A with 1.2V as this is the logical level I'd have on the input, and Vcc_B with 3.3V?Thanks again,Thomas"
},
{
"post_id": "",
"author": "langwadt",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 07, 2023, 11:41:42 pm",
"content": "Quote from: twitzelbos on February 07, 2023, 11:24:51 pmyes"
},
{
"post_id": "",
"author": "twitzelbos",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 08, 2023, 02:01:36 am",
"content": "Thank you!!"
}
] |
2025-10-17T16:59:17.196586
| 7
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-3v-as-voltage-drop-of-a-blue-led/
|
1.3V as voltage drop of a blue LED? - Page 1
|
[
{
"post_id": "",
"author": "bitwelder",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "August 12, 2023, 05:57:58 pm",
"content": "I'm checking an issue with the blue power LED of my desktop computer.I noticed that lately it's much less bright, so first I checked the contacts but it looks ok.Then I checked what voltage comes from the motherboard when the computer is on: 5VThen I measure with a multimeter the voltage drop of the LED: 1.33V which looks suspiciously lowIn fact if I get a fresh 3mm blue LED from by my bins and do the same measurement: 2.53VSo, is the LED failing?"
},
{
"post_id": "",
"author": "DavidAlfa",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 12, 2023, 06:24:43 pm",
"content": "At 1.5V it shouldn't shine at all. That's the drop of a red led!Maybe it's not DC, but high frequency pulses?"
},
{
"post_id": "",
"author": "bitwelder",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "August 13, 2023, 04:44:49 am",
"content": "In fact it doesn't shine while testing it.In the last days it had a weird behavior, most of the time it was so dim that it was visible only in a dark room,but sometime was returning to its original brightness, but only for ~30 minutes.I'm curious about the LED failure mode.I'm not sure how the LED is driven by the motherboard, whether in DC or in pulses,but I'll add anyway a ~220 Ohm resistor to my replacement LED."
},
{
"post_id": "",
"author": "Faranight",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "August 13, 2023, 05:33:25 am",
"content": "I've had something like this happen on a green LED in my custom RGB Christmas decoration string where one LED would suddenly lose luminosity down to like 20% and maybe flicker a little.But after an hour or so it would light up back to normal for a while, and then the phenomenon would repeat. No idea what caused it, the contacts were all good. Must have been a faulty LED."
},
{
"post_id": "",
"author": "bitwelder",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "August 13, 2023, 06:02:56 am",
"content": "Anyway, problem solved by replacing the blue LED with a new one, with a 390 Ohm resistor in series(it's a little less than full brightness, but on the other side it's only a signaling LED, and this way it's not disturbingly bright in a dark room)As I had the computer front panel open, I thought about applying a similar treatment to the red HDD LED, but meh,after all it's a mostly-off, or shortly blinking LED, so let it stay as it is."
}
] |
2025-10-17T16:50:04.573737
| 5
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-5-volt-electric-motor-inductance/
|
1.5 volt electric motor inductance - Page 1
|
[
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "April 12, 2013, 02:24:06 pm",
"content": "Hi,The motor is now on the 7 volts battery. the shema is :https://www.eevblog.com/forum/beginners/dc-motor-kicker-capacitor/15/If I have a 150 Omhs resistor and it takes .200 A to start then it continue at .070 A, can I find the inductance of the motor with E/di/dt = L ?If I put a L meter on the black and red wire I have jumping readings from 7 mH to 0 mH.Thanks for your concern,JP"
},
{
"post_id": "",
"author": "hlavac",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "April 13, 2013, 03:46:18 pm",
"content": "It makes not much sense to talk about motor inductance in a commutated DC motor like that.There are multiple windings inside (usually 3) that are switched in and out by mechanical contacts and brushes as the rotor rotates.Any movement of the rotor will cause EMI that will put reverse voltage across the motor power leads.That is throwing off your measurement..."
},
{
"post_id": "",
"author": "6502nop",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 13, 2013, 06:18:00 pm",
"content": "If I may add...That looks like a bog-standard Mabuchi motor used in toys and such. So as not to go about re-inventing the wheel, why not point you to all the info you need, right from the horse's mouth:http://www.mabuchi-motor.co.jp/en_US/technic/index.htmlI'm wondering, though, why you wouldn't just use a fan? The contraption shown would be \"torque-challenged\" and unbalanced, both problems which make motors very unhappy. A simple thermal switch (as used in coffee makers) attached to the heatsink, wired to the fan, and Robert's one of your parent's siblings. Or just leave it running. There's no such thing as having a heatsink \"too cool\" (Josephson junctions not withstanding).nop"
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "April 13, 2013, 07:43:45 pm",
"content": "Thank you very much.>\"I'm wondering, though, why you wouldn't just use a fan?\"To spare the battery.>\"Robert's one of your parent's siblings\"I dont understand.)>\"Or just leave it running\"Indeed.JP"
},
{
"post_id": "",
"author": "c4757p",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 13, 2013, 07:48:41 pm",
"content": "Quote from: J4e8a16n on April 13, 2013, 07:43:45 pm\"Bob's your uncle\"..."
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "April 10, 2014, 04:29:07 pm",
"content": "Quote from: J4e8a16n on April 13, 2013, 07:43:45 pmThey are all too big. I build a small helice for the motor. It is balanced."
}
] |
2025-10-17T20:04:24.627780
| 6
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-5v-signal-converting-to-0-2v/
|
1-5v Signal Converting to 0-2V - Page 1
|
[
{
"post_id": "",
"author": "Instro_Spark",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 19, 2014, 04:07:00 am",
"content": "Hey guys as the post sugests im trying to convert a signal from 1-5V to 0-2V i it possibe using a single supplyCircuit details+24v single supply+5v Single supplyLM324 Op amps"
},
{
"post_id": "",
"author": "sacherjj",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 19, 2014, 04:34:03 am",
"content": "How accurate do you need the conversion?What is the signal? i.e. Do you need to accurately reproduce it all down, or are you concerned with steady state, like with logic signal?"
},
{
"post_id": "",
"author": "Frenchie",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "March 19, 2014, 04:38:06 am",
"content": "One quick and dirty solution is to use a differential applifier configuration, (seehttp://www.electronics-tutorials.ws/opamp/opamp_5.html). Tie the V1 (smaller) input to a 1V reference and then configure your differential amplifier to give you a gain of 1/2. Output will be (5-1)*1/2 = 2V max and (1-1)*1/2 = 0V min. How applicable this will be will depend on what your signal actually is, how fast it is, etc.Depending on your application your reference can be a suitably stiff resistive divider, a high impeedance divider buffered by a spare opamp in the LM324 or an actual voltage reference. If your signal is high impeedance, look into an instrumentation amplifier, which is more or less the same principle with an additional buffer stage at the front end."
},
{
"post_id": "",
"author": "linux-works",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 19, 2014, 05:07:32 am",
"content": "and for the digital approach, an arduino sensing an input pin and creating an output via a dac of some sortthen its just a table lookup or mapping problem."
},
{
"post_id": "",
"author": "Instro_Spark",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 19, 2014, 07:48:19 am",
"content": "accuracy would be good im sensing a 4-20ma output signal then measuring the VD across a sense resister=250R im then using a voltage divider across that resistor into an opamp at the moment.It then will go into a microcontroller im going to be using a 2.048v refrence for the micro"
},
{
"post_id": "",
"author": "tszaboo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 19, 2014, 09:33:22 am",
"content": "Quote from: linux-works on March 19, 2014, 05:07:32 amOr you can even buy a National instruments rack, filled with an analog input and a analog output card, and program it in Labview, and run the program on a reliable IBM serverDifferential amplifier and voltage divider is definitely the way to solve the problem.But. If you are going to use an ADC, I would use a simpler. If you would use a smaller resistor, say 100R, then your output signal is 0.4V-2V and (after the amplifier) route this to your ADC directly. The ADC has better linearity, and accuracy than your resistor divider, unless you make it from 0.05% resistors, so the total accuracy is higher."
},
{
"post_id": "",
"author": "Rerouter",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 19, 2014, 09:38:29 am",
"content": "using the 100 ohm method also allows you to do things when over/under range, something that almost every commercial controller does (usually +- 3%) equally you can also tell when there is no sensor / no power to the sensor"
},
{
"post_id": "",
"author": "Instro_Spark",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 19, 2014, 10:04:34 am",
"content": "Ok thanks for the replies got another problem when i was measuring with my meter across the 250 resistor i was getting 1-5v ouput but now putting in the voltage divider across the resister measuring voltage at the wiper im getting 23v and 19v obviously my supply voltage 24v minus the volt drop idiot (DOH!!!) so how would i go converting that to 1-5v or something similar ive attched a schematic below cheers"
}
] |
2025-10-17T20:05:55.843829
| 8
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-5vdc-to-4-20ma-converter-(plc-stuff)/
|
1-5VDC to 4-20mA Converter? (PLC stuff) - Page 1
|
[
{
"post_id": "",
"author": "robobeamer",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "May 17, 2016, 11:12:54 pm",
"content": "Hello, I work in and am new to the industrial control world. One of my coworkers pointed out to me that while converting a 4-20mA signal to a 1-5VDC signal is fairly easy, we typically don't convert voltage signals to current. He challenged me to figure out why. Hoping to get some help here."
},
{
"post_id": "",
"author": "uncle_bob",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "May 18, 2016, 01:15:18 am",
"content": "HiOk, first, what has to be isolated from what?I would *assume* that both the ground reference and the voltage signal need to be fully isolated from the current loop.Is this correct in your case?Bob"
},
{
"post_id": "",
"author": "robobeamer",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "May 18, 2016, 01:44:09 am",
"content": "No. Interestingly, even the return of all DC buses are connected to earth on everything I work on. I come from the electronics industry, and I'll tell you what, the industrial control field is a very strange beast. Everything that can be grounded is grounded."
},
{
"post_id": "",
"author": "jeroen79",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 02:14:59 am",
"content": "Quote from: robobeamer on May 18, 2016, 01:44:09 amJust to rule out any surprises?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 09:44:32 am",
"content": "Quote from: jeroen79 on May 18, 2016, 02:14:59 amThere are numerous reasons for earthing the DC PSU, such as EMC and to ensure it doesn't float at a high voltage, with respect to earth, due to a fault."
},
{
"post_id": "",
"author": "hamdi.tn",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 09:57:06 am",
"content": "Quote from: robobeamer on May 17, 2016, 11:12:54 pmtechnically there is no reason why you couldn't. The unique reason i can think of is voltage drop across long wires in industrial environnement that will effect measurement precision. but to locally convert 1-5VDC to 4-20mA signal that will be transmitted somewhere else there is no reason why you can't ! 4-20mA sensors do that !! wth he's talking about."
},
{
"post_id": "",
"author": "Ammar",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 10:11:36 am",
"content": "Could be that an analog to digital converter deals with voltage? Weird question. Where there is smoke, there is fire. Hence where there is voltage, there is current. The two sort of go hand in hand. Not sure what the person is talking about. Good luck with it!"
},
{
"post_id": "",
"author": "Jeroen3",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 10:19:58 am",
"content": "You can chain 4-20 mA receivers.The receiving end is often isolated."
},
{
"post_id": "",
"author": "retrolefty",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 10:57:30 am",
"content": "I suspect your co-worker was trying to convey one of the main advantages of loop powered 4-20 ma control loops. That is that no matter how long (up to a 1,000 ft or more) the wires are in a specific loop are there is no requirement to 'calibrate' for the length of the loop wires, as the signal is a constant current proportional to the measurement value and will measure the same value no matter where in the loop you make the measurement.Attempting to measure a 1-5 vdc value on loops of long lengths would be more difficult and less accurate in real world environment.A second advantage of current loops is that the field end can utilize some of the loop current (< 4ma) to self power the field device (transmitter)."
},
{
"post_id": "",
"author": "nowlan",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 12:31:07 pm",
"content": "\"we typically don't convert voltage signals to current\"who is we? you being an electronics guy, or the industrial control tech? I was under the impression everything is either pwm or current loop in PLC land. The advantage is that current loop doesnt pick up noise, well probably does, but the transceiver adjusts."
},
{
"post_id": "",
"author": "Jeroen3",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 02:03:50 pm",
"content": "To answer your original question.Converting 4-20mA to 1-5Vdc requires a resistor.Converting 1-5V to 4-20mA requires a more sophisticated circuit."
},
{
"post_id": "",
"author": "N2IXK",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 18, 2016, 04:12:51 pm",
"content": "Voltage in/Current loop out functionality is available in a single chip. An old Burr-Brown part now sold by TI:http://www.ti.com/product/XTR115"
},
{
"post_id": "",
"author": "uncle_bob",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "May 19, 2016, 12:10:46 am",
"content": "Quote from: robobeamer on May 18, 2016, 01:44:09 amHiOk, so if your current loop is grounded to the same ground as your voltage signal the conversion process is quite easy. In 99.99% of all current loop setups, that's not the case (the loop floats).Bob"
}
] |
2025-10-17T19:18:21.053836
| 13
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-778mm-dip-spacing-what-was-this-used-for/
|
1.778mm DIP spacing - what was this used for? - Page 1
|
[
{
"post_id": "",
"author": "JoeN",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "June 16, 2016, 10:37:39 pm",
"content": "I just got into electronics seriously in 2012 and I just ran across something I have never seen before. Apparently there were 1.778mm spaced DIPs for some applications. It looks like it never caught on. I found out about this non-standard spacing looking for ZIF sockets on eBay and discovered this:http://www.ebay.com/itm/401115647481After doing some research I find that Digikey sells sockets like these, probably very old stock. I can't find any components in this pin pitch, though, a few more sockets on eBay and Digikey, but zero actual components:http://www.ebay.com/sch/i.html?_nkw=1.778mmWere there actual 64 pin devices made in this pin pitch? What was it used for? Anyone have a history on 1.778mm pitch packaging?Just curious. Thank you."
},
{
"post_id": "",
"author": "bitslice",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 16, 2016, 10:52:49 pm",
"content": "There was a bunch of VDU processors like the V9958 that used 1.778mm spacing, hence the supply of suitable sockets (Shrink Plastic Dual In-line Package (SPDIP))Probably a halfway house to flat packages"
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 16, 2016, 10:59:39 pm",
"content": "Probably get more results for: 0.07\" pitch shrink DIP package.I've seen that package before in some '90's consumer entertainment gear, but they weren't exactly common and AFAIK are obsolete due to the rise of surface mount technology.N.B. 'SPDIP' is more commonly used nowadays for Slim PDIP - 24 or 28 pin package with 0.3\" width rather than 0.6\". e.g. Microchip commonly use 0.3\" wide 0.1\" pitch SPDIP for their 28 pin devices."
},
{
"post_id": "",
"author": "mikeselectricstuff",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 16, 2016, 11:11:16 pm",
"content": "Shrink-DIPs were popular for consumer electronics where they wanted a high pin count on through-hole PCBs.Mitsubishi did a lot of their 6502 based MCU family in this package - ISTR 64 pins.ST also did some ST7 parts -http://www.digikey.co.uk/product-search/en/integrated-circuits-ics/embedded-microcontrollers/2556109?k=st7&k=&pkeyword=st7&pv16=8678&FV=fff40027%2Cfff800cd&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=250I think shrink-DIPs died out as surface mount became more widely used.Digikey shows only 4 out of 64 listed Shrink-DIP MCUs in stock"
},
{
"post_id": "",
"author": "McBryce",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 17, 2016, 09:34:18 am",
"content": "The rather famous Commodore 64 used one on one of the later cost reduction models. You can see the 64 pin IC in this picture with 1.778mm pitch:http://ist.uwaterloo.ca/~schepers/MJK/pics/c64pcbr4a.jpgMcBryce."
},
{
"post_id": "",
"author": "mikeselectricstuff",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 17, 2016, 11:14:52 am",
"content": "Here are a few in my box of random old MCUs"
},
{
"post_id": "",
"author": "McBryce",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 17, 2016, 11:38:15 am",
"content": "I don't think I've ever seen sockets for these though? Were there ever sockets available?McBryce."
},
{
"post_id": "",
"author": "mikeselectricstuff",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 17, 2016, 12:02:22 pm",
"content": "Yes, there were both turned-pin and stamped sockets"
},
{
"post_id": "",
"author": "JoeN",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "June 17, 2016, 08:26:16 pm",
"content": "Quote from: McBryce on June 17, 2016, 11:38:15 amSecond ebay link in my original message above has quite a few sockets. Some are still available at Digikey, probably very old DCs.http://www.ebay.com/sch/i.html?_nkw=1.778mmThanks to all who replied, especially Mike who took images of his IC collection. I never saw sockets for double-row DIPs before. I figured those ICs just got soldered in."
},
{
"post_id": "",
"author": "German_EE",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 18, 2016, 07:32:22 am",
"content": "The weird thing is that I can't find a conversion for 1.778mm to inches. I can't see anything between 1/16 inch (1.5875mm) and 5/64 inch (1.9844mm)"
},
{
"post_id": "",
"author": "JoeN",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "June 18, 2016, 07:44:34 am",
"content": "Quote from: German_EE on June 18, 2016, 07:32:22 amYou are thinking like a carpenter. It's exactly 0.07\", which is what they were going for, just a tighter pitch than 2.54mm. There are a lot of non-fractional pin pitches out there - 0.8mm, 0.65mm, 0.5mm, etc. As far as I know, only 2.54mm (whole tenth of an inch), 1.27mm (1/2 of a tenth of an inch) and 0.635mm (1/4 of a tenth of an inch) seem to have been set up to convert into something that you can think of as fractional inches nicely."
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 18, 2016, 10:52:01 am",
"content": "Oh yes, the (in)famous QIL package. much loved as you could get almost the density of PLCC in a plastic package that would still be usable by regular auto insert machines. Of course once inserted and soldered they were almost impossible to unsolder, especially on SRBP boards where they often were used, as they would gladly peel off the copper pads.I just used to clip all the leads, or run a sharp brand new Stanley knife blade down the edge a few times, till I was through all the leads, then do the same the other side and unsolder each stub individually. Never saw the sockets they had there Mike."
}
] |
2025-10-17T19:16:41.355074
| 12
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-8-volts-2-5-volts-what-for/
|
1.8 volts 2.5 volts what for ? - Page 1
|
[
{
"post_id": "",
"author": "ez24",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "May 29, 2015, 08:16:19 pm",
"content": "HiThere is a topic on this forum and one comment on it was \"it does not have 1.8 volts\". In Art of Electronics Ed 2 there is a statement regarding what a power supply should have: \"2.5 volts\" (among other voltages)Why do people think 1.8 and 2.5 volts are necessary in a power supply and what are they used for ie what kind of circuit or components?My ps will have an adjustable voltage and fix 3.3 v, 5v and 12v. Just wondering if I should also have fixed 1.8 and/or 2.5 volts or another adjustable voltage.thanks"
},
{
"post_id": "",
"author": "suicidaleggroll",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 29, 2015, 08:21:54 pm",
"content": "1.8 is becoming increasingly common with new digital logic devices. It started with 5, moved to 3.3, and is in the process of moving to 1.8. I'm not sure what the draw of 2.5 is. About 75% of my designs use 3.3v, about 20% use 1.8v, and the remaining 5% are 5v."
},
{
"post_id": "",
"author": "c4757p",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 29, 2015, 08:31:27 pm",
"content": "You're not going to be breadboarding 1.8V parts, though, no need for an external power supply to supply that. Just stick a regulator on the board. Reduces the risk of accidentally blowing something up, too."
},
{
"post_id": "",
"author": "bobcat",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "May 29, 2015, 08:55:39 pm",
"content": "To reduce power consumption, often complex devices will have a core that operates at 1.8 or 2.2 or 2.5 volts. The I/O operates at 3.3v or 5V. Two power supplies are required for operation. Usually it is best to provide a local (on board) regulator for the core voltage. Some chips even have a core voltage regulator built in."
},
{
"post_id": "",
"author": "mariush",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 29, 2015, 09:20:06 pm",
"content": "SDRAM works at 3.3vDDR 1 RAM works at 2.5vDDR 2 RAM works at 1.8v (default JEDEC voltage) but some manufacturers at the beginning used up to 2.1vDDR 3 RAM works at 1.5v (default JEDEC voltage) but up to 1.65v was often used (Intel chipsets and processors had trouble handling more than that so most manufacturers restricted themselves to using maximum that value)A lot of 8bit microcontrollers (think PIC, attiny etc) work fine at 3.3-3.6v with all functions enabled, can work with 2.5v at reduced frequencies (but still all features) and can work at 1.8v but potentially with some features inactive.SD cards (to the best of my knowledge) work with voltages between 2.0v and 3.6v (or at least some spec says, other documents online say 1.1v-3.6v) so for example if you want to load some code from a SD card or do some data logging to a SD card, you may want to simplify a design and use same voltage for both a microcontroller and a SD card (so you'd use 2.5v , 2.8v, 3.3v)Otherwise, what everyone else said."
},
{
"post_id": "",
"author": "Howardlong",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 29, 2015, 09:32:02 pm",
"content": "It's not at all unusual, even five years ago I did a USB stick design with 1.2, 1.8, 3.3 and 5V domains, and there were actually two 3.3V domains as it was mixed signal. Five regulators in one USB stick!Thankfully chips with multiple power domains are increasingly incorporating on chip regulators, but often they're linear so for battery powered stuff it's sometimes necessary to provide an SMPS.For battery powered stuff, prolonging battery life is a key product differentiator so as part of the design, innevitably lower voltage devices are often chosen.Frequently particularly on modern digital devices the operating voltage range is fairly wide, so operating at a lower voltage than, say, 3.3V, is part of the give and take of the engineering design. For example I'm working on an ARM Cortex M4 based design at 2.5V simply because that's the lowest voltage I can get away with with all the devices on that power domain, and therfore the lowest power consumption and longest battery life. If it was a USB bus powered device, I'd almost certainly be running it at 3.3V."
},
{
"post_id": "",
"author": "Richard Crowley",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 29, 2015, 09:45:00 pm",
"content": "Quote from: bobcat on May 29, 2015, 08:55:39 pmLower operating voltage also enables higher clock speeds. It takes a lot less time to drag a node up and down between logic levels at 1.8V than at 3.3V or 5VThe original question makes almost no sense without some kind of context.WHY should a power supply \"have: 2.5 volts (among other voltages)\"It is almost a complete non-sequitur."
},
{
"post_id": "",
"author": "con-f-use",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "May 29, 2015, 10:39:24 pm",
"content": "Quote from: Richard Crowley on May 29, 2015, 09:45:00 pmAnd the question should answer itself: \"Because there are many chips that use it.\""
},
{
"post_id": "",
"author": "SL4P",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 30, 2015, 03:06:57 am",
"content": "Quote from: Richard Crowley on May 29, 2015, 09:45:00 pmThanks Richard - You beat me to it!I was wondering whensomeonewas going to bring that in... the primary reason for lower supplies appearing... slew rate!"
},
{
"post_id": "",
"author": "LaurentR",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 02, 2015, 12:57:09 am",
"content": "Modern fabrication processes use core voltages <1V.With special thick oxide I/O transistors and a bit of trickery you can do 1.8V and 2.5V I/O, but anything higher is complicated.http://www.tsmc.com/english/dedicatedFoundry/technology/28nm.htm"
},
{
"post_id": "",
"author": "timb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 02, 2015, 01:02:07 am",
"content": "Quote from: Howardlong on May 29, 2015, 09:32:02 pmThe new TI MSP432 has a built-in LDO and DC-DC, giving you the choice of a smaller footprint (no need for an inductor) or better power management.Sent from my Tablet"
}
] |
2025-10-17T19:39:38.934414
| 11
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-8v-rs232-transceiver-where/
|
1.8V RS232 transceiver, Where? - Page 1
|
[
{
"post_id": "",
"author": "Dot",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 09, 2016, 07:55:53 pm",
"content": "HiI built a SIM7100 daughter board and I would like to debug it through RS232 before moving on and mounting it on its motherboard. The problem is that UART I/O voltage levels are rated for 1.8V and I can't find an RS232 transceiver that can receive 1.8V and output 1.8V to meet with module's I/O. I'm working with 6 UART signals: TX, RX, CTS, RTS, DTR, DCD.I would prefer to get something on a breakout board.Thanks"
},
{
"post_id": "",
"author": "Richard Crowley",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 09, 2016, 08:58:02 pm",
"content": "SparkFun Logic Level Converter - Bi-DirectionalThe SparkFun bi-directional logic level converter is a small device that safely steps down 5V signals to 3.3V AND steps up 3.3V to 5V at the same time. This level converter also works with 2.8V and 1.8V devices.https://www.sparkfun.com/products/12009"
},
{
"post_id": "",
"author": "rob77",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 09, 2016, 09:08:46 pm",
"content": "i would rather suggest a level shifter IC which is guaranteed to work with 1.8V. e.g. TXB0108PWR from TI.it can translate from anything between 1.2V - 3.6V on port A to anything between 1.65 to 5.5V on port B , it's bi-directional and transparent so it's pretty versatile.the mosfet shifter Richard suggested above is a great & cheap way of doing it, but i wouldn't go as low as 1.8V with that mosfet solution. it's not so reliable with very low voltages (specially for outputs with \"weaker\" pull down)"
},
{
"post_id": "",
"author": "Monkeh",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 09, 2016, 09:33:06 pm",
"content": "One of the wide variety of FTDI ICs with 1.8V supplied to the I/O cells."
},
{
"post_id": "",
"author": "st_ashcroft",
"author_rank": "Newbie",
"is_op": false,
"timestamp": "January 09, 2016, 09:48:11 pm",
"content": "MAX218 works in a similar way to a MAX232 but at lower supply voltages.https://www.maximintegrated.com/en/products/interface/transceivers/MAX218.htmlIf you really need all 6 lines you'll need 2.Cheers,Scott"
},
{
"post_id": "",
"author": "matseng",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 10, 2016, 02:55:18 am",
"content": "Do you really mean RS232 or \"TTL-Serial\"?RS232 is using -12V for Idle/bit-high and +12V for bit-low. The Serial like you get out from a FTDI chip have the levels inverted, so +5 for Idle/bit-high and 0 for bit-low.So while a straight levelshifter like the one from Sparkfun would work if converting from Serial, you'd need something else - like the MAX chips that does the inverting as well."
},
{
"post_id": "",
"author": "Dot",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 10, 2016, 05:32:01 am",
"content": "I will need only TX, RX, CTS and RTS signals for debugging. I found a transceiver like the one below, which is based on SP3232 transceiver IC. I looked in the datasheet, but I'm not sure if it can work with 1.8V.SP3232 Datasheet:http://www.dexsilicium.com/Sipex_SP3232.pdf"
},
{
"post_id": "",
"author": "rob77",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 10, 2016, 07:15:52 am",
"content": "considering the very first sentence in the datsheet of SP3232 \"True +3.0V to +5.5V RS-232 Transceivers\" - i would say it wontwhat you need is either of the following 3 options:- RS232 transceiver capable of working with 1.8V logic- logic level shifter 1.8V <-> 3.3V (or 5V) followed by a RS232 trasceiver like the sp3232 or max232 or similar- logic level shifter 1.8V <-> 3.3V (or 5V) followed by a USB serial module (non RS232) e.g. FT232, CP2102..or similar.for debugging it makes no sense to convert to RS232, the USB serial would be my choice (unless you're using an ancient computer without USB for debugging)"
},
{
"post_id": "",
"author": "Dot",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 10, 2016, 09:17:07 am",
"content": "I was thinking of one breakout board to shift from 1.8V to RS232 voltage levels, but in this case, it seems that two breakout boards are the way to go.PC <-> SP3232 Board ( VCC = 3 V) <-> TXB0104 Board (VCCA = 3V, VCCB = 1.8V) <-> SIM7100 ModuleActually, I have a SIM7100 Evaluation Board and I looked into the schematic to find out that they're using the same setup as above.If there's anyone else in the know of one breakout board that can do all of this, please submit a link.Thank you all for your inputs."
}
] |
2025-10-17T19:27:00.772032
| 9
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-8v-to-3-3v-level-shifting-(small-footprint-low-power-cheap)/
|
1.8v to 3.3v level shifting (small footprint, low power & cheap) - Page 1
|
[
{
"post_id": "",
"author": "clem",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "May 20, 2014, 06:00:14 am",
"content": "I'm working on a small (the board is under 30x30mm) very low (average) power design. One part on the board has 5 input control pins (MOSI, SCLK, CS, +2 others) at 3.3V (@ ~1.5mhz max), however the CPU (a cortex-m0) has 1.8V IOs.So I'm trying to find a small footprint (but no BGAs), low power & cheap way (choose any two?) to accomplish this.A digikey search turned up many different level shifter parts to solve this, but they all seem to be overly expensive for the functionality (the CPU is < US$2.50). Parts like the 74LVC8T245 or 74LVCH8T245 would do the trick, but the DHVQFN24 is a bit large at 3.5x5.5mm and it seems to be ~US$0.65 Q100.I'm only translating in one direction (low to high) so I don't need a bi-directional translator, or output enables. I would have thought the cheaper solution would be a small/cheap octal non-inverting buffer that can accept 1.8v inputs with a 3.3V supply. But the cheap buffers tend to have a Vhi of ~2-2.2V and the cheap parts where all in monstrous TSSOP packages.Any ideas? Space and power are a premium, but at the same time I don't want to spend 30% of the CPU cost to shift 5 signals 1.5V.--Clem"
},
{
"post_id": "",
"author": "ivaylo",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 20, 2014, 06:34:29 am",
"content": "You are probably aware but a simple way of doing it is this -http://www.adafruit.com/products/757.It is two way and you say you don't need it but it's tiny, probably cheap in quantity, etc."
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 20, 2014, 07:15:13 am",
"content": "A discrete solution needn't be very large (a couple SC-70-6 transistor pairs and fine pitch resistor networks?), but the speed and power consumption of open collector/drain outputs tends to be poor. I wouldn't suggest it for battery operation and signals over 1MHz.Offhand I don't know of any level translators like that. There's a bunch of those damn SN74CBDHVCOMGWTFBBQ60245XYZs out there, in as many alphabet-soup-FN packages, but I don't think I've seen any in low bit widths.Don't suppose you can convince one party or the other (the MCU or peripheral) to operate on something else. Say, what's an M0 doing at 1.8V anyway? There are oodles of those available in 3.3V. If you're so strapped on current that you absolutely must use a low voltage part (I assume the power specs on it are better than most?), you're probably equally well off reconsidering the codebase.. I'm sure heavy optimizations can be done to facilitate at least as much power savings, for at least as much bother as fixing it in hardware.Tim"
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 20, 2014, 05:57:50 pm",
"content": "This is easy to do with transistors but low power cuts against open collector/drain outputs and simple circuits may have noise margin issues. 3.3 volt input tolerant buffers or inverters can be used as level shifters.Depending on your speed requirements, analog comparators can handle this easily with a minimum of power and space requirements. Just be sure to use ones that have push-pull outputs."
},
{
"post_id": "",
"author": "senso",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 20, 2014, 06:19:52 pm",
"content": "If its just inputs, why not use just a simple resistor divider to get those 3.3v down to 1.8?"
},
{
"post_id": "",
"author": "clem",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "May 21, 2014, 04:44:13 am",
"content": "Quote from: T3sl4co1l on May 20, 2014, 07:15:13 amYeah I was swimming in a sea of choices, but none quite did what I wanted or where too expensive for such little functionality. I was hoping someone here came across this problem and could point out a cheap solution.QuoteThe lower the core voltage the lower the power consumption, because the switching power is C * V^2 * f. So lowering the voltage has a bigger impact then lowering the frequency. It's why larger processors can directly control their own core voltage, so they can run the part at the lowest voltage for a given frequency (and temperature, etc.). The Cortex-M0 part can run at 3.3V but running at a lower core (and IO) voltage is an easy way to save power.This is my first foray into very-low power (micro watts) parts. I've worked on larger devices where you put the interrupt handlers in SRAM (or lock them in the icache) so you can put the DRAM in self-refresh mode and power most of the IOs, DLLs etc. But never something where every microwatt counts. It seems like it is another world.When the system goes idle I turn off the 3.3V supply and put the regulator in a low power mode. The CPU switches off the main clock and runs off of a 32khz clock for timers. They even have a mode where you turn the entire part off except for a small bit that can turn the processor back as if from reset.I'm mostly using components that run at 1.8V or have split VDD/VDDIO rails. All the wakeup events come from devices on the 1.8V supply. However the LCD (a Sharp Memory Display) has a 3.0V minimum supply and a minimum Vhi of VDD-0.1V so there isn't any room there. I wonder if the entire control interface on the display is implemented in transistors on glass or if there is a bit of silicon hiding someplace. Transistors on glass aren't know for being overly fast or low voltage."
},
{
"post_id": "",
"author": "miguelvp",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 02, 2014, 01:57:05 am",
"content": "There is the old philips application note for I2C level shiftinghttp://www.adafruit.com/datasheets/an97055.pdfI believe there is an updated one by NXP but pretty much is the same thing but I can't find it.This only deals up to 400kbps not sure how it will behave at higher rates. And it's bidirectional.Not sure if it will fit your low power small footprint."
},
{
"post_id": "",
"author": "rxxbxyhxxb",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "June 02, 2014, 05:36:02 pm",
"content": "http://www.nxp.com/documents/data_sheet/74LVC07A_Q100.pdfI hope it could help you."
},
{
"post_id": "",
"author": "Jeroen3",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 02, 2014, 07:59:56 pm",
"content": "While searching for such a relatively simple part it is best to look at the websites of manufacturers themselves. Most of the time they are better organised than the farnell or digikey database."
},
{
"post_id": "",
"author": "nsayer",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "June 02, 2014, 08:20:10 pm",
"content": "In the \"downward\" (3.3 -> 1.direction, my first inclination is a reverse-biased diode and a pull-up resistor. In the \"upward\" direction, I'd check to see if maybe the lower levels were still high enough to work - 1.8 volts is more than 1.5, so it's conceivable that your 3.3 volt might be able to take the 1.8 volt input directly."
}
] |
2025-10-17T20:01:14.056476
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-8v-to-5v-level-shifter-(single-direction-using-a-mosfet)/
|
1.8V to 5V level shifter (single direction, using a mosfet) - Page 1
|
[
{
"post_id": "",
"author": "robca",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 10, 2021, 02:23:13 am",
"content": "I'm working on a project where the designer had a simple pull up to try and level-shift a 1.8V output to a 5V input. The signal is monodirectional: from a MEMS IMU device to a PMIC that has a wake-up pin using 5V logic levels. Speed is not important, the signal is just a wake up pin going low and triggering the PMIC wake up. Low power is critical, so being able to use bigger pull up resistors (470k?) would be nice. The MEMS output can drive 3mA max, btwThe current circuit is not working properly and actually pulls up the MEMS output to ~2.4V, which is higher than the max rating for the chip. I need to manually fix a couple of boards by dead-bug soldering the mosfet and a couple of resistors.I have a BSS138 based module at home, but it seems to be marginal at 1.8V.What n-mosfet in SOT23 form factor (hand solderable) would you suggest? And what resistor values can I get away with?I'm ok with logic circuits and firmware development, but I get hopelessly lost with analog circuits, so appreciate any suggestion"
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 10, 2021, 02:31:29 am",
"content": "Maybe SSM3K329R,LF1.8V drive ok (0.289 ohm)SOT-23https://www.digikey.co.nz/en/products/detail/toshiba-semiconductor-and-storage/SSM3K329R-LF/3522374If you don't need speed 470k pullup should work, assuming the PMIC input is high impedance like a MCU input.Just be aware that with a resistor that high if the PCB gets wet the water can overpower the pullup.This one might have slightly larger legs for hand solderinghttps://www.digikey.co.nz/en/products/detail/taiwan-semiconductor-corporation/TSM2314CX-RFG/7360258"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 10, 2021, 09:47:02 am",
"content": "How about a BJT, if component availability/cost are issues?Although the schematic shown below is for 3.3V to 5V, it will work with 1.8V. If speed isn't important, C1 isn't needed.Level shift bi-direc BJT.asc"
},
{
"post_id": "",
"author": "Renate",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 10, 2021, 12:57:37 pm",
"content": "How about just making that transistor common emitter? Add a base resistor and you're done?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 10, 2021, 02:41:04 pm",
"content": "Quote from: Renate on November 10, 2021, 12:57:37 pmYes, that's much simpler.The circuit shown below will work fine from 1.8V and 5V."
},
{
"post_id": "",
"author": "robca",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 10, 2021, 06:19:54 pm",
"content": "First of all, thanks!I simulated both circuits in Falstad, and here's what they look liken-Mosfethttps://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWcMBMcUHYMGZIA4UA2ATmIxAUgoqoQFMBaMMAKADMQ84QAWHvTtwQoB2FOGjiYkFCwDOyPAOEDmhZSKjgQbAIYAbOXXm9+FTQj7mBVCHsPGA5qY0C+Awih5bILZ2tdwMHUQT28qXwAlUIRCEBQvGLiwDDiI3ltoGx9oBBZosjiE70LwVJ8M6nSYPIAnJOsG7BCqHgx4X3rSlRBS5uyEjpYAdwbippaR3vL+6aLE31GuVrNlkFnFwSpZwlj1ydnLbx6j3mCfFlmwfEDrpV4xC9HTnt24ns23xow8Y81NvDnHrdf5TEGqG6NXxAANPN BJThttps://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWcMBMcUHYMGZIA4UA2ATmIxAUgoqoQFMBaMMAKAGcRCUAWCjQkDgEJ+UcCABmAQwA2bOiwDmnHnwFdehBAKqQWAFxB4ww7r2PDRVCA2zQwpYlrCQMmYnmzckt+4TfEKGB4CNwoCCJ45C5UACZ00gCuMvosAE5GJhRmmQLc2Chi3BjwegDuRgVqIIF41XoZtdVN+YXWpfAsAEq5IK292AhtRdbQdbpQ0AjdNSh1-U2Dw1TctGK6UywVQtV4cPVbs3UiAi6rB9iEdWe0ojd9TussQAIf you wonder why I'm using weird resistor values, it's because the PMIC input (5V side) has an internal pull up that can be 220K or 10M (a programmable setting), so I'd rather use that pull up than hand soldering one more resistor.The mosfet one is bidirectional, but in my case that's not important. Assuming that the Falstad simulation is roughly on point, when the input and output is floating, the current is in the order of the hundreds of uA.The NPN one is only mono directional, which once again is not important, but seems to have a much lower current at rest, in the order of tens of pA. The current when the input is low is roughly the same as the other one, but in my case the input is always floating high, unless activated, in which case it goes low for a short amount of time. So low current at rest is more important to me than when pulling lowThere seem to be a lot of SOT23 BC547 or BC847 available, so that makes it easy to sourceAm I right in thinking that using a BC547 I would get lower power usage overall? Especially when the device is in sleep mode, longer battery life is everything"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 10, 2021, 06:46:51 pm",
"content": "The BJT isn't critical. Most small signal BJTs will work.I think BJTs generally have a lower leakage current, than MOSFETs, especially those with a low threshold voltage.I get a little anxious about seeing such high resistor values, because current leakage can be more of an issue. I strongly recommend building a prototype first. I suppose you have the advantage of the pull-up being programmable and 220k is a more sensible value, if 10M is too high. At the very least, you could add a space for an external pull-up, even if it's not used."
},
{
"post_id": "",
"author": "Renate",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 10, 2021, 06:55:49 pm",
"content": "10 M is not a resistor.It's a cough on a PCB."
},
{
"post_id": "",
"author": "robca",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 10, 2021, 06:57:10 pm",
"content": "Quote from: Zero999 on November 10, 2021, 06:46:51 pmThanks again. Yes, I can choose resistors. I can even put a parallel pull up on the PMIC input, if needed, as you say (e.g., with another 220k pullup, the actual pullup would be 100k), and I will definitely check what happens with an oscilloscope to ensure it works without problems. And, since it's a dead bug soldering, I can easily change component values if needed.And thanks for confirming that BJTs should be overall lower power."
},
{
"post_id": "",
"author": "Peabody",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 10, 2021, 07:21:21 pm",
"content": "Quote from: Zero999 on November 10, 2021, 02:41:04 pmBut R2 could be much higher, right? 100K? 220K?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 10, 2021, 08:10:49 pm",
"content": "Quote from: Peabody on November 10, 2021, 07:21:21 pmCorrect.Quote from: robca on November 10, 2021, 06:57:10 pmIt's not a matter of lower power. The problem is, when the transistor is supposed to be off, a small leakage current will still flow, causing a voltage drop across the load resistor. As you've got a pull-up of 10M, a leakage current of just 300nA, would cause it to drop 3V, giving an output of 2V, when it should be 5V.Looking at the datasheets, at 25oC, the BC846 will leak a maximum of 15nA, whist the SSM3K329R can leak up to 1µA. Of course this is specified, when the voltage is 30V, rather than only 3.2V, as per this application, but the leakage current from the MOSFET might be a problem, especially at higher temperatures, whist the BJT is likely to be fine.https://www.mouser.co.uk/datasheet/2/408/SSM3K329R_datasheet_en_20140301-1150400.pdfhttp://www.farnell.com/datasheets/79215.pdf"
}
] |
2025-10-17T17:19:52.981196
| 11
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-bit-permanent-memory/
|
1 Bit permanent memory - Page 1
|
[
{
"post_id": "",
"author": "ChrisGreece52",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 19, 2015, 10:07:55 pm",
"content": "Hello i wrote again about a project i am working on and need help again ... i need a memory cell to store a 5v signal for a long time i am talking about months here... i dont need it to store the bit without power but as long as it is plugged in i need to be able to store one bit of info.I did a google search and i found memory modules using not and nand gates but i am not sure if this is permanent or just temporary (for a few minutes)I need your help with this .Thank you in advance"
},
{
"post_id": "",
"author": "ataradov",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 19, 2015, 10:21:45 pm",
"content": "74HC574 will let you store 8 bits for as long as you like.You can create an equivalent circuit from NAND gates, but you won't save any space on the board."
},
{
"post_id": "",
"author": "ChrisGreece52",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 19, 2015, 10:22:42 pm",
"content": "Quote from: ataradov on November 19, 2015, 10:21:45 pmThank you very much now i can get down designing the final circuit"
},
{
"post_id": "",
"author": "dmills",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 19, 2015, 10:23:24 pm",
"content": "A \"D\" Flipflop, does exactly what you want, or maybe a set/reset latch, which is better depends on your available control signals.Regards, Dan."
},
{
"post_id": "",
"author": "jeroen79",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 19, 2015, 10:30:03 pm",
"content": "How about using a very low current fast fuse?(or something else that will blow quickly at the slightest but of current)Connect it between GND and a pullup resistor.When read it will read Low.To write once you connect it to VCC. Current will flow and the fuse blows.When you read it again there is no short to GND and the pullup resistor will give a High reading.Takes just 2 components and will retain it's value even after poweroff."
},
{
"post_id": "",
"author": "ChrisGreece52",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 19, 2015, 11:06:18 pm",
"content": "i would like to be able to write and read several times... so the d type flip flop is a good solution"
},
{
"post_id": "",
"author": "zapta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 20, 2015, 05:16:30 am",
"content": "You can use a dual coil latching relay. It will remember the bit even without power.http://www.ebay.com/itm/10x-Panasonic-TQ2-L2-5V-Two-Coil-Latching-Signal-Relay-DPDT-5V-/321905891998?hash=item4af3161a9e:g:S1EAAOSwwbdWMdaT"
},
{
"post_id": "",
"author": "Richard Crowley",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 20, 2015, 06:25:18 am",
"content": "TI \"Little Logic\" SOT-23 size D flip-flop"
},
{
"post_id": "",
"author": "amyk",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 20, 2015, 08:29:58 am",
"content": "Quote from: Richard Crowley on November 20, 2015, 06:25:18 amThat's so cute. I wonder if anyone has built a computer out of these... TTL and through-hole transistors have been done a few times already."
},
{
"post_id": "",
"author": "rgawron",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "November 20, 2015, 10:56:39 am",
"content": "You may use a thyristor made from two transistors."
},
{
"post_id": "",
"author": "jeroen79",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 20, 2015, 11:08:22 am",
"content": "Quote from: rgawron on November 20, 2015, 10:56:39 amOr use a thyristor made from one thyristor ; )"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 20, 2015, 01:06:01 pm",
"content": "A bistable can be made from a couple of transistors.https://en.wikipedia.org/wiki/Multivibrator#Bistable"
},
{
"post_id": "",
"author": "Kalvin",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 20, 2015, 01:28:21 pm",
"content": "OP may also want to add a Led, and use it as a very cheap logic analyzer."
},
{
"post_id": "",
"author": "zapta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 20, 2015, 01:34:05 pm",
"content": "Quote from: jeroen79 on November 20, 2015, 11:08:22 amBut how do you make the first thyristor?"
},
{
"post_id": "",
"author": "MatthewEveritt",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "November 20, 2015, 02:01:39 pm",
"content": "Quote from: zapta on November 20, 2015, 01:34:05 pmOut of a thyristor, obviously."
},
{
"post_id": "",
"author": "Karel",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 20, 2015, 02:17:34 pm",
"content": "Quote from: zapta on November 20, 2015, 05:16:30 am+1https://en.wikipedia.org/wiki/Relay#Latching_relay"
},
{
"post_id": "",
"author": "zapta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 20, 2015, 02:25:52 pm",
"content": "Quote from: MatthewEveritt on November 20, 2015, 02:01:39 pmTouche."
}
] |
2025-10-17T19:29:58.695108
| 17
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-button-power-onoff-ui-button/
|
1 button power on\off + UI button - Page 1
|
[
{
"post_id": "",
"author": "ignislion",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 09, 2019, 12:48:14 pm",
"content": "I am in the process of making a very simple beginner project in a somewhat serious manner with own PCB, plexiglass cover, lion battery with charger etc. all fancy and shining ready-to-use device, no more breadboard+modules crap. Just for fun and practice.It is basically a bunch of sensors over atmega8 and display. Because you know everyone needs to know how many moisture you have in your air sometimes =)What I am interested to do is 1 button device. 1 click to power on, then clicks to switch what to display then hold on to power off. To make this I mix some tricks I already know with parts I own.The idea is when you press the button current goes to VCC through diode and powers on the controller which then pulls up MOSFET by PCON pin. then you can use the button to interact with SW pin by clicking. And if you press the button for a couple of seconds PCON goes low and power switches off.Well, my question is \"am I doing it right?\". Because for me as a beginner it seems a little too easy to work fine =)Thank you for your time!"
},
{
"post_id": "",
"author": "ignislion",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 09, 2019, 12:54:38 pm",
"content": "Sorry I had to clarify +5V is a source of power VCC is just going to the controller and other stuff."
},
{
"post_id": "",
"author": "ignislion",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 09, 2019, 12:55:48 pm",
"content": "I swear there was someone's comment!"
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 09, 2019, 01:01:48 pm",
"content": "That's not going to work unless you can drive PCON to about +7V when you want the BSH105 NMOSFET to stay on. Its typ. gate threshold voltage is 0.58V, and to get it turned hard on, the gate needs to be at least double the threshold voltage above the source, which is providing the MCU Vcc.I assume SW is meant to be an output going to a MCU input pin. The 100nF filtering cap needs to go to ground not +5V_in otherwise you risk blowing the input pin when +5V is first applied, before the button is pressed and the MCU is powered."
},
{
"post_id": "",
"author": "ignislion",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 09, 2019, 01:27:45 pm",
"content": "Oh, I see.So maybe use p-channel MOSFET?The capacitor is a sad mistake."
},
{
"post_id": "",
"author": "ignislion",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 09, 2019, 01:34:35 pm",
"content": "I even can get IRLML5203 -VGS ± 20 VVGS(th) -1.0 ––– -2.5 VID @ TA = 25°C -3.0RDS(on) 98mOhm VGS = -10V, ID = -3.0AIt looks fine for this usage. Or I cant see something?"
},
{
"post_id": "",
"author": "AndyC_772",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 09, 2019, 01:39:27 pm",
"content": "Usually this kind of thing is done by leaving the microcontroller permanently powered, but in a very low power sleep state. Most have a mode in which they can either run from a slow internal clock, or are stopped entirely but can wake up on an interrupt (eg. from an input being switched).The trick then is to ensure that the rest of the circuit can also sit in a state where it draws essentially zero power. Switching the supply can be one way to do this, but it's not the only one.What's the power source, and how low does the current draw need to get?"
},
{
"post_id": "",
"author": "ignislion",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 09, 2019, 02:02:45 pm",
"content": "The power source is one cell of 18650 Li-ion and some step-up circuitry. Being honest I am not sure how low I need to go. essentially I just trying to do my best and see. The rest of the components needs to be powered off in some way because it is sensors with heaters and 0.36\" LED display so there is no way to control its power consumption internally. Maybe I can use a MOSFET to cut power off the periphery and switch data pins to HIgh-Z. I think I going to try this on the breadboard."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 09, 2019, 03:20:00 pm",
"content": "Show us the proposed system lineup - at least a full block diagram + schematics of interesting bits like the boost converter that provides the +5V supply, and the power switching circuit.If you get the power switching wrong, it may appear to work, but actually leave a small load on the 5V rail when off. The result would be the boost converter would slowly drain the 18650 cell, which would be disastrous if its ever stored with low charge and the cell isn't protected by a low voltage cutoff."
},
{
"post_id": "",
"author": "ignislion",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 12, 2019, 09:09:23 am",
"content": "Sry for a delayed answer! Here is what I have for a moment:https://easyeda.com/ignisilion/weather"
},
{
"post_id": "",
"author": "ignislion",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 22, 2019, 09:43:27 pm",
"content": "Well I havent done yet! =)First of all, I am very curious why I ever have seen only p-MOSFET, \"positive side\" power on schemes? N-mosfets have better performance and it seems to me that there is not so must difference on which side of load to operate.I kinda draw some schema and going to test it on weekend. Maybe you can say to me why I am wrong before I going to waste time.Another question is it ok to just connect external 5v power directly to the controller when the battery is charging?? Like in screenshot. I need to use LDO in between but overall is it OK to connect 5v after step-up? it has diode anyway so i thought it is going to work.Here is all the schema I have at the time:https://easyeda.com/ignisilion/weather"
},
{
"post_id": "",
"author": "ignislion",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "June 03, 2019, 04:38:51 pm",
"content": "As for the power switching circuit here is on what I am stopped:"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 03, 2019, 04:53:35 pm",
"content": "In order for an N-MOSFET to switch the positive side, its gate voltage needs to be above its source voltage, which is connected to the load. If there's no higher voltage in the circuit, then it would need to be generated using some kind of boost converter, which is costly and increases complexity. It's just cheaper to use a P-MOSFET or an N-MOSFET and switch the negative side.This sounds similar to another recent thread. Refer to the link below. It might be relevant.https://www.eevblog.com/forum/beginners/push-button-power-circuit-for-arduino-trying-to-modify-it-for-12v-input/"
},
{
"post_id": "",
"author": "ignislion",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "June 04, 2019, 08:05:12 pm",
"content": "Sorry, my message was badly composed. The stuff with VGS +/- is understood. My question was why i have seen so much pchannel high side switches other than nchannel low side? Because n mosfets have better rds on. It looks like i canr see something more"
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 04, 2019, 11:50:47 pm",
"content": "Probably because we don't want any voltage drop when pulling to ground."
},
{
"post_id": "",
"author": "ignislion",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "June 05, 2019, 07:17:29 am",
"content": "That's a very good reason. Thank you!"
}
] |
2025-10-17T18:09:12.251453
| 16
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-conducting-diode-pfcboost/
|
1 Conducting Diode PFC/Boost - Page 1
|
[
{
"post_id": "",
"author": "TheDood",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "December 21, 2019, 02:23:55 am",
"content": "I've been trying to build a low wattage high efficiency + good PF power supply and curious if the attached schematic showing a generalized topology is currently used or if it'd work with a traditional PFC IC that senses and controls the boost/PFC. I couldn't find any JFETs preloaded into LTSpice that were greater than 50Vds, and not sure exactly where to place ground nodes, or if it's simulating correctly?The general idea is to use \"On-until-acted-upon\" switches on the ground leg of a traditional rectifier (as well as adding a coil to each AC leg) so that during the coil charging time period the current doesn't have to go through the rectifier (dissipating power), and then during the coil discharge time period only 1 passive diode is needed to be turned on to charge the DC cap? All PFC would still be controlled by a PFC IC (PWM ect), only an \"either or\" type of cct would be added between the PFC IC switching output pin, and the JFETs (tradionally a single N-Channel FET), perhaps an inverted \"either or\" cct?During coil charge up no signal would be given to either JFET so they'd conduct simulataneously and allow current to short through the coils. Then when it was time to charge the cap, only 1 JFET (high side) would be signaled to turn off, which would direct current towards the DC side and allow the coil to discharge through only a single diode on its way to charge up the capacitor on the DC side? This way during coil charge up there's no diodes conducting, and during coil discharge only 1 diode dissipates energy?Would 2 coils in series be beneficial, ie would it be easier/cheaper/more efficient to source 2 inductors of the same rated current rated but lower rated inductance? Is the relationship between coil Ω's and their inductance linear? If not which is more efficient, 2 smaller in series, or 1 larger one?The reason I'm thinking JFETs is due to my assumption that no power is dissipated at the gate in order to flow current, but actually the time period for coil charging is probably less than 50% duty cycle, so perhaps N-Channel FETs would be more efficient? Do they make GaN JFETs?Anyways, just trying to reduce diode losses and curious if it was more efficient than a typical bridgeless rectifier? Maybe 2 coils is a waste and 1 coil is same as 2, or cheaper/more efficient?Thanks"
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 21, 2019, 05:03:02 am",
"content": "You're looking for \"bridgeless PFC\":https://www.ti.com/lit/an/slyt750/slyt750.pdfIt's a fine method but it requires an actual controller, not just comparators and pulse generators.The two inductors are in series, but they are better kept balanced, for EMI purposes.Tim"
},
{
"post_id": "",
"author": "TheDood",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "December 21, 2019, 05:53:36 am",
"content": "Quote from: T3sl4co1l on December 21, 2019, 05:03:02 amThanks Tim,Yes that was the inspiration, and thanks I know Ill need to use a controller (per your guidance). The topology posted reduces an additional conducting diode from the totem pole PFC I was looking at. There's only 1 conducting diode per half sine wave and 0 conducting diodes during coil charge (or that was the intention).Previously I wanted to see if I could use OPAmps to create a crude controller by themselves. I was curious if I understood the principles of PFC and wanted to try to implement dynamic signaling in LTSpice to test out my comprehension. After simulating and calculating what the power consumed by the comparators would be, I've given up for a dedicated controller when it comes to practicality.I was wondering if the above posted operation, in principle, is sound, or possible? Can (2) N-Channel JFETs operate like I'm intending, in terms of high side and low side? Can I eliminate a conducting diode? In theory, I was thinking Id have to put some sort of inverting opamp config between the controller output pin and JFET gates (+ a hide side/low side switch selector), but otherwise I could use a typical single FET PFC controller?EDIT:Well after looking at your link its pretty much the exact same thing as the first example except using JFETs. Perhaps it's not any more efficient.I think I can use an Arduino programmed MC to sense storage cap V, line V and line current, and use those measurements to manage the switching FETs. I know I can buy a dedicated controller but I'm a tinkerer and curious lol I still will probably buy a few controller chips to test out and compare with."
},
{
"post_id": "",
"author": "TheDood",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "December 21, 2019, 06:20:28 am",
"content": "Also, where do I put the GND node on a cct like that? If I put under cap will it solve weird when both FETS are conducting the AC signal?"
}
] |
2025-10-17T17:58:45.646023
| 4
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-hz-crystal-clock-signal-not-1-hz/
|
1 Hz crystal clock signal not 1 Hz - Page 1
|
[
{
"post_id": "",
"author": "buck converter",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 27, 2017, 09:12:09 pm",
"content": "My friend and I built this circuit and it was spot on 1 Hz, measured by our multimeter. 1 day later without moving a wire, it is now closer to 0.6 Hzhttp://www.hackersbench.com/Projects/1Hz/When we replaced the crystal, it did not fix anything. This is the crystal we used:https://www.digikey.com/product-detail/en/abracon-llc/AB38T-32.768KHZ/535-9034-ND/675229."
},
{
"post_id": "",
"author": "bson",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "July 27, 2017, 09:19:54 pm",
"content": "You missed connecting a bunch of pins on the counter to ground. Floating CMOS gates will collect charge."
},
{
"post_id": "",
"author": "pigrew",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 27, 2017, 09:21:12 pm",
"content": "The first thing I'd do is as decoupling capacitors to your ICs. Add around 0.1uF from the vdd pin to ground on each IC. It probably won't make it work, but it's a good idea to do."
},
{
"post_id": "",
"author": "MK14",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 27, 2017, 09:22:11 pm",
"content": "The second IC (on the right), seems to be missing a power pin connection. Since there are no visible wires on one entire side of it.Maybe your Cat/Pet got hungry during the night ..."
},
{
"post_id": "",
"author": "rdl",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 28, 2017, 12:18:32 am",
"content": "The web page where you got the circuit has a layout already done that you can duplicate exactly on your bread board. Try changing your circuit to match that layout and see how it works.(1Hz Time Base Layout, Standard Radio Shack style protoboard.)"
},
{
"post_id": "",
"author": "buck converter",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 28, 2017, 01:58:22 am",
"content": "Tracked the problem down to the 32.7680 KHz crystal, which is oscillating at 4 KHz. Is this waveform normal? picture athttp://imgur.com/a/vsqO4"
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 28, 2017, 02:15:20 am",
"content": "The datasheet for the crystal shows 12.5pF load capacitance but your circuit has 30pF plus all the capacitance between the connector strips of the breadboard. Use 12pF capacitors and get rid of the breadboard and use a properly designed pcb instead."
},
{
"post_id": "",
"author": "lowimpedance",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 28, 2017, 02:15:40 am",
"content": "Quote from: rdl on July 28, 2017, 12:18:32 amExactly this, then report back if it still doesn't work.As it stands by the photo its never going to work."
},
{
"post_id": "",
"author": "rdl",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 28, 2017, 08:05:58 am",
"content": "At one time, I built a 1 Hz generator using a CD4521B and a 4.194304 MHz crystal on a plastic breadboard and it worked fine. It was used to set the gate time of a frequency counter and I think I may still have that project somewhere in a box."
},
{
"post_id": "",
"author": "nali",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 28, 2017, 08:29:46 am",
"content": "Looks like pins 10 & 11 are transposed..."
},
{
"post_id": "",
"author": "Gyro",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 28, 2017, 08:36:12 am",
"content": "Quote from: rdl on July 28, 2017, 08:05:58 amIronically (for a breadboard) it was actually the high crystal frequency that saved you. They run at much higher drive level and load capacitance than a whimpy little 32kHz crystal can tolerate."
}
] |
2025-10-17T18:51:47.325650
| 11
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-hz-generator-based-on-crystal-(32-768-khz)-issue/
|
1 HZ generator based on crystal (32.768 khz) issue - Page 1
|
[
{
"post_id": "",
"author": "Mate_Well",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 26, 2019, 06:01:57 pm",
"content": "I'm planing to build a digital clock with 7 segment and BCD outputs, that part should work (will work on it later, a bit irelevant atm) and i need to make 1hz clock signal, lookedonline if there is better option then555 timer that would be more acurate, and i found one that \"divides\" 32.768khz to 2hz and in next \"stage\" it chops it further to 1hz (bingo right?) Built it on breadboard and worked fine, and thus decided to build it on a veroboard (\"cracker\" with copper dots), and it didn't work (even thought i checked all conections 10 times) after a minute or 2 (i accidently forgot to disconect it from psu) it started to work fine... for 30 seconds or so, then stoped. i have been trying to make it oscilate with no luck (hocked up a led after 1st \"diving stage\") only low frequency when i phisically touched one of the pins for the crystal, probably mains frequency coupled. Soo i decided to make 2nd board (the 1st was a chaos after trying to make it work) without the 2nd \"stage\" (2hz to 1hz) checked everything like 50 times just to be sure (last crystal i had) and behold nothing, same issue. When i touch anything from pin 10 to crystal (or pin 11) it couples the mains on it, i have zero idea what could be wrong, i checked every single thing and nothing made the 2nd board work ( the 1st board \"worked\" like 2 times and both were flukes, that jabaited me soo hard ;[ ) i will send picture of the board tomorow (and i have done my best to put all of it close together to minimalise other \"factors\")in short : issue with 32.768 khz to 2 hz \"divider\" (4060 based), worked on breadboard, no oscilation and \"works\" when ac coupled by body (except the fact that i got 50hz instead of 32.768khz) (all parts from trustworthy shop)scheme is in attachments (gray part was not done on 2nd part, since it needs the 1st \"stage\" to be working), and all values are same, voltage will be 5V and soo i tested it on 5V, only difrence is that i have got 4060B (and i have not found any difrence on interned betven them) (datasheet :https://www.gme.cz/data/attachments/dsh.427-167.1.pdf)Thanks in advance o/"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 26, 2019, 06:25:31 pm",
"content": "C1 and C2 are rather high. The 32kHz watch resonators are designed for a single 6 or 12pF capacitor. afaik."
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 26, 2019, 06:32:27 pm",
"content": "^^^What imo said.Normally you don't needanycaps on a 32k crystal, the input capacitance of the CMOS IC is sufficient."
},
{
"post_id": "",
"author": "Mate_Well",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 26, 2019, 06:33:25 pm",
"content": "Thanks i will try to put 2 in series or 3 in series (if i have that many) and if that fixes it it would be golden, and i didn't gave 2nd look to the values tbh, only the 6M8 resistors semt big to me (no point of refecne when it comes to crystals) (and would be +1 to wrong cap value strugle counter, had isseu with too small cap value on 555s)Edit: or try without one as Benta said TY"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 26, 2019, 07:49:43 pm",
"content": "The parasitic capacitancy of the 4060 (plus package plus wires) pin is around ~6pF, therefore try it first without capacitors. In case you would need to tune, you may try with a gimmick capacitor (a 5mmshortlong 0.2mm thin twisted wire) wired to the 4060's xtal oscillator input."
},
{
"post_id": "",
"author": "Mate_Well",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 27, 2019, 09:19:45 am",
"content": "Ok i have tried it with 2 in series, soo half of the original value (33/2 = lets say 16pf) and nothing changed, soo gone to no caps, and also no mayor change, except the fact that when i put finger on the tracks the 2hz \"work\" faster not 20 seconds but more like 10 soo i kinda have no clue how to fix it, no caps and \"looks\" like it has way too much of capacitance even now (both boards same issue)board pics in attachments as \"promised\" and it brings me to a possible issues (both seem stupid but may actualy be critical) 1 there is a capacitance cause by the tracks (yeah i doubt it but meh) and 2 the flux might cause issues ? (considering there is 12-13M resistor it may make sence (6M8s in series))"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 27, 2019, 09:26:25 am",
"content": "Do it step by step. Do not use R1 and the Mohm resistors. Wire the bare xtal to the 4060. Look at the 4060 outputs (do not touch the xtal pins with probes). When not oscillating wire 6M8 in parallel. When not oscillating add 220k in series. When not oscillating wire 1M in parallel. Etc. Etc."
},
{
"post_id": "",
"author": "MagicSmoker",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 27, 2019, 09:31:12 am",
"content": "The crystal might have been damaged from overdrive as a result of using too much load capacitance; 32.768kHz crystals are notoriously sensitive to this.Post the part number of the crystal or its datasheet for more specific guidance, but as of now I'd say your crystal has cracked... literally."
},
{
"post_id": "",
"author": "Mate_Well",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 27, 2019, 09:38:32 am",
"content": "ok will do that the issue is i don't have an osciloscope, will try to do and \"judge\" it with led acrod pin 8 (ground) and 7 (after 1st divishion (that is ofc when it doesn't work))also labeled board in attachments (pin 9 and 10 aren't shorted, i have \"depined\" few pins including pin 9)and datastheets of crystal :https://www.gme.cz/data/attachments/dsh.131-036.1.pdfhttps://www.gme.cz/data/attachments/dsh.131-036.2.pdfoh and if the crystal is dead (which wouln't suprise me) i don't have any replacement rn, but i have \"random\" salvaged ones with difrent freqguencies (most likely much higher) can i connect them instead of for testing or will they break ? (without the caps)"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 27, 2019, 09:48:09 am",
"content": "You may test your digital stuff by wiring an RC 4060 oscillator instead. After debugging the digital part you may start with the Xtal elaboration. Do you use CD4060B or 74HC4060?The watch crystals like low powers, like few uWatts, therefore the serial xxx Kohm resistor. The parallel xx Mohm is there to push the inverter inside the 4060 into a \"linear mode\" creating some gain thus the stuff oscillates. The prerequisite is the XX4060 supports the xtals like the 32kHz watch ones. For example the datasheet of the 74HC4060 does not mention an xtal as an option at all.."
},
{
"post_id": "",
"author": "MagicSmoker",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 27, 2019, 10:14:06 am",
"content": "Quote from: Mate_Well on October 27, 2019, 09:38:32 amIt probably wouldn't do you any good, anyway, because the capacitance of the scope probe is significant compared to a crystal's load capacitance. It is usually the case that touching the probe to one of the crystal's pins either causes it to start oscillating when it wasn't or vice versa.Quote from: Mate_Well on October 27, 2019, 09:38:32 amI checked the first datasheet and it says the load capacitance needs to be 12.5pF - which, btw, is thetotalcapacitance seen by the crystal. The load capacitors are considered to be in series as far as the crystal is concerned, and don't forget there will be stray capacitance added to this from the traces and the IC itself. I would try using 22pF capacitors here."
},
{
"post_id": "",
"author": "Mate_Well",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 27, 2019, 10:22:38 am",
"content": "I use CD4060B, and i will try to do the RC oscilator but i have no idea what values to use (looked on a eguasion and should het 1-7hz with 6M8 and 4700uf cap, i have these and should \"work\" if my math is correct)Time t = 2 n / f osc = Secondsn is the selected Q output number2 n = Q output number = 2 x Q no times Eg. Q3 output = 2x2x2 = 8f osc = 1 / 2.5 (R1xC1) = in Hertz32768 / (1 / 2,5 * (6800000 * 0,0068)) = 1,77....... secondsis the result actualy somewhere close reality becouse i have 0 point of refence when it comes to this (personally i would say it would take hours to charg e but idk)and the 22pf is issue to me, since i would have to order the parts (shipping in czech is like 8€ for parts that cost 0.04 each) and i have tryed 16pf with no luck (worked \"better\" without one) and sice i have now only 1 crystal with the right frequency that may or may not be working i will probably troubleshoot on RC circuit and if even that won't work i will just say screw this and do temporarry 555 timer instead (since i will be ordering parts in like a month or so and will revisit it then (with the crystal) and with the RC i will try it untill i break the 4060s i have (2 of them, since that is the only thing i can't rly replace until i order more)TY all for the ideas and explainingEDIT: soo i have decided to test the crystal and this circuit on breadboard, with the 33pf caps, guess what it bloddy worksand boards don't, is there a possibilitty that the flux/rosin i used (the uncleaned residue) \"shorts\" the crystal pins (well shorts relative to the 6M8 since the tracks are close to each other) again the circuit works on breadboard which makes me wonder what could be the issue"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 27, 2019, 10:59:15 am",
"content": "For you the T=30usecs (for your testing purposes it does not need to be such precise value)Below the formula (from DS).For ~32kHz, for example Rx=10k, Rs=33k-100k, Cx=1.2nF-1.5nF"
},
{
"post_id": "",
"author": "Mate_Well",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 27, 2019, 12:24:49 pm",
"content": "the RC one works fine on breadboard (soo did the crystal one), and haven't tested it on the vero board (partly cuz the 2nd board took last bit of veroboard i had) but i still can't wrap my head around why it works on breadboard but doesn't on vero board. (breadboard works perfectly and when i touch one of the crystal's legs it \"pauses\", unlike on the veroboard where it is normaly \"paused\" and i literally need to touch one of the legs for the circuit to do anything (coupled 50hz from mains most likely instead of the crystal's frequency) but that a] is not remotely acurate (instead of 2hz it is more like 0.13hz) and b] is not even remotely practical. soo just to ease my mind and distract myself i have cleaed the residual flux of the board with alcohol (or something like that) and that didn't change anything (as expected, but made the board look a bit new-er)Edit: and found out that if i turn on my soldering gun (the heavy one with transformer inside, and i use that for all projects atm) near the 4060B it basicaly does 1 \"oscilation) (changes the state of the led across pin 8&9 (not the one on board))and It kinda feels like it is stuck in reset but only for ascilator when on the board (and thus i have put 100nf cap across ground/reset&vcc (just to be sure, and \"smoothing\" cap never hurted anything yet)) but still wouldn't explain why the same ic works fine on breadboard"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 27, 2019, 12:59:49 pm",
"content": "The stray capacitance of the adjacent rows on the solderless breadboard is around 3.5pF. On your pcb it is much less. Also doublecheck whether your capacitor's and resistor's values are the right ones.Do not use transformer tesla iron with cmos chips..Blocking capacitors (ie 100n ceramics) at the chip's Vcc and Vgnd pins are important with cmos logic.Your problems are pretty standard, we all have them, and we like to debug them"
},
{
"post_id": "",
"author": "Mate_Well",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 27, 2019, 01:14:43 pm",
"content": "^ i have thought i'm insane when i done that on my last project (forgot vcc on 555 timer) and heureka found the issue resistance was wrong, but not on resistors, i have been close with the flux/rosin messing things up, except it was the vero board, measured 5M betven 2 pads, that would explain a lot of things, i have used this board in psu and other projects soo i never gave it inspection, but fact is i have never ever yet used resistors with value over 1M, sooo that explains a lot of headache, and i just jumped to finding issues with ic, crystal, and connections when all the time it was the pcb/vero board (for once it wasn't my brain with it's last 2 braincells completly failing :p )Thanks all who helped you guys taught me a lot in the apst 2 days, and i hope this might be helpfull to someoneand as always, the problem is always the biggest bs that it could have been <3 u guysand it is not technically solved yet, i will take cold one for that and hopefully finish a working board today (and i have a new thing to test when i will try to use pcbs) thankfully i have failed projects with pcb that i can still \"salvage\" but i would never ever thing about this being it (realised when the resistance of the series 6M8s was like 3M)"
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 27, 2019, 06:48:00 pm",
"content": "Quote from: imo on October 26, 2019, 07:49:43 pmI have used this trick in the past and it works well.A couple years back I was repairing an old CRT TV that had problems with the color and it turned out that the frequency of the oscillator had drifted a tiny bit but just enough that the TV decoding part was not working. The frequency varied ever so slightly with temperature so the color would start failing after a while of use. It took me a while to figure it out but in the end adding a few pF in the form of a couple twisted wires brought the frequency back to where it should be."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 27, 2019, 07:01:11 pm",
"content": "Decades back I tried to adjust my counter's oscillator, the 22pF trimmer was sooo coarse I had to go with the gimmick cap. You twist for example a 12mm long one, and then slowly cut off the free end, 0.5mm steps, till you get the frequency. When you cut off too much of it? Twist a new one"
}
] |
2025-10-17T18:01:23.516562
| 18
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-hz-low-pass-filter/
|
1 Hz Low Pass Filter - Page 1
|
[
{
"post_id": "",
"author": "fourierpwn",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "August 24, 2017, 06:43:18 am",
"content": "Hi all,A typical measurement setup used to measure 1/f noise is to use a 1 Hz low pass filter in order to filter out any noise that is present on the DC bias voltages from a given SMU and obtain \"clean\" DC.All attempts at building a simple RC filter have not yielded results that seem correct. This filter is not specific to the type of measurements it is being used for, so essentially I am just after a ? 1Hz LPF to clean up some DC voltages. Sounds simple enough (probably is, I'm just too noob) but I would appreciate as far as practical designs."
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 24, 2017, 07:39:15 am",
"content": "At frequencies that low, component values get so large that it's practically unmanageable and you get into all sorts of leakage and other parasitic problems.If at all possible, I'd recommend an active filter, but even there you'll have to watch out for parasitics."
},
{
"post_id": "",
"author": "bson",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "August 24, 2017, 04:01:45 pm",
"content": "Use an active filter for such low frequencies!"
},
{
"post_id": "",
"author": "eliocor",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "August 24, 2017, 04:25:54 pm",
"content": "Switched capacitor filters?https://www.maximintegrated.com/en/products/analog/analog-filters.htmlhttp://www.linear.com/product/LTC1059http://www.linear.com/parametric/Filter_Building_Blockshttp://uk.farnell.com/c/semiconductors-ics/filters-active/switched-capacitor-filters @Benta: sorry, I was in a hurry and I didn't take care of the requirement for 1/f measurements!!!"
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 24, 2017, 06:52:09 pm",
"content": "If you read the OP, the goal is to measure 1/f noise. I'd expect any kind of switched filter to counteract that goal. Just sayin'"
},
{
"post_id": "",
"author": "jpanhalt",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 24, 2017, 08:40:47 pm",
"content": "How about lead-acid batteries? We ran our Beckman DU spectrometers from them."
}
] |
2025-10-17T18:49:57.574631
| 6
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-lcd-display-controlled-by-2-microcontrollers/
|
1 LCD display controlled by 2 microcontrollers - Page 1
|
[
{
"post_id": "",
"author": "symbianas",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "April 13, 2020, 02:16:10 pm",
"content": "Hi, I would like to control display which is controlled by microcontroller with another microcontroller. I would need to override all lines (D0,D1,D2,D3,D4,D5,D6,D7,RD,WR,RES,A0,CS1,CS2).I guess something like relays would work but I would need many relays and maybe there is batter solutions? Any ideas?All D0-D7 pins can be input/output.Is there a chip which could do that?The reason I want to do is to display additional info on car radio display."
},
{
"post_id": "",
"author": "Manul",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 13, 2020, 02:27:30 pm",
"content": "Hi there, nice to see someone from LTI suggest to use I2C LCD, or get an I2C converter board for your existing LCD. Then it will be simple. Or use tripple state output buffer IC's (complicated and plain overkill)."
},
{
"post_id": "",
"author": "Back2Volts",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "April 13, 2020, 02:28:54 pm",
"content": "Yes, look for a serial solution."
},
{
"post_id": "",
"author": "DrG",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 13, 2020, 02:35:31 pm",
"content": "Your situation lacks some details, but maybe the easiest answer is to establish a serial connection between controllers only and leave the LCD connected to only one controller. Essentially, the controller not directly connected to the LCD, sends \"commands\" to the connected controller that are then sent to the LCD."
},
{
"post_id": "",
"author": "tooki",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 13, 2020, 02:52:00 pm",
"content": "I don’t understand why you’d want to do this, since it adds complexity. Why not just do as DrG says and have one microcontroller send the data to the other microcontroller, which then handles all the display signaling? This can easily be done with UART or I2C, among other ways."
},
{
"post_id": "",
"author": "madires",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 13, 2020, 03:37:36 pm",
"content": "With GPIO pins supporting HiZ, some simple glue logic for /RES and a signal between the MCUs to control which one is the current LCD master it should be possible. But it will waste a lot of GPIO pins. As already suggested it might be more reasonable to drive the LCD with just one MCU and let the other MCU send the display data to the first one via a serial bus."
},
{
"post_id": "",
"author": "symbianas",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "April 13, 2020, 04:01:35 pm",
"content": "The main reason I want to do this is because I want to use same display which is already used in another circuit (car radio display). So I don't think I can switch to serial solution?Display is a car radio display. I want to connect Arduino to show additional information from CAN BUS on same display. I know how to display data on that display, but missing the \"switch\" part between the original controller of the car radio and my Arduino. So searching for solutions I could use."
},
{
"post_id": "",
"author": "madires",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 13, 2020, 04:07:46 pm",
"content": "In that case you don't have any control over the radio's MCU. So you'll need a dedicated display for the Arduino."
},
{
"post_id": "",
"author": "Manul",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 13, 2020, 04:17:52 pm",
"content": "The problem is how you will synchronize access? If arduino will take ownership of LCD for a moment, you may miss some LCD update event from car radio. Also there could be data corruption because of this unsynchronised access. The only solution seems to be \"man in the middle\". Arduino will be receiving car radio LCD data, relaying, buffering it if needed and also writing custom data. So LCD will be connected just to Arduino board in this case."
},
{
"post_id": "",
"author": "symbianas",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "April 13, 2020, 04:30:16 pm",
"content": "I tried to do \"man in the middle\" approach, but signal seems to be too fast for Arduino.This is the signal capture form car radio:The parallel data which I need to capture in this case is available for 187nano seconds. So not sure if its possible to do with software, I think I need hardware solution."
},
{
"post_id": "",
"author": "Manul",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 13, 2020, 04:46:08 pm",
"content": "Does radio MCU also reads from LCD? Two way comm?"
},
{
"post_id": "",
"author": "symbianas",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "April 13, 2020, 04:53:12 pm",
"content": "Yes, that's the second problem I am facing, even if I could read data correctly I would also need to replay."
},
{
"post_id": "",
"author": "Manul",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 13, 2020, 05:18:14 pm",
"content": "Well, your project is a hard thing to do. Maybe it is possible to give radio MCU an external clock and stall it when needed (to at least solve sync problem). Thats a long shot. Probably will cause a crash or misbehaviour."
},
{
"post_id": "",
"author": "symbianas",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "April 13, 2020, 05:30:38 pm",
"content": "I will try to disable RD pin and see if reading stops drawing on the display or if reading is not mandatory, but I guess it is..."
},
{
"post_id": "",
"author": "symbianas",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "April 13, 2020, 05:45:43 pm",
"content": "I put 3.3V to RD pin which should stop read command from radio MCU. It seems it still draws the data on the screen, but it tries to reset and draw again, so its blinking. I guess If I could capture the data when it draws it could be enough just to read data and not send it back to radio controller. So it turns out it would be enough to make one way communication."
},
{
"post_id": "",
"author": "Ground_Loop",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "April 13, 2020, 07:35:17 pm",
"content": "How about a couple of 74HC157 multiplexers controlled by one of the uCs to switch the data and control lines. Or maybe use SN74CBT3257C if it needs to be bidirectional."
},
{
"post_id": "",
"author": "ozcar",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "April 13, 2020, 09:04:32 pm",
"content": "In another thread here (https://www.eevblog.com/forum/projects/hd44780-reading-sniffing-data/) somebody wanted to sniff or spy on data sent to an HD44780 LCD. I think they managed to do that using an Arduino, but it looks like the timing for your LCD is a lot tighter (even for a HD44780 it could be just about impossible depending on the device driving it).Maybe something with a faster processor could do it in a tight loop doing nothing else, or maybe using DMA on a processor that has that, at least if you are correct about not needing to send data back to the radio."
},
{
"post_id": "",
"author": "tooki",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 14, 2020, 05:36:01 pm",
"content": "Quote from: symbianas on April 13, 2020, 04:01:35 pmIf you know how to drive it, presumably you've got a datasheet or something. If you could share with everyone what kind of display it is, its driver IC, etc, that'd probably help a lot."
},
{
"post_id": "",
"author": "gcewing",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 15, 2020, 02:07:07 pm",
"content": "Are you sure it's absolutely necessary to share the radio display? It seems like giving the arduino its own display would be vastly simpler."
}
] |
2025-10-17T17:52:06.610443
| 19
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-mhz-crystal-options/
|
1 MHz crystal options - Page 1
|
[
{
"post_id": "",
"author": "netdudeuk",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 21, 2024, 03:57:18 pm",
"content": "HiI need a 1 MHz crystal for use with a SFC96364 VDU chip.The only easy / cheap options seem to be either oscillator modules or ceramic resonators.I'm thinking that you can't just put the two output pins of a module across the crystal pins on the IC. Right ?Would a ceramic resonator be good enough ?Thanks"
},
{
"post_id": "",
"author": "ledtester",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 21, 2024, 04:41:55 pm",
"content": "Quote from: netdudeuk on July 21, 2024, 03:57:18 pmIt might be possible to feed the oscillator module output into one of the crystal pins.Figure 2 and 3 in this article:https://www.analog.com/en/resources/technical-articles/replacing-crystals-and-ceramic-resonators-with-silicon-oscillators.htmlshows the basic idea. Using an oscillator you just feed the output into one of the crystal pins and leave the other one open.It might matter which one you feed the signal into."
},
{
"post_id": "",
"author": "wasedadoc",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 21, 2024, 04:46:58 pm",
"content": "It certainly will matter. Feed oscillator into pin 1."
},
{
"post_id": "",
"author": "netdudeuk",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 21, 2024, 05:47:51 pm",
"content": "Thanks both.@ledtester, I really appreciate that article you linked to. I shall read it now."
}
] |
2025-10-17T16:32:48.005077
| 4
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-minute-of-power/
|
1 minute of power. - Page 1
|
[
{
"post_id": "",
"author": "renzoms",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "October 20, 2019, 08:55:41 pm",
"content": "So I’ve got an LM3302N (IC COMPARATOR QUAD DIFF 14-DIP), LT1101CN8 (IC VOLTAGE COMPARATOR 5-V 8-DIP), and a TLC373CP (IC DUAL DIFF COMP 8-DIP) and I want to build a circuit inspired of the “1 minute of power” circuit in the Art of Electronics 3rd Ed.I looked at the data sheets and I only understood the maximum voltage and I/O current ratings. I’m at chapter one in AOE. I’ve read about 700 pages textbook, so some of the data sheet, buffers, and comparators were not incomprehensible.I think they would all work as long as I don’t exceed 20mA and LT1101 is confusing me with it’s title “voltage comparator.”Sorry if this was too lengthy for you, I’m just getting into electronics.I appreciate any input about data sheets and these chips, keep in mind I’m working through these textbooks.Thanks members of the EEVblog forum."
},
{
"post_id": "",
"author": "alsetalokin4017",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 21, 2019, 08:25:07 pm",
"content": "Well, I can't find a datasheet for the TLC373CP but the LM3302 looks pretty good to me for this project. You will only be using one of the 4 comparators in the chip but that's OK.So you want to build a circuit that starts with an LED (for example) dark, and when you push a momentary-contact pushbutton the LED (for example) lights up, remains lit at constant power for one minute, then goes dark. And you want to do this with an RC circuit and a comparator. Right?Elementary my dear Watson. How far have you gotten so far? Do you have a breadboard, some kind of power supply, some resistors and capacitors in addition to the LM3302 chip?(I don't actually own a copy of TAOE, I only have access to a text edition without diagrams....)So very briefly the Voltage Comparator works by ... comparing voltages! It compares the voltages detected on the inverting and noninverting inputs and changes output state when the two voltages match. The output state can be either High (near the chip's supply voltage) or Low (near zero or ground voltage) while the voltages on the inputs can be anywhere in that range. So in this case you want to compare a fixed voltage that you set, with a varying voltage on a capacitor in an RC circuit as it charges or discharges, and you want the comparator output to flip state when the two voltages match. And of course you want to calculate the correct values for your fixed voltage and your resistor and capacitor so that you get precisely one minute of power at the comparator output as the cap discharges through the resistor.Right?"
},
{
"post_id": "",
"author": "alsetalokin4017",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 21, 2019, 08:51:43 pm",
"content": "So start with a little design.Let's assume you use the LM3302 chip since it is very flexible in terms of supply voltage.Power supply? Assume a 9volt battery for now.Max output of the chip is 20 mA but we can get a LED to shine brightly for much less current than that. So let's figure on sending 5 mA through a green LED when the comparator output is HIGH. Current-limiting resistor needed, what is its value if 9V is supply voltage?What if we use 5 Volts power supply? Or 12 volts? Same idea, but different value resistors needed to achieve 5 mA thru our nice green LED."
},
{
"post_id": "",
"author": "vk6zgo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 21, 2019, 11:48:45 pm",
"content": "There used to be (maybe still is) a radio/TV religious programme called \"Hour of Power\".When I read this heading, I thought it must be a version of that for people with short attention spans!"
}
] |
2025-10-17T18:01:43.116466
| 4
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-ne555-timer-and-1-led-circuit-question/
|
1 NE555 timer and 1 LED circuit question - Page 1
|
[
{
"post_id": "",
"author": "Lucky-Luka",
"author_rank": "Unknown",
"is_op": true,
"timestamp": "June 01, 2019, 07:49:14 pm",
"content": "Hi allI've done a simple flashing LED circuit using a NE555 IC.I've simulated it in LTspiceIV.And no, I haven't got an oscilloscope.It looks like that the LED takes two moments to flash to its full brightness.This is the video I've done regarding my circuit:https://www.youtube.com/watch?v=-vjMvDEyco4&feature=youtu.beI expected a crisp ON and OFF behaviour but it looks like it's not the case. Can anybody help me to understand what's going on?Cheers"
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 01, 2019, 08:30:52 pm",
"content": "I always put a 0.1 uF cap between pin 5 and gnd."
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 01, 2019, 10:05:31 pm",
"content": "When an old fashioned 555 switches its output then it draws 400mA for a moment (shoot through) that sags your battery for a moment.Any other kind of power oscillator dont doo dat."
},
{
"post_id": "",
"author": "Lucky-Luka",
"author_rank": "Unknown",
"is_op": true,
"timestamp": "June 02, 2019, 12:11:38 am",
"content": "That's interesting.ThanksCheersp.s. is there a way to find all my threads or posts in this forum?"
},
{
"post_id": "",
"author": "drescherjm",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "June 02, 2019, 12:57:37 am",
"content": "QuoteIts in your profile.Profile->summary"
},
{
"post_id": "",
"author": "ArthurDent",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 02, 2019, 02:52:39 am",
"content": "Here's a post I made a year ago about the 555 output problem with high current pulses just mentioned.\"------ there appear to be many variations of the ‘555’ and although they should functionally work the same, the circuitry inside is different and can cause many different types of problems. A lot of 555 chips may have what is known as a totem pole output where there are 2 transistors, stacked one on top of the other, between the + and – supply with the output from their common junction. This configuration allows the 555 to either source or sink current. There is an extremely small moment of time when switching that both transistors could be on, producing a short and having a large current flowing through the transistors. The way around this is to wire a, say 22 ohm, bypassed resistor in series with the + for the 555 to limit the current to a safe value.The second problem is somewhat related to the first and relates to the NE555 you are using. Here is an answer to a question I found on line.“You've discovered one of the best kept secrets of the 555. That is, they aren't all the same. In fact, I know which one you have. It's the NE555 from Texas Instrument (silver top, right?), because that's what RadioShack stocks even though the catalog says LM555. The difference is that the LM555 is a bipolar chip and the NE555 is a CMOS chip. And I bet that pin 2 of this circuit is waving in the air — picking up static electricity. When the first CMOS 555s showed up on my workbench, I had the same problem until somebody told me they were CMOS, then the light went on. When working with CMOS technology, every pin has to go somewhere, used or not. What you need to do is tie pin 2 high through a 10k resistor, that's pretty close to its bipolar equivalent, and the circuit will work.”\"The above may not be your problem but not having a capacitor from pin 5 to ground and not putting a 22 bypassed resistor in series with the chip supply voltage certainly are good design choices."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 02, 2019, 02:18:48 pm",
"content": "Quote from: ArthurDent on June 02, 2019, 02:52:39 amThis problem with bipolar transistors in totem pole configuration is not restricted to the 555 IC but can happen in any IC or discrete circuit with similar configuration if the circuit does not leave enough dead time between switching one transistor off and switching the other one on. The problem is called \"shoot through\" and a lot of discussion and ways to deal with it can be found online.The best way to deal with this problem is, obviously, to provide enough dead time. If that is not possible or practical a resistor and small capacitor can be used. Even better, instead of a resistor an inductance can be used as it tries to keep a constant current and returns the energy it stores."
},
{
"post_id": "",
"author": "Arjunan M R",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "June 02, 2019, 02:31:31 pm",
"content": "Maybe add a bypass capacitor to the input.If the problem is the high current draw it should solve it.As clearly explained in great scott's video"
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 02, 2019, 02:46:23 pm",
"content": "\"I once crossed the street without looking first and nothing bad happened.\" Bad advice.\"I text while driving and haven't had an accident yet.\" Bad advice.Quote from: Arjunan M R on June 02, 2019, 02:31:31 pmBad advice.Bad advice: costs nothing and it's worth the price."
},
{
"post_id": "",
"author": "Arjunan M R",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "June 02, 2019, 02:51:53 pm",
"content": "Quote from: soldar on June 02, 2019, 02:46:23 pmSorry, removed it ."
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 02, 2019, 02:56:40 pm",
"content": "There are only TWO 555 spec's: The old bipolar one and the newer Cmos one.The NE555 is made by many IC makers. Its max output current is 200mA. Its minimum supply voltage is 4.5V.The Cmos one is made as LMC555, TLC555 and ICM7555 and is low power and has a low max output current, especially when its supply is 5V or less.The LMC555 is guaranteed to work with a supply as low as 1.5V!"
},
{
"post_id": "",
"author": "Arjunan M R",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "June 02, 2019, 02:57:29 pm",
"content": "Quote from: soldar on June 02, 2019, 02:46:23 pmI said so because I built this circuit a lot of times but I never had a problem =I said so because I texted many times while driving and haven't had an accident yet. = bad adviceSorry, removed the first two lines.I was not aware of that I was posting it in the beginners section."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 02, 2019, 03:13:23 pm",
"content": "Quote from: Arjunan M R on June 02, 2019, 02:51:53 pmOh man, I did not intend to pick on you and I am sorry if it came across that way. I was just attempting a little humor.All I meant is that it is better to follow good practices all the time. You can get a way with a lot but bad practices will catch up with you sooner or later.Pin 5 of the 555 should not be left floating. It is better to put a capacitor that will avoid false triggers."
},
{
"post_id": "",
"author": "StillTrying",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 02, 2019, 03:46:43 pm",
"content": "With long power wires the 100nF to 10uF decoupling across a bipolar 555 power is more important than the Pin5 decoupling.Just to add to the confusion.On a supply with high impeadance such as a half discharged battery, there are occasions when decoupling to Pin5 to GND when the timing or triggering is tied to V+ can make false triggering worse."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 02, 2019, 03:49:03 pm",
"content": "Decoupling the power pins goes without saying. There, I said it."
},
{
"post_id": "",
"author": "ArthurDent",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 02, 2019, 06:41:58 pm",
"content": "Here is a pulse stretcher I designed years ago to lengthen the 25us 1pps pulse from a Z3801A GPSDO so I could have it flash an LED and also be used as an output. Note I used supply decoupling and supply bypassing and pin 5 has a capacitor to ground. It worked flawlessly for years, 24/7."
}
] |
2025-10-17T18:09:26.921275
| 16
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-ohm-load-across-leads-when-multimeter-is-measuring-current-in-the-ma-range/
|
1 ohm load across leads when multimeter is measuring current in the Ma range? - Page 1
|
[
{
"post_id": "",
"author": "Light Science",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 24, 2023, 03:09:41 am",
"content": "Before you knock my dmm's, I know. I have an agilent bench dmm on the way, but for now, my crap kaiweets dmm's agree at least, but both of them exhibit this... thing.When I was monitoring a 500 milliamp current, I ran the load through my meter in the milliamp range, but noticed the power supply was showing a higher resting voltage. I moved the meter to the amp range, and the leads, and everything was fine.I used the other meter to measure the resistance on the probes basically there is 1 ohm of resistance between the probes in the milliamp range, but not the amp range. Is this normal? Both meters had it and it's annoying. How can I measure milliamp currents if it is going to drop a 1 ohm resistor in the path? Please tell me this is just something with my shit dmm's?Thank you!This is my first post! But I've been watching for 13 years.Christian"
},
{
"post_id": "",
"author": "Kim Christensen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 24, 2023, 03:19:12 am",
"content": "That's perfectly normal. Any amp, milliamp, microamp, meter is going to have some series resistance. The lower the range, the higher the resistance will be."
},
{
"post_id": "",
"author": "EEVblog",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "October 24, 2023, 03:32:01 am",
"content": "That's called burden voltage. All meters have it, good or bad quality.It's a combination of the shunt resistor and the fuse resistance.Well done on noticing it!, many people are completely unaware of it.That's why I designed the uCurrent project, it's designed to minimise this.Also my 121GW multimeter has a Low Burden voltage amplifier in it.https://www.eevblog.com/projects/ucurrent/Read the article from Silicon Chip magazine here:https://eevblog.com/files/uCurrentArticle.pdfAlso:"
},
{
"post_id": "",
"author": "ejeffrey",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 24, 2023, 03:42:23 am",
"content": "Generally the sense resistor will be sized to have a few hundred millivolts dropped at the maximum current for the range as that provides the best sensitivity for the ADC. The exception is the amps range which is usually something like 10 mOhm to limit power dissipation.If you don't care about losing some resolution moving up to a higher current range is usually an easy fix.Other approaches are to measure voltage after the current meter. If you are using a power supply with sense leads, connect them after the current shunt. You can use an amplifier like the uCurrent adapter to get better resolution with a lower sense resistance.Hall sensors are sort of the ultimate in low burden current measurement but tend to be low accuracy and low sensitivity."
},
{
"post_id": "",
"author": "TimFox",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 24, 2023, 03:46:17 am",
"content": "Another method, not useful in the 500 mA (note correct spelling) range is to use a transimpedance amplifier (op amp with feedback resistor) that can have negligible voltage across its input.This is what is found in, for example, Keithley electrometers.The op amp has to supply the feedback current to balance the input current, which is why it can be used for low currents (nA up to several mA), but is not practicable for 500 mA.Otherwise, the meter must have a finite burden resistance, as described above."
},
{
"post_id": "",
"author": "bdunham7",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 24, 2023, 05:04:07 am",
"content": "Quote from: Light Science on October 24, 2023, 03:09:41 amYou may be disappointed when you get your Agilent bench DMM depending on the model. A 34401A, for example, will have a 5 ohm shunt plus the fuse in the 100mA range. The 1A range will be a bit better with a 0.1R shunt and fuse, but still about 0.4R overall. Better meters with a 10A range and the typical modern fuse may have lower resistances, like 0.05R total or less. Your Kaiweets may simply lack any fuse in the 10A range and thus have a reasonably low burden as well. To measure 500mA with low burden, just switch to a higher range, like 3A, 5A or 10A depending on the meter. You'll lose a digit or so of precision, but if you have a good 4.5-6.5 digit meter you can still get a pretty good reading.As mentioned, some meters do have an active input system that reduces the burden voltage. These meters don't really appear to have a fixed resistance, more of a constant burden voltage over the range. These are typically only available in the lower ranges. Meters with this feature include the EEVBlog 121GW, Fluke 850xA series, Fluke 8808A and my handy Keithley 414A Picoammeter, just to name a few."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 24, 2023, 09:55:28 am",
"content": "Some burden voltage is normal, as the meter need enough voltage drop to measure. How much depends on the meter and some DMM, especially those with autoranging and a 5000 or 6000 count display may have a rather high burden (e.g. 500 mV range at full scale). Part of the burden is from the resistance of the fuse, that can be an issue when close to the limit of the fuse. How much voltage is lost depends on the meter and range - some use 1 shunt for 2 ranges and this way have a low burden in one range and a relatively high burden in the next. This is expecially the case with autoranging.Even with an active (transimpedance amplifier) current measurement system there is still a relatively fixed resistance, e.g. from the fuse and wires and possibly other protection / filtering. The resistance is however usually smaller. There is an additional offset voltage and thus current flow with shorted terminals, but this usually small (e.g. < 1 mV).AFAIK the Sigilen SDM3045 /3055 also use this for the lower range(s ?). Because of the extra power needed it is usually not found in battery operated meters - so not so sure about the EEVBlog 121GW. AFAIK this meter uses low value shunts and an extra amplifier stage and thus way gets relatively low burden voltage also for the higher current ranges."
},
{
"post_id": "",
"author": "Light Science",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 24, 2023, 03:41:33 pm",
"content": "Thank you so much!"
},
{
"post_id": "",
"author": "Light Science",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 24, 2023, 03:43:53 pm",
"content": "The man himselfThank you for the reply!I just found the 121gw a few days ago.What a meter! A buddy of mine is gifting me a Brymen 789 because I fixed his tube amp and he's not interested in this glorious world.Thank you Dave, truly, for everything. You've helped me get through some long weeks."
},
{
"post_id": "",
"author": "Light Science",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 24, 2023, 03:45:37 pm",
"content": "Very interesting. Burden voltage isn't a foreign idea to me, but higher resistance on lower ranges seems backwards, because it will have such a large effect. Thank you for the reply!"
},
{
"post_id": "",
"author": "wasedadoc",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 24, 2023, 03:46:08 pm",
"content": "Please learn to get your units correct.M means one million. 1,000,000m means one thousandth. 0.001A is the unit of current. Not a.So you should have written mA, not Ma."
},
{
"post_id": "",
"author": "Light Science",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 24, 2023, 03:47:38 pm",
"content": "I do have the 34401a on the way, but I am really needing that for accurate voltage in tubes, or \"valves\" and a number of other things. Hopefully this Brymen 789 that is coming my way will be of service. At least I can trust it. Thank you!"
},
{
"post_id": "",
"author": "Light Science",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 24, 2023, 03:51:51 pm",
"content": "Very interesting.For me, if I was charging a battery in the constant current mode, the voltage will shoot up so high if running through the meter, it will make accurate charging impossible.Ya'll have given me a lot to think about. I want to design a little circuit that counteracts the drop. Just for fun.Do I need to @ the user I am replying to? I don't see my replies linked to the users, despite hitting \"reply\" on that users post.I know, I should RTFM of the forum, I was just too excited to wait. 38 year old man with a family giddy over electronics and connecting with like minded people... (Shaking my head)Thank you!"
},
{
"post_id": "",
"author": "Light Science",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 24, 2023, 03:53:52 pm",
"content": "Yes, you are right, I need to correct my units. My phone autocorrect was being a pain. Coming from the IT world I am well versed in similar unit/capitalization rules, but did a poor job here. I will correct in the future. Thank you for the check."
},
{
"post_id": "",
"author": "bdunham7",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 24, 2023, 03:56:18 pm",
"content": "Quote from: Light Science on October 24, 2023, 03:51:51 pmYou can use @, but the norm here is to press the \"quote\" button instead of reply, then the post you are replying to will appear as a quote, which you can edit or trim if you like. This is what I've done here.Your new 789 will have the exact same issue in the 600mA range (>1R total burden resistance) but should work fine for 500mA in the 6A range."
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 24, 2023, 04:04:42 pm",
"content": "If I am measuring 500 mA, I generally would not use the mA range of a meter. There is a risk of blowing the fuse if you accidentally let the current get too high (ask me how I know).The series resistance of the meter in mA and µA ranges is not always a problem because often the source impedance of the current is much higher than the meter itself (consider that an ideal voltage source has zero impedance, and an ideal current source has infinite impedance).In the case of a constant current source, for example for charging a battery, the source impedance will be close to the ideal infinite value."
},
{
"post_id": "",
"author": "Kim Christensen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 24, 2023, 04:06:20 pm",
"content": "Quote from: Light Science on October 24, 2023, 03:45:37 pmMost meters use a resistor to turn the current into a voltage drop which is what they are actually measuring with the ADC. Therefore it makes sense that they use higher resistances for lower current ranges. Ohms law:200uA thru 1K= 200mV200mA thru 1= 200mV2A thru 0.1= 200mVetcThen they just move the decimal point on the display and add a uA, mA, A symbol as needed."
},
{
"post_id": "",
"author": "Light Science",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 24, 2023, 04:08:34 pm",
"content": "Quote from: bdunham7 on October 24, 2023, 03:56:18 pmOkay cool. Thank you. I am such a forum noob.."
},
{
"post_id": "",
"author": "Light Science",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 24, 2023, 04:10:50 pm",
"content": "Quote from: IanB on October 24, 2023, 04:04:42 pmVery interesting. I didn't even think about the source impedance. I will save and think about your reply. Thank you."
},
{
"post_id": "",
"author": "Light Science",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 24, 2023, 04:12:20 pm",
"content": "Quote from: Kim Christensen on October 24, 2023, 04:06:20 pmAhh. Yes, that does make sense. Interesting how they don't basically have some tiny version of a clamp meter inside them. So much to learn!"
},
{
"post_id": "",
"author": "Light Science",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 24, 2023, 04:16:40 pm",
"content": "Quote from: ejeffrey on October 24, 2023, 03:42:23 amHeck yeah! That is a good idea.My next challenge is to either filter the output of my crap bench psu for switching noise, or eventually replace it. I started with a bunch of junk stuff before this was a hobby for me, so I could accomplish some minor things, but now that stuff is all getting sold and replaced with much better stuff. When working with audio circuits, currently, I have to run them from battery to avoid the noise in the signal, which is really really not ideal for bigger power stuff. But, building a filter would be fun, if it worked. Don't even know if a good bench psu wouldn't have the same switching noise. (Not to jam another topic in. Can be ignored.)Thank you!"
},
{
"post_id": "",
"author": "TimFox",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 24, 2023, 04:46:17 pm",
"content": "Quote from: Light Science on October 24, 2023, 04:12:20 pmDC-responding clamp meters take up a lot of room: see \"flux gate\" for the usual method.The -hp- 428Ahttps://usermanual.wiki/Manual/HP428A.387943453is a classic: the actual flux gate is not very large, but it requires a reasonable amount of support circuitry.Its most sensitive full-scale range is 3 mA fs.It has no burden voltage, but inserts < 500 nH in series with the wire being clamped."
},
{
"post_id": "",
"author": "Light Science",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 25, 2023, 07:52:09 pm",
"content": "Quote from: TimFox on October 24, 2023, 04:46:17 pmI love this!"
},
{
"post_id": "",
"author": "EEVblog",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "October 26, 2023, 01:29:42 am",
"content": "Quote from: Light Science on October 24, 2023, 03:43:53 pmNice! The 789 is a solid meter."
}
] |
2025-10-17T16:46:23.408761
| 24
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-or-2-power-supply/
|
1 or 2 power supply(s) - Page 1
|
[
{
"post_id": "",
"author": "paul18fr",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "September 12, 2014, 02:17:34 pm",
"content": "Dear All,I'm trying to understand if there 1 or 2 power supply in the figure 1 herebellow ?From my understanding, the goal is to provide +/- 15 V (from DC adapters), as we can see in the figure 2 with 9V batteries: am I right ?ThanksPaul"
},
{
"post_id": "",
"author": "Simon",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "September 12, 2014, 02:22:24 pm",
"content": "you have two there, one is negative and one positive"
},
{
"post_id": "",
"author": "paul18fr",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "September 12, 2014, 02:26:12 pm",
"content": "that's what I've been thinking to ... thanksNB: I've been wondering why in Fig 1, the 2 capacitors are differents ... hummmit sounds like \"unabalanced\" signal.... many things to learn (not just \"mimic\"), just the beginning of a (long but interesting) walkPaul"
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 15, 2014, 06:24:24 am",
"content": "Quote from: paul18fr on September 12, 2014, 02:26:12 pmCost effective integrated circuit processes generally have NPN power transistors and not PNP power transistors. Because of this, the negative regulator (7912) uses an NPN transistor in as a common emitter configuration which is more unstable and requires larger input and output capacitors for stable operation. This is also why the 7912 pinout differs from the 7812 pinout."
},
{
"post_id": "",
"author": "Simon",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "September 15, 2014, 07:23:42 am",
"content": "yes it used to be the thing that regulators needed lots of input and output capacitance but the positive regulators which are the most used by far have come a long way and are now able to work with as little as 100-330nF rather than the proverbial 100nF ceramic + 10-100uF electrolytic."
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 15, 2014, 05:18:56 pm",
"content": "Quote from: Simon on September 15, 2014, 07:23:42 amThat is still the case but higher performance designs pay more attention to it.Modern low dropout positive regulators which use PNP or P-MOS pass elements have the same input and output capacitor requirements as old negative regulators which use NPN pass elements and for the same reason. The common emitter/source pass transistor has voltage gain which depends on the output load making frequency compensation more difficult. The common collector designs used in high dropout regulators are a lot more stable and can often get by with no bulk output capacitance."
},
{
"post_id": "",
"author": "paul18fr",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "September 15, 2014, 09:13:38 pm",
"content": "well,The schematics come from the Girino project (A big challenge for the newbie I am, but nothing more than a project to learn).I think I understand almost all the philosophy (not in detail, the big lines):- I think the design have been made so that either LM324 or TL084 can be used ... with the help of the jumpers- as the author says, LM324 needs a single power supply whereas TL084 needs two,- ok for the offset role (practical example of the non-inverting summation role of the op-amp),Nevertheless I'm a bit disturbed by the two power supplies:- LM7812 and LM7912 involve a drop in the voltage, that's why 15V is necessary- But why 15V for the Arduino that accepts 12V max from the specification?- I would have used 2 specific 15V power supplies and another 9V for the Arduino separately- The author speaks about power supplies in series ()Ambitious project (personal) challenge calling for additional tools (LTspice for example)Paul"
},
{
"post_id": "",
"author": "paul18fr",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "September 15, 2014, 09:19:16 pm",
"content": "the author document (zipped due to its size)"
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 15, 2014, 09:52:28 pm",
"content": "Quote from: paul18fr on September 15, 2014, 09:13:38 pmThere is an interesting symmetry between the LM324 and TL084 which they might have considered; the input common mode range of the LM324 extends to the negative supply while the input common mode range of the TL084 extends to the positive supply.These days lots of amplifiers have those properties but in the past an input common mode range which included the positive supply was relatively rare or maybe unappreciated. The even older LM301/LM301A has this useful property also which is why it is sometimes found in high side current sense circuits."
},
{
"post_id": "",
"author": "janoc",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 15, 2014, 10:18:57 pm",
"content": "Quote from: paul18fr on September 15, 2014, 09:13:38 pmGood learning project, IMO. Just don't expect to get an oscilloscope out of itQuote from: paul18fr on September 15, 2014, 09:13:38 pmArduino uses a 7805 regulator at the input. According to the spec (https://www.fairchildsemi.com/datasheets/LM/LM7805.pdf), these can take up to 35V input, so 15V should be safe. The Arduino doesn't likely take much current alone (the \"shield\" is not powered from it), so it should be OK.The 9-12V recommendation for Arduino is due to the fact that the \"extra\" input voltage gets turned into heat and has to be dissipated. If you have 15V input, your Arduino + some shields take 500mA, you are going to have to dissipate (15-5) * 0.5 = 5W of heat. That will make the regulator extremely hot very fast, it doesn't have much of a heatsink. It will most likely turn off or even fail. Dave did a good video on this type of problem ()If you use only 9V as input, then you are dissipating (9-5)*0.5 = 2W only, with the same load, requiring less cooling. That's why you need to keep the input voltage as low as possible or use a different type of regulator - an LDO or (better) a switching regulator.Quote from: paul18fr on September 15, 2014, 09:13:38 pmYou could use a separate supply for the Arduino, but it would be an overkill in this case. It would be justified if you wanted to make sure that the digital noise from the micro isn't getting into your sensitive input circuitry or something similar, but that is not really going to matter within usable limits of this design. Good bypassing of the power supplies is a good idea, though.Two 15V power supplies are in series, so that he gets +-15V against the common pin for powering the opamps. It is an overkill, IMO - he could have used +-9V or even a single supply and rail-to-rail opamps and saved the extra circuitry. He mentions that possibility, though. The Arduino is connected only to one of the power supplies, so it gets only 15V, not 30.Quote from: paul18fr on September 15, 2014, 09:13:38 pmNaw, not really. There is no point in simulating the power supply, that is just standard datasheet circuit. Build it up on a breadboard and measure it to make sure you understand it, though!The opamp part is also simple - all he has there are two buffers (he calls them \"emitter followers\" for whatever reason) to buffer the input signal (he wants 1M input impedance as on a regular scope) and to buffer the output of the summing amplifier. The second buffer is likely not even needed, the opamp should have more than enough power to drive the relatively high impedance analog comparator and ADC inputs of the ATMega. The summing circuit is there to add 2.5V offset so that he can measure negative signals too (the ATMega can take only signals between 0-5V).To understand the circuit, I suggest looking at some opamp tutorials, e.g.:http://www.eevblog.com/2014/04/06/eevblog-600-opamps-explained/or(Sparkfun - probably simpler for start)Or look at any EE textbook, opamp circuits are for sure going to be covered.Good luck!"
},
{
"post_id": "",
"author": "liquibyte",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 15, 2014, 10:29:23 pm",
"content": "Quote from: janoc on September 15, 2014, 10:18:57 pmNot that I'm an expert, or even close, but I found the \"Op Amps for Everyone\" book to be very helpful in beginning to understand op amps and what you can do with them. These little chips are amazing in their versatility."
},
{
"post_id": "",
"author": "paul18fr",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "September 16, 2014, 12:27:32 pm",
"content": "Quote from: janoc on September 15, 2014, 10:18:57 pmMy children and I have different projects, and in parallel to the purposes previously described, we just want to be able to see some specific signals at low frequencies (I do not expect signals lower than few KHz) - the signal generator is one of the next steps; I've planned to invest to an x-scope, in a near future (the ones I found in internet - 2nd hand - are not really interesting so I wait to purchase one such as Siglent or Rigol one)NB: there are very happy to learn how to apply schematics on the breadboard, how to braze components on the veroboard, how , to build electronic devices and so on … I don’t know who plays the much (father or children)Quote from: janoc on September 15, 2014, 10:18:57 pmOne more thing to see ...Quote from: janoc on September 15, 2014, 10:18:57 pmI need to assimilate that …Quote from: janoc on September 15, 2014, 10:18:57 pmI’m interested in simulating the whole circuit in order to learn how to use this kind of solver (it is a professional distortion) and maybe to verify I’m right in my analysesThanks for your feedbacks and advicesPaul"
}
] |
2025-10-17T19:55:22.049258
| 12
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-or-better-precision-resistor-combo-pack/
|
1% or better precision resistor combo pack? - Page 1
|
[
{
"post_id": "",
"author": "rwgast_lowlevellogicdesin",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "August 21, 2015, 12:03:45 am",
"content": "I was wondering if someone knows of a decent precision through hole resistor kit? Radio shack has a nice package but there 5% and the \"1%\" blue resistors I bought on ebay are a joke..... is the best idea to just order a bunch from mouser or digikey?"
}
] |
2025-10-17T19:35:08.482154
| 1
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-page-resume-rule-does-it-apply-to-engineers/
|
1 Page Resume Rule - Does it apply to engineers? - Page 1
|
[
{
"post_id": "",
"author": "geratheg",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 19, 2015, 07:18:55 pm",
"content": "I've been reading about Resume tips and found that a lot of suggestions were to keep the resume just 1 page long or it will be thrown away. However, I think that they were talking about resumes for jobs that are not related to science fields such as engineering.Should a resume for an engineering position be limited to 1 page?What are your suggestions about resume length?How long did you make your resume before you got hired?What other suggestions do you have that will strengthen an engineering resume so that an employer won't automatically throw it out?What works and doesn't work?"
},
{
"post_id": "",
"author": "kolonelkadat",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "June 19, 2015, 08:01:24 pm",
"content": "Its less to do with the type of job and more to do with the level of the job.If you are going for a top level/grey beard job, and your resume is 2 pages, no problem.If youre after an entry level/mid level job, and your resume is 2 pages, its going in the trash. You dont have 2 pages worth of experience. If you did, you wouldnt be after a low level position. If you DO then you are over qualified.Also keep in mind that Greg from HR is not an engineer and knows nothing about science and has 1000 other resumes on his desk; meanwhile, Senior Engineer Sally is busy and doesnt have time to read your 2 pages of nonsense.What has worked for me is a very nice 1 page resume layed out by a professional graphic designer. Its still very professional, but it stands out from all those made from a Word template."
},
{
"post_id": "",
"author": "geratheg",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 19, 2015, 09:15:08 pm",
"content": "Thank you for the tips.As a student, I don't have work experience but have several relevant projects and awards to list which take up about 1.5 pages.Also, where can I find a sample of what a resume with a nice professional layout looks like?Before, I've only ever made the standard layout resumes made in Word because those are the ones I was introduced to. I certainly wouldn't mind an upgrade."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 19, 2015, 09:19:14 pm",
"content": "Page 1: personal statement, buzzwords, career/tech competentcies.Page 2: career overviewPage 3+: selected career achievements justifying statements on page 1 and 2Always worked for me, when I was experienced.Software filters satisfied by P1 and P2HR-droids satisfied by P1 and P2, couldn't understand P3+Engineers liked P3+ since they could see P1,2 weren't bullshit, they could relate to it, and it gave them something to discuss during interview"
},
{
"post_id": "",
"author": "Yansi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 19, 2015, 09:23:02 pm",
"content": "I hope you aren't mixing a CV/resume with a motivation letter. I can't imagine a student with two pages of award or eperiencehttp://jobsearch.about.com/cs/curriculumvitae/f/cvresume.htm(also interesting to know)"
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 19, 2015, 11:01:58 pm",
"content": "Quote from: Yansi on June 19, 2015, 09:23:02 pmI did. My daughter did. It isn't that difficult.When she first tried out her (1 page) CV on an agentbeforeuniversity, heinitiallydisbelieved she could have had that experience.But then some of her experiences while at school (not uni) still enable her to \"dine out\" and stop boastful conversations in their track. Example: \"you do realise that aircraft don't fall out of the sky when their engines stop?\" resulted in the questioner being neatly skewered by \"yes, I was a solo glider pilot before I was allowed to start driving a car\". And as for the dreary HR-droid question \"describe a situation when you though your life was in danger\", she could and did make grown men blanche and swallow hard"
},
{
"post_id": "",
"author": "geratheg",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 21, 2015, 07:39:21 pm",
"content": "Thanks for the responses.I have never heard of a CV before this thread. Seems like something for PhD students when the want to get hired in industry."
},
{
"post_id": "",
"author": "Electro Fan",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 21, 2015, 08:58:58 pm",
"content": "You can find links on the web that will outline the differences between a resume and CV but the two terms are often used interchangeably. For a first job I wouldn't worry too much about resume vs. CV or the length of the document - if it all fits on one 1 page, fine; if you need a 2nd page (or possibly more) it's not the end of the world (but if the first page isn't impactful it's possible readers won't get to the 2nd page).The key is not the length but the substance. You want to show not only what you have been doing (where you worked and where you studied) and what you know (areas of study/knowledge) and what you can do (your skills) but what you have accomplished. So in addition to titles, duties and responsibilities or other descriptions of the work undertaken it's good to list key results and achievements. Sometimes these are individual accomplishments and sometimes these are contributions to team accomplishments but employers want to see if you are likely to just be marching in place or making good things happen."
},
{
"post_id": "",
"author": "zapta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 22, 2015, 02:33:11 am",
"content": "Quote from: tggzzz on June 19, 2015, 11:01:58 pmThat's a sign off bad parenting"
},
{
"post_id": "",
"author": "ivaylo",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 22, 2015, 02:46:53 am",
"content": "You are right to be confused. I get to read all resumes for technical positions which our company gets and I'd say they split 50/50 (2 pagers vs 3+). I see good candidates from both groups. Do what makes sense to you. If you are working with a recruiter it's a legitimate question to ask which school they belong to. Which country is this for, btw?"
},
{
"post_id": "",
"author": "Tomorokoshi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 22, 2015, 03:45:24 am",
"content": "I've had to review resumes of various lengths for various levels. What and why some get through HR and some don't is a mystery not solvable by engineers. There's too much illogic involved.For entry-level jobs, I've seen a lot of \"experience\" sections that list about 30 different technical keywords from the industry. When asked, I get answers like, \"Oh, we did that last year in the Junior lab.\" or something.As people get more experience, they realize more about what they know and don't know, and so become more sparing in the keyword lists.Whatever the level, there is some reasonable amount of strategy to crafting the resume to fit the specifics of the job, the company, the industry, etc. There is no point if the interview doesn't happen.Once in, if you get past the HR screening, for me anyway show-and-tell outweighs the resume. A few items turns the conversation from being interrogated by them to allowing you to lead a fair amount of the conversation. They will see what they like, and ignore what doesn't apply.For an engineering job, types of show-and-tell could be:- A homebrew hardware project. Doesn't matter if it works or not. What problems did you have? What technologies were used?- A homebrew software project. Maybe it worked with the hardware project.- Schematics and other documentation from the homebrew project.- Examples from a previous employer. This can be tricky if the interviewer is hung-up on if you got the example legitimately. If possible, a letter from the previous employer stating the acceptability of bringing in an old revision PCB or circuit board might help. Me? I don't care. Some might.If you are given tests, realize that those interviewing you know the test inside and out. They've been through it in other interviews a few times and know the traps. Ask questions when it seems appropriate.Know the basics. If electronics, know how to analyze an op-amp and some common uses. If software, know the basic syntax of the language you expect to be using.Be on time but not too early. The engineer is probably not looking forward to interviews anyway, because it will just set the schedule back even more.Have your resume get reviewed by several people you know both in and out of the engineering industry."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 22, 2015, 09:00:48 am",
"content": "Quote from: Tomorokoshi on June 22, 2015, 03:45:24 amI've been in a company where the engineers explicitly forbade HR from discarding CVs, because we discovered the HR-droids were discarding interesting people.QuoteI've used the technique of marking experience as either \"core serious\" keywords, or \"have used when I found it necessary\" keywords. That indicates I am flexible and can choose to use a hammer for nails and a screwdriver for screws.QuoteAsking questions has several benefits: it shows you know what you don't know, you don't rush in with inappropriate solutions, you know how to elicit what's important to the customer, it buys you time while you think, and it helps you get a solid answer."
},
{
"post_id": "",
"author": "EEVblog",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "June 22, 2015, 12:07:43 pm",
"content": "Quote from: tggzzz on June 22, 2015, 09:00:48 amI always did that and demanded that they give me all of them. Of course being nice about it and making them think I think they are doing a useful job.In reality I'd just mix the piles together and ignore what they did, because it was always invariably not what we wanted. In fact it seemed that HR seemed to finely tuned Dick Magnets, because the dicks always seems to be the ones they'd recommended"
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 22, 2015, 12:13:26 pm",
"content": "It totally depends on the country and whats normal.My CV a few years out of Uni was 3 pagesIf you want to be sure you get an interview, make your resume as 2 sheets of 1mm FR4 PCB with ENIG and black soldermask and post it to the company.You can be damn sure every engineer at the company will read it.The disadvantage is A4/letter sized PCBs aren't cheap (~$100). But if you like the job and really want an interview...(no, i didnt do my CV like this, was just an idea)"
},
{
"post_id": "",
"author": "tron9000",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 22, 2015, 12:26:19 pm",
"content": "Mine was 2 pages long for my current job, but obviously I left out all the positions that weren't relevant experience. But that still made it over 2 pages, so I tweaked the margins to make it fit!"
},
{
"post_id": "",
"author": "JuKu",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 22, 2015, 12:37:27 pm",
"content": "You don't have to list everything. Mine reads \"several awards\" and \"20 patents\", but I don't see a point listing each."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 22, 2015, 12:58:10 pm",
"content": "Quote from: JuKu on June 22, 2015, 12:37:27 pmVery true, especially as theonlypurpose of a CV is to get an interview. Tease them into giving you an interview!"
},
{
"post_id": "",
"author": "geratheg",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 23, 2015, 02:03:52 pm",
"content": "More interesting responses. For those who are curious which country I'm from: USA."
}
] |
2025-10-17T19:38:14.548496
| 18
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-phase-motion-detector-how-does-it-work/
|
1-phase motion detector, how does it work? - Page 1
|
[
{
"post_id": "",
"author": "somlioy",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 06, 2012, 06:15:25 pm",
"content": "HiMe and some of my colleagues had a discussion about how 1-phase motion detectors work. They're used for controlling lights etc. Connected like this:How do they power the electronics inside the detector?Normally we would use two phase in and get both out to the lights.Talking about 230v 50hz mains for the records."
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 06, 2012, 06:24:48 pm",
"content": "Could just be a mercury switch?"
},
{
"post_id": "",
"author": "somlioy",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 06, 2012, 06:52:58 pm",
"content": "Theres definitively electronics inside. Including a coil, triac, some caps etc. You have the option to choose on-time, lux sensitivity and movement sensitivity with some onboard pots or something.It's this detector:http://translate.google.com/translate?sl=no&tl=en&js=n&prev=_t&hl=no&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Felko.no%2Fwsp%2Felko2_nor%2Ffrontend.cgi%3Ffunc%3Dcatalog.show%26table%3DPRODUCT%26prod_id%3D12321%26func_id%3D1001%26l3exp%3D1848%26l2exp%3D%26l1exp%3D1845%26template%3DproductDatasheet (page 2 for english):http://elko.no/elko2_nor/frontend/mediabank/17942/Bruksanv4860.pdf"
},
{
"post_id": "",
"author": "cybergibbons",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 06, 2012, 07:11:43 pm",
"content": "It will either charge a battery or supercap when the lights are on, or pass a very small current through the lamps (not enough to light them) and use this."
},
{
"post_id": "",
"author": "somlioy",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 06, 2012, 07:14:13 pm",
"content": "Quote from: cybergibbons on March 06, 2012, 07:11:43 pmHow does that work considering its the same mains potential at the both side of the detector when the switch is closed.Quote from: cybergibbons on March 06, 2012, 07:11:43 pmWhat about the first power up? And you only have one potential."
},
{
"post_id": "",
"author": "aluck",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "March 06, 2012, 08:48:42 pm",
"content": "Quote from: cybergibbons on March 06, 2012, 07:11:43 pmthat's exactly how they work, and for that exact reason they are not suitable for driving energy-saving bulbs"
},
{
"post_id": "",
"author": "T4P",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 07, 2012, 11:05:44 am",
"content": "Well , a phototransistor .Then the relay on the live line ."
},
{
"post_id": "",
"author": "somlioy",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 07, 2012, 06:38:59 pm",
"content": "Quote from: aluck on March 06, 2012, 08:48:42 pmOk, so how does that work in practice?"
},
{
"post_id": "",
"author": "cybergibbons",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 07, 2012, 07:12:46 pm",
"content": "Quote from: somlioy on March 06, 2012, 07:14:13 pmAre you stating that there is the same mains potential at each side of the device because you have measured it? Or because you are viewing it as a simple switch, and have assumed that is the case?"
},
{
"post_id": "",
"author": "aluck",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "March 07, 2012, 07:20:31 pm",
"content": "Quote from: somlioy on March 07, 2012, 06:38:59 pmWhy don't you just disassemble one?"
},
{
"post_id": "",
"author": "somlioy",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 07, 2012, 07:28:11 pm",
"content": "Quote from: cybergibbons on March 07, 2012, 07:12:46 pmThe latter.Quote from: aluck on March 07, 2012, 07:20:31 pmYeah, I will. But since I'm an electrician tracing pcb routes arent my stronges side."
},
{
"post_id": "",
"author": "sacherjj",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 07, 2012, 07:37:25 pm",
"content": "These are just a PIR sensor:http://en.wikipedia.org/wiki/Passive_infrared_sensorThe information from that controls a power switching circuit, either solid state or relay."
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 07, 2012, 08:21:28 pm",
"content": "Generally they have a capacitor power supply, with a triac providing the drive. They get power when on by only switching the triac on after the instantaneous voltage is over around 20V, so they can have an internal regulated rail.The problem with them and energy saving lamps is the low power draw when off is often enough to charge up the internal capacitors in the lamps, and this causes the lamp to flash every few seconds ( a single short dim flash normally) as the internal lamp circuit starts up and discharges the capacitor. This kills the CFL unit quite fast from the repeated failed starts."
},
{
"post_id": "",
"author": "T4P",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 07, 2012, 09:28:07 pm",
"content": "Quote from: SeanB on March 07, 2012, 08:21:28 pmBeyond normal operation ( like if they are pulsed , as you might have seen with capacitive dividers ) they get pure DC and what does that do ! Well , THE CAPS ARE KILLED !If you pulse a capacitive divider they are gonna blow up !CFL's die from repeated starts yes , but the capacitor blows up first ."
},
{
"post_id": "",
"author": "qno",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 10, 2012, 08:47:14 pm",
"content": "I think these devices use a thyristor.They work the same way as a dimmer.Only the potmeter has been replaced wit a LDR.If you look to the voltage over these devices with a isolated scope or a scope with a differential input (do not use a standard scope) you can see that the first 5 or 10 volts of the mains sinus is used to trigger the the thyristor."
}
] |
2025-10-17T20:35:22.645937
| 15
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-sec-on-1-sec-off/
|
1 sec ON - 1 sec OFF - Page 1
|
[
{
"post_id": "",
"author": "pub2024",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 26, 2024, 06:25:30 pm",
"content": "Please give me some advice how I could create the following circuit to transform 1Vrms sine into 1 sec pulses. ON - 1 sec. OFF and still like that?I also posted below an image with a sketch of what I want to do."
},
{
"post_id": "",
"author": "oPossum",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 26, 2024, 06:51:45 pm",
"content": "74HC14 (sine to square) -> 74HC390 (divide by 100)"
},
{
"post_id": "",
"author": "sparkydog",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "January 26, 2024, 06:52:58 pm",
"content": "...use a voltage comparator? This is a fairly basic problem;a web searchoffers many possible solutions...Be sure, however, that you're aware of the issues with feeding negative input voltage to an op amp and how to correctly address them."
},
{
"post_id": "",
"author": "Mechatrommer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 26, 2024, 07:10:23 pm",
"content": "Quote from: sparkydog on January 26, 2024, 06:52:58 pmmy first thought too (without carefully reading)... but comparator cannot divide... if what OP wants is 100Hz sine -> 1Hz square, then opposum is right.."
},
{
"post_id": "",
"author": "pub2024",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 26, 2024, 07:21:09 pm",
"content": "Quote from: oPossum on January 26, 2024, 06:51:45 pmThank you for the advice. Can you show me an application with these circuits!"
},
{
"post_id": "",
"author": "oPossum",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 26, 2024, 07:32:00 pm",
"content": "Schematic attached"
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 26, 2024, 08:08:28 pm",
"content": "First the O.P. needs to specify the range of input conditions that shall result in the 1s on / 1s off output. e.g. Should 1V RMS 60Hz give the same output? What about 0.1V more or less?Second the O.P. needs to specify the output when the input conditions are not met.Third, the O.P. needs to specify tolerances for the output signal. An upper limit of 5V has already been specified, but it still needs a lower limit voltage and tolerances for period and duty cycle (or on and off time), and max. output current or specs on the load it must drive.Fourth, the O.P. needs to state what power sources are available, or is it a requirement to power it entirely from the input signal?Edit: added need for output current specs"
},
{
"post_id": "",
"author": "pub2024",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 26, 2024, 08:28:53 pm",
"content": "The rectangular impulses on the output must also appear when on the input we have at least: 0.1Vrms. To do this, I will add a buffer with an operational amplifier that will bring at least 1Vrms to the 74HC14 input - is that enough ?"
},
{
"post_id": "",
"author": "pcprogrammer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 26, 2024, 08:51:38 pm",
"content": "First take a look at the74HC14 datasheetand check the threshold voltages for what it needs. There is a dependence on supply voltage and temperature.Now design for a worst case scenario of the to expect input voltage range and add an amplifier on the input to supply the correct range for the 74HC14 to make it work.Also make sure that a to high input voltage does not destroy your circuit, so add some protection if needed. Also the 74HC14 does not like negative voltages on its input, so the resistors in the schematic given by oPossum need to be sized correctly to make sure the max ratings are not surpassed, or add a schottky diode to ground for protection."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 26, 2024, 08:54:42 pm",
"content": "Quote from: pub2024 on January 26, 2024, 08:28:53 pmThat makes it considerably harder - 0.1V is low enough that you may have to worry about noise pickup being mistaken for the required signal.Read my list of questions above and answer them and you'll be offered better solutions. The more answers we get, the better the results. Note that you should *NOT* specify tolerances any tighter than required, or it may make the solution far more expensive or even impossible, missing out on a simple circuit that cant meet the closer tolerances."
},
{
"post_id": "",
"author": "JustMeHere",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 29, 2024, 01:15:28 am",
"content": "I wonder how many college professors monitor this forum."
}
] |
2025-10-17T16:41:28.430658
| 11
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-to1-voltage-regulator-with-external-power-ind/
|
1 to1 voltage regulator with external power ind - Page 1
|
[
{
"post_id": "",
"author": "bwinddk",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "January 12, 2020, 07:46:54 am",
"content": "Hello good people :-) i hope this is a simple question, have a 3dprinter but because of chines cheap engineering the mosfet of the fan control is stuck at 6v i am getting a new motherboard, but want to remove the strain of the mosfet with a external board, but cant fore the love of my life find out what it is called. the range is 0-12v under 1A need a board that regulate one to one ( 5v in 5v out, 12v in 12v out) but with a external power in... does something like this exist??Just need the name of something like this, ore a link so i can find something to search for :-) want to do the work but hard when you don´t know what to search for :-/ :-)Hope you guys can help med :-DThanks in advancekind regards Brian"
},
{
"post_id": "",
"author": "ZaphodBeeblebrox",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 12, 2020, 02:06:34 pm",
"content": "So, you have a regulator that regulates the voltage of a fan in the range of 0-12V, with a maximum current draw of 1A at 12V? You noticed a MOSFET of said regulator is deffective because it \"is stuck at 6V\". What do you mean by the latter? When a MOSFET goes to the eternal silicium fields, it shorts out most of the time...Could you either:[li}Provide the schematic of the regulator, so we know what is going on? Maybe it's easier to just take the input of the regulator an feed it to a more powerfull regulator, but to know that, schamatics are required.Confirm that you in fact need an analog/digital (which of the two?) power amplifier that takes an input signal of 0-12V and outputs the same voltage but with more current capacity?"
},
{
"post_id": "",
"author": "bwinddk",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "January 20, 2020, 07:20:52 am",
"content": "Hi thx for the replyi got a Anycubic i3 mega S 3dprinter and people warn that the main board i a bit small for the loads, so modding it with external relays to not burn out the main board for the hot end and heated build plate, but min is stuck a 6.1V on a fan output and it cant adjust anymore and it is not software, the fan runs as soon as i give the printer power, but there is a small start up on the main board so normal no fans runs before this is done. Anycube is sending a new main board, i can´t do anything to the main board i don´t got schematics on it just need to find a external solution. i got the error on a other forum other has this problem but nobody got a solution except a new mainboard. i am thinking i can make one out of a arduino but i am thinking something like this must exist??? i am still just a noob :-/Kind regards Brian"
}
] |
2025-10-17T17:57:21.292305
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-uart-in-gt-16-uart_out/
|
1 Uart In -> 16 Uart_Out - Page 1
|
[
{
"post_id": "",
"author": "ElectricGuy",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "April 20, 2015, 02:55:02 am",
"content": "Hi;I did the attached circuit. It is supose to acept one TX Uart from a micro and provide 16 outputs so i can connect 16 devices.They all are close, 30cm away maximum, and it has to me Uart, so I2C, SPI or 485, its out of question.What do you think about the circuit, it will work?Thank you."
},
{
"post_id": "",
"author": "matseng",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "April 20, 2015, 03:10:11 am",
"content": "If all your devices doesn't load the signal too much (like if it goes more or less directly into a microcontroller made after the 70'ies) then I'd guess you really don't need any circuitry at all. A fanout of 16 on a slow signal like an uart sounds more than reasonable to me.But if you really want to have something between the uart and the receivers then your schematics seems just fine."
},
{
"post_id": "",
"author": "ElectricGuy",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "April 20, 2015, 08:15:02 am",
"content": "Quote from: matseng on April 20, 2015, 03:10:11 amThank you for your answer.Actually it's based on recent PIC micro."
},
{
"post_id": "",
"author": "daqq",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 20, 2015, 08:33:42 am",
"content": "QuoteThe extra buffer might provide some protection for the USART - if one device fails in a shorting way, then this is better - one dies, the rest still live. But yeah, if you don't mind that and are not running at some obscene frequencies, then a direct connection should be OK.By the way, you have 16 bit wide ICs like this (of most 74xx bus like logic), seehttp://www.nxp.com/documents/data_sheet/74LVC_LVCH16245A.pdf"
},
{
"post_id": "",
"author": "ElectricGuy",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "April 20, 2015, 08:35:26 am",
"content": "Quote from: daqq on April 20, 2015, 08:33:42 amThank You for your advice!"
}
] |
2025-10-17T19:42:30.647697
| 5
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-wire-adc-chip/
|
1-Wire ADC chip - Page 1
|
[
{
"post_id": "",
"author": "RobBarter",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 06, 2018, 05:07:12 pm",
"content": "HiI'll put this in the beginner section as I am oneI need to measure a couple of voltages (1-5V) 100ft up a mast (approx. 50m cable length). There is already a temp sensor (DS18B20) up there, or will be once I've assembled it, so was looking to add two ADC channels on a 1-Wire bus back down to the ground to measure FWD and REV power. However, the only device I can find is a MAXIM DS2450 but that is discontinued although available from China and several weeks delivery.In my searches the MAXIM DS2438 came up but it isn't very good at measuring below 1.5V. It was designed for Li batteries.Also found a BAE0910 but at £10 each (I need min 2) puts it above the cost of an Arduino.The Arduino would be fine but it will be sitting approx. 10cm from a 300W 1296MHz RF amp and I'm a little concerned at it being effected by the RF or, more importantly, it effecting the pre-amp next to it. It will also more wires down and probably require something like an RS485 line driver at each end. However, it does mean I can add other stuff later.Any thoughts as route to go or any 1-Wire adc's I'm missing?CheersRob"
},
{
"post_id": "",
"author": "tpowell1830",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 06, 2018, 05:41:47 pm",
"content": "Sorry, I am not familiar with those chips. I don't know anything about your project but LoRaWan is very useful for remote sensor measurements.Check out Marco Reps' video:There are many other videos about LoRaWan as well, just do a YT search.Hope this helps..."
},
{
"post_id": "",
"author": "RobBarter",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 06, 2018, 05:47:13 pm",
"content": "Thanks tpowell,I actually have a LoRaWan gateway setup at home. A Raspberry Pi with IMST iC880A. However, would not like to put a 868MHz transmitter right next to a very sensitive preamp for 1296Mhz. It's a Ham Radio competition system.Thanks for the suggestion though.Rob."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 06, 2018, 05:54:52 pm",
"content": "Although any small MCU could be programmed to operate as a 1-Wire compatible slave, or you could try to source N.O.S. DS2450 ADCs, IMHO you'd be crazy to do so. With a high power UHF TX amp in close proximity, that's just asking for trouble. Even the DS18B20 is likely to misbehave unless it and the bus feeding it are fully screened.You'd be better off biting the bullet and designing a RS-485 based solution with a MCU in a fully screened box with feedthrough caps for power, data and any sensor wires and using resistive analog temperature sensors that wont misbehave with a stray RF field. At 1285MHz, a quarterwave is only 5.8cm so if the screening box has a removable lid, it will need conductive fingers at less than 6mm spacing, or a copper braid or high conductivity elastomer crush gasket to get sufficient screening integrity - alternatives would be soldering the lid on or covering the seam with copper foil tape with conductive adhesive."
},
{
"post_id": "",
"author": "RobBarter",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 06, 2018, 07:06:54 pm",
"content": "The DS18B20 comes already fitted to the copper spreader of the commercial 300W amp. I'll tell you later how that goes"
},
{
"post_id": "",
"author": "Inverted18650",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 07, 2018, 12:05:15 am",
"content": "off topic. Is the creator \"Marco Reps\" here on the blog? I've been binge watching his videos today and would I'd like to send him some toys to play with. Love his video style and share the Keithley passion."
},
{
"post_id": "",
"author": "Kalvin",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 07, 2018, 06:46:20 am",
"content": "Not sure whether this is useful for this particular application, but you can also use Arduino as a 1-wire slave. Just google with following terms: arduino 1-wire slave"
},
{
"post_id": "",
"author": "Cliff Matthews",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "March 07, 2018, 12:33:29 pm",
"content": "Quote from: Inverted18650 on March 07, 2018, 12:05:15 amYes he's here as user \"baltersice\" but his channel now seems to be deleted from our YouTubers list (I'll notify Roger EZ24).https://www.eevblog.com/forum/other-blog-specific/a/msg1352598/#msg1352598"
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 07, 2018, 06:19:52 pm",
"content": "Since you are already sharing a ground with the 300 watt transmitter to measure the forward and reflection signals, I would use the same power or use a single point ground at the top of the mast to power a microcontroller like an Arduino to make the 1-wire measurement and any other measurements. For communications, I would use 3 wire asynchronous serial with a pair of optocouplers at the bottom of the mast or wherever the RF and power lines terminate.You will just have to deal with any interference from the RF transmitter. This would exist whether you used a 1-wire ADC or not and attaching the ADC to the transmitter defeats having separate grounds anyway leading to more problems."
},
{
"post_id": "",
"author": "RobBarter",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 07, 2018, 07:10:33 pm",
"content": "Thanks DavidLooking more towards an Arduino at the top of the mast (I can put it in a tin to help) and keeping the earths separate from the bottom of the mast. Good point on the opto couplers."
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 07, 2018, 07:24:49 pm",
"content": "Quote from: RobBarter on March 07, 2018, 07:10:33 pmIf I was not clear, that is what I am suggesting; put the Arduino at the top of the mast.I would not rely on a non-isolated differential communications link going that far when a variable 300 watt load is at the end which shares a ground with the low level forward and reverse signals. Maybe the power amplifier includes isolation for those signals but you did not say and even if it did, I would still use galvanic isolation on the communications link. Optocouplers at the bottom of the mast are just the easiest moderately effective way to do that.Note that both optocouplers go at the bottom of the mast or where the power and RF terminate because if they were at the top, coupling between the signal cable and RF/power cable would reduce their effectiveness."
},
{
"post_id": "",
"author": "RobBarter",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 08, 2018, 08:40:07 am",
"content": "Definitely clear. My comment \"Looking more towards an Arduino at the top of the mast\" was because of your comments and my own thoughts. Acknowledging Ian's comment, I may put it in a tin enclosure.I'll keep the thread updated as to how it goes. The transverter is already built for the bottom end (which can drive two separate antenna systems/PAs) although the wiring needs a little tidying."
}
] |
2025-10-17T18:36:35.456091
| 12
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-wire-and-ground-voltage-offset/
|
1-Wire and ground voltage offset - Page 1
|
[
{
"post_id": "",
"author": "Tantalum",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "August 28, 2021, 02:58:12 pm",
"content": "HelloI have a 3 wire cable over 5m (H05RN-F, 0.5mm^2, ~170mOhm per wire) with:- GND- 12V- 1-Wire bus (3.3V)On both sides of the cable there are micro-controllers with their 3.3V voltage regulators.Now I need to know if the 1-wire bus will still work if a 2A current or more, flows through the cable?There will be a ground voltage offset of at least 0.3V (probably more because of the connectors resistance).Thank you"
},
{
"post_id": "",
"author": "Manul",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 28, 2021, 06:18:47 pm",
"content": "If we talk CMOS levels, then rule of thumb is 0.3 x VDD and 0.7 x VDD for low and high level threshold respectively. But you need to add some margin to that if you want something robust. So I would say voltage drop of 0.5V should be absolute maximum. You might choose a thicker wire.Also, suggested maximum drop of 0.5V is because you don't want ESD diodes to start conducting. Levels will shift, so one side will see high levels above 3.3V and another side low levels below 0V (negative). 0.5V above VDD or 0.5V below ground is usually the limit after which ESD diodes might turn on.That is not full story though, because piece of wire also has inductance and voltage drop might be a lot higher for short periods of time if current is changing. So you need some electrolytic capacitors at both ends for 12V. Avoid ceramic because they have low ESR and might cause ringing and voltage overshoots.There is still possibility of some voltage transients, so consider adding protection for IO pins used for 1-Wire if you want real robust solution. Series resistors together with clamping schottky diodes, zenner diodes or TVS diodes are some options.And this is why you generally should avoid using same ground return path for both signals and high currents."
},
{
"post_id": "",
"author": "Tantalum",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "September 14, 2021, 08:45:50 am",
"content": "Ok thanksYet another question.How about the radiated EMI from several 1-Wire buses using a NYY-J 2,5mm² over 5-20m cables (= not shielded, no twisted wires, and wires SIG/GND spaced by 3-4mm causing a little ground loop)?Could it be harmful or exceed any regulation?"
},
{
"post_id": "",
"author": "perieanuo",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 14, 2021, 10:22:09 am",
"content": "just don't do ground loop, make a star configuration and start powering from the star centeras for emi, after telling us you have 2amps and no spec about those 2 amps and some real bus architecture, you can't be serious about putting this question"
},
{
"post_id": "",
"author": "Manul",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 14, 2021, 06:48:24 pm",
"content": "Quote from: Tantalum on September 14, 2021, 08:45:50 amAnd you are planning to use 1-Wire at 3.3V logic levels? Not so sure about it. It is not only about radiated EMI (which is hard to predict, depends on rise/fall times and many other factors), but also about absorbed EMI. How sensitive is your bus to external interference. I don't know about bit rate of your bus, but in some industrial environment it will likely fail. However, you are free to try it.For long distances or harsh evironments I would go for differential signaling and a twisted pair (see RS485). Again, you might know better what you need."
}
] |
2025-10-17T17:22:39.065562
| 5
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-wire-bus-esd-surge-protection/
|
1-Wire bus - ESD & surge protection - Page 1
|
[
{
"post_id": "",
"author": "Tantalum",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "May 31, 2022, 06:15:27 pm",
"content": "HiI want to use a 1-Wire bus for an outdoor application over a cable with 20m length.Now I want to protect the bus from ESD surges.I saw that Bourns utilizes a TBU for current limiting and an TVS diode for voltage limiting for a rs485 bus, but also a GDT on the front.I'm ok to use a TBU-CA085-050-WH (850V and triggers at 50mA) and an STS321050B100 5V 350W 30kV 1.5pF TVS diode.The problem is that I don't have space to put the GDT 90V on the board.Do you think it's necessary or is the TBU+TVS enough?Thank you"
},
{
"post_id": "",
"author": "jwet",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 15, 2022, 02:37:55 am",
"content": "Maxim/Dallas has a good app note on running one wire in bad environments. Worth a read. A TVS give you a lot. Add a little R if you can, even 10 ohms can help. The peak currents in ESD spikes are BIG.Maxim PDF Format TUTORIALS 148: Guidelines for Reliable Long Line 1-Wire Networks"
},
{
"post_id": "",
"author": "MarkL",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "July 15, 2022, 02:20:56 pm",
"content": "You might also want to consider the DS9503. It's specifically designed for 1-wire ESD protection, and has integral resistors:https://www.maximintegrated.com/en/products/interface/signal-line-protection-ics/esd-protection-diodes/DS9503.htmlMouser has them in stock, US$1.46 (qty 1)."
}
] |
2025-10-17T17:08:02.509619
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/1-wire-bus-ground-reference-common-mode-filter/
|
1-Wire bus, ground reference & common mode filter - Page 1
|
[
{
"post_id": "",
"author": "Tantalum",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 10, 2022, 08:43:26 am",
"content": "HelloI need to power a PCB over a cable of several meters. I will use 24VDC but also a 1-Wire bus to communicate with a microcontroller.I need to use a common mode and differential mode filter on the input of the board.But now I have those 2 questions:1. What about the ground reference and the 1-Wire bus? Is the common mode filter on the 24V/GND line a problem? Will I need to decouple the 1-Wire signal also with an isolator?2. How do I trace the 1-Wire bus on the PCB since there is a ground plane \"discontinuity\" because of the common mode choke?Thanks"
}
] |
2025-10-17T17:09:38.153956
| 1
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/10-000-eur-for-small-scalle-cell-phone-production-line/
|
10.000 EUR for small scalle cell phone production line? - Page 1
|
[
{
"post_id": "",
"author": "dds737",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "May 20, 2015, 06:03:31 pm",
"content": "While reading this blog:http://blog.p2pfoundation.net/business-models-for-open-hardware/2011/03/19I've read this: \"Significantly, the Shanzai companies are almost universally bootstrapped on minimal capital with almost no additional financing: Mitchell Tseng reported that 10.000 € are enough to start such a company, and it may eventually scale to over 50 million € revenue per year within a couple years.\"Could this be a possibility elsewhere, or only in China?What kind machines are needed to let's say, small scale cell phone production? (Off course with Mediatek Chipset)"
},
{
"post_id": "",
"author": "Ice-Tea",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 21, 2015, 05:19:59 am",
"content": "To actually produce smartphones all on your own you'll need several 100k$. SMD production line, plastic moulding,...So with a budget of 10k$ you'll be looking at outsourcing most or all of it. Of course, the 10k$ iscapital. That doesn't mean you can't buy stuff (such as a production line) on credit."
},
{
"post_id": "",
"author": "Ice-Tea",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 21, 2015, 06:49:24 am",
"content": "Would love to see a link for the MTK stuff, but I guess it's something likehttp://neoden.eu/en/smt-production-line-bundle?That's nice and dandy for a few prototypes and low volume stuff but for actual volume? And in addition to that, most of these cheapo placers crap out at 0402 which would kinda suck for mobile phones. And I would imagine that the rest of the packages would be out of their league as well..."
},
{
"post_id": "",
"author": "Ice-Tea",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 21, 2015, 07:09:31 am",
"content": "Oh, with \"MTK sells entire solutions you mean they sell chips and offer schematics, BOM, SW a complete DK for 10k$? I figured you wanted to start a SMD production line on a 10k$ budget"
}
] |
2025-10-17T19:40:17.756630
| 4
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/10-7mhz-amplifier/
|
10.7MHz amplifier - Page 1
|
[
{
"post_id": "",
"author": "Brian2003",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "December 07, 2023, 04:59:05 pm",
"content": "hi,I'm trying to build 40dB 10.7MHz amplifier with opamp. I found a couple of LMH6628 and I thing with 3 stage I can reach 40dB anyone tried something similar.That is not to easy I need to use single 5V supply. Any comment on the circuit below?"
},
{
"post_id": "",
"author": "TimFox",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 07, 2023, 05:11:36 pm",
"content": "In simulating that circuit, you should add a resistor after the voltage source to represent its output impedance, make sure your op amp model includes its capacitances, and possibly add some \"stray\" capacitance to represent the circuit board capacitances.Check for oscillation/stability: you may need to add a very small capacitor across the feedback resistor.In construction, you need to be paranoid about coupling backwards across three amplifier stages at high forward gain: probably should include series resistance or inductance in the power-supply decoupling at each stage."
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 07, 2023, 05:55:57 pm",
"content": "You can definitely do that, but keep in mind that high gain will require good isolation between the input and output to prevent oscillation. 40dB total gain is possible but will require some care in layout."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 08, 2023, 04:35:48 pm",
"content": "The 10.7MHz amplifiers are usually not made of opamps (assuming you want to build an IF amplifier). There are IF RF chips for that, or discrete transistor amps, with some impedance matching and selectivity as well.."
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 08, 2023, 05:52:28 pm",
"content": "Linear Technology published a couple of examples of current feedback operational amplifiers in IF applications.Besides cost, I think the major disadvantage is inherently higher noise, but in most IF applications noise is not a limitation."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 08, 2023, 06:01:18 pm",
"content": "40db gain at 10.7MHz with 3 opamps - a good exercise to try, but nobody would do that in real life, imho.."
},
{
"post_id": "",
"author": "Brian2003",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "December 08, 2023, 08:17:57 pm",
"content": "I know the device which works in real life with 3x TSH110 opamp exactly with 40dB gain and after that AGC.I will try with OPamp too to see in the realIf any can suggest any useful IC for IF ampliers I will be very grateful as I found yet many of them is obsolete MC1350, CA3028."
},
{
"post_id": "",
"author": "MarkT",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "December 08, 2023, 10:00:50 pm",
"content": "These days I guess you'll have to find a generic low power broadband RF amp and add IF filters on input and perhaps output. Or go to the SDR approach (which its lower selectivity). Analog RF modulation is dying out fast."
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 08, 2023, 11:49:58 pm",
"content": "Quote from: iMo on December 08, 2023, 06:01:18 pmWhere they would do it is a video or baseband application where instead of 10.7 MHz it is DC to 10.7 MHz."
},
{
"post_id": "",
"author": "vk6zgo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 09, 2023, 12:15:01 am",
"content": "Quote from: David Hess on December 08, 2023, 11:49:58 pmYes, the OPs schematic looks a lot like a video amplifier.Over time, we have had quite a few Beginners complaining that their clever Op Amp tuned RF amplifier simulated perfectly, but oscillated in real life, thus learning an interesting lesson about Op Amps, & the similarity of the effect to that which made the old school \"Tuned Plate, Tuned Grid\" oscillator work.I tend to wonder what the application is, as 10.7MHz is usually used for IF stages which are required to be selective.If this thing is fed from conventional LC tuned circuits & outputs to similar circuitry, it will almost certainly oscillate."
}
] |
2025-10-17T16:44:07.316822
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/10-amps-power-supply-with-lm723/
|
10 Amps power supply with LM723 - Page 1
|
[
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "November 03, 2018, 10:10:13 pm",
"content": "Hello,I am planning to build a new power supply using LM723 and NPN power transistors. I saw that there are a lot of schematics on the internet, but I am wondering which of them is a good one ?So my questions are:1. Can you recommend a good 10 Amps power supply with LM723 ?2. Is there the possibility to appear oscillation in this power supply that you recommended ? How can I prevent the oscillations ?3. What are the layout guidelines for such a power supply ?4. What other problems can appear in the circuit ?"
},
{
"post_id": "",
"author": "Wolfgang",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 04, 2018, 12:40:02 am",
"content": "The ARRL (American Radio Relay League) has some 30V/10A supply suggestions.Important things are:- adequate cooling (fan)- bridge rectifier with sufficient current loading capability (20A min)- 4 x 2N3055- frequency compensation (see ARRL schematics)- overtemp protection- output crowbar to protect your load if something goes wrong.http://www.dd1us.de/Downloads/an%20rf%20proof%2030%20amps%20power%20supply%201_0.pdf"
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "November 05, 2018, 03:16:22 pm",
"content": "Thanks for the document. It is very interesting.I built the power supply from the link:http://www.electronics-lab.com/project/3-30-v2-5-a-stabilized-power-supply/The single difference was that I used 0.33 R in parallel with 0.18 R for R5.I tested the power supply using a 24V ac / 100VA transformer.The output voltage was 19.97Vdc without load and with load it was 19.94Vdc. The load was a resistive load of 2.90A.It is normal the difference of 0.03V between the output voltage with and without load ?The output voltage was measured on the divider formed by R4 and R3."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 05, 2018, 03:36:03 pm",
"content": "I would add a small resistor, like 100ohm, into TR1's base.30mV change with 2.90A load? -> the723 NS datasheetsays the load regulation with an external NPN pass transistor is 15mV per 1A change. With thin wires and larger currents it could be even more..PS:Quotewith your 0.18ohm || 0.33ohm the over-current protection trips at something like 5.5Amperes.."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "November 05, 2018, 07:22:14 pm",
"content": "Can you be more explicit ?I saw in the datasheet that load regulation is maximum 0.6% of Vout, so in my case it is about 0.11V (0.6% * 19.97V). Is that correct ?"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 05, 2018, 07:36:05 pm",
"content": "Read above datasheet. Figure n4."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "November 05, 2018, 07:58:47 pm",
"content": "I don't know which one is fig n4. The figures does not have a number.Are you talking about the attached one ?Thank you."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 05, 2018, 11:52:01 pm",
"content": "Figure 4 means Figure 4"
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "November 14, 2018, 09:34:50 am",
"content": "I have a question regarding the LM723 power supply. I built this power supply on a PCB that was made in China.I verified the output voltage drop with different load currents at different output voltages. BUT, before making this verification, somebody tried to take out the PCB from the power supply case. The PCB was glued inside the power supply case using hot glue. He tried and managed to take out the PCB using a screw driver that he put underneath the power supply PCB and then he lifted up the PCB. I checked the PCB visually, with the naked eye and I did not found any problems.My questions are:1. It is possible for this circuit to work correctly if it was damaged by the screwdriver action ?2. It is possible that if I will build another power supply (using exactly same schematic and a exact copy of the PCB) the circuit to work bad ?3. It is possible for this circuit to work good because if it was damaged and to work bad if it was not damaged ?"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 14, 2018, 09:46:42 am",
"content": "Specify your voltage drops at different loads."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "November 14, 2018, 09:52:23 am",
"content": "V without load = 19.84V, V with load = 19.80V, load = 2.90AV without load = 25.0V, V with load = 25.0V, load = 2.20A.for the tests, I used a 0.33R resistor in parallel with the 0.18R.So the circuit PCB was forced out of the power supply case, using the screwdriver, but on the PCB I did not found any problems while I was inspecting the PCB using the naked eye."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 14, 2018, 02:09:41 pm",
"content": "What is your problem then? It seems it works fine."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "March 18, 2019, 06:23:18 am",
"content": "Hello, quick question about the attached schematic: somebody said to me that the current limit (current sense) is temperature dependent. Can you explain why is this happening ?"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 18, 2019, 07:56:28 am",
"content": "In 723 the current sense is done via an NPN transistor on the chip (like your Fast CC). With temperature the trigger shifts -2mV/degC. Calculate what current do 2mVolts represent on the shunt resistor and you get the dependency in mA/degC."
},
{
"post_id": "",
"author": "lycralout",
"author_rank": "Newbie",
"is_op": false,
"timestamp": "March 18, 2019, 08:12:27 pm",
"content": "A nice summary of design rules to note when using the 723 is contained inhttps://electronicprojectsforfun.wordpress.com/power-supplies/a-collection-of-proper-design-practices-using-the-lm723-ic-regulator/"
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 10, 2019, 02:11:35 pm",
"content": "Hello. I build the power supply from the attached schematic, but I found that there is a problem regarding the current limit control.If I short between the pins 2 and 3, the output voltage varies from 1V to about 30V. But if I connect pins 2 and 3 to the circuit, the voltage varies up to about 12V. I also tried to use an external NPN small power transistor (BC548) and I found the same problem is happening again. I used only POT1, POT2 and POT3 from the original schematic. I did not used any Ammeter, I just connected a wire. The BE voltage of the small power NPN transistor is always about 0.55-0.6V.I am uploading the original schematic: original_schematic.pngAnd I am uploading the schematic when I used the external small power NPN transistor: schematic_img.png.More details about the problem:1. Input voltage 33Vdc, from 24V/160VA transformer.2. Voltage on pin 12: about 33Vdc.3. Voltage on pin 11: about 32.5Vdc.I tried the following solutions:1. I changed the potentiometers with some new ones, but the problem is the same with the new pots.2. I checked the PCB for bridges and it is OK.What should I do to make this circuit work correctly ?"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 10, 2019, 03:28:26 pm",
"content": "In the original schematics if you short 2 and 3 the current limit is off.If 2 and 3 is wired into the circuit and it triggers at 12V it means at 12V output the current through the shunt 0.15ohm is high enough to create 0.6V voltage drop on the shunt and open the the current limit transistor.Probably a problem with your wiring or shunt value.You do not use 723's pins 2 and 3 in your schematics (eagle). The external transistor T4 is doing the limiting. So let 2 and 3 shorted (and connect to COMP maybe).Double check the voltage drop at the 0.15ohm shunt while varying the output voltage.Doublecheck the value of the 0.15ohm shunt!"
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 10, 2019, 04:20:43 pm",
"content": "I changed the 0.15R resistor with a new one and I checked the voltage on the 0.15R resistor and it is about 2.8 miliV, when the output voltage is 12V.The BE voltage of the transistor is still 0.55-0.6V.I connected the pin 2 and pin 3 together but the situation is the same, the output voltage is still about 12V, and sometimes it is varying around 12V.Edit: When I powered again the power supply, the voltage was about 17V and not 12V as it was when I powered it initially.When I set the output voltage at about 2.1V, the voltage on the 0.15R resistor is 2.1mV.I also changed LM723 with a new one, but without succes."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 10, 2019, 04:41:03 pm",
"content": "Quote from: mike_mike on April 10, 2019, 04:20:43 pmHow you can have BE=0.6V when the voltage at the shunt is 2.8mV??It has to be the same when CL(base) and CS(emitter) are wired to the shunt.."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 10, 2019, 05:05:34 pm",
"content": "I found that the 0.5-0.6V voltage drop at BE junction is because there is 0.5-0.6V voltage drop on the 120R resistor ...I changed the 120R resistor with a new one, but it did not changed the situation.Somewhere on the PCB is a component that makes the BE jonction to be at 0.6V... i think."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 10, 2019, 05:20:51 pm",
"content": "When the pot's wiper is at the lower side the BE voltage cannot be higher than 0.16V.The Vref is say 7.2V and the divider is 120/(4k7+500+120)*7.2=0.16V."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 10, 2019, 05:40:24 pm",
"content": "Yes. When the pot is at lower side and the output voltage is at minimum, then the BE voltage is 0.165V.But if I rotate the Voltage pot, then the BE voltage increases slowly from 0.165V to 0.595V, even if the current pot is at the lower side."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 10, 2019, 05:55:36 pm",
"content": "There is a wiring problem then.When increasing the output voltage, AND the current through the shunt is low (say 10mA), the BE voltage should not change much.With set constant 0.165V at the current limit pot you would need 3Amps through the 0.15ohm shunt to get 0.6V at the base-emitter."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 11, 2019, 03:28:54 pm",
"content": "I built another schematic, and I hoped that it will work. But it doesn't and I do not know why.When I power up the circuit, the 500R trimmer gets hot and the output voltage is always about 32.5-33Vdc. I changed the LM723 with a new one, I changed the 10K pot with a new one, I changed the power transistor (for the tests I used only one power transistor) with a new one. I also checked the layout and the PCB and there are no problems.This schematic is 100% functional, it was build by someone from my country and it works.What should I do ?"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 11, 2019, 03:40:03 pm",
"content": "I've done a simulation of your original schematics above and it works.FYI:CL POT Current LIMIT (14.6V Vout)5ohm 3.17A250ohm 1.00A300ohm 0.55A330ohm 0.29A350ohm 0.12A"
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 11, 2019, 03:52:17 pm",
"content": "I know that it works.But my circuit does not, and I am not capable of finding were is the problem...Probably I could find someone in my city for help."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 11, 2019, 03:54:44 pm",
"content": "Be careful with grounds.There are 2 \"grounds\" - in my simulation the left hand side of the R_Shunt is COM and the right hand side is GND. I often connect the input filter capacitor to GND (wrong).Doublecheck how did you wire the stuff.When the simulation works it should in HW too..Enclosed the simulation source - try it and compare it carefully with your kludge"
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 11, 2019, 04:57:54 pm",
"content": "Thank you for your help. I will try to find the problem.Meanwhile, a quick question: does the attached schematic have current limit down to 0A ?"
},
{
"post_id": "",
"author": "Wolfgang",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 11, 2019, 10:39:56 pm",
"content": "... in fact yes, but with low precision. The 723 is not very well suited to lab grade current limiting.An obvious problem here is the Vbe tempco of the pass transistors when running under high power."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 12, 2019, 11:20:07 am",
"content": "I finally managed to make the schematic from post #23 to work, but I found that the current limiting pot does not regulate linear the output current (I don't know how to explain exactly), so if I set the pot at half of its way, then the output current is about 0.5A, while the maximum current is 3A. The pot is a linear one, B500R.If the pot is at half, then the output current should be 1.5A ?Is that true ?"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 12, 2019, 11:57:56 am",
"content": "1. What was the problem, could you tell us?2. See my previous post with 500ohm pot's wiper value (measured from its low side) vs. current limit. In the mid position it shows 1A limit. It is a simulation only.."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 12, 2019, 12:12:45 pm",
"content": "The problem was the PNP transistor. There was a bridge between the C and E of this transistor, and I did not saw it when I made the inspection...Later Edit: If I use 2 220R resistor in series instead of the 500R pot, then the output current is about 1A. The connection between the 2 200R resistor is connected to the point were the pot wiper was connected before.I do not have any other 500R pot or trimmer to check if the first one was faulty, can there be used 1K pot instead of 500R pot ?I checked again with 1k pot for current limit, and at the half of the pot, the current is 0A. Only on the other half the current starts to rise from 0A to 3A."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 12, 2019, 04:21:53 pm",
"content": "In case of 1k pot you have to increase the 4k7 resistor.I would put, say, a 22k trimmer instead of the 4k7, set the 1k pot's wiper to the top position and set the minimal current limit with the 22k trimmer. Replace the 22k trimmer with a close valued resistor finally.For example a simulation with 10k the top resistor, 1k pot, 120ohm bottom, AND a 10k resistor from pot's wiper to gndPOT's wiper CLimittop 23mAmid 1.8Adown 3.8A"
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 12, 2019, 05:00:06 pm",
"content": "I checked using a 22k trimmer, the 1k pot, and I found that the proper value is around 12.7K for the trimmer.The current limit starts from 0A and goes up to 3.31A.I found that when I rotate the pot, it starts from 0A, then if I rotate it a very little then the current suddenly increase to more than 200mA, and there is a very little \"space\" on the pot for 1mA or 5mA. Is that normal ?Later Edit: only now I have saw your edit."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 12, 2019, 05:12:48 pm",
"content": "The pot setting is highly none-linear. It follows the Vbe characteristics.The 10k (or similar) from wiper to gnd could make it \"more linear\"..PS: or use 1k \"logarithmic\" potentiometer."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 12, 2019, 08:35:09 pm",
"content": "Quote from: imo on April 12, 2019, 04:21:53 pmI used the modification specified above and it works a little bit better, but at mid, the output current is about 1.20A, instead of 1.8A, and the maximum output current is 3.06A. The current starts to rise from only at about 1/4 of the pot course.For the tests I used only one TIP3055 and only one 4700uF capacitor.v Also, for the tests I did not used D1 and D2.Is the Rwiper connected correctly ?Please have a look at the schematic and at the results above and tell me what you think."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 13, 2019, 05:46:23 am",
"content": "I would play with those 3 caps see below.Also I would make the Voltage setting at the Vref side around the +IN (fixed divider at the output)."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 13, 2019, 05:55:14 am",
"content": "The role of those caps is to filter the voltage, for example the 10uF polarized capacitors is to filter the the voltage reference for voltage regulation and current regulation ?The results of the output current pot are good ?What are the advantages of using the pot at the Vred side ?"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 13, 2019, 06:00:07 am",
"content": "Yes.Yes.The output divider values contribute to the feedback control loop dynamic parameters.When changing them the feedback response is changing.Therefore it is better to have the Voltage regulation at the IN+ side.For example with fixed 9k/1k output divider (/10) the output voltage will be aprox. 10*V(IN+)."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 13, 2019, 07:31:50 am",
"content": "I tested the attached schematic, but the minimum output voltage is about 9V, and if I reduce the R3 to 0 ohms, the minimum output voltage is about 7V.I also tested with R12=8k2, R10=2k2, R1=0R and R3=680, and the minimum output voltage vas 3.5V and the maximum was about 29.5V. The voltage pot has a part where if the voltage is at maximum (29.5V) then the output voltage does not go down until the pot is at 1/4 of the course. I found those values on a schematic on the internet:http://www.electroniq.net/power-supply/lm723-variable-power-supply.html"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 13, 2019, 08:01:48 am",
"content": "You wired the C9 10u capacitor at wrong place.Look at my schematics above.Try with R1=12k, R2=10k pot, R3=0 and with the divider by 10 at the output.Wire C5=10u from the bottom of R1 against gnd of 723."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 13, 2019, 08:47:59 am",
"content": "I tested the attached schematic but it goes only from about 7V to about 30V.The voltage on pin 5 is 0V and on pin 4 is 0.74V, while on the output is about 7V."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 13, 2019, 09:48:16 am",
"content": "I also tested with 4k7 and 3k9 resistor for R12. The value for R1 was 1k2.The output voltages were:with 3k9: from 3.7V to 29.8V, but when the output voltage was 3.7V, and if I started to rotate the pot, the voltage started to rise only when the pot was at 1/4 of the course."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 13, 2019, 06:10:12 pm",
"content": "I tested with the following values, and the output voltage varied from 3.1V to 25.9V. The maximum that I need is 25V, so 25.9V is OK. The lowest output voltage is also OK.R1=1.2K, R2=10K pot, R3=680R, R12=6K8 and R10=2K2.There is a problem that still persists, the 10K pot has a \"dead\" portion on the low voltage. When the output voltage is abut 3.1V, the voltage starts to rise only when the pot is at about 1/4 of its course."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 14, 2019, 09:41:47 am",
"content": "I try to make a simulation of the attached schematic in LTSpice, but the program does not show the .raw file when I run the simulation.At the beginning I set to DC op pnt, but after I run the simulation, I set it to transient.Can you please tell me where I am wrong ?"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 14, 2019, 09:55:05 am",
"content": "GND is missing in your schematics."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 14, 2019, 10:07:05 am",
"content": "Thank you. Now the simulation works.Regarding the previous posts, are the results good ? Are there any problems ? I mentioned that the voltage pot has a \"dead\" portion, can it be solved ? It is not such a big problem, if the power supply works correctly..."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 14, 2019, 10:25:31 am",
"content": "It is many decades I messed with 723 PSUs. Afaik the minimum output voltage is 2V with 723."
},
{
"post_id": "",
"author": "Wolfgang",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 15, 2019, 12:01:53 am",
"content": "Correct. Below that the 723 inernal error amp does not work properly anymore. Below the emitters there is a current source, and its collector voltage is the error amp input voltage minus Vbe, so when you have 2V at the inputs, its about 1.4V Thats already not too much, so below that the current source is simply not working with a good and high output resistance."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "September 22, 2019, 11:41:55 am",
"content": "Hello,I have found the attached power supply schematic.Can you please help me with part numbers for replacement transistors TR3-TR6 (A823) and TR2 (3223) ?The replacement transistors are not really necessary to be pin to pin compatible, because I can redesign the pcb layout.I would also like to know the voltage for ZD3, the part number for D4 (1N4148 ?) and the secondary voltage of the transformer."
},
{
"post_id": "",
"author": "xavier60",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 22, 2019, 12:16:40 pm",
"content": "Quote from: mike_mike on September 22, 2019, 11:41:55 amBC556 will be Ok for TR3-TR6. Even BC557 would do if the unreg rail isn't much higher than 30V. T3 sees very little voltage.D45H11 for T2.Quoted from ON Semiconductor,\"These series of plastic, NPN and PNP power transistors can be used as general purpose power amplification and switching such as output or driver stages in applications such as switching regulators, converters and power amplifiers.\"https://www.onsemi.com/products/discretes-drivers/general-purpose-and-low-vcesat-transistors/d45h11"
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "September 22, 2019, 12:37:27 pm",
"content": "Quote from: xavier60 on September 22, 2019, 12:16:40 pmI need output voltage up to 50V (as it is written on the schematic). In this case, the unreg rail will be more than 30V. This means that I will need to use transistors with higher collector to emitter voltage...For example, 2N5401 is a good replacement for TR3-TR6 ?"
},
{
"post_id": "",
"author": "xavier60",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 22, 2019, 12:42:31 pm",
"content": "Quote from: mike_mike on September 22, 2019, 12:37:27 pmThat should be fine."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "September 22, 2019, 02:41:20 pm",
"content": "What replacements (equivalents) do you recommend for BF422 and BF423 from the attached schematic ?Can BF422 be substitute by 2N5551 and BF423 by 2N5401 ?They do not need to be pin to pin compatible, I can redesign the pcb layout."
},
{
"post_id": "",
"author": "xavier60",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 22, 2019, 09:13:28 pm",
"content": "Quote from: mike_mike on September 22, 2019, 02:41:20 pmThe current ratings of the 2N5551 and 2N5401 are unnecessarily high but should not cause a problem.That circuit has delayed over current shutdown but no fast limiting.Which can be fixed by putting C3 across BE of TR2.More: I'd be curious to know what the current gain measures when you receive the 2N5551 and 2N5401 transistors."
},
{
"post_id": "",
"author": "LaserTazerPhaser",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "September 23, 2019, 08:46:59 pm",
"content": "Quote from: Wolfgang on November 04, 2018, 12:40:02 amPower supply doesen't need stud diode heatsinks, D1 & D2 studs can be replaced with a few ganged high efficiency schottkies dpak or other smt parts.Aren't electrolytics inappropriate for mains side applications?"
},
{
"post_id": "",
"author": "ArthurDent",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 23, 2019, 09:17:56 pm",
"content": "LaserTazerPhaser - \"Aren't electrolytics inappropriate for mains side applications?\"The capacitors you marked are not polarized. The curved electrode generally indicates outside foil. There is no + or - that you would see on electrolytics. Check the values and you'll see they can't be electrolytics."
},
{
"post_id": "",
"author": "mike_mike",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "September 26, 2019, 06:26:42 pm",
"content": "Quote from: xavier60 on September 22, 2019, 09:13:28 pmhFE for 2N5401 is 180 and for 2N5551 is 163."
}
] |
2025-10-17T18:02:58.292225
| 58
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/10-current-bleed-resistor-on-voltage-divider-how/
|
10% current bleed resistor on voltage divider, how? - Page 1
|
[
{
"post_id": "",
"author": "FriedMule",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 27, 2021, 03:07:55 pm",
"content": "I thought I knew that a bleed resistor was a resistor made to dissipate power to avoid electric chock to the user, but now do I learn that a bleed resister can be the first resistor in a voltage divider.If I understand a voltage divider correctly, should the schematic be correct when looking at the voltage, I do just not understand how it is possible to get a 10% current bleed on R1?"
},
{
"post_id": "",
"author": "bdunham7",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 27, 2021, 03:35:40 pm",
"content": "Where did you get that circuit diagram??"
},
{
"post_id": "",
"author": "Terry Bites",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 27, 2021, 04:23:22 pm",
"content": "R1, R2 and R3 need to be recalculated. None of the values shown will work.Note that the first step is to convert the loads to their actual resistances.Use superposition:www.allaboutcircuits.com/textbook/direct-current/chpt-10/superposition-theorem/Calculate the currents that will meet the criteria of Kirchhoff's law(s)."
},
{
"post_id": "",
"author": "FriedMule",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 27, 2021, 06:09:53 pm",
"content": "The circuit comes from this 10-hour long video about basic electronic:https://youtu.be/nb4ovfwqup8?t=26078Terry Bites, thanks, I am truing to learn about that law, y values do come from another video that only told about how a voltage divider works. I.e. two resistors with the same value, gives ½ the voltage between the resistors, three similar resistors gives 1/3 of the value. That's why I thought that 48V / 4 = 12, so between 200 ohm and 100 ohm + 100 Ohm would give 24V and after 200 Ohm + 100 Ohm would be 12V."
},
{
"post_id": "",
"author": "fourfathom",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 27, 2021, 06:28:36 pm",
"content": "Quote from: FriedMule on November 27, 2021, 06:09:53 pmAnd it will, if you disconnect the loads. As said upstream, the loads become part of the divider so you need to allow for that."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 27, 2021, 09:48:00 pm",
"content": "Quote from: FriedMule on November 27, 2021, 06:09:53 pmThat video is an example of everything that's wrong with American education!The instructor either doesn't understand the practical application of potential dividers or is being forced to teach a syllabus that's fundamentally broken. Its nearly as bad as:https://en.wikipedia.org/wiki/Indiana_Pi_BillSkip to:https://youtu.be/nb4ovfwqup8?t=26824where the instructor starts introducing a bogus rule of thumb: \"The bleeder current needs to be 10% of the total load current.\" and he then goes on to say that's the current through the bottom divider resistor.Anyone who's ever done anything practical with dividers knows that the rule of thumb is the other way around. i.e the standing divider current needs to be ten times the load current (or more refined: ten times the difference between the minimum and maximum load currents), and that assumes you can tolerate a 10% voltage drop at full load!If you are going to do the math properly, you need to calculate the Thévenin equivalent resistance of the divider at each tap you are going to use and calculate the voltage drop due to your load current through the Thévenin equivalent resistance of that tap to see if its acceptable. If its not, scale the divider resistors down in proportion till it is.See:https://en.wikipedia.org/wiki/Th%C3%A9venin%27s_theorem"
},
{
"post_id": "",
"author": "FriedMule",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 28, 2021, 12:31:24 pm",
"content": "Thanks, this makes a lot of sense, does that mean I add like this (math not my strong side):(1/R3 + 1/Rx)^-1 = T3T3 + R2 = T2(1/T2 + 1/Ry)^-1 = T1T1 + R1How do I then calculate the optimal bleed, why the same word for two different functions?"
},
{
"post_id": "",
"author": "BeBuLamar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 28, 2021, 02:05:49 pm",
"content": "The guy in the video chose different values for the resistors which made the divider works but unrealistic because first the would throw away more energy in the divider resistors than in the load. Besides the resistors will be very hot.With your resistor values the divider would give you 12, 24 V if you don't have the load connected. Once you have the load connected the voltage will go down a lot."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 28, 2021, 02:18:47 pm",
"content": "That does look like how to calculate the equivalent resistance of the divider chain as seen by the source powering it. However that's of little use for calculating a divider that will 'work' for the instructor's problem.He's got two loads:12V 6W, allegedly a CB radio24V 200W, allegedly a radarLet *US* make a further assumption - that they can operate over a +25%, -12.5% voltage range from nominal 12V or 24V typical for automotive or marine equipment fed from a Lead Acid battery.Its obviously undesirable to overvoltage the loads and their current draw in the off or standby state may be negligible, so the unloaded divider mustn't exceed15Vat the lower tap and30Vat the upper tap.Lets further assume that the loads are modern ones with switching supplies so will draw more current at lower voltages. At their lower operating limit of10.5vand21Vrespectively they will thus draw 6W/10.5V =0.571Apeak*, and 200W/21V =9.52Apeak.Also, the fully loaded current 'from' the upper tap must include the lower tap load current, even though its drawn through R2 not directly from the tap, so we must use Iload1+Iload2 =10.1Ain further calculations involving the upper tap, not the Iload2 9.52A peak current.Lets get the upper tap done first:30V no load and 21V fully loaded is a 9V drop,9V/10.1A =0.891 ohmsThévenin resistance.That's R1||(R2+(R3||Rload1)).We've also got (R2+R3)/(R1+R2+R3)=30V/48V, and Rload1=10.5V2/6W.I'll let you do the math . . .Todo:solve the lower tap, for max. 15V when the upper and lower taps are unloaded and to supply 0.571A without dropping below 10.5V when the upper tap is fully loaded. Hint: calculate the voltage at the upper tap due to ONLY the radar full load current (no radio current) and use that when calculating the required lower tap Thévenin resistance.Conclusion:Its already obvious that the divider is going to be dissipating over one KW with both loads off, which is going to make a very effective wheelhouse heater, so the boat had better be fishing for Alaska king crab or similar where you *NEED* the heat!I've got another rule of thumb for you: If you are attempting to draw over 1mA from a potential divider tap your design probably *SUCKS*!* extremely unrealistic for a 12V CB radio unless its receive only, but we already suspected the instructor is a pig-ignorant ass-hat!"
},
{
"post_id": "",
"author": "FriedMule",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 28, 2021, 04:25:22 pm",
"content": "Thank you so much! I do not understand the \"R1||(R2+(R3||Rload1))\" part, what does the \"||\" mean?I was concerned that I had understood nothing of what I have tried to learn because what he is saying is somewhat conflicting with what I think I know.I thought how could you get 10% loss there, would that not be insane to get 20W trough that resistor!?"
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 28, 2021, 04:36:53 pm",
"content": "||is (or maybe was, as I think it was a USENET sci.electronics 'thing) 'in parallel with' used due to the limitations of describing circuits in a text-only medium. You might describe a typical scope input as1Meg||20pFand I'm using it here as an operator invoking the resistors in parallel formula. i.e. if used in the expressionRpar = Rx||Ryou'd expand the RHS to eitherRx*Ry/(Rx+Ry)or1/(1/Rx+1/Ry)"
},
{
"post_id": "",
"author": "BeBuLamar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 28, 2021, 04:52:25 pm",
"content": "Voltage dividers are generally used for very light load like transistor bias or speed reference for a motor drive. It's not good to supply power to any significant load. There are many other way like switching or even linear voltage regulation. But if you have to do it with only resistors then I would skip the resistor parallel with the load. It's useless unless it actually draws a lot more current than the load in which case way too much energy is wasted but does make the voltage stable when the load is varying."
},
{
"post_id": "",
"author": "fourfathom",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 28, 2021, 05:00:18 pm",
"content": "To emphasize what has already been said, that voltage divider is a terrible way to provide power to the loads in that example. You can calculate the mathematically correct resistor values, but nobody who know what they are doing would use such a circuit as the power loss and dissipation would be ludicrously large.An appropriate use of the voltage divider is to provide specific voltages to low-power loads. And that 10% business is just a rule of thumb, not particularly useful in most situations and can be ignored in most real-world cases where the loads are stable."
},
{
"post_id": "",
"author": "FriedMule",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 28, 2021, 05:02:58 pm",
"content": "Thanks for the great explanation.I do just wonder if it is \"smart\" to run both 12V and 24V in the same circuit, if you have a 200W 24V load and an 8.33W 12V load, is it not better to run it separately with transformer and components build for that purpose, instead of budging it all on a resister?"
},
{
"post_id": "",
"author": "FriedMule",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 28, 2021, 05:06:47 pm",
"content": "I have only once used a voltage divider to a high load, but it was to build a sort of own for some components, did later change it to a transistor circuit."
},
{
"post_id": "",
"author": "bdunham7",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 28, 2021, 05:15:31 pm",
"content": "Quote from: FriedMule on November 28, 2021, 05:02:58 pmAs said previously, this is a terribly stupid example of an impractical circuit. I was astonished to realize, as I watched a bit of the video that you linked, that this seems to come from a textbook of some sort. I have stated before and will again in the future that there is no reason that you cannot teach the principles of electronics with actual, practical circuits. Teaching them with awkward, idiotic examples is just the result of laziness and lack of imagination and it confuses students."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 28, 2021, 05:21:54 pm",
"content": "Its not smart at all, hence my suggested rule of thumb:If you are attempting to draw over 1mA from a potential divider tap your design probably *SUCKS*!The further idiocy was the instructor said the 48V was from a telecom power supply. -48V (with respect to Earth ground) is a common supply voltage in the telecoms industry inherited from the days of copper POTS circuits and Strowger electromechanical exchanges. However you'd never find it in anything much smaller than a cruise liner, and then only for an internal phone system.An electric powered boat might well have a 48V battery system as its a nice voltage for propulsion motors - keeps the current down while not having the electrical safety issues of exceeding SELV voltages. However you'd then have a SMPSU, probably float charging a 12V or 24V battery to provide backup power for emergencies, supplying your navionics, comms and 'house' circuits. You might also have one or more 20V-30V in 13.8V out buck converters to supply '12V' equipment if your main instrument &house supply was nom.24V. You certainly wouldn't have a power resistor divider - even in the days before power transistors it would have been a rotary converter (motor-generator set)."
},
{
"post_id": "",
"author": "polarKaung",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "November 28, 2021, 05:26:55 pm",
"content": "Quote from: Terry Bites on November 27, 2021, 04:23:22 pmSo, to my basic understandings, Rx needs to be at least ten times that of R3 while Ry needs to be ten times that of combination of R2, R3 and Rx(so 10R3)?"
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 28, 2021, 05:50:59 pm",
"content": "That's backward! Rx (Rload1) is what it is, and so is Ry (Rload2). You need to calculate R1, R2, and R3.*IF* you were going to use the divider current > 10x load current rule of thumb, and also design for nominal voltages at no load:Ry = (24V2/200W) = 2.88 ohms.=> R1=0.288 ohms, and so is R2+R3 as Vload2 is half Vsupply.As Vload1 is half Vload2, R2=0.144 ohms, and so is R1However that gives 83.3A through the divider no load and 4KW quiescent dissipation! That's not a viable power supply, its a large electric heater.Note that the 10x 'rule of thumb' gives a stiffer, higher standing current divider than my assumptions in reply#8."
},
{
"post_id": "",
"author": "BeBuLamar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 28, 2021, 06:06:41 pm",
"content": "Quote from: FriedMule on November 28, 2021, 05:02:58 pmIf you have a 48V power source like a 48V battery and want to power the 2 loads in example I would use 2 of thesehttps://www.amazon.com/Adjustable-Programmable-Step-Down-Regulated-Converter/dp/B01N0VKTC2/ref=asc_df_B01N0VKTC2/?tag=hyprod-20&linkCode=df0&hvadid=241973970700&hvpos=&hvnetw=g&hvrand=3287969246773027355&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9026816&hvtargid=pla-399690329417&psc=1Very little wasted power and the voltages are steady when load current draw changes."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 28, 2021, 06:25:04 pm",
"content": "That could be problematic as IIRC those have low side current shunts, and as both the radar and radio are likely to have other ground connections, the buck modules current shunts could get shorted out, resulting in no over-current protection and possible damage to the buck modules. Also good luck running a 200W 24V radar (8.3A) from a 5A buck module!"
},
{
"post_id": "",
"author": "fourfathom",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 28, 2021, 06:42:19 pm",
"content": "The problem here isn't how to power those 24V and 12V loads from a 48V supply. If it were, the answer would likely be to use appropriate switching regulators.No, the problem is how to design a voltage divider. Unfortunately, the example is an impractical one, and this leads to unnecessary confusion. Let's help FriedMule (the OP) with voltage dividers. Actually, I think there is enough here in the replies that they can figure it out. If additional examples are needed, we can provide them."
},
{
"post_id": "",
"author": "BeBuLamar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 28, 2021, 08:09:44 pm",
"content": "Quote from: Ian.M on November 28, 2021, 06:25:04 pmI don't think there would be a problem with grounding but yeah I would need a bigger unit for the radar. But that I would do to power 24 and 12V devices from a 48V power source."
},
{
"post_id": "",
"author": "FriedMule",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 29, 2021, 09:32:39 am",
"content": "I know this is a large question when we are talking about the length of the video, but this voltage divider is not the only strange thing I have stumbled upon, i.e. that current moves through the wire with light speed or as he says \"a matter of fact, instantaneously\" I took this as a simplification that was to not complicate the basic course. He is also talking about \"hole\" movement contra electron movement. So in short, is he useful as a beginner course or does he \"harm\" more than help?"
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 29, 2021, 10:46:35 am",
"content": "Good question. However expecting anyone competent to understand this s--t to wade through a 10H video looking for pig-ignorance is a bit of a stretch, so why don't you provide us with half a dozen timestamped links to bits you feel are dodgy, with a brief summery of what you felt was wrong with each and how long a waffle we have to suffer (i.e. time from start of clip to incidence of foot in mouth). Then those of us who are feeling masochistic enough can tackle each in a coffee break rather than giving up days to it."
},
{
"post_id": "",
"author": "BeBuLamar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 29, 2021, 12:14:52 pm",
"content": "Why use voltage divider instead of a simple single resistor? If the load draws a constant current or the resistance of the load is constant like in the case of a heater then a single resistor in series would waste less power. But a load may draw varying current and thus the voltage divider would provide a more stable voltage but only if the voltage divider itself drawing significantly more current than the load. So voltage divider can really only be used in case the load draw negligible current."
},
{
"post_id": "",
"author": "FriedMule",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 29, 2021, 02:21:15 pm",
"content": "Great idea, but I have almost seen it all, I do just think I will not recommend the video to anybody else and take a look for something better for the next part of my journey. :-)"
},
{
"post_id": "",
"author": "gf",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 29, 2021, 03:52:55 pm",
"content": "There exist an infinite number of R1,R2,R3 combinations which result in Load1=12V/6W, and Load2=24V/200W.So an additional border condition needs to be specified in order to get a unique solution.This could be a condition like \"among all possible sulotions, choose the solution which has minimum power dissipation\", which leads to R3= infinite, R2= RLoad1, and R1= RLoad2|| 2 * RLoad1then.Of couse various other border conditions are imaginable, too, which lead to different solutions."
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 29, 2021, 09:23:47 pm",
"content": "Quote from: FriedMule on November 29, 2021, 09:32:39 amThere's nothing wrong with hole theory. It is a common understanding in semiconductor devices where an electron moves from - to + into a hole leaving behind a hole for another electron to fill. As the electrons move from - to +, holes are apparently moving from + to -.The theory is useful in understanding flow in all electronic devices. It's just accepted by everybody except the US Navy that current flow is + to -. The US Navy wants to deal with electron flow from - to +. That's one of the reasons I don't mention the NEETS program. It just adds confusion to newcomers.https://energyeducation.ca/encyclopedia/Electron_holeHere's more:https://eng.libretexts.org/Bookshelves/Materials_Science/Supplemental_Modules_(Materials_Science)/Solar_Basics/D._P-N_Junction_Diodes/I._P-Type%2C_N-Type_SemiconductorsQuote"
},
{
"post_id": "",
"author": "FriedMule",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 30, 2021, 05:12:23 pm",
"content": "Thanks, but he does not explain that at all, or at best does he hint some of it. I do not understand why he is not telling about how the normal convention is in reverse direction of reality."
}
] |
2025-10-17T17:18:54.963375
| 30
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/10-meters-effective-electromagnetic-field-how/
|
10 meters effective electromagnetic field. How? - Page 1
|
[
{
"post_id": "",
"author": "sinan",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "January 16, 2025, 05:11:31 pm",
"content": "I recently retired and moved to a village, but where I am staying I have a problem with cats. Especially at night, because it is hot, they go into the attic to sleep and sometimes they make noise and wake me up. I bought an ultrasonic repeller and tried it, but it did not cure the cat noise. I know the negative effect of the electromagnetic field on living things. I also know that they cannot sleep when they stay in this field. I need a solution that will cover at least 10 meters. Is that possible? If you know of a project on this subject, can you share the link? I found a video on Youtube, but I don't know if it covers 10 meters ()"
},
{
"post_id": "",
"author": "golden_labels",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 07:05:09 pm",
"content": "National High Magnetic Field Laboratory has one. Covers only about 5 meters,(1)but if it sucks in a ferropurrous cat, you’ll never see the beast again. Beyond that distance the cat will only get slightly tilted. Not sure, how much they charge for moving it to your house.Others will correct your beliefs below, but even without that: let’s look at what you propose. You believe that “electromagnetic field has a negative effect on living things.” So your idea is to shoot yourself and everybody around with one. You need no knowledge of physics, electronics, or maths to see something is off with the idea, do you? Rationalizing it through distance isn’t going to work. If your original premise was right, the harmful effect wouldn’t instantly drop to zero after the 10 meters mark.Fortunately it doesn’t. Neither electromagnetic field nor waves in that field have any known harmful effect on living organisms. Associating word “electromagnetic,” or just any arbitrary kind of radiation, with harm is a common misconception, and also disinformation associated with it. Not only you’re swimming in all kinds of electromagnetic radiation all the time, not only it’s crucial for survival of any known life, but at this very moment you’re emitting around 100 watts of electromagnetic radiation. At frequencies closer to carcinogenic and ionizing radiation than anything you’d ever obtain in any electric circuit.If you want to get rid of cats, consider chemical repelents likeIBI-246and similar. Combined with understanding what causes the problem: trying to limit it, or redirect cats’ attention to other places.Ultrasonic devices supposedly work, but there are two problems. First: it’s not some magical feature of ultrasonic waves, but simple noise that makes cats unwilling to be in the affected area. While higher frequencies may be less comfortable to cats, the pitch is so chosen primarily to not disturb humans. Since it’s nothing but noise, animals may either not hear it at all (hearing problems are not only a human thing), not be sensitive to it, or… adjust to it, if the incentive is high enough. The second problem is that many such devices are fakes.It also takes time for any measure to take effect. A cat will not sit in cold simply because there is something unpleasant in a warm place. It needs to have somewhere else to go. Not to mention cats are clever beasts. They learn pretty quickly to find safe spots and avoid nuisance.(1)From Veritasium:"
},
{
"post_id": "",
"author": "Hr_Satch",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 07:53:55 pm",
"content": "Haha, LoL,jup, indeed, in our nowadays -all over too technically inclined- world,we are swinging 24/7 in *radiation* under the form of electro-magnetic fields.Or you should wonder: why we receive a radio station broadcast,? only ? when we turn on our radio ?How do they do that for millions of people, LoL-- --Now about the cat thing: overhere in Europe, some are getting smarter with their relentic hunton wolves, and the why farmers, and such refuse to invest in a decent fencing, . . .=> it has been discovered that wolves, and even dogs:avoid places with big cats urine smell of Tigers, Lions, pumas, etc . . .So why not try that to get rid of surrounding cats, without any harm: just bigger cats piss ;-?To where to get a sample, that's everyones search in their living country.Haha, nice topic, Harry tha Belgian."
},
{
"post_id": "",
"author": "TimFox",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 07:55:07 pm",
"content": "I never watch that type of YouTube episode, but the “vise” in the image has a useful range of less than 10 cm, to hold a steel plate for machining purposes (e.g. surface grinding) that can be released with a switch or lever.Absolutely noradiationis involved."
},
{
"post_id": "",
"author": "special_K",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "January 17, 2025, 01:38:22 am",
"content": "Perhaps you can team up with the pig electrocution guy and kill cats with professor x mind rays"
},
{
"post_id": "",
"author": "Hr_Satch",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 19, 2025, 11:14:35 am",
"content": "Dunno, how pungent Big Cats scent smells around a house, LoL ;-?But it sure is green, as to no energy required,works even when cloudy and no wind"
},
{
"post_id": "",
"author": "Sorama",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 19, 2025, 11:50:21 am",
"content": "A simple and effective solution would be to close all the openings to the attic.Can’t be that difficult as an attic should be airtight by default."
},
{
"post_id": "",
"author": "Haenk",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 21, 2025, 11:53:12 am",
"content": "My wife bought a cat repeller: A watergun with selenoid, actived by PIR sensor. Place that near the entry point, and I assume most cats will not pass.Other than that, cats are clever and will ignore most disturbances."
},
{
"post_id": "",
"author": "Siwastaja",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 21, 2025, 12:15:02 pm",
"content": "Quote from: Haenk on January 21, 2025, 11:53:12 amEven simpler: close the entry point."
},
{
"post_id": "",
"author": "Xena E",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 21, 2025, 01:00:59 pm",
"content": "I'm not going to even acknowledge the EMF, wo wo nonsense, but just leave citrus peel where you dont want cats!(Grapefruit skin zest is best).X"
},
{
"post_id": "",
"author": "Haenk",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 23, 2025, 10:29:33 am",
"content": "Quote from: Xena E on January 21, 2025, 01:00:59 pmI bet our cat would just try to eat it"
},
{
"post_id": "",
"author": "valcher",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 23, 2025, 12:43:12 pm",
"content": "Cats really love the smell of valerian root, maybe you have some drying in your attic?"
},
{
"post_id": "",
"author": "Terry Bites",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 23, 2025, 04:39:35 pm",
"content": "Fix your attic?"
}
] |
2025-10-17T16:24:14.313730
| 13
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/10-mh-inductor-(28r)/
|
10 mH inductor (28R) - Page 1
|
[
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 20, 2013, 11:28:18 pm",
"content": "Hi,What is the meaning of 28R ?JP"
},
{
"post_id": "",
"author": "Jebnor",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "June 20, 2013, 11:54:10 pm",
"content": "Non reactive resistance? as in 28ohms?"
},
{
"post_id": "",
"author": "Mandelbrot",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "June 21, 2013, 12:02:22 am",
"content": "28 ohms does seem like a reasonable resistance of a 10mH inductor. That could be the case."
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 21, 2013, 01:43:10 am",
"content": "Maybe it is a reactance?"
},
{
"post_id": "",
"author": "c4757p",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 21, 2013, 01:49:04 am",
"content": "No, that timer will run around 2 kHz, and the reactance of a 10mH inductor at 2 kHz is 126 ohms."
},
{
"post_id": "",
"author": "TerminalJack505",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 21, 2013, 02:00:37 am",
"content": "That schematic originally comes fromhere, by the way. That's Colin Mitchell'sTalking Electronicssite. The 28R is the inductor's ESR. The site eludes to thishere."
},
{
"post_id": "",
"author": "Unknown",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "June 21, 2013, 01:47:25 pm",
"content": "The DC metered resistance would depend on the wire gauge used, an example I have, the DC resistance comes out at 390 ohms ?Interesting to find the 555 frequency is near 2.220 Htz and reactance is 139.42 ohm... that's assuming a 50% duty cycle, due pin 3 output provides about that percentage duty."
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 24, 2013, 03:57:22 pm",
"content": "Hi,Should I set the oscilloscope to dc?I have build the circuit here are the results.The inductance resistor from the multimeter reading is 15 Oms. I bought the inductance it is supposed to be 10mH.1451 Hz.The power supply delivers 23 mAThe zener uses about 7.5 mA.I used a zener witch is readed at 2.5 volts.If I measure the output with a multimeter, I get 97 volts!"
},
{
"post_id": "",
"author": "Unknown",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "June 24, 2013, 04:16:06 pm",
"content": "Try finding a resource that explains the difference between (DC) resistance and reactance without introducing stuff like complex math. I don't have one handy, AllAboutCircuits.com might have a good write-up.A perfect inductor will have an inductance, but no DC resistance. A DMM set to resistance would measure zero Ohms (it uses DC), but an AC signal will be affected, because it has reactance (AC resistance). The reactance is caused by its inductance, which is measured in Henry. So a perfect inductor might have an inductance of 10 mH but a DC resistance of 0 Ohms.In the real world, copper wire has a finite resistance. Especially many turns of fairly thin copper wire. This causes a DC resistance in addition to the current. This real inductor might measure 28 Ohms with a DMM (its DC resistance), but still have a 10 mH inductance. A DC signal would see it as a 28 Ohm resistor (since DC is not affected by inductance), but an AC signal will see it as a 28 Ohm resistor with an ideal 10 mH inductor in series (a decent approximation for low frequency work). Both the ideal and the imperfect coil will have the same inductance, but will behave slightly differently because of the difference in DC resistance.This zener diode tester will deliver a fairly high DC voltage, but limited to a low current. A reverse-biased zener should start conducting as soon as the voltage across it exceeds it nominal voltage (eg. 2.5 V), thereby limiting the voltage across it. If you measure the voltage without a diode across the output, then you should expect to measure a very high voltage. If you measure the same with the zener connected, then the zener might be open circuit.It looks like the DC resistance of the coil limits the current through it when BD679 is conducting, so you might get a higher maximum voltage/current with a lower series resistance. From the 63v, I would expect the maximum output voltage to be well below 100 V. You could try putting a ~12 Ohm resistor in series with the coil and see if that lowers the voltage."
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 24, 2013, 08:38:05 pm",
"content": "Thank you for te answer.Does the diode split the frequency by 2?Does the oscillating coil create an ac current?Does the 555 create an ac curent at pin 3?If I measure the voltage between the PS + terminal and the neg side of the diode. I get 3.3 volts.Between the PS + side and the diode + side, I get 3.8 volts!I took other measures. The DC and AC makes things complex. The multimeter and oscilloscope too !JP"
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 25, 2013, 03:08:44 pm",
"content": "Quote from: alm on June 24, 2013, 04:16:06 pmI know the maths. My problem is understanding them in a real circuit.Thanks for the explanations.>when BD679 is conductingthe inductor build is MField>when BD679 is closedthe inductor discharge in the 1uF, 47K and the output?"
},
{
"post_id": "",
"author": "TerminalJack505",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 25, 2013, 06:40:09 pm",
"content": "Here's how I would explain that circuit...When the transistor conducts a current will flow through the inductor. This current will cause a magnetic field to be created. This is why the current through the inductor builds-up slowly, rather than instantly--the energy goes into building the magnetic field. Once the inductor saturates (as I assume it will due to the low frequency but that may not actually be the case) the magnetic field no longer builds-up and the current is at its maximum.When the transistor turns off the magnetic field begins to collapse. All the energy that went into building the magnetic field is returned to the circuit. (Naturally, there's some loss. We're just talking theory here.) The current through the inductor wants to continue flowing because of the collapsing magnetic field. If it can't find somewhere to flow to then the voltage across the inductor begins to rise. The topmost terminal of the inductor is held at a constant 5.8V so the rising voltage is seen at the other terminal. (The 1N4148 diode's anode.)When you have a Zener diode in the circuit then it will clamp the rising voltage to whatever the Zener is rated at. If you don't have a Zener diode in place then the voltage will rise as high as it can. One of the biggest factors in how high it will go is the Q factor of the inductor. (The DC resistance of the inductor is one of the factors in the inductor's Q factor.) Everything else being equivalent, an inductor with a higher Q factor will generate higher voltages than one with a lower Q factor. The inductor shown in the schematic with the higher DC resistance likely produces lower voltages.Since you are seeing the voltage rise to 100V you probably want to put a permanent Zener in the circuit to limit how high it goes--to protect the components as well as the operator. The transistor is rated only to 80V and the capacitor, as shown in the schematic, is rated at 63V."
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 25, 2013, 07:19:53 pm",
"content": "Quote from: TerminalJack505 on June 25, 2013, 06:40:09 pmThanks for your clarification.It can always flow throughout the 47k resistor. Maybe not fast enough....JPD"
},
{
"post_id": "",
"author": "TerminalJack505",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 25, 2013, 07:23:14 pm",
"content": "Correct. I think the resistor is primarily meant to bleed the charge off the capacitor once the circuit is powered down."
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 26, 2013, 02:25:35 pm",
"content": "I red 103 volts with a Fluke.So, if the impedance is at 0 while discharging, the current would be 103/ 28 = A ?The circuit draws 162mA from the power supply. 10mA goes throughout the multimeter and to the zener, 5 to the 555 , could the remaining xmA go for the Inductor?JPNB I have updated the file in the June 25, 2013, 06:38:05 AM message"
},
{
"post_id": "",
"author": "c4757p",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 26, 2013, 02:35:18 pm",
"content": "Think of an inductor like momentum for current. You build up momentum when the transistor is on, then when you shut it off, the current slams through the diode instead. It's not going any higher than what the current through the inductor was at the moment the transistor shut off, which is determined by the inductance, series resistance and switching rate. I think I got the switching rate right (out of memory from when I calculated it a few days ago), so here's a rough model of the circuit testing a 51V Zener diode. Green is the transistor current, blue is the diode current.The output diode and capacitor, which I did not include (lest they make the plot harder to understand) will take the edge off that, as well, because the capacitor will gulp the peak current."
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 26, 2013, 03:41:44 pm",
"content": "Hi,I have got ltspice. Would you attach the asc file?Thanks.JP"
},
{
"post_id": "",
"author": "c4757p",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 26, 2013, 03:45:04 pm",
"content": "I didn't keep it. Should take all of a minute to throw together. The only invisible property is the inductor's DC resistance - right click on it to add that."
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 26, 2013, 05:20:06 pm",
"content": "Here is an asc file. The curve is an envelope of a jigsaw wave forL1."
},
{
"post_id": "",
"author": "c4757p",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 26, 2013, 05:23:23 pm",
"content": "I didn't open the file, but from the screenshot, it looks almost perfect.1. Isn't it easier to use the ground symbol to ground things, instead of a twisting ground trace? It would be much easier to read...2. Turn the Zener diode around. Zener breakdown is reverse breakdown. You have it configured to measure forward breakdown."
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 28, 2013, 01:26:54 pm",
"content": "Hi,I sill dont understand why the voltage goes so high.Without capacitor , resistor and zener: 1.4 KVoltsWith cap only: 110 volts.If I put a 1uf cap and a 220 Ohms resistor: 16 voltsIf I put a 1uf cap and a 47k Ohms resistor: 77 voltsSo that resistor controls the 'thing' .JP"
},
{
"post_id": "",
"author": "c4757p",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 28, 2013, 01:48:09 pm",
"content": "Like I said, momentum for current. It tries to keep the current equal, and if it can't, it gives a voltage proportional to how fast the current was changed. Without those things, there is nowhere for current to flow, so it's just pushing against the breakdown voltage of the transistor.Trap for young players: SPICE only supports breakdown if it's included in the particular component model, and it's often not. 2N2222 breaks down around 70-80V, so it wouldn't be able to go any higher than that."
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 28, 2013, 08:25:37 pm",
"content": "It is more an energy balance. You put energy into the magnetic field in the coil when the transistor is on, and when you turn off the transistor you have to dissipate the energy somehow. If there is no load the voltage rises until the energy is dissipated. Whether it goes into a resistor, capacitor or killing the transistor is immaterial, the energy is going to be going somewhere."
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 29, 2013, 02:20:22 am",
"content": "The voltage rises because it sees higher voltage (transistor voltage or else) and try to overcome it?If the transistor breakdown would be at 200 volts , would the inductor voltage rises up to 200 volts?JP"
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 03, 2013, 01:52:05 pm",
"content": "I noticed that the inductoor does not have enough time to discharge completely through the iu capacitor or 47k resistor.So it discharche to ( lets say) 10 , 20, 30, 40, etc volts. Then it charges from 20, 30, 40 , volts climbing a staircase.SO,Quote from: SeanB on June 28, 2013, 08:25:37 pmThank for your answer.JP"
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 10, 2013, 09:36:44 pm",
"content": "Does that make sense?The inductor charges and discharge when the base is closed?The ringning can occur because of the 1 uf cap. See Reply #18JP"
},
{
"post_id": "",
"author": "rvof11",
"author_rank": "Newbie",
"is_op": false,
"timestamp": "July 11, 2013, 01:13:47 pm",
"content": "Quote from: SeanB on June 28, 2013, 08:25:37 pmIsn't this suppose to be an exact science?"
},
{
"post_id": "",
"author": "TerminalJack505",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 11, 2013, 08:41:03 pm",
"content": "Quote from: J4e8a16n on July 10, 2013, 09:36:44 pmThat ringing might be due to something else. Notice how the voltage at the base is ringing as well. This might be causing the ringing at the collector since the transistor would be quickly switching off and on. The ringing at the base might be due to the probe's capacitance along with some parasitic inductance (the probe's ground lead and other wiring, for example) creating an (unwanted) tank circuit.You might try using the probe's low inductance ground attachment (the little spring) to see if the circuit behaves differently."
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 11, 2013, 09:34:05 pm",
"content": "Quote from: TerminalJack505 on July 11, 2013, 08:41:03 pmGreat idea.JPD"
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 12, 2013, 07:31:08 pm",
"content": "Only a small ringning at the base... from the 555 probably..."
},
{
"post_id": "",
"author": "TerminalJack505",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 12, 2013, 08:34:50 pm",
"content": "Those waveforms look a lot better. It was the probe then?I'll have to built one of these for myself. I bet a joule thief circuit can be modified to get the same functionality."
},
{
"post_id": "",
"author": "J4e8a16n",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 13, 2013, 01:16:51 am",
"content": "Not the probe.The pcb was directly on my bench and there was weak join between the zener and the output.QuoteInteresting.JP"
}
] |
2025-10-17T20:19:37.569583
| 32
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/10-mhz-from-signal-generator-differs-from-gpsldo/
|
10 MHz from signal generator differs from GPSLDO - Page 1
|
[
{
"post_id": "",
"author": "Moriambar",
"author_rank": "Unknown",
"is_op": true,
"timestamp": "May 06, 2021, 05:37:41 pm",
"content": "Hi, I have a GPSLDO, an arb gen (SDG1032X) and a scope (SDS1104X-E).I have one of the distribution box output hooked up directly to the scope, showing a steady 10MHz waveform (I'm doing this after 45 minutes of uptime, so I got gps lock AND alm off).One other output of the distro box is hooked it to the Aux In of the SDG1032 set to have an external clock reference.Then I set the arb to generate a 10MHz Sine and hook it up to the scope, which is triggered on the GPSLDO 10MHz.What I see is that the arb sine seems to move relative to the other one, towards the right of the screen. Why does it do that? I thought that perhaps adjusting the \"phase\" parameter it could magically fix the thing (if anything has to be fixed) but nothing changes at all…Can you please explain a bit more what is happening, please?cheers!"
},
{
"post_id": "",
"author": "rfclown",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 06, 2021, 06:53:34 pm",
"content": "The 10 MHz from the \"distribution box output\" should be connected to the \"10 MHz In/Out\" connector on the rear of the arb, and the arb configured for external 10 MHz In.I looked up the arb manual to see if it had a 10 MHz in. Read the manual."
},
{
"post_id": "",
"author": "Moriambar",
"author_rank": "Unknown",
"is_op": true,
"timestamp": "May 06, 2021, 06:58:14 pm",
"content": "Quote from: rfclown on May 06, 2021, 06:53:34 pmSorry, My bad, I misspoke. That's where I hooked it up (the 10MHz in/out). As I said I set the arb for 10MHz external source.So the connection is correct but the problem is still there"
},
{
"post_id": "",
"author": "radiolistener",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 07, 2021, 04:52:46 am",
"content": "Quote from: Moriambar on May 06, 2021, 05:37:41 pmif they are moving, then your GPSDO and signal generator generator are clocked from different oscillators. They are asynchronous.I'm not sure how external reference works for SDG1032, but I guess that it uses external reference period just to tune it's own oscillator frequency. It is very easy to implement in FPGA - just divide oscillator and ext ref to the same frequency, XOR them and then filter to get tuning voltage for VCO pin of it's own oscillator. If it works in such way, it still use it's own oscillator as a clock, so it will be asynchronous to the ext reference clock."
},
{
"post_id": "",
"author": "Joel_Dunsmore",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "May 07, 2021, 05:17:30 am",
"content": "often test instruments internal ref oscillators are phase-locked to the external input thru a analog phase detector (puts out a voltage for a given phase). usually this is set to some small offset like 45 degrees to produce a small DC which goes into an op-amp used as an integrator. The other input is sets the offset voltage to set the offset-lock angle. But, all these elements are subject to drift, temperature changes and aging and so you might find the phase of the 10 MHz output wanders relative to the 10 MHz input signal, but the integrated frequency error will be zero. The phase lock give zero frequency error but NOT zero phase error."
},
{
"post_id": "",
"author": "TurboTom",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 07, 2021, 05:56:35 am",
"content": "Depending on the frequency the phase comparator works at, there may be some initial drift that will stabilize within milliseconds to seconds. But after that, despite some minor jitter (phase noise), the phase should stay locked. For all practical reasoning, the generator's reference frequency can be considered synchronous to the externally supplied one in this condition.A \"walk-through\" of the two frequency signals isn't acceptable. Did you enter the output frequency on the AWG with the encoder or typed in as a decimal value? Sometimes, this may make a (tiny) difference. The AWG shoud indicate on the screen that it's using the external clock. Also, you may want to verify that you're using the latest firmware."
},
{
"post_id": "",
"author": "Anthocyanina",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 07, 2021, 07:12:38 am",
"content": "Hi! do you have a frequency counter? when a signal moves relative to another it means their frequencies are not exactly the same, close but not exactly. When they are the exact same frequency, they both look static on the oscilloscope, but there may be some phase shift. In this short video you see 3 signals, channel 2 and 3 are at the same frequency exactly. but there is a slight phase shift, yet both are \"locked\" to each other, and channel one has a slightly lower frequency. so when triggering on channel one, we see the channel 2 and 3 signals move around, but when triggering on channel 2, we can see channel 2 and 3 are locked and we can see the phase difference between them, and only the channel one signal is moving, wich is why in these captures sometimes we can see channel one's edge and sometimes not.https://youtu.be/omTYe5WgHVw(edited the post to attach the other captures since it wouldn't let me post them when i first made this post)"
},
{
"post_id": "",
"author": "tautech",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 07, 2021, 09:11:14 am",
"content": "Quote from: TurboTom on May 07, 2021, 05:56:35 amThis ^^Also you need ensure the Ext clock meets SDG1000X datasheet specs:https://www.siglenteu.com/wp-content/uploads/dlm_uploads/2017/10/SDG1000X_DataSheet_DS0201X_E01G.pdfP10 Reference Clock InputEdit to add, most aux inputs are rated for 5V max so it would be wise to not exceed this."
},
{
"post_id": "",
"author": "Moriambar",
"author_rank": "Unknown",
"is_op": true,
"timestamp": "May 07, 2021, 03:13:49 pm",
"content": "Quote from: TurboTom on May 07, 2021, 05:56:35 amHi, and thanks for your reply.I have the latest firmware installed, also I tried both with the knob and by manually inputting the frequency, but no difference.The screen indicates the external clock reference correctly as the menu does"
},
{
"post_id": "",
"author": "Moriambar",
"author_rank": "Unknown",
"is_op": true,
"timestamp": "May 07, 2021, 03:18:08 pm",
"content": "Quote from: Anthocyanina on May 07, 2021, 07:12:38 amHello, and thanks for your reply.Unfortunately no, I don't have one [they seem quite expensive] but I have an ongoing project for building one. anyhow no.QuoteOK I see something similar of what's in the video, but the nonstatic signal is going right lol. The rest is exactly thatThanks"
},
{
"post_id": "",
"author": "Moriambar",
"author_rank": "Unknown",
"is_op": true,
"timestamp": "May 07, 2021, 03:20:43 pm",
"content": "Quote from: tautech on May 07, 2021, 09:11:14 amAs I stated elsewhere that is correct, all points to the fact that the arb is using the external clock.QuoteIt's 3Vpp, which is well in spec"
},
{
"post_id": "",
"author": "jpb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 07, 2021, 05:10:39 pm",
"content": "The generator is a DDS one, I presume - it may be that it can't exactly represent 10MHz, it should be able to at 150MS/s there should be an integer number (15) of samples per wavelength but maybe the digital representation isn't exact (the spec sheet says to within a microhertz).It may be worth generating say square waves and see if the same drift occurs to find out if it is a DDS thing or if it is the PLL.You could try generating a slightly different frequency to see if you can get rid of the drift say 10,000,000.000001 Hz or 9,999,999.999999 Hz then you could find out what the effective frequency is."
},
{
"post_id": "",
"author": "fourfathom",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 07, 2021, 05:35:20 pm",
"content": "Arb Waveform Generators usually use Direct Digital Synthesis to generate the output frequency, and these typically use a binary power-of-two NCO (Numerically Controlled Oscillator) to set the output frequency. The arb generator also will multiply the input reference up to a much higher frequency, using this high frequency to clock the NCO. There will be many output frequencies that can't be generated exactly with the NCO, as the necessary divide ratio isn't possible with the binary NCO. You can get extremely close, but not exact.Simple example:10 MHz reference, multiplied by 50 to get a 500 MHz internal clock.16-bit NCO (They are usually wider than that, even if the Analog to Digital Converter is only 12 or 16 bits.)This NCO can divide the 500 MHz clock by n/216, where 'n' is the frequency control value.To get an exact 10 MHz output you would need to divide 500 MHz by 50. Unfortunately, with the 16-bit control word this would be 1310.72 / 65536, so the closest we can get is actually 1311/65536, which will give you an actual output frequency of about 10.000213 MHz.With a wider control word you can get arbitrarily close, but often not exact."
},
{
"post_id": "",
"author": "fourfathom",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 07, 2021, 06:51:11 pm",
"content": "Quote from: fourfathom on May 07, 2021, 05:35:20 pmI should have inverted that fraction. In any case, for a binary NCO Fout = Fin * C / 2N, where 'C' is the control value and 'N' is the bit-width of the NCO accumulator."
},
{
"post_id": "",
"author": "Moriambar",
"author_rank": "Unknown",
"is_op": true,
"timestamp": "May 07, 2021, 07:40:42 pm",
"content": "ok apparently 9.99999999 MHz or similar does the trick. The frontend still rounds it up at 10MHz but…Cheers"
},
{
"post_id": "",
"author": "Anthocyanina",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 07, 2021, 08:03:03 pm",
"content": "Quote from: Moriambar on May 07, 2021, 03:18:08 pmThe direction in which the signal moves depends on how its frequency differs from the frequency of the signal you're triggering on. Higher frequency than the triggered signal, it will move to the left, lower frequency than the triggered signal, and it will move to the right."
},
{
"post_id": "",
"author": "fourfathom",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 07, 2021, 09:16:04 pm",
"content": "Quote from: Moriambar on May 07, 2021, 07:40:42 pmPerhaps this just reduces but doesn't eliminate the intrinsic error. If you have a classic binary DDS / NCO, there are some ratios (divisors) you just can't get. Try to represent 1/3 or 1/10 or 7/25 as a binary fraction. You can't do it exactly."
}
] |
2025-10-17T17:28:56.865353
| 17
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/10-mhz-ocxo-standard/
|
10 Mhz OCXO standard - Page 1
|
[
{
"post_id": "",
"author": "M0BSW",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "December 09, 2013, 10:13:09 am",
"content": "Hello Everyone,What I've made a start on building is a 10 Mhz square wave frequency standard, which is something I've been itching to build for quite a while, and I'm sure you will know is very useful device in my radio shack.I do have a couple of questions regarding this project, you may I hope like to ponder over and hopefully give some advice on.1/ The ocxo is in a can, to I need to also mount it to a heat sink, or are they ok with out!!!.2/ I want to have 4 bnc outputs, so would it be advisable to make 4 buffer outputs one for each output, I'm not following any particular circuits. so \"anyone ever built one\". Always any of your help would be appreciated.PaulM0BSW UK Radio Amateur"
},
{
"post_id": "",
"author": "peter.mitchell",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 09, 2013, 11:07:40 am",
"content": "http://gerrysweeney.com/build-a-10mhz-rubidium-frequency-standard-and-signal-distribution-amp-for-my-lab/this might help"
},
{
"post_id": "",
"author": "KJDS",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 09, 2013, 11:14:07 am",
"content": "There is no need to try and cool an OCXO, the internal oven is designed to heat up and the less heat you drag away from it the better. Just make sure that the ambient doesn't get too near the oven temperature."
},
{
"post_id": "",
"author": "peter.mitchell",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 09, 2013, 12:20:18 pm",
"content": "I linked that mainly for the amp/buffer bit, the amp chip is EOL, but can still be found aroundhttp://octopart.com/partsearch#!?q=CLC409"
},
{
"post_id": "",
"author": "M0BSW",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "December 09, 2013, 04:12:28 pm",
"content": "Thanks Peter"
},
{
"post_id": "",
"author": "Matje",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "December 09, 2013, 11:57:45 pm",
"content": "Quote from: M0BSW on December 09, 2013, 10:13:09 amThink about the square wave part again. Usually frequency standards use sine waves, because these have way less harmonics and are much easier to distribute. Most test equipment takes sine waves as reference inputs AFAIK.Lots of harmonics are a very bad thing in a radio shack I think.Quote from: M0BSW on December 09, 2013, 10:13:09 amNo heatsink needed, nor would it be a good idea.Quote from: M0BSW on December 09, 2013, 10:13:09 amThe keyword would be buffer amplifier or distribution amplifier.Think about and check what signal level you'll usually need, I think something like +7 to +10 dBm sine wave into 50 ohms is quite common.Also think about whether you want electrically isolated (floating) outputs. I personally feel these are very nice to have - but it's more effort/costs of course."
},
{
"post_id": "",
"author": "G0HZU",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 10, 2013, 12:14:42 am",
"content": "One thing I would advise (if you want to preserve accuracy and stability of a good OCXO) is that you buffer the output well before you then fan it out to 4 outputs. This is to prevent short term load pulling of the OCXO each time you connect something to one of the outputs.I wouldn't worry too much about using a 10MHz square wave as my 10MHz OCXO (in a box) has a square wave output and this makes it compatible as an external reference for various counters or signal generators I have here.You can always filter the square wave to a sine wave for some of your outputs anyway?A lot depends on what accuracy you want or expect from it. Don't get too drawn into trying for fabulous stability or accuracy because there is little point in having this. I'm happy if my 10MHz OCXO is within 0.2Hz of 10MHz over several months of ageing. Usually it's better than this but I have resisted going for Rubidium or GPS locked standards. I did design and build a 10MHz (locked to 198kHz) offair standard many years ago and I use this to check all my various 10MHz references and keep them within 0.2Hz at 10MHz"
},
{
"post_id": "",
"author": "M0BSW",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "December 10, 2013, 07:22:31 am",
"content": "Quote from: G0HZU on December 10, 2013, 12:14:42 amThank you , I just want it for referencing , and for the experience of building one, because I'm at a stage where I can, I have emailed Gerry Sweeney, who has had a lot of experience with these, and has given me some valuable advice on the OCXO and in particular the one I've bought, plus how to make it go to sine wave by the use of a 10Mhz filter, re amplifying the signal in the buffer stage, so I could I guess have two sine wave and two square wave outputs.Paul"
}
] |
2025-10-17T20:12:00.471148
| 8
|
electronics
|
beginners
| true
|
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