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2025-10-19 01:29:01
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https://www.eevblog.com/forum/beginners/2n2222a-complementary-is-realy-2n2907a-!!/
|
2N2222A complementary is realy 2N2907A ?!?! - Page 1
|
[
{
"post_id": "",
"author": "Axel1973",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "December 25, 2011, 09:27:57 pm",
"content": "Hi there,today i downloaded a datasheet for the 2n2222A NPN transistor and i got curious about what transistor would be its complementary one. some internet search got me to the 2N2907A which is mentioned as its complementary on many websites...BUT..i figgured that there seem to be DIFFERENT Ic Ratings on this one!The 2N2222a is rated with a max Ic as 0.8A.The 2N2907A is rated with max Ic as 0.6A.HOW COME??Is a complementary not supposed to support the same ratings, just at the opposite polarity ??Thanks for your help!best regardsAxel"
},
{
"post_id": "",
"author": "Simon",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "December 25, 2011, 10:16:04 pm",
"content": "not sure how it works but I think IRF540 and 9540 are complements (mosfets) but the N channel is 33A and the P chanel one is 23 amps while the N channel has lower full on resistance so well put of balancefor your BJT's gain and base specs are probably what need to be matched"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 25, 2011, 10:20:16 pm",
"content": "P-type devices generally have poorer characteristics to their N-type counterparts."
},
{
"post_id": "",
"author": "amspire",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 26, 2011, 01:37:16 am",
"content": "Since the properties of P-Type and N-Type semiconductor are so different, it is impossible to make geniune totally matching complimentary pairs.So when you see a complimentary pair, they are usually two completely different transistor designs chosen so that they have a similar voltage capability, current rating, current gain, collector to base capacitance and package type. Usually this means the PNP transistor has to be larger then the NPN for the same current capability. Here are some typical chip layouts:The layouts are different, but they are at least in the same type of layout. A small signal low-noise transistor, a RF transistor, a high voltage transistor or a switching transistor all have noticeably different styles of layouts.In many ways, the maximum current rating is not that important as the transistor is performing pretty poorly at that point. The 2N2222A and the 2N2907A would be usually used at 300mA or less and a working voltage of less then 50V, and they are great general purpose transistors in this range.Richard"
},
{
"post_id": "",
"author": "westfw",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 27, 2011, 09:56:57 am",
"content": "Huh. Just what does it mean for transistors to be \"complimentary\", anyway? I mean, even within a particular part number one expects some significant variation in parameters, which you then go on to compensate for by careful circuit design. There have to quite a broad number of transistors that will \"complement\" the parameters of any particular transistor, if you only want some significant \"overlapping but opposite\" parameters."
},
{
"post_id": "",
"author": "amspire",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 27, 2011, 12:41:46 pm",
"content": "Back in the days of Germanium transistors, they did actually sell matched complimentary pairs selected to give the best performance in the fairly basic output amplifier stages of transistor radios. We are talking about reducing the 1kHz distortion from 5% down to perhaps 2%. In the 60's, the high price of transistors meant that designs used the absolute minimal transistor count. An example was the Mullard (bought by Philips) AC127 and AC128 1W output transistor pair.But I think for at least the last 40 years, people have been designing amplifiers to use any off the shelf parts. The cost of transistors is no longer a big issue, so you can use as many as you need to avoid any special custom-selected parts in manufacture.So the meaning now of a \"complimentary pair\" is really a NPN and a PNP transistor pair that have broadly similar specs.Richard."
},
{
"post_id": "",
"author": "ejeffrey",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 27, 2011, 03:47:21 pm",
"content": "Quote from: westfw on December 27, 2011, 09:56:57 amIt means that they are considered suitable for use in a push-pull driver (such as a class AB amplifier output stage). They will generally be lots of devices you could use, but the designated compliments will be suitable choices from the same manufacturer and process generation with similar characteristics. Generally you should be able to pick a complimentary pair and design around the P device.A big advantage of using complimentary pairs is that they are likely to be available together from the same supplier. Picking two random transistors nearly doubles your chances of having one of the parts discontinued or unavailable."
},
{
"post_id": "",
"author": "Axel1973",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "December 27, 2011, 04:56:02 pm",
"content": "WOW!Well THANKS TO ALL who replied! There been realy good explainations with it so i just learned something new again.Question SOLVED!best wishesAxel"
}
] |
2025-10-17T20:37:04.395261
| 8
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2n2222a-pins-are-ebc-or-cbe/
|
2N2222A - pins are EBC or CBE? - Page 1
|
[
{
"post_id": "",
"author": "YurkshireLad",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "March 02, 2022, 12:52:57 am",
"content": "I have a plastic TO-92 NPN transistor marked 2N2222A-1726. Searches for 2N2222A show datasheets for metal body transistors. P2N2222A show a TO-92, with pins from the front of CBE. I've seen references online to TO-92 2N2222A with pins of EBC. I found an old thread on these forums with a similar question (the site said \"do you really want to reply to this old thread?) but it didn't really make it any clearer. How do I know exactly what I have and what the pins are?The old thread is -https://www.eevblog.com/forum/beginners/identify-manufactor-for-simple-2n2222a/msg3671485/#msg3671485"
},
{
"post_id": "",
"author": "free_electron",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2022, 01:09:06 am",
"content": "measure it ... some manufacturers use different pinouts... bc817 is another notorius one . same for bs170 and bs250 ..."
},
{
"post_id": "",
"author": "YurkshireLad",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "March 02, 2022, 01:16:38 am",
"content": "Thanks. I will have to read how to measure it."
},
{
"post_id": "",
"author": "bob91343",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2022, 02:02:41 am",
"content": "Measuring is easy. I suggest either of two methods.1) An ohmmeter will show which pin is the base, as it will be the only pin that, when made positive, will conduct.2) The cute little Chinese component tester will show you immediately what the pinout is.You can also contact the manufacturer, if you know who they are."
},
{
"post_id": "",
"author": "edavid",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2022, 02:48:50 am",
"content": "The PN2222A EBC part was much more popular than the P2N2222A CBE part.Normally I would say try EBC first, but considering the way your part is marked... who knowsDo you have a DMM with an HFEtest function? That should be good enough."
},
{
"post_id": "",
"author": "Terry Bites",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2022, 11:56:04 am",
"content": "I'm inclined to believe the ON Semi data sheet- they are one of the few (only) suppliers of the TO-92 packaged part.https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwik0LS7raf2AhX6QUEAHe4SBagQFnoECAMQAQ&url=https%3A%2F%2Fwww.onsemi.com%2Fpdf%2Fdatasheet%2Fp2n2222a-d.pdf&usg=AOvVaw07YtuP6oWOLXEudI62AaUO"
},
{
"post_id": "",
"author": "themadhippy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2022, 12:40:58 pm",
"content": "QuoteBog standard low ohms range or diode /continuity range will do."
},
{
"post_id": "",
"author": "YurkshireLad",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "March 02, 2022, 01:14:44 pm",
"content": "Quote from: edavid on March 02, 2022, 02:48:50 amI will check today. Thanks all."
},
{
"post_id": "",
"author": "RoGeorge",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2022, 01:39:36 pm",
"content": "Typical BE reverse breakdown voltage is about 6V, while the BC breakdown voltage is much higher. Based on this, you can do one of these:- measure each junction resistance reverse polarized. Depending on the DMM you have, you might be able to see the difference between BE and BC by measuring the resistance of each junction when reverse polarized, the BE has a smaller resistance than the BC when reverse polarized, but this might not work.- measure the reverse voltage drop on each junction. Put in series a 20-30V power supply, a 100 k\\$\\Omega\\$ resistor, and the junction of the transistor as a diode reverse polarized. Measure the voltage drop on the transistor junction while reverse polarized. The reverse voltage on the BE should be much lower than the reverse voltage on BC.- same as above, but use the internal voltmeter's resistance instead of the 100k limiting resistor. Put the voltmeter in series with the reverse polarized junction and the source. BE will only \"take away\" about 6V out of the total voltage, the rest will be to be seen on the voltmeter, while the CE will \"take away\" most of the volts so the DMM will should display close to nothing (or less volts anyways than when doing the same with the BE)."
},
{
"post_id": "",
"author": "macboy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2022, 02:19:19 pm",
"content": "This is one case where the much loathed \"Transistor tester\" capability of a DMM comes in very handy. It takes only a few seconds to poke the device into the socket a few different ways until a sane hFE is displayed."
},
{
"post_id": "",
"author": "edavid",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2022, 03:17:50 pm",
"content": "Quote from: Terry Bites on March 02, 2022, 11:56:04 amYou are missing the point - there were (at least) 2 different TO-92 versions of the 2N2222A, with different part numbers and pinouts. OP's part's marking doesn't match either part number.PN2222A EBChttps://www.onsemi.com/pdf/datasheet/pn2222a-d.pdfP2N2222A CBEhttps://www.onsemi.com/pdf/datasheet/p2n2222a-d.pdf"
},
{
"post_id": "",
"author": "CaptDon",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2022, 03:41:55 pm",
"content": "If you don't know how to measure a transistor to figure out its basing what are you doing with the transistor in the first place? Nobody even mentioned the rare but existing ECB basing for rebranded 2N2222A parts shipped from the land of opiates and shitty fake electronic parts. It is anybody's guess these days."
},
{
"post_id": "",
"author": "Ground_Loop",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 02, 2022, 05:35:37 pm",
"content": "The typically unhelpful reply not withstanding. Do this:1. With a multimeter that has diode check connect the positive meter lead to any pin and the negative lead to one of the remaining. if you get a voltage reading somewhere between 0 VDC and 1 VDC (typically 0.5-0.7) the positive lead is on the base terminal.2. if no reading repeat 1. until you have identified the base terminal.3. With the base identified, move the negative lead to the third terminal. A slightly higher voltage reading indicates the the negative lead is now on the emitter. A slightly lower voltage reading indicates the negative lead is on the collector.This procedure is for NPN transistors. For PNP reverse the lead polarities. If at any point you get a 0 VDC reading the device is shorted."
},
{
"post_id": "",
"author": "TimFox",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2022, 05:37:52 pm",
"content": "Note that the plastic-case versions of this transistor are labeled PN2222A or P2N2222A.The original nomenclature 2N2222A (JEDEC registration) should be reserved for the metal case part (TO-18 case).Besides the pin order, the electrical specifications of the plastic versions differ from the JEDEC 2N2222A metal version."
},
{
"post_id": "",
"author": "edavid",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2022, 05:55:16 pm",
"content": "Quote from: Ground_Loop on March 02, 2022, 05:35:37 pmFor a PN2222, and a random cheap DMM in diode test mode, I found the difference was about 10mV (630mV vs 620mV). You have to act fast since it drifts quickly as the part warms up."
},
{
"post_id": "",
"author": "YurkshireLad",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "March 02, 2022, 07:42:22 pm",
"content": "Quote from: Ground_Loop on March 02, 2022, 05:35:37 pmIt may be EBC. For step 3, I get 0.72v with the negative on the first pin, and 0.72v with the negative on the third pin, though it drops to 0.71v after a second or so.Thanks"
},
{
"post_id": "",
"author": "fourfathom",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2022, 08:24:13 pm",
"content": "I think HFEor base-emitter reverse breakdown are the better ways to determine pinout. The forward-biased B-E and B-C junction voltages are just too close."
},
{
"post_id": "",
"author": "TimFox",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2022, 08:57:34 pm",
"content": "Base-emitter breakdown should be a definitive test, but be careful not to run much current for a long time in that condition, since it will result in degradation inhFEand noise.Almost all silicon transistors have a B-E breakdown between 5 and 7 V, but the C-B breakdown is usually above 20 V. ON rates the P2N2222A for minimum 70 V forVCBObreakdown (emitter open), but 6 V forVEBO(collector open).This articlehttps://downloads.hindawi.com/journals/apec/2001/053209.pdfspecifically tested 2N2222As."
},
{
"post_id": "",
"author": "Ground_Loop",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 02, 2022, 10:47:48 pm",
"content": "Quote from: fourfathom on March 02, 2022, 08:24:13 pmAgree this is more definitive, but forward voltage drop can be done with minimal equipment and connections."
},
{
"post_id": "",
"author": "TimFox",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 02, 2022, 11:49:47 pm",
"content": "As shown above, the forward voltages of the two PN junctions in an NPN transistor cannot be differentiated reliably. The breakdown voltages are very different."
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 03, 2022, 02:19:57 am",
"content": "I just did some testing and had no problem distinguishing the emitter from the collector by the emitter's slightly higher voltage drop. It may be only 5 millivolts, but the readings were always stable.A reverse breakdown test risks damaging some transistors, and some rare transistors have a high base-emitter breakdown anyway."
},
{
"post_id": "",
"author": "YurkshireLad",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "March 03, 2022, 02:45:25 am",
"content": "My DMM is too cheap and inaccurate."
},
{
"post_id": "",
"author": "TimFox",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 03, 2022, 03:51:04 am",
"content": "Quote from: David Hess on March 03, 2022, 02:19:57 amIf the difference between forward-bias voltages is only 5 mV out of 600 to 700 mV, how do you know which one is which? Certainly not by the datasheet."
},
{
"post_id": "",
"author": "bob91343",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 03, 2022, 05:16:22 am",
"content": "Just measure the breakdown voltage. Or rather, connect the junction in reverse polarity to a power supply via a series resistor of, say, 10,000 Ohms and measure the current. Raise the voltage on each junction until you start to see some current. When the voltage gets to 10 Volts, the base-emitter should draw about 50 microamperes. The base-collector junction very much less, essentially zero."
},
{
"post_id": "",
"author": "magic",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 03, 2022, 06:30:47 am",
"content": "Or build the hFE test circuit used in cheap DMMs.It assumes 0.7V base voltage, sends ~10µA to the base and measures the resulting collector/emitter current.Not super accurate, but you will easily see a difference if you insert the transistor backwards.Another simple solution: smash it with a hammer; the terminal connected with a big metal plate behind the front face of the packageiswas the collector."
},
{
"post_id": "",
"author": "CaptDon",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 03, 2022, 02:46:30 pm",
"content": "To the O.P., Many digital multimeters today use a somewhat standard method to measure things using the DIODE position. It is often a constant current source set to 1 milliamp. The current alone is deemed insufficient to damage solid state devices. Typical diodes will read something between .625 to .685 (or maybe 625 to 685 depending on your meter) and that is the actual measured voltage drop across the junction when forward biased. When reverse biased it will generally read like an open circuit although old germanium transistors often show a lot of leakage. Some transistors have internal diodes that may throw you off. Mosfets often have a body diode from S to D and that will throw you off unless you expect it. As you are testing mosfets they may appear shorted S to D if there is a residual gate charge remaining. Be aware that good meters limit the open circuit test voltage to 1vdc up to maybe 1.5vdc, this will not harm 99.99% of solid state devices. There are SOME meters that use as much as 9vdc and I have one that is 22vdc. This will destroy many fets and mosfets by breaking down the sensitive gate layer so be careful and know your meters O.C.V.!! As other posters have stated the forward biased E/B junction will tend to be a few millivolts higher than the B/C junction. It varies with design. I have good transistors with identical readings, although generally 'identical readings' indicate a transistor with some sort of failure mode present, usually shorted E to C or very high leakage and low gain. Meters with 1vdc O.C.V. won't test LED's very well. Cheers!!"
},
{
"post_id": "",
"author": "TimFox",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 03, 2022, 02:54:22 pm",
"content": "A simple test using not much more than a DMM:First, using either the diode mode or a resistance mode, identify the two PN diodes in the NPN structure and their forward direction.Then, use a 9 V battery in series with, say, 40 k ohms (anywhere from 30 to 50 would do).Connect that to the 10 megohm input of the DMM in voltage mode, and you will measure close to 9 V.Connect that to each of these diodes:If you measure < 1 V, you are in the forward direction and should reverse the connections to the diode.If you measure close to 9 V, you have found the C-B diode, whose breakdown voltage should be larger than 9 V.If you measure between 5 and 7 V, you have found the B-E diode, and are applying between 100 uA and 50 uA (with 40 k)--disconnect quickly.Really old germanium transistors had BE breakdown voltages comparable to the CB breakdown, but virtually all planar silicon transistors have this low breakdown voltage as a feature."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 06, 2022, 06:41:54 pm",
"content": "If the diode check is inconclusive. I recommend the hFEtest, over breakdown voltage, because it doesn't damage the transistor and a much lower voltage is more convenient. All that's needed is a resistor 10k to 1M and a 1V to 5V power supply. Connect the base to the collector/emitter via the resistor, with the power between the collector and emitter and measure the current draw. The circuit will pull the most current, when the resistor is connected between the base and collector and the emitter is negative. Don't leave it connected for too long, as the hFEincreases with temperature which means the transistor can get too hot. It's better to start with lower voltages/higher value resistors."
},
{
"post_id": "",
"author": "RoGeorge",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 06, 2022, 07:38:04 pm",
"content": "Quote from: Zero999 on March 06, 2022, 06:41:54 pmThat would make a very clean distinction (in case measuring Vbe and Vbc doesn't).I didn't try, but instead of a 3V power supply those 3V could be as well coming from the DMM set on measuring diodes. Q1 will show open, and Q2 about 1V (on the DMM set on diodes range)."
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 06, 2022, 11:16:23 pm",
"content": "Quote from: TimFox on March 03, 2022, 03:51:04 amI tested a bunch where I already knew the pinout, and the emitter junctions all had higher voltage drop than the collector junctions."
}
] |
2025-10-17T17:13:52.461995
| 30
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2n2907-pnp-transistor-as-temperature-sensor/
|
2N2907 PNP transistor as temperature sensor - Page 1
|
[
{
"post_id": "",
"author": "alex.martinez",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 10, 2019, 06:46:00 pm",
"content": "Howdy!,I have been recently into temperature sensing applications and I'm testing different methods to read this magnitude. Thermocouples and dedicated IC's are cool, but using a diode-connected BJT is even cooler (no pun intended). From what I have read in Analog Devices application notes, a current has to be injected into the diode-connected transistors. I achieve this by using a sketchy current source consisting of another 2N2907 and an opamp (I'm using an LM324).In order to read the temperature I probe the Vbe through a voltage buffer (to isolate it) and then I try to subtract a DC offset of 500 mV for latter amplification. Point is, that I cannot get to amplify it correctly.The current source is set to output 250 uA (probed, and it does maintain such level) and the Vbe stays at around 580 mV. Whenever I heat it there is a variation in temperature (drop in voltage due to a negative temperature coefficient). However, when it comes to probing and amplifying it, I'm getting some unknown issue to me. That is why I wanted to ask in the forum if there is any wrong assumption in the schematic, attached below.Thanks in advance,Alex.EDIT1: Fixed opamps on schematic."
},
{
"post_id": "",
"author": "StillTrying",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 10, 2019, 07:51:00 pm",
"content": "The center op amp is connected in a nonsense way, input should be to its non inverting input."
},
{
"post_id": "",
"author": "alex.martinez",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 10, 2019, 07:57:32 pm",
"content": "Quote from: StillTrying on February 10, 2019, 07:51:00 pmThank you, I assembled the schematic quickly on LTSpice, the opamp is wired correctly on the breadboard (I'm using an LM324N with 4 opamps)."
},
{
"post_id": "",
"author": "StillTrying",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 10, 2019, 08:09:33 pm",
"content": "The feedback on the VOUT op amp is wrong! After that work out what the inputs of 580mV and 450mV should do."
},
{
"post_id": "",
"author": "alex.martinez",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 10, 2019, 08:20:43 pm",
"content": "Quote from: StillTrying on February 10, 2019, 08:09:33 pmYup...I messed up when orienting the opamps in the draft...Im an idiot. Just fixed it. with the resistor names in the re-uploaded schematics, VOUT = -Vbe*(R6/R5) + Vcc(Rb/(Ra+Rb))(1+R6/R5) = -4.54Vbe + 2.6This amounts to -0.06 V at the output and I guess it's outside the rails of the opamp...Thanks."
},
{
"post_id": "",
"author": "StillTrying",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 10, 2019, 08:56:09 pm",
"content": "Assuming inputs of 454mV and 580mV I make the output -118mV, but I don't use the formulas."
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 10, 2019, 11:46:35 pm",
"content": "Check out figure 11 ofLinear Technology application note 45shown below for how delta-Vbe temperature measurement works without calibration. The Tektronix DM501, DM502, and 7D13 all used this technique.Triple Vbe measurementis also possible to remove the effects of series resistance."
},
{
"post_id": "",
"author": "alex.martinez",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 11, 2019, 09:07:26 am",
"content": "Quote from: David Hess onTodayat 10:46:35 amLinear Technology application note 45shown below for how delta-Vbe temperature measurement works without calibration. The Tektronix DM501, DM502, and 7D13 all used this technique.Triple Vbe measurementis also possible to remove the effects of series resistance.Thank you! I had already read this application note, together with AN137. I am intending to perform a deltaVbe measurement with the schematic I attached on the original post, simple by chsnging the voltage reference on the opamp that is part of the current source to inject another known value, then mwasure both Vbe and obtain the change in potential.However, first I wanted to optimize the full scale voltage for the ADC that I am using."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 11, 2019, 12:16:39 pm",
"content": "250 µA is quite a lot of current and will heat up the sensor quite a bit. An advantage of the diode as a temperature sensor is that it can work with a low current and still have a relatively low impedance. So something like 1-10 µA should be sufficient.The amplifier can be non inverting - so no need for the extra buffer.Using digital decoding for the difference is a good idea, though it might need a little more resolution for the ADC: the difference is proportional to the absolute temperature. So a 8 Bit ADC would only get steps of a little over 1 K if the gain and offset are well chose.Just direct voltage reading could give higher resolution as higher gain could be used."
},
{
"post_id": "",
"author": "dzseki",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 11, 2019, 12:25:24 pm",
"content": "Professional industrial diode temperature sensors exclusively run at 10uA bias current and as it seems they prefer the CB junction instead for whatever reason, these are meant for cryogenic use manily down to only a few Kelvins."
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 11, 2019, 11:54:57 pm",
"content": "Quote from: alex.martinez on February 11, 2019, 09:07:26 amTektronix includes a detailed circuit description in their service manuals for theDM501,DM502, and7D13which is also worth reading."
},
{
"post_id": "",
"author": "jackthomson41",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "February 12, 2019, 08:18:43 am",
"content": "You are using2N2907as a temperature sensor, that's kind of a new thing for me and I still can't understand this how you are gonna implement it?Btw when I need temperature sensor I useDS18B20. I think you are trying to design a new temperature sensor may be. You can also check thisDS18B20 Simulation in Proteus."
},
{
"post_id": "",
"author": "alex.martinez",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 12, 2019, 10:17:15 am",
"content": "Quote from: Kleinstein on February 11, 2019, 12:16:39 pmTrue, but according to the datasheet if the transistor is at 250 uA the temperature coefficient is the most linear. I'm still tinkering with it, so I will try 10 uA as well.What I want to do in terms of ADC is to obtain the 100°C ∆Vbe and he 0°C ∆Vbe. Then subtract that offset and amplify to the full scale of the ADC (Arduino's 10 bit).Quote from: David Hess on February 11, 2019, 11:54:57 pmGonna check it this afternoon.Quote from: jackthomson41 on February 12, 2019, 08:18:43 amIt's just a bit of an experiment. Thilese parts are absurdly cheap when compariled to a dedicated temperature chip. Plus, a the end of the day, a diode connected BJT is what most silicon based chips use, but with different kinds of control systems."
},
{
"post_id": "",
"author": "StuartA",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "February 12, 2019, 06:16:29 pm",
"content": "Re the use of transistors as temperature sensors, am I right that they offer a more-linear response than a simple diode?I built a thermometer using a simple diode (silicon signal) many years ago, and that has linearity adequate for my purposes over 0-100'C when calibrated. The advantage it may offer over a transistor is that you can configure it so that one lead projects forward and is then folded back again, thus forming a very compact 'sensing pad'.I used it recently on a flanged resistor, together with K-type thermocouple sensor right along side. During fast heating, the diode was really fast to respond, always showing an appreciably higher reading than the thermocouple. During slow cooling, the two probes gave the same reading.S"
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 12, 2019, 07:14:17 pm",
"content": "Transistors are sometimes a little closer to an ideal diode than most real diodes, as the material tends to be a little cleaner. However there are plenty of diodes to choose from, so some can also be good enough.In some cases the transistor case may be more convenient (e.g. TO126)."
}
] |
2025-10-17T18:16:32.497336
| 15
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2n3569-in-odd-package/
|
2N3569 in odd package - Page 1
|
[
{
"post_id": "",
"author": "l0rd_hex",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 19, 2016, 09:39:33 pm",
"content": "Hi folks,I came across a project that has some Fairchild 2N3569 transistors in it but I don't see much documentation on the particular package... I think it might be the TO-105 but I'm not sure.I've attached a picture of it.I also tried to figure out which pins are which using the diode setting on my DMM. I get 2.044V between one pin (#1) and the other (#2), 0.715V between the same pin (#1) and another (#3) and 2.898V between #2 and #3. I am measuring this in-circuit however.Does anyone recognize this package and know the pinout?Thanks!"
},
{
"post_id": "",
"author": "nour",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 19, 2016, 09:45:12 pm",
"content": "how old those components"
},
{
"post_id": "",
"author": "dcel",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "February 19, 2016, 09:49:24 pm",
"content": "Case is to-39 plastic variant.CrOn edit: i just put 2n number into google with 'case' and found visual match."
},
{
"post_id": "",
"author": "Paul Price",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 19, 2016, 09:50:17 pm",
"content": "Usually the center lead is the base, the tab is the collector. If the center lead is the base you will see <.7V with an ohmmeter to the collector and emitter from the base. If you then hook the transistor up in a common-emitter circuit, emitter grounded, collector to +5V and apply a 100k to +5V to the base, you will find that reversing the collector and emitter will result in one configuration resulting in lower collector current, this is then the reversed connection of C and E. You can use a 1K resistor from the collector to +5."
},
{
"post_id": "",
"author": "chris_leyson",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 19, 2016, 10:08:45 pm",
"content": "Thats old school TO-105. Ceramic lead frame with epoxy encapsulation. Don't see it much but they did LEDs TO-105 style back in the day."
},
{
"post_id": "",
"author": "Cliff Matthews",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "February 19, 2016, 10:14:33 pm",
"content": "They're humorously called Glob top's. Collector is left of the flat side, and base is the middle on a 2N3641 I have in stock."
},
{
"post_id": "",
"author": "chris_leyson",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 19, 2016, 10:23:57 pm",
"content": "An amazing piece of metal glass ceramic dare I say valve or tube manufacturing, fucking good gas seal, and the semiconductor guys call them Glob top's. wtf"
},
{
"post_id": "",
"author": "chris_leyson",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 19, 2016, 10:50:19 pm",
"content": "Yeah man, keep it, it's semiconductor history. You don't find many glob tops, FETs LEDs Transistors. If I dig really deep I still won't find a glob top be it transistor fet or led."
},
{
"post_id": "",
"author": "Paul Price",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 19, 2016, 10:55:10 pm",
"content": "Having worked on more than a few instruments using this type of transistor cases, I can attest to the chance of these devices failing due to any combination of time and temperature to be quite high. Device reliability is not this case's strong point and that is likely why this device packaging has long-since been abandoned."
},
{
"post_id": "",
"author": "l0rd_hex",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 20, 2016, 12:12:39 am",
"content": "Wow, what an amazing response! Thank you one and all.For those who are curious this was from a vacuum pump controller I picked out of the electronics scrap pile at my University Chemistry department. There was an external head gauge that was hooked up to a UA741TC op-amp (on the board I showed), along with a potentiometer to set the desired trigger point (when the pumps should switch back on). From what I can tell the opamp switched on the transistor(s) which then switched on a relay which switched on a 30A / 120V mercury reed switch which powered some plugs on the back.The date code on the opamp is from late 77 so I imagine the rest of the components date from there too. I've included some pictures for the curious:"
},
{
"post_id": "",
"author": "timb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 20, 2016, 12:19:40 am",
"content": "I just pulled one of these out of an old Power Designs 2005A I was parting out last night. Never seen one before myself, either. Cute little packages."
},
{
"post_id": "",
"author": "Paul Price",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 20, 2016, 12:22:48 am",
"content": "The obvious question is, does that thing still be able and going to be put to work..or you just wanna whatsa whatsit?"
},
{
"post_id": "",
"author": "l0rd_hex",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 20, 2016, 01:11:04 am",
"content": "This beauty is long retired, I just snagged it from the electronic scrap pile because it looked interesting... plus my ZD-985 vacuum desoldering pump is hunnnnngry,"
},
{
"post_id": "",
"author": "timb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 20, 2016, 01:27:18 pm",
"content": "Quote from: timb on February 20, 2016, 12:19:40 amTook some closeup photos to share with the class. You can really see the \"Glop Top\" on the ceramic base in detail!"
}
] |
2025-10-17T19:24:16.703363
| 14
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2n3773-confusion/
|
2N3773 Confusion - Page 1
|
[
{
"post_id": "",
"author": "460voltclub",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "September 10, 2020, 04:13:35 pm",
"content": "I am building a subwoofer amplifier from a schematic. I have two 2n3773 transistors Pin #1 Base #2 Emitter #3 Collector. I have a +35V and a -35V rail. One 2n3773 transistor has the base connected to the emitter of a 2n6292. The 2n3773 emitter is connected to a 0.33 Ohm 5 Watt resistor at the speaker output. The 2n3773 collector is connected to +35 vdc.My confusion is how do I connect +35 vdc to a 2n3773 collector mounted on a heat sink."
},
{
"post_id": "",
"author": "TimFox",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 10, 2020, 04:19:56 pm",
"content": "If you are mounting both 2N3773s on a common heat sink, then you need to insulate both from the heat sink, or insulate one transistor and insulate the entire heat sink.There are TO-3 mounting packages available, with a thin insulating washer and insulated screw/nut/washer sets. You need to add a #6 solder lug on any insulated transistor to connect to the case, which is the collector of the 2N3773.The TO-220 and similar plastic power packages that are somewhat compatible with the TO-3 metal package have a third lead for the collector, along with the mounting pad on the back of the transistor.The Keystone mounting kithttps://www.mouser.com/ProductDetail/Keystone-Electronics/4734?qs=fP5bVVCrK%2FcGQnu5Gb90jQ%3D%3Dincludes a socket that has a connection through the screws to the TO-3 case.Be sure to put a thin coating of thermal grease on both sides of the washer to ensure good thermal contact to the TO-3 case and the heat sink."
},
{
"post_id": "",
"author": "dietert1",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 10, 2020, 04:31:05 pm",
"content": "Take care with the electrolytic capacitors C2 and C3. As far as i understand your schematic shows both of them in wrong polarity. An easy to correct mistake. C4 seems to be correct. C1 should be a foil capacitor.This is a typical beginner project. There are many parts missing that a commercial product would include. In my opinion the main omission is an output current limiter (output short circuit protection). Another omission is a capacitive voltage divider in the feedback (parallel to R5/R6). It helps a lot against unwanted high frequency instability. On the output a commercial amplifier would have a 4.7 Ohm & 100 nF absorber, also to avoid instability. Anyway, such projects are a very good starting point, and building a good audio amplifier is an art that some people spend their whole life on. Others just wire up some kind of integrated \"gain clone\" and it may appear simple but it isn't.Regards, Dieter"
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 10, 2020, 04:43:02 pm",
"content": "It feels so weird looking at a color bitmap rendition of what was high technology.....back in 1968.Suffice it to say, the schematic faithfully reproduces that level of development, and hasn't been updated in any way to offer such desirable features as:- Using cheap and available transistors- Stable biasing network- Wide frequency response- Low offset voltage- Class AB operation- Low distortion- Protected outputs (current limiting, thermal overload)These can be added through various means, but rather than discussing them, it would be much easier to just shop around for a newer circuit.A note, R14 isn't in the right place; I'm not sure if this oversight is historically correct or a transcription error, but it should be in the emitter circuit of Q6. That is, keep Q6 emitter tied with Q7 collector, and put the resistor between them and the output. This way, bias current creates a symmetrical voltage drop through R16 and R14, above and below the output voltage. These voltage drops correspond to D1-D2-(R9 || R10), which sets the bias current. I think between the rectifier diodes and the tiny resistance, this will be in class B operation, which saves on bias current and stability I suppose, but isn't well renowned for low distortion.Tim"
},
{
"post_id": "",
"author": "460voltclub",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "September 10, 2020, 05:33:36 pm",
"content": "Thanks for the input. I build and fix electronics for the fun of it. I have a 12 x 12 shed that is my \"Lab\" and I have a Pioneer car stereo for music. I have a subwoofer and power transistors in my \"maybe make something parts box\" and I wanted a simple sub amp to build.I repair truck PCM's and I have repaired 3 Tek O-scopes which I own. But for some reason I was having a brain fart and just couldn't get my head around this issue.Once I read your posts I had a \"Crap I remember now\" epiphany.Thank YouStevenTrue to my username I have been jolted with 120v, 208v, 240v and 460v several times.The last three phase 460 left three deep scars on my right arm.Sometimes you can't fix stupid."
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 10, 2020, 08:13:05 pm",
"content": "It'll certainly work, and it doesn't sound like you'd mind repairing it from time to time if it goes tits up... Maybe more inconvenient if a shorted transistor puts full DC in your speaker, extracting its magic smoke. I'd spend the few more components on a nicer design though. Can still use old transistors like 3773, they're slow and low gain, but that's just tweaking the compensation components, so long as you don't need the bandwidth. (Which, 10kHz BW would still be fine here, that gives plenty of loop gain down at subwoofer frequencies to help reduce distortion.)Yeah... Lower voltages are shocking in varying degrees, but 480V is just outright angry... You're lucky!Tim"
},
{
"post_id": "",
"author": "floobydust",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 10, 2020, 09:26:02 pm",
"content": "I get a kick out of people taking older 1970's circuits and giving them a trendy label, keeping the old transistors that are long obsolete, and voila it's all over the Internet.I would say C3 is too small for a \"subwoofer amplifier\" I think -3dB at 23.4Hz great back in the day when playing a warped record lol. R9 and R10 at 22R 1/2W seem way huge for the 11R 1W resistor they make, something is wrong with that. R3 is huge compared to R2.So when I see a couple design copy-pasta mistakes, I kinda wonder what the original design is. It seems to be British with BC108's and not Elektor font (BC108 pic) but from another UK hobby magazine or maybe Maplin.480V is fine but I did not like crawling around VFD's with hissing corona discharge, the DC bus is up there."
},
{
"post_id": "",
"author": "srb1954",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 11, 2020, 03:02:19 am",
"content": "Quote from: floobydust on September 10, 2020, 09:26:02 pmThe -3dB cut-off increases to something like 28Hz when you also take into account the effect of the input coupling cap C1 and input resistor R1."
},
{
"post_id": "",
"author": "srb1954",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 11, 2020, 03:09:03 am",
"content": "Quote from: T3sl4co1l on September 10, 2020, 04:43:02 pmIt is curious that the person drafting the schematic chose to colour code the transistors by type but kept the all resistors the same colour."
},
{
"post_id": "",
"author": "WattsThat",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 11, 2020, 03:52:29 am",
"content": "QuoteSays the guy from Canada while he is surrounded by 575V vfd’s with 900 volt rated dc busesBack in the days before insulated/CAT rated screwdrivers and touch safe terminal blocks, got nailed by 480, tightening terminal blocks with power on. It wasn’t pleasant. Rated right up there with peeing on an electric fence"
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 12, 2020, 12:39:34 pm",
"content": "Quote from: 460voltclub on September 10, 2020, 04:13:35 pmTypically the TO-3 transistor and hardware are electrically isolated from the heat sink and a tab is attached to one of the mounting screws. There are also insulated TO-3 sockets made to go under the heat sink which make this easier.So the collector connection is through one or both of the mounting bolts."
}
] |
2025-10-17T17:42:38.284822
| 11
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2n3904-ce-current-when-off/
|
2n3904 CE current when off? - Page 1
|
[
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 01, 2020, 03:00:29 pm",
"content": "I have a high side LED switch as per the arrangement in the first diagram on this page:https://learn.sparkfun.com/tutorials/transistors/applications-i-switchesMy Q1 is a 2n3904, my Vcc =10V, and I'm switching a white LED, for which I have no datasheet. However, I've measured the fully on voltage as about 3V at 20-25 mA, which is what I've used to choose the value of the collector resistor.I've noticed that when Q1 base is pulled to ground, the LED is visibly dark, but the off voltage is around 2V. I found this surprising, so I've measured the off collector current to be about 7 microA. I have two questions:1) Is an I-V characteristic of 2V at 7 microA usual for a white LED?2) Is the collector current quoted above unusual for a 2n3904 with a grounded base? It strikes me as high, but I can't find anything on the datasheets that allows me to confirm this."
},
{
"post_id": "",
"author": "Vovk_Z",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 01, 2020, 03:52:49 pm",
"content": "Fully on (closed) 2n3904 must have less then 0.5V CE voltage.Off state CE current is in \"Off characteristics\" on the second page of datashee from ONsemi. It is typical value at 25 C degrees, and can be higher with higher cristal temperatures."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 01, 2020, 04:09:18 pm",
"content": "Your statements aren't particularly clear, in terms of what values are measured simultaneouslyHowever, AoE x-chapters 2x.1 has measured the collector current with Vce=2V and Vbe=0V, to be <1nA, often several orders of magnitude less. But it doubles every 10 degrees C rise."
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 01, 2020, 05:58:21 pm",
"content": "Were you by any chance measuring by difference, and thus involving the 10Mohm (or whatever) resistance of your meter in the measurement?Also entirely possible that you have eBay/Ali special floor sweepings, and your \"2N3904\", isn't.Tim"
},
{
"post_id": "",
"author": "BravoV",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 01, 2020, 06:12:21 pm",
"content": "Quote from: T3sl4co1l on February 01, 2020, 05:58:21 pm"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 01, 2020, 07:30:58 pm",
"content": "Quote from: aneevuser on February 01, 2020, 03:00:29 pmYour post is very confusing. The first diagram in the link is a low side, not a high side switch.A white LED will light dimly with 7μA. The leakage current for the 2N3904 should be much less than that, with a collector-emitter voltage of 10V. Is it possible you've got the emitter and collector pins reversed?"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 01, 2020, 07:40:08 pm",
"content": "When electronics were your hobby I would recommend you to download the LTSpice and look at the results. The results are pretty good these days."
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 01, 2020, 11:06:47 pm",
"content": "Thanks for the replies - however, I've been seeing some other odd behaviour that I can't currently understand, so I want to rule out strange breadboard gremlins by making up a soldered circuit on veroboard. If all the problems then go away, at least I'll know where to start looking."
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 01, 2020, 11:11:49 pm",
"content": "Quote from: T3sl4co1l on February 01, 2020, 05:58:21 pmNot sure what you mean by \"difference\"QuoteThat's unlikely though not impossible, as I have two lots from different sources, one lot being at least 20 years old - transistors from both lots show the same behaviour AFAICS. The newer lot could be potentially be floor sweepings, though I've built several linear circuits from them without obvious problems."
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 01, 2020, 11:15:52 pm",
"content": "Quote from: Zero999 on February 01, 2020, 07:30:58 pmNo, it's definitely not that - in a moment of desperation I flipped the device wondering if it was mispackaged or I was blind or something, with no improvement."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 01, 2020, 11:23:35 pm",
"content": "Quote from: aneevuser on February 01, 2020, 11:06:47 pmWait a minute, are you using a solderless breadboard? If so, then weird behaviour is standard!Rule of thumb: you will spend more time debugging the solderless breadboard than your circuit."
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 02, 2020, 06:57:59 am",
"content": "Well, unless you've spilled tea on it, it shouldn't be particularly leaky. I've measured nA on one before, only obvious problem really, is the obvious physical problems, namely the ~4pF between rows.Can you show where and how you have taken these measurements?Tim"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 02, 2020, 09:25:38 am",
"content": "The resistance between the slots (long or short) is not measurable here on a cheapo solderless breadboard (34401A). The capacitance is typically 3.5pF between short slots (my measurements from past).Double check - take a 9V battery and solder 3904 with shorted base-emmiter with 220ohm resistor in collector.You should see <<1nA current.PS: to see the 7uA current the resistance has to be 1.1Mohm between the slots = (10V-2V)/7uA."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 02, 2020, 09:34:52 am",
"content": "Quote from: imo on February 02, 2020, 09:25:38 amThere certainly shouldn't be any measurable DC leakage on a decent solderless breadboard, but some aren't decent and there may be contamination.Your suggested test is sound. If done outside the breadboard it will also test whether the 2n3904 is working as expected."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 02, 2020, 10:00:06 am",
"content": "I've done the measurement on a cheapo solderless - 9v battery 200ohm and 3904 inserted into 3 slots. With shorted base-emitter I see no current (34401A). With floating base I see no current."
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 02, 2020, 02:34:37 pm",
"content": "Quote from: imo on February 02, 2020, 09:25:38 amYeah, I'll try this - I'm still baffled as to what's going on with the breadboard. I'll have to leave it till next weekend probably though - busy today and for a while.I've tried removing the LED from circuit and switching the resistor alone.When switching the resistor alone, I get V_BE(sat) = 0.8V and V_CE(sat)=65mV.When switching the LED+resistor, I get V_BE(sat) = 0.79V and V_CE(sat)=50mV.Both of these seem to be in spec. for a 2n3904.Anyway thanks - I'll remove the breadboard from the picture when I've got time."
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 02, 2020, 02:39:45 pm",
"content": "Quote from: T3sl4co1l on February 02, 2020, 06:57:59 amI'll try to put up more details next weekend if I haven't got to the bottom of it by then.Regardless, I'm not sure what you mean by \"where\" and \"how\" - I'm measuring the voltages and currents on a breadboarded circuit, using a couple of cheapish but adequate hand held multimeters. What specifically do you think I could be screwing up measurement-wise?"
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 02, 2020, 02:43:25 pm",
"content": "Quote from: tggzzz on February 01, 2020, 11:23:35 pmYeah, it's the prototyping system of Satan, but you know, millions do the same. Anyway at some point I'll solder up a dead-bug circuit to remove possible breadboard evilness from the picture."
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 02, 2020, 04:08:25 pm",
"content": "Stuff like --- What meter, what is its resistance, and at what voltages? Most meters are 10Mohm, but some switch to Hi-Z at low voltages, some are... like, who knows what kinds of bullshit from those $3 yellow thingies? (Which IIRC weren't so much bad because of impedance, but they were completely, utterly unfiltered, unprotected, useless in any real world environment.)- Were you measuring from +V to LED, or LED to GND? Or anywhere else?- Uh, I suppose if you were measuring in reverse, that might be a concern as well but I don't know offhand any meters that just screw up so badly when they read negative numbers. The fixed range POSs just read OVL I think, and reasonable ones just say it's negative.I suppose the circuit itself could be picking up RF too, for that matter? Unlikely, but possible.Tim"
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 03, 2020, 12:49:31 am",
"content": "7 microamps is way too high. The 2N3904 specification is something like 50 or 25 nanoamps maximum but this only represents the lowest value that the automatic test equipment can test for in a short period of time; in practice the leakage should be 10s of picoamps or even less in most cases.A small value capacitor across the base-emitter junction will suppress RF if that is a problem.To help with noise immunity, sometimes a diode is placed in series with the emitter which a high value resistor pulls up to 0.6 volts. Then the base can be pulled to -0.6 volts with respect to the emitter."
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 03, 2020, 12:27:57 pm",
"content": "OK, a couple more comments:1) I can't reproduce the 7 muA that I originally measured. That may have been user error, or breadboard problems or something - the off current I'm now measuring is 0 microA, which is the best my cheapo meter will do. I'll try to make up a current source to check the accuracy of the meter at some point - I did this in the past, but I didn't record the details, and I can only remember that I wasn't unhappy with the results (not sure how low I took the current either). (I've also measured a burden voltage of about 10mV/mA at 20mA, should anyone be interested)2) I've replaced the LED with a resistive load of 100 ohms, which is roughly the dynamic resistance of the LED at 30 mA. When I do this, everything looks just as I would expect - the voltage across the resistor drops to 0V when the the transistor is off - with the LED present, the voltage across it drops to about 2VThat mean anything to anyone?"
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 03, 2020, 01:07:12 pm",
"content": "Quote from: aneevuser on February 03, 2020, 12:27:57 pmNormally written µA or uA.QuoteThe LED isn't a linear resistor. Look at the LED's V-I curve to correlate the expected value with what you see."
},
{
"post_id": "",
"author": "fcb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 03, 2020, 01:10:25 pm",
"content": "Is it possible that your LED is acting as tiny solar cell? Does the 7uA change if you subject the LED to more or less ambient light?"
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 03, 2020, 01:30:12 pm",
"content": "Would have to be direct sunlight to get that much current from most LEDs, I think. PV yes, but awful efficiency.Could just be the I-D-ten-T effect, or the observer effect. Shrug.Tim"
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 03, 2020, 02:33:08 pm",
"content": "Quote from: tggzzz on February 03, 2020, 01:07:12 pmIf I had an I-V curve for the diode, I'd hardly need to post this thread. I don't have a spec. for the diodes, and I can't find a datasheet that specifies the I-V characteristics for white LEDs at the low currents I'd expect when the transistor is off. I guess it's not impossible that the 2-ish V that I see is expected, but without the I-V data, I have no idea."
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 03, 2020, 02:37:55 pm",
"content": "Quote from: T3sl4co1l on February 03, 2020, 01:30:12 pmIf you're talking about the 7 muA, then I'd forget it - I can't reproduce that measurement now, so I'm assuming that was spurious.Quote\"I-D-ten-T effect\" ? You'll have to clue me in there."
},
{
"post_id": "",
"author": "fcb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 03, 2020, 02:53:28 pm",
"content": "Quote from: aneevuser on February 03, 2020, 02:37:55 pmJust measured the C-E (with B connected to E) leakage on a similar transistor (2N4401) at 10V at <0.1nA (7000x less than your measurement). So something wrong with what you are doing, please show a schematic of how you are measuring stuff."
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 03, 2020, 05:35:37 pm",
"content": "Quote from: aneevuser on February 03, 2020, 02:37:55 pm\"ID10T\". Also, \"error exists between user and keyboard\", etc.Happens to us all, from time to time.Tim"
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 04, 2020, 09:10:43 am",
"content": "Quote from: fcb on February 03, 2020, 02:53:28 pmYes, as I mention in the text you quoted, I can't reproduce that measurement - ignore it, it's probably spurious."
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 04, 2020, 09:21:31 am",
"content": "Quote from: T3sl4co1l on February 03, 2020, 05:35:37 pmAh, right - for some reason, I was reading it as \"identity\". The current measurement probably is indeed a fine example of that effect.But to return to the main issue, I've found a datasheet for a random white LED -https://www.vishay.com/docs/81159/vlhw5100.pdf- which presents an I-V curve. I note that the scale ends at I = 1mA with V = 2.6V, which goes nowhere near the currents that I'd be interested in - anyone know what the significance of these values are? I guess you could try to extrapolate the curve assuming that it remains exponential all the way down to, say, 1 nA, but that's 6 orders of magnitude - is that sensible?"
},
{
"post_id": "",
"author": "fcb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 04, 2020, 09:45:49 am",
"content": "There is literally no point in plotting an IV curve below say 1mA (or whatever puts out a useful amount of light)."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 04, 2020, 11:48:20 am",
"content": "Quote from: aneevuser on February 04, 2020, 09:21:31 amUnsurprisingly the manufacturer thinks users aren't interested in operating the LED in that regime, and they can't be bothered to test/guarantee it.I'd try extrapolating, and see what you come up with.However, \"strange\" things can and do happen, e.g. with leakage in BJTs and JFETs - download 2x.1 fromhttps://x.artofelectronics.net/the-book/sample-chapter/for some measurements"
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 06, 2020, 11:16:19 am",
"content": "OK folks, I've had some time to play around with this a bit more, and I think I know what is going on.1) I'm driving the base resistor of the 2n3904 from a sig. gen. switching between 0 and 5V.2) If I measure the voltage between ground and the bottom of the diode with either a scope or a multimeter, the off voltage across the diode is about 2.2V, as measured by another meter. The diode does not visibly illuminate. I have found that even with the scope turned off but the probe connected this situation holds.3) If I make no measurement from ground to the bottom of the diode (i.e. scope or meter disconnected), but measure only the voltage across the diode, the off voltage is about 0.1 mV at most.4) If I touch the bottom of the diode with a finger, the off voltage across goes up to about 50mV; if I simultaneously touch ground with another figure, the off voltage goes up to 2.2V.From this, I deduce that when measuring the voltage between ground and the bottom of the diode, the measuring device is allowing a small but in-this-case-significant leakage current which corresponds to the 2.2V measured but which is insufficient to illuminate the diode.Makes sense?"
},
{
"post_id": "",
"author": "Howardlong",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 06, 2020, 11:59:25 am",
"content": "Quote from: T3sl4co1l on February 02, 2020, 06:57:59 amI concur, last week I was making some SMU measurements on a micorcontroller claiming 1nA sleep current, showing low hundreds of picoamps on solderless breadboard."
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 06, 2020, 01:01:38 pm",
"content": "Yup, that was my guess, measurement method -- if you're measuring across the switch, the meter's leakage (typically 10MΩ) biases the diode. It will be visible in a dark room, with dark-adapted eyes, but not really otherwise. Measuring across the diode, you measure the transistor's leakage, which is small.The true answer is somewhere inbetween -- you'd need a hi-Z meter to measure the voltage at that node without influencing its voltage. A nulling measurement with a potentiometer can be performed to get a closer answer, for example.You can then take the difference of the two measurements, and determine the impedance of the node.Tim"
},
{
"post_id": "",
"author": "Howardlong",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 06, 2020, 09:06:22 pm",
"content": "Quote from: Howardlong on February 06, 2020, 11:59:25 amJust measured adjacent rows on one of these on an SMU:https://www.rapidonline.com/K-H-AD-102-Advanced-Solderless-Breadboard-456-Tie-Points-34-0676?IncVat=1&pdg=pla-301834875110:kwd-301834875110:cmp-757438067:adg-44804851896:crv-207912323492:pid-34-0676:dev-c&gclid=CjwKCAiAj-_xBRBjEiwAmRbqYgidQlCW4OlHqXF41tdvRWRvCuUjU5v1K1YE_D-S_p5YaaPHqr__WRoC9SwQAvD_BwE6.0pA at 100V, or 16 terra ohms."
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 07, 2020, 07:12:54 pm",
"content": "Quote from: T3sl4co1l on February 06, 2020, 01:01:38 pmWell, the mystery seems to be solved, but it's a bit of a pain - I can't use my standard scope probes to look at the voltage on that diode - are there some fancy HiZ scope probes that I need?"
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 07, 2020, 07:16:34 pm",
"content": "Quote from: Howardlong on February 06, 2020, 11:59:25 amI'm reasonably certain now that the transistor is not at fault, given what I have discovered - I've used them in linear circuits a fair bit, and I probably would have noticed if they were significantly out of spec. I don't have any meter fancy enough to measure currents low enough to confirm it for sure though."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 07, 2020, 08:34:57 pm",
"content": "Quote from: aneevuser on February 07, 2020, 07:12:54 pmDepending on the specific ratios of parameters, you may be able to use a standard 10Mohm *10 probe, but you would have to factor in the effect it has on the measurement.But that is true for any probe, and indeed any measuring device and measurement."
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 15, 2022, 03:36:08 pm",
"content": "I've just spent about 2 hours being baffled by this phenomenom once again, with a different circuit (constant current mosfet LED driver) before déja vu kicked in, and I recalled this thread.Having investigated it a little further, I find that with 8 V at the top of a white diode:a) and nothing but a x10 scope probe at the bottom, there's a diode current of about 500 nA with 2.2 V across the diode, which is enough to illuminate the diode sufficiently to be just visible with normal room illumination, and clearly in a darkened room.b) and the mosfet (IRLZ34N) turned fully off, there's no measurable diode current, and no visible illumination of the diode even in a darkened room.which I guess tells me that the drain-source leakage current of the mosfet is much less than 500 nA when off. So at least I've learnt something."
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 15, 2022, 04:05:00 pm",
"content": "Is your LED unique or is it likely to have the same IV characteristics of any other while LED?http://www1.futureelectronics.com/doc/EVERLIGHT%C2%A0/334-15__T1C1-4WYA.pdf"
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 15, 2022, 04:16:11 pm",
"content": "Quote from: aneevuser on February 07, 2020, 07:12:54 pmI don't know the status of Dave's Microcurrent Gold:https://www.eevblog.com/projects/ucurrent/It shows as Out Of Stockhttps://www.eevblog.com/product/ucurrentgold/The design info is readily available so you could build your own."
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 15, 2022, 05:01:00 pm",
"content": "Quote from: rstofer on May 15, 2022, 04:05:00 pmIt's unlikely to be unique but the datasheets don't give useful information for intensity/forward voltage at the low currents (sub micro-amp) that I'm seeing (the one above shows a forward 2.6 V at 0 mA, for example) so they're not particularly useful for clueless individuals who don't know when to expect to see the LEDs glowing, or what-seemed-to-me suspiciously high forward voltage when \"off\".Anyway, it's not really a problem, now that I've reminded myself of the cause, and the unmeasured circuit seems to behave correctly w.r.t LED illumination when off, so I'm happy for now. Anyway, I'm really using this thread to as an online note-to-self (and maybe other noobs) for when I run into the problem again, in a year or two."
},
{
"post_id": "",
"author": "aneevuser",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 15, 2022, 05:03:24 pm",
"content": "Quote from: rstofer on May 15, 2022, 04:16:11 pmThat looks to be pretty interesting - I'll take a look at it. Thanks."
},
{
"post_id": "",
"author": "Doctorandus_P",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 17, 2022, 06:21:13 pm",
"content": "TLDnR.Some LED's also work a bit as photocells, and can generate a voltage close to their \"on\" voltage when a bright enough light shines on it."
},
{
"post_id": "",
"author": "Howardlong",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 17, 2022, 07:25:38 pm",
"content": "Quote from: Doctorandus_P on May 17, 2022, 06:21:13 pmCorrect, and of you use LEDs for status or debugging ultra low power applications, this can lead to some head scratching.eg, the DUT doesn’t work as expected under the microscope where there’s lots of light."
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 17, 2022, 07:47:43 pm",
"content": "Quote from: Doctorandus_P on May 17, 2022, 06:21:13 pmAll of them in fact; it's an intrinsic property of semiconductor junctions.It's just not usually very much, some ~uA in bright light even, I think? The LED chip is quite small, and the lens (let alone diffused) doesn't work well as a receiver. But yeah, still something.Tim"
}
] |
2025-10-17T17:10:39.277916
| 47
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2n3904-datasheet-small-signal-specs-are-for-common-emitter-or-common-base/
|
2N3904 datasheet small signal specs are for common emitter, or common base? - Page 1
|
[
{
"post_id": "",
"author": "RoGeorge",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "September 22, 2024, 12:34:18 pm",
"content": "In page 2 of the datasheethttps://www.onsemi.com/pdf/datasheet/2n3904-d.pdf, at the table for \"SMALL− SIGNAL CHARACTERISTICS\", what does theCoboandCibo(input and output capacitance) refers to?"
},
{
"post_id": "",
"author": "Roehrenonkel",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 22, 2024, 12:40:19 pm",
"content": "Hi RoGeorge,...since it's for Ic/Ie=0 i'd say it's neither of them.Best regards"
},
{
"post_id": "",
"author": "G0HZU",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 22, 2024, 12:51:31 pm",
"content": "Pretty sure it’s for common base. That’s what the b refers to for Cibo.The i is input and the final o means output open.Cobo is for output with the input open. Both are common base."
},
{
"post_id": "",
"author": "RoGeorge",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "September 28, 2024, 07:31:10 am",
"content": "Just for the docs, accidentally found today this 2 pages AN from Infineon, which defines the notations:Application Note No. 024 - Parasitic Capacitance in Bipolar Junction Transistorshttps://eva.fing.edu.uy/pluginfile.php/68403/mod_resource/content/1/Parasitic_Capacitances_Bipolar_Transistors_AN024_Infineon.pdf"
}
] |
2025-10-17T16:29:52.409919
| 4
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2n3904-emitter-looking-funky/
|
2N3904 emitter looking funky - Page 1
|
[
{
"post_id": "",
"author": "sy",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "December 11, 2023, 07:42:30 am",
"content": "Hello, I am trying to rapidly switch a transistor (2n3904) on and off by using a square wave input.The square wave is 3Vpk-pk running at 200Hz with a 50% duty cycle and 1.5V offset.When I probe the emitter terminal (in orange) there seems to be some exponential decay. Is this a result of frequency response? I am new to this and not sure what I should be looking at to fix up the signal"
},
{
"post_id": "",
"author": "Andy Chee",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 11, 2023, 08:14:08 am",
"content": "If you're measuring the emitter, you should use an emitter resistor to ground, and probe the emitter-resistor junction."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 11, 2023, 08:26:33 am",
"content": "You cannot see that signal at the emitter, because the emitter in your schematics is grounded (and your o'scope probe is grounded as well).And in case you see a signal there in your real circuit - there has to be some parasitic impedance or resistance between the emitter and the \"ground\".And the decay comes from some parasitic capacitancies in your circuit (and in the transistor as well)."
},
{
"post_id": "",
"author": "gamalot",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 11, 2023, 08:44:28 am",
"content": "Could it be a very low quality breadboard? I once bought 2 pieces from a local store in Australia, and their contact resistance was very high!"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 11, 2023, 08:50:09 am",
"content": "Some breadboards have got split ground and Vcc (blue and red segmented) power lines - double check that.So your emitter is floating perhaps.."
},
{
"post_id": "",
"author": "ArdWar",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "December 11, 2023, 08:57:57 am",
"content": "There must be some misunderstanding here regarding your actual schematics and/or measurement setup. Not even the worst breadboard in the world will give ~1 volt drop at that level of current (and if itdid, it probably won't be that steady)."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 11, 2023, 09:11:36 am",
"content": "Your transistor with the floating (not grounded) emitter and the o'scope probe.."
},
{
"post_id": "",
"author": "sy",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "December 11, 2023, 12:05:21 pm",
"content": "I have separated the collector resistor to have an emitter loading resistor as suggested.My signal now looks more square, but I was wondering why the pk-pk voltage drop is around 1V?If the collector emitter voltage (Vce) is about 0.3V across a silicone diode, and I have a voltage divider between 33Ohm and 100Ohm, should I be expecting a ~2Vpk-pk?My scope channel is 1MOhm input impedance and AWG output impedance is high-z.I've gone ahead and measured the longest rail of the breadboard and it gives 0.1Ohms resistance so I dont think it would load the circuit down that muchProbing from ground to the collector (between R3 and pin3), the square wave jumps to 2.62V-2.92V. Does this mean my transistor is giving a 1V drop across Vce for some reason?"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 11, 2023, 12:30:04 pm",
"content": "That is because the transistor is a current controlled/acting device.The collector-emitter current is aprox 9mA, therefore at 100ohm emitter resistor you get 9mA*100ohm=900mV voltage.The aprox 0.3V voltage drop is at the collector's 33ohm resistor, therefore the collector voltage jumps from 3.0V to aprox 2.7V, therefore the collector-emitter voltage will not be 0.3V in your setup.You have to provide a larger base current to open the transistor more (Ic=beta*Ib) in order to saturate the transistor and thus get small collector-emitter voltage."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 11, 2023, 12:51:19 pm",
"content": "Look at this - various base currents..The simulation shows in order to get less than 0.4V between collector-emitter you would need the base resistor have smaller than 4k7 (aprox).You may calculate the base current as your homework"
},
{
"post_id": "",
"author": "sy",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "December 11, 2023, 01:03:36 pm",
"content": "Quote from: iMo on December 11, 2023, 12:30:04 pmI see, so that means if the transistor is not fully saturated then there will be a greater voltage drop across Vce?This was my thought process in terms of calculations:Ib = (3V-0.7V)/47k = 48uADC current gain for this transistor is 300Ic = 300*Ib = 14mABut already it seems off since you said there was 9mA flowing from collector to emitter.Say for example I wanted 15mA from collector to emitter, how would I do the calculations to choose a lower value resistor at the base to provide more current and open the transistor more?And also, what parameter are we looking for in the data sheet to know that the transistor is fully saturated?Thanks for all the help thus far @iMo"
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 11, 2023, 01:49:44 pm",
"content": "Quote from: sy on December 11, 2023, 01:03:36 pmYes.The base current calculation to saturate the transistor depends on the wiring you actually follow.Imagine you want to have 133ohm in your collector and 0 ohm in emitter (simplest example).When fully on the current via the 133ohm resistor will beIc = (3V-0.2V)/133ohm= 22mA (aprox), where 0.2V is the Vce saturation voltage (example)In order to create such an Ic you would need at leastIb = Ic / beta = 22mA / 300 = 73uA, for switching purposes we use say 5x more = 0.35mA (in order to saturate the transistor fully under all conditions, with high power apps it is even 10x)Resistor for the base (aprox):Rbase = (3V-0.7V)/0.35mA = 6500 ohm (aprox), where 0.7V is Vbe for silicon transistor (aprox).With the emitter resistor the calculation has to incorporate the voltage drop at the emitter resistor as well.In the datasheet for switching purposes at lower frequencies the most important params are the max Vce, max Ice, beta/h21e at the specific Ice current, sometimes the Vce_sat at the specific Ice current. Also the SOA (safe operating area graph) when messing with high voltages and currents is good to look at."
},
{
"post_id": "",
"author": "macboy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 11, 2023, 02:17:14 pm",
"content": "Q1 can source current to the output, so the output turns on rapidly.There is nothing to sink current from the output, except for the the probe's 10 Mohm to ground. This, combined with some stray capacitance of the breadboard, and the capacitance of the probe, results in the exponential decay you see. Just adding a resistor from emitter to ground will solve the problem by providing a current path from the output to ground, when the transistor is turned off (and when it is turned on of course). Try different values to see the effect. Don't go so low in value that excessive current is driven through the transistor and resistor. 10 ohm is too low, 100 ohm is probably fine... up to 100 Kohm or more will likely work too, but try it and observe the difference.edit:Haha, I just saw the grounded emitter and output - or what I assumed was the output, the yellow highlighted node... didn't expect that so my mind must have filtered it out.My comment above is only valid if the ground connection on the emitter/output is completely omitted, so the output is just the emitter of the transistor."
},
{
"post_id": "",
"author": "Yuu",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "December 11, 2023, 08:47:38 pm",
"content": "I recommend reading a book on analog analysis/design.Quote from: sy on December 11, 2023, 12:05:21 pmYou cannot assume \\( V_{CE} = 0.3\\, V \\). Look up regions of operation for the BJT. In the forward active region, \\( V_{CE}\\) can vary quite a bit while maintaining relatively constant \\(I_C\\). The only thing you can assume is that, when the transistor is on, you have about a 0.6V drop across the base-emitter junction (or across the emitter-base junction in the case of a PNP BJT).To figure out why you have a 1V drop from emitter to ground, analyze your circuit. Using Ohm's law when the input is high, we can derive a set of equations and then solve:\\[ V_B = V_E + 0.6,\\]\\[ 3 - V_C = 33 \\cdot I_C,\\]\\[ V_E = 100 \\cdot I_C,\\]\\[ 3 - V_B = 47000 ( I_C/\\beta) = 47000 (I_C/300).\\]I get \\(I_C = 9.4\\,mA\\), \\(V_C = 2.7\\,V\\), and \\(V_E = 0.94\\,V\\). The emitter voltage lines up with what you have which is about \\(1\\,V_{pp}\\).If you wanted \\(I_C = 15\\,mA\\), you could divide that by \\(\\beta\\) (to get the base current you need) and also solve for emitter voltage and then add \\(0.6V\\) to get \\(V_B\\). Then do Ohm's law to find required base resistor.Usually when biasing BJTs, I think about what signal swing range I need and bias accordingly. Textbooks talk about biasing schemes such as biasing so that \\(V_E = 1/3 V_{CC}\\) and \\(V_{CE} = 1/3 V_{CC}\\) and so on.Also, it should be noted I've approximated \\(I_C \\approx I_E\\). You can be more exact with your analysis although I suspect variance in beta will probably throw off calculations from reality more than exact \\(I_E\\)."
}
] |
2025-10-17T16:43:59.827756
| 14
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2n4401-c-e-2-2v/
|
2N4401 C-E 2.2V - Page 1
|
[
{
"post_id": "",
"author": "stafil",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 08, 2020, 11:32:00 pm",
"content": "I have a circuit like the one in the image (plus a few more caps)P1 on the MCU is a PWM pin, 270Hz frequency and 60% duty.What I am trying to achieve is convert the PWM output from the MCU to a 12Volt open drain output.According to my oscilloscope the voltage on the collector is about 2.2V (when it's ON). I would expect it to be closer to 0V. Any idea what am I doing wrong?"
},
{
"post_id": "",
"author": "fcb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 08, 2020, 11:47:47 pm",
"content": "https://www.mouser.co.uk/datasheet/2/68/2n4400-31590.pdfI would have thought you'd get aa little lower than that, you might have to tip more current through the base (lower the base drive resistor).Also, if you want to achieve much closer to zero, probably use a small MOSFET (2N7000/2N7002), or something like an FDN337 to be sure."
},
{
"post_id": "",
"author": "stafil",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 08, 2020, 11:56:04 pm",
"content": "Quote from: fcb on March 08, 2020, 11:47:47 pmThanks I just tried with a 2N7000 MOSFET and the output on the oscilloscope is the same.. Could it be that I am measuring things wrong?If I change the scale on the oscilloscope to 5V my signal looks fine. When I reduce it to 1V, I see the wrong base.(PS: Also tried reducing the resistor at the base down to 100Ohm, but the signal is the same, minus some more under/overshoot)"
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 09, 2020, 12:06:25 am",
"content": "Probably exceeding the input range of the scope. Try moving the trace to the bottom of the screen, or another measurement method.Tim"
},
{
"post_id": "",
"author": "stafil",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 09, 2020, 12:39:41 am",
"content": "I think you are right. The EspoTek Labrador oscilloscope shows the ON voltage to be around 0V, which is the expected."
}
] |
2025-10-17T17:54:28.883887
| 5
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2n5818-transistor-replacement/
|
2n5818 transistor replacement - Page 1
|
[
{
"post_id": "",
"author": "cowboy303",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 03, 2012, 12:20:58 am",
"content": "OK I have a BK Precision 1730 that has a little 2n5818 transistor that is bad. And I need a replacement for it but the cheepest I can find it is $1 each and that's on eBay which I don't want to do. So I was wondering if there is a replacement for it that's a bit cheaper."
},
{
"post_id": "",
"author": "rsjsouza",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 03, 2012, 01:22:59 am",
"content": "Hi,When searching at Jameco, the result is a very common BC337 (its characteristics seem very similar)http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_254810_-1Some repair sites also list this (and others) as equivalents:http://www.lcdtvrepair.us/transistor/2N5818_Driver_de_audio_--13440However, always keep in mind that, if the equipment requires precision or depends on a very specific characteristic of the device, an equivalent is not identical..."
},
{
"post_id": "",
"author": "vk6zgo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 03, 2012, 05:15:35 am",
"content": "One trick if the transistor characteristics are very critical to the circuit,is to examine the schematic to see if they also use the same type in a non-critical application,such as turning on an LED,or whatever.Very carefully remove that transistor,use it to replace the critical one,& fit a substitute part in the non-critical position.Manufacturers frequently use one type of transistor both in circuits that need its special characteristics,& in other positions that don't,as a method of reducing inventory.Of course,If the original transistor is in a non-critical position,just replace it with a substitute."
},
{
"post_id": "",
"author": "Codemonkey",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "July 03, 2012, 07:53:47 am",
"content": "FWIW, towers international transistor selector book also lists the BC337 as an equivalent."
},
{
"post_id": "",
"author": "cowboy303",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 03, 2012, 01:14:19 pm",
"content": "Quote from: vk6zgo on July 03, 2012, 05:15:35 amGood idea I will switch it out with the transistor that runs the constant current led."
}
] |
2025-10-17T20:32:43.859658
| 5
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2n5912-replacement/
|
2N5912 replacement - Page 1
|
[
{
"post_id": "",
"author": "txescientist",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "September 15, 2013, 12:45:08 pm",
"content": "I have to repair some old equipment and need replacement for 2N5912 Dual N JFET. Found that replacement chip is LS5912, but I can't buy it i my country. Can I use two identical JFETs instead and which one? Any recommendations will be greatly appreciated !"
}
] |
2025-10-17T20:16:43.675302
| 1
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2n7000-strange-behaviour/
|
2N7000 strange behaviour - Page 1
|
[
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 12, 2017, 10:34:06 pm",
"content": "I want to use a 2N7000 as a switch to protect my circuit for over voltage.I have a scenario when i feed 5 volts and everything should be fine.But is i feed 24vdc the fet should start conducting and blow the fuse.On data sheet of 2N7000 trigger si 0.8 to 3 vdc.I attached 2 pictures which should explain better.Even if i make GS 1.92 volts, the fet stay open and the fuse does not blow.I need help as it is first time when i work with Mosfets."
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 12, 2017, 10:58:51 pm",
"content": "Which will blow first, the fuse or the Mosfet? I think the Mosfet with its absolute maximum allowed continuous current of only 280mA will blow much faster than the fuse.The datasheet for the 2N7000 Mosfet shows that some sensitive ones conduct 1mA when the gate-source voltage is 0.8V and others that are not sensitive conduct 1mA when the gate-source voltage is as much as 3V. The gate voltage requirement changes when the temperature changes and when the Mosfet is replaced so it cannot be used as a comparator like you have. All 2N7000 Mosfets partially turn on when their gate-source voltage is 4.5V and all of them completely turn on when their gate-source voltage is 10V and they are not hot.You need a 5V reference and a comparator circuit to provide 10V to the gate ofa power Mosfetwhen the supply voltage is higher than 5V. Since the inputs of a comparator do not work as high as its supply voltage then use a lower reference voltage, maybe 1V and use a voltage divider to feed the scaled down supply voltage to the other input of the comparator."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 12, 2017, 11:06:55 pm",
"content": "You should use a crowbar circuit, which uses a zener diode and an SCR to short circuit the supply and blow the fuse.https://www.electronics-notes.com/articles/analogue_circuits/power-supply-electronics/over-voltage-protection.php"
},
{
"post_id": "",
"author": "timb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 12, 2017, 11:09:32 pm",
"content": "What you're after is called a crowbar circuit and it's traditionally done with SCRs, as they latch. However, if you want to use a MOSFET, try it with a Zener instead of a voltage divider:In this circuit I used a 12V Zener, but you could go with a 20V one if you want. Basically it will trigger at the Zener voltage + the N-FET's threshold voltage. So if your FET has a threshold voltage of 5V and you want the crowbar to fire at around 25V you'd use a 20V Zener. (Ideally you'd use maybe an 18V Zener to give you a bit of margin.)In this image you can see it in action:The fuse blows about 100ms after the crowbar triggers.You may also want to either add a resistor to your input to limit the current to about twice what the fuse is rated for (to protect the MOSFET) *or* (ideally) use a large MOSFET rated for the pulse current of your source.(That is to say, if your source can put out 10A during a short circuit, make sure your FET has a pulse rating of at least 10A. Keep in mind the pulse current rating is different from the sustained current rating; it may only be rated for 1A sustained current, but can handle ten to one hundred times that for short durations [commonly 100ms max]. Remember, even a fast blow fuse can take 100ms or more to open, so it doesn't hurt to generously derate the MOSFET!)"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 12, 2017, 11:18:04 pm",
"content": "Quote from: timb on April 12, 2017, 11:09:32 pmI wouldn't recommend a MOSFET at all for a crowbar or any form of overvoltage protection. Power MOSFETs typically aren't specified for analogue operation, only as a switch which either on or off and the gate threshold voltage varies considerably. If the zener doesn't have a high enough power rating on its own, then add a BJT to it."
},
{
"post_id": "",
"author": "timb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 12, 2017, 11:21:21 pm",
"content": "Quote from: Hero999 on April 12, 2017, 11:18:04 pmAs a crowbar it *is* working as a switch. The normal working voltage (5V) of the circuit is *well* under the Zener's turn-on voltage, so it shouldn't really be an issue. In a case like this, the circuit shouldn't be hovering around the threshold voltage, so I don't see an issue. It should be on or off, period.Edit: Of course there won't be a sharp turn on, like with an SCR. The MOSFET will turn on over a couple of milliseconds as the voltage rises and the MOSFET's threshold voltage is overcome, but that's no different than how a MOSFET-as-a-Switch normally operates (if the dV/dT isn't super fast there's a \"soft knee\" to the turn on curve)."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 13, 2017, 12:21:20 am",
"content": "Thank you everybody for help and suggestions.For me Analog is a strange language.I know the basic, but i am focused mostly on Microprocessors.I know i did a bo bo with the mosfet selection, but as i said is first time i touch them.Timb, i want to ask you two questions.First, is what software you use for simulation.I use Proteus, but is not the greatest.I use it because i can load a schematic an processor hex file and simulate it there.For rest, is kindergarten.I like your and i like to try it.Now, about the circuit. The power supply is short circuit protected at 3A. Max voltage is 24VDC. Can you suggest me a through hole fet that can resist and i can try it before i put it on the board.My problem i that during the assembly process in the plant, the electrician wire some times the board at 24vdc , instead of 5 vdc.Also can you suggest me the other parts number to use, like the zenner, or value of other components.I know i ask the moon, but i need help this time.Thanks again to all for helm."
},
{
"post_id": "",
"author": "timb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 13, 2017, 11:58:31 am",
"content": "Quote from: igeorge on April 13, 2017, 12:21:20 amFor normal analog simulation I use (and recommend) LTspice. There's a bit of a learning curve, but there's plenty of videos and tutorials online to get you started. The UI isn't much to look at, but it's got one of the best SPICE engines in the world (and certainly the best free one).I also use iCircuit quite a bit (which is what's in my images). It's only a couple of dollars and runs on iOS, Mac and Windows. It's got a fairly basic (though complete) simulation engine, but I find it nice for quickly sanity checking analog circuits. It also simulates digital parts as well (basic logic gates and a handful of 74-series and 4000-series logic). The nice thing is the simulation runs in real time and it lets you visualize current flow and magnitude through your circuit.I assume your FET needs to be through hole, or is SMD OK? I can give you part numbers for a couple good candidates once I know.You should be able to pick out the Zener yourself. There's nothing special about it; any 1W 5% Zener of the appropriate voltage rating will suffice."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 13, 2017, 12:32:47 pm",
"content": "Thank you Timb,I use also LT Spice , but like you said it needs time to get use to it.I use it for small blocks of the whole circuit , just to make sure they works.I found yesterday Icircuit, and i have to install it on my Chrome browser.I do not have a pad, and my phone screen is too small.The Mosfet i will use a through hole for start.When you pickup the Mosfet , please suggest me the voltage for zenner.Does the 4.7k stay the same ?Sorry for questions but this is not MikroBasic or MikroC, then i am lost.For future, i will put some time aside to start exploring at least the basic analogThank you."
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 13, 2017, 08:44:01 pm",
"content": "You can use a MOSFET to blow a fuse, sure.It needs to be fuckoff massive, like, a couple milliohms Rds(on). You also need a schmitt trigger circuit: this is not optional, as the zener-dropping circuit will simply shunt regulate and vaporize the transistor.If a shunt regulator was sufficient, you should choose a TVS diode instead: they are much faster, cheaper per peak watt capability, and much sharper (the voltage is limited to a modest value, guaranteed in the datasheet).An SCR is much cheaper per peak ampere of capacity, has a much lower voltage drop under surge conditions, and is latching all its own (though you should still have a schmitt trigger circuit, so it fires abruptly).Remember that surges deliver currents of tens or hundreds of amperes, and fuses need tens to thousands of amperes to blow. And remember that, even under such fault conditions, fuses take tens of milliseconds to blow, while the poor 2N7000 expires in ten microseconds.Tim"
},
{
"post_id": "",
"author": "exoticelectron",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 13, 2017, 08:57:37 pm",
"content": "A 0.300ma fast blow fuse from bussman will blow in 100ms at 800ma.http://www.mouser.com/search/ProductDetail.aspx?R=0virtualkey0virtualkeyBK-AGC-1-2I dont think there is anything wrong with your circuit from a topology standpoint. Just get a different mosfet that can definitely handle the crowbar current and will turn on enough with the VGS you can supply.Also, you need to make sure the mosfet does not go into a linear region at some intermediate point between your normal (5V) and fault (24V) situation or it will destroy even a high power mosfet. A comparator would make sense.Looks like a fun project!"
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 13, 2017, 11:00:00 pm",
"content": "To T3sl4co1lMaybe you suggest like here ? I used 3 diodes in parallel for REVERSE VOLTAGE PROTECTION 1N5819 and a 6 volts TVS SMAJ6.To exoticelectronI mentioned before that in rush i did a mistake and i did not read properly the data sheet, and i end up with 2N7000, but what is the suggested Through hole mosfet i can use ?I get lost reading the parameters because it is first time i use mosfet, so what i need for my project. Do you have a part number ?Also, how and where i should find the trigger voltage ? If i trigger it on, do i need to read any other parameters to keep it on until the fuse blow(latch it) ? My power supply, either 5 or 24VDC is short circuit protected, and the max current is 6A in the big one."
},
{
"post_id": "",
"author": "exoticelectron",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "April 13, 2017, 11:11:57 pm",
"content": "Quote from: igeorge on April 13, 2017, 11:00:00 pmYour divider + the mosfet Vgs to Igs characteristics are acting as your comparator right now..and a very poor one that will be destroyed by a slow rising 24VDC. Replace the divider with a comparator circuit that drive the mosfet gate.For the mosfet, find something with a low enough RdsOn that it will not dissipate anywhere near enough power to hurt itself, even if the fuse doesn't blow, continuously. Also, it needs to have a low enough Vgs @ Igs relationship so that its fully on at the voltage your comparator can drive it to. Uhhhhh other than that pick a package and price. Digikey search engine is your friend here. Oh probably make sure its Vds is well above 24VDC tee heeDoesnt have to be through hole...see what you can come up with with the above requirements before you worry about package"
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 13, 2017, 11:24:58 pm",
"content": "A current-limited power supply will still deliver very large surge currents, because of capacitors.The above circuit is okay as long as there is enough series resistance that the fuse and diodes are not overloaded.MF-R050 is rated for 0.41 ohms minimum, and 40A maximum. A surge of -24V therefore delivers I = (24V - Vf) / (0.41 ohm) = 53 amps. I would suggest adding a 0.33 ohm surgeproof resistor in series with the fuse, to limit current safely.You can also use a series blocking device for polarity protection, usually a diode or PMOS.There are also polyfuse+TVS diode combo parts, so that overvoltage causes the polyfuse to heat up rapidly.Tim"
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 13, 2017, 11:40:47 pm",
"content": "Thank you guys.For polarity protection i use the 3 diodes in parallel like in the above drawing.If polarity is reversed the diode will conduct, and all 3 in parallel will take the hit.I will order the suggested mosfet and the resistor.But as you suggest to do a search at digikey it means i have to know what to look for.What i did after my first mistake with 2n7000, was to check for DS voltage to be above 30V, Trigger voltage to be high enough so at 5 volts it will not be triggered.Never looked at I/gs because i do not know what it is.I also selected a fet with a DS current above 6 Amps.As i do not have a clue about them, and no time to study them now, of course i select the wrong part.Here you guru you come, to take the poor blind man by hand and helping him to cross the road"
},
{
"post_id": "",
"author": "timb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 14, 2017, 12:08:36 am",
"content": "Thinking more about this afternoon, you could use a TL431 as a cheap comparator with a much sharper turn on than a Zener diode:A simple 2N3906 would work fine for the PNP transistor. Essentially the TL431 acts as the programmable comparator. You can set the trip voltage by adjusting the voltage divider feeding the ref pin.This circuit is commonly used for SCR crowbars, so it should work fine with a properly rated MOSFET. It's the circuit I would use."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 14, 2017, 12:54:09 am",
"content": "Thank you Timb.I will get the parts next week (FedEx went for egg hunting:) and try it on a bread board.What is the part number for FET ?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 14, 2017, 01:57:20 pm",
"content": "Attached are two ways of implementing over-voltage protection, on in the same circuit.A crowbar with an RC delay. This will will short circuit the supply and blow the fuse but I've added a capacitor to slow it down. The trigger voltage is just over 6V: the TL431 is set to 5.5V and the SCR triggers when its gate hits above 0.6V.An amplified TL431 which clamps the supply when the voltage exceeds 7V and acts fairly quickly. At extremely high currents, the supply voltage will rise considerably, as Q1 can't increase its collector current indefinitely. You might be able to swap it with a lateral MOSFET, the kind designed for analogue operation and used in some audio amplifiers.The result is. A 25V pulse is clipped to 15.5V fairly swiftly, without triggering the SCR and blowing the fuse but applying 7V continuously will blow the fuse. This is desirable, since most components can withstand very brief, extreme over-voltages for short periods of time, yet can be destroyed by continuous, less extreme over-voltages.Note that you can see there is a small delay before the amplified TL431 circuit clamps, resulting in a spike of nearly 20V, so you might want to consider adding a much faster transient suppression diode, such as the 1N6276A, in parallel with the whole the circuit."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 14, 2017, 04:10:47 pm",
"content": "Thank you Hero999,A complete different solution. And according with your LTspice graphs seems to work.By \"adding a much faster transient suppression diode, such as the 1N6276A, in parallel with the whole the circuit.\" you mean replacing D1?In your opinion, what do you suggest as being the most reliable and cost effective ? Transistor or SCR ?My processors, mostly from Microchip support up to 6.5V, but i prefer to have the whole system to blow the fuse at 6.1VDC.Any changes to do here to achieve this limit ?With all this support and many detailed solutions,i do not know what to do? I will buy for next week parts and experiment each proposal and keep you posted.All of you were so kind to help me.Thank you all again."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 14, 2017, 08:00:23 pm",
"content": "Quote from: igeorge on April 14, 2017, 04:10:47 pmYes.QuoteSCR because it acts as a switch with a sharp on action and is very rugged compared to transistors.QuoteIs 6.5V the absolute maximum rating or operating voltage? Most parts rated for 5V will tolerate 7V for a short length of time.The values of R1 & R2 set the tripping point for the SCR circuit. With the values shown it will trip at about 6.1V. C1 just slows it down and can be removed, if an instant trip is required. The trouble is, if the voltage is set too near the nominal supply voltage and it trips quickly, then there's a risk of nuisance tripping. This is why it's a good idea to have a transient suppressor for, short, fast voltage spikes and a crowbar for the longer pulses. The crowbar should always be set to a slightly lower voltage than the transient suppressor (whether it be a diode, TL431 & BJTs or both) otherwise the crowbar is unlikely to trip.Vtrip = (1 + R1/R2)×2.495 + 0.62.495 is the typical reference voltage for the TL431The 0.6V is the nominal trigger voltage for an SCR, which varies depending on the temperature and characteristics of the SCR.Since R1 and R2 form a potential divider, a potential divider calculator program can be used to help you select resistors from the standard values available. Here's a link to the online one I use:http://www.random-science-tools.com/electronics/divider.htm"
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 14, 2017, 09:01:41 pm",
"content": "OK Hero999,I am still waiting and answer from Timb aboutthe part number of the used mosfet, but yours I will try it next week and let you know the real life.About the processor ,6.5 it is the MAXvalue of VDD\"Voltage on VDD with respect to VSS .... -0.3V to +6.5V\"from datasheet.VDD is the positive side and VSS is the negative side, usually called ground , or digital ground and is 0.Can you post please your LT file ?Thank you"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 14, 2017, 09:53:06 pm",
"content": "Quote from: igeorge on April 14, 2017, 09:01:41 pmI didn't answer your question on the MOSFET because I wouldn't recommend using a MOSFET. If you do go for this option, you want something in a large case, with the appropriate voltage rating. The current rating an on resistance aren't very important.Attached is the LTSpice file. It looks different than the picture I posted previously because there's no way to embed symbols so had to use a generic 8 pin DIL for the TL431. If it doesn't work on your PC, it'll be because a model is missing. If so, let me know and I'll fix it."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 14, 2017, 10:01:20 pm",
"content": "Thak you.I will try it and let you know if it works on my LT or not.You see, my mind is simple. For me, in digital is 0 or 1, no\"50 Shades of gray\"I assumed that if the fuse is 300 mA, i do not need a 10A mosfet. I was wrong again."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 14, 2017, 11:32:51 pm",
"content": "I try it and is missing theTecor SCR S4025LDo you have it ?Also is missing definition for model\"BC327S\"The capacitor is ceramic or tantalum ?To be clear in my mind, i will use just the part of the schematic with SCR, and ignore the part with transistors.Is this correct ?Sorry for so many questions, but i want to see it working and move back to my programs."
},
{
"post_id": "",
"author": "timb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 15, 2017, 12:35:41 am",
"content": "igeorge, you can use my last circuit with the single TL431 and simply replace the MOSFET with an SCR. That would work equally well, if not a bit better.That said, if you're intent on using a MOSFET, it'll still work fine. I think Hero999's circuit is way, way too complex for what it does. In this specific case, considering you have a current limited power supply and a fast blow fuse, an appropriate MOSFET should be able to crowbar the circuit without damaging the MOSFET. You can always add a 500mOhm resistor to the FET to limit current, which will prevent damage if your power supply has a large amount of capacitance on the output.I thought I posted that mosfet part number in my last post, but I guess I didn't. Let me look it up again."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 15, 2017, 12:42:09 am",
"content": "for this\"500mOhm resistor\"do you mean milliohms or megaohms.I know it might look like stupid question but i need to know."
},
{
"post_id": "",
"author": "timb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 15, 2017, 12:46:58 am",
"content": "Quote from: igeorge on April 15, 2017, 12:42:09 amm=milliM=Mega500 milliohms, yes."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 15, 2017, 12:49:41 am",
"content": "Thank you"
},
{
"post_id": "",
"author": "timb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 15, 2017, 01:01:05 am",
"content": "Quote from: igeorge on April 15, 2017, 12:49:41 amFor your MOSFET, try the STP16NF06. It's got a very nice dV/dT rating and can handle up to 50A for at least 10mS. That should be more than enough time to discharge any output capacitance on the power supply. (A power supply should, ideally, have less than 100uF on the output.)Add a wirewound 500mOhm resistor to the drain of the FET, rated for 2W or 3W (wirewound resistors have high peak surge current capability).Based on some tables from fuse data sheets, a 1A fast blow fuse shouldn't have any trouble opening before the MOSFET is damaged. You could also add a small heatsink to the FET if you need to extend the pulse duration.I can also get you a part number for an SCR that would be a drop in replacement for the MOSFET in my circuit, if you want.Edit: As I understand it, you only need this crowbar to protect the rest of the circuit from overvoltage stemming from a technician hooking up the wrong power supply during initial install, correct? Even if the MOSFET is somehow damaged, it'll still save the rest of your circuit."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 15, 2017, 01:10:50 am",
"content": "Quote from: Hero999 on April 14, 2017, 09:53:06 pmIf you make a new folder for the project save the schematic to it and copy the symbol (.asy) to the same folder as the schematic (.asc), and also put the model (.sub, .lib. or .mod, or hierarchical .asy) there, and use the Top Directory dropdown in the Component browser to add the parts from the current folder when creating the schematic, instead of your original copies you have added to the installed component library, then zip the project folder (after cleaning unwanted generated files), the result is *ENTIRELY* portable.A TL431 model and symbol can be found here:http://www.audio-perfection.com/wp-content/uploads/TL431.zipI seem to have the BC327S model installed. I probably upgraded my standard.bjt transistor library from the Yahoo group or the LTspice wiki at some point.The symbol for the Tecor SCR S4025L (Misc\\SCR_Teccor) is missing (and presumably the model as well) which means your crowbar sim is still broken for anyone else . . . .I try to keep symbols for 3rd party parts NOT supplied by L.T. in a separate folder (Lib\\Sym\\3rd Party) to reduce the risk of me inadvertently posting a non-portable simulation. It doesn't help with transistors or other stuff that lives in a standard.* file as there is no easy way of keeping them separate and still easily accessible in the selector."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 15, 2017, 01:13:39 am",
"content": "Thank you for all info.I do not mind the part number for SCR.i can experiment with both.One thing i do not understand.Why everybody oversize Mosfets, Scr, or resistors.If the fuse is just 300 milliamps fast blowing fuse, whey i need components rated at 5W or 30A ?For testing i want to do it on a breadboard, but in real life, it will be on a PCB using SMD.Oversized components will need a big heat sink or space around, which i do not have on the PCB to spare.I was under the impression that a simple SOT23 SCR of mosfet will do the job.Maybe i am wrong."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 15, 2017, 01:19:31 am",
"content": "Hi Ian,Can you please post a working zip for me ?Thank you."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 15, 2017, 02:22:49 am",
"content": "I don't have the Teccor SCR model or symbol so cant easily post a working zip.The BC327S model I have is:Code:.MODEL BC327S PNP(IS=0.230E-12 ISE=39.284E-15 ISC=0.118E-15 XTI=4.800+ BF=504.327 BR=23.0 IKF=0.780 IKR=0.195 XTB=1.700+ VAF=26.0 VAR=4.500 VJE=1.0 VJC=1.0+ RE=0.203 RC=0.262 RB=0.800 RBM=0.400 IRB=0.100E-3+ CJE=57.177E-12 CJC=28.600E-12 XCJC=0.650 FC=0.750+ NF=1.0 NR=1.002 NE=1.944 NC=3.025 MJE=0.470 MJC=0.520+ TF=0.664E-9 TR=2.600E-9 PTF=1.0 ITF=0.250 VTF=2.0 XTF=6.350+ EG=1.110 KF=1E-9 AF=1 MFG=SIEMENS)Copy it and paste it onto the schematic as a dot command.There seems to be a model for the SCR at:http://www.littelfuse.com/technical-resources/technical-centers/semiconductors-technical-center/~/media/Electronics_Technical/SPICE_Models/Switching_Thyristor/Thyristor_SCR_Sxx20x_Sxx25x_A_SPICE_Model_lib.htmThe key bit you need is:Code:.SUBCKT S4025L 1 2 3* TERMINALS: A G KQpnp 6 4 1 Pfor OFFQnpn 4 6 5 Nfor OFFRfor 6 4 500MEGRrev 1 4 500MEGRshort 6 5 15Rlat 2 6 2.64Ron 3 5 9.4mDfor 6 4 ZbrkDrev 1 4 ZbrkDgate 6 5 Zgate.MODEL Zbrk D (IS=10F IBV=1U BV=400).MODEL Zgate D (IS=10F IBV=100U BV=10 VJ=0.3).MODEL Pfor PNP(IS=10P BF=3.5 CJE=200p CJC=200p TF=0.3U).MODEL Nfor NPN(IS=10P ISE=1E-9 BF=100.0 RC=13.6M CJE=1000p CJC=200p TF=0.3U).ENDSAgain add it to the schematic as a dot command.There's a SCR symbol in Misc. Insert it in the gap by the bottom left corner of U1 and change its value fromSCRtoS4025Lwhich should fix that problem albeit with a different symbol.I'll give Hero999 a chance to post a fixed portable version in case I've found different models.P.S. its better to use a TRIAC as they can be triggered by current OUT of the gate, then you can directly drive it from the TL431 cathode, as any resistance or other load in the anode circuit of a TL431 adds negative feedback and makes its setpoint rather mushy. See Figure 24. TRIAC Crowbar in theOnSemi TL431 datasheetYou can use a SCR but it needs an inverting driver as used in Hero999's 2N3055 baced circuit - just drop in a S4025L in place of the 2N3055! See Figure 25 in the TL431 datasheet."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 15, 2017, 02:33:36 am",
"content": "Thank you IanI got it and works.On the probe i got the same signal like Hero999"
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 15, 2017, 02:38:47 am",
"content": "At the right hand end of the LTspice toolbar you will find an icon '.op'. Hover over it and it says 'SPICE Directive'. Click it. Copy/paste the command text I posted into the edit box, click then click on a blank part of the schematic where you want to put the new dot command."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 15, 2017, 02:50:07 am",
"content": "Thank you Ian.Founded did it and posted.I can sleep well now.I will play with it tomorrow morning.But i rephrase again my previous question.If the fuse is fast blowing fuse, only 0.3Amps, why i need the over rated components to work with 10-20 amps, or 3-5Wats ?I believe the fuse will blow before the component.Am i wrong ?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 15, 2017, 08:44:48 am",
"content": "Quote from: timb on April 15, 2017, 12:35:41 amThen you have a similar circuit to mine, plus an extra PNP transistor, which helps because it takes the variance in SCR trigger voltage out of the equation.QuoteThat's because it showstwo methodsof accomplishing the same thing. It may not be necessary here but it's often a good idea to have both non-latching, as well as a hard latching crowbar form of overvoltage protection.QuoteA resistor may help but I don't see how the MOSFET in your circuit remains fully switched on. When the power supply voltage falls, the gate voltage will also fall, turning it off, until it reaches equilibrium.Quote from: timb on April 15, 2017, 12:46:58 amYes, m = milli and M = Mega but watch out for LTSpice which is not case sensitive and treats M as mill, so you have to use Meg for Mega.Quote from: igeorge on April 14, 2017, 11:32:51 pmYes, you can just use the part of the schematic with the SCR and ignore the transistors. If you want fast acting remove C1.Sorry about the missing models, I was unaware they weren't included in the default install.Quote from: Ian.M on April 15, 2017, 01:10:50 amI did think about posting a zip but quite often people are wary about downloading zips from unknown sources because they can contain anything. Having it all embedded in one asc file makes life much easier, until someone like me makes a mistake and they have to hunt for models.Thanks for posting the missing models.Quote from: igeorge on April 15, 2017, 02:50:07 amBecause huge currents can flow before the fuse blows which is not instantaneous. Everything in the current path of the fuse needs to be able to pass the huge short circuit current, at nearly the power supply voltage, until the fuse blows."
},
{
"post_id": "",
"author": "timb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 15, 2017, 12:58:07 pm",
"content": "Quote from: Hero999 on April 15, 2017, 08:44:48 amA 300mA fuse *should* blow well before the voltage bottoms out, but I suppose that depends on the impedance of the supply. I have used a similar circuit (with a MOSFET) before to crowbar a power supply. If the fuse can act quickly enough it works fine.That said, an SCR *is* the traditional way to do this, and the most robust.Also, I didn't look closely at your circuit, but I see now you were showing two methods.Frankly, if it were me, I'd just use a TL431 and an SCR, the PNP transistor isn't even needed (it just adds precision to the threshold).This is only being used to prevent someone plugging the wrong voltage in during initial setup of whatever this device is, so it doesn't need to be precise or durable.To be honest a crowbar might not even help him here as, by the time it activates and the fuse blows the damage could be done to the rest of the board. Even tens of milliseconds is a long time when it comes to over voltage and silicon.A better solution may be one of Linear Tech's Ideal Diode/Over Voltage Protection parts. Basically, these place a MOSFET inline with your power supply input and monitor the voltage, if it goes above a set threshold it will control the gate of the FET and either shut down the output *or* try to regulate the output (like a linear regulator), depending on the part.The would be the most robust and safest choice in this scenario, and would be basically guaranteed to work."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 15, 2017, 03:03:52 pm",
"content": "To Timb:Thanks Tim, but i am still waiting for your Mosfet to buy Monday.To both of you:Wow ... I made a new world war here from a simple dummy question, but reading the comments i can see a truce coming.Just to give you more info. The board is made and from time to time the electrician which wire the machine and boards make one of two mistake.1.wire the input of the board at 24VDC which is the main voltage in the whole machine. The 24 is wire some time correctly + to + and- to -, or in reverse polarity.2.wire the proper 5VDC but reverse polarity.The customer refuse to have a new board done with 24VDC in (that will solve part of the problem). He sticks with5 VDC.This end up with complain that the supplied boards are defective and NO WAY to prove the wrong job of electrician. I come with the idea to have a NON REMOVABLE fuse soldered to the board. Electrician make a mistake, the fuse is blown.Now, to make my life simpler, i wanted to still protect the board and not trow it in the garbage.In this way i will stop arguing with the customer that his man did a lousy job.The customer agreed with this, but he does not want to spend the sun and the moon for an upgrade of the board. Like any other customer he is cheap.He buys 30-50 boards a year so his budget for this is already fixed, and him must absorb the cost (he is just a machine builder).I hope now you are more clear for my constraints.Attached are the look of the whole board and the zoom on the protection side i tried to make it with diodes and TVS.I did not try it yet."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 15, 2017, 03:25:09 pm",
"content": "That's pretty standard solution, as far as over voltage protection goes. The TVS diode will be good for clamping short high voltage spikes but is likely to blow before the fuse does."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 15, 2017, 03:33:41 pm",
"content": "I have to comply.Ian suggested to use a Triac instead of SCR like here\"P.S. its better to use a TRIAC as they can be triggered by current OUT of the gate, then you can directly drive it from the TL431 cathode, as any resistance or other load in the anode circuit of a TL431 adds negative feedback and makes its set point rather mushy. See Figure 24. TRIAC Crowbar in the OnSemi TL431 datasheet You can use a SCR but it needs an inverting driver as used in Hero999's 2N3055 baced circuit - just drop in a S4025L in place of the 2N3055! See Figure 25 in the TL431 datasheet.\"Data sheethttps://www.onsemi.com/pub/Collateral/TL431-D.PDFAny suggestion for part number to test for Triac?"
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 15, 2017, 04:24:35 pm",
"content": "To Ian and Hero:Where i can find a fuse and put it in the LT circuit just before D1.On the latest LT i download yesterday is no fuse symbol or component.I would like to see the graph with a fuse on the circuit.Can you help me on this ?Thank you"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 15, 2017, 04:58:26 pm",
"content": "Quote from: timb on April 15, 2017, 12:58:07 pmIt sounds like a similar thing could be implemented using the TL431. Obviously it won't be as fast and won't protect against reverse voltage, unless another MOSFET is added.Quote from: igeorge on April 15, 2017, 03:33:41 pmA TRIAC could be used but the circuit would need to be modified. The part number is not important. Anything which can pass the current for long enough to blow the fuse will do.Quote from: igeorge on April 15, 2017, 04:24:35 pmI'm not aware of any fuse models for LTSpice. I don't see any benefit in simulating it. because it's something which varies quite widely, depending on the temperature and there's quite a wide variance from fuse to fuse. If you know the short circuit current, then you can predict whether the fuse will blow and how long it will take by looking at the fuse's datasheet."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 15, 2017, 05:07:15 pm",
"content": "Thank you HeroI will try the triac version after Easter holiday when Digikey and FedEx start working again."
},
{
"post_id": "",
"author": "timb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 15, 2017, 05:10:29 pm",
"content": "Quote from: igeorge on April 15, 2017, 03:03:52 pmI already recommended it several posts back:Quote from: timb on April 15, 2017, 01:01:05 am"
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 15, 2017, 05:18:53 pm",
"content": "Thanks Hero, i missed.It comes in 2 flavorsvgs(th) 2.5 v or 4 vAny preference?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 15, 2017, 05:42:43 pm",
"content": "Quote from: igeorge on April 15, 2017, 05:18:53 pmAs this is running off 5V, the lower threshold is better."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 15, 2017, 05:45:19 pm",
"content": "Thank you very much."
},
{
"post_id": "",
"author": "timb",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 15, 2017, 08:45:40 pm",
"content": "Quote from: igeorge on April 15, 2017, 04:24:35 pmAs Hero999 said, you don't need one. You can just determine when the fuse should trip based on the various data points in your plot.That said, I did build a \"fuse\" sub-circuit in my other simulation software (iCircuit) for fun:Unfortunately, LTspice doesn't have digital parts like D-Latches (though I suppose you could build one out of discrete transistors, but it might significantly slow the simulation down).In my circuit, I used a dependent voltage source whose voltage is equivalent to the current (1V=1A) flowing through the switch labeled \"Fuse\" (top right). This feeds into an RC network, to give a slight time delay of a real fuse (and smooth out pulsed loads).This time delayed and smoothed voltage is then fed to the non-inverting input of a comparator and if the voltage is higher than the reference voltage on the inverting terminal (which represents the trip point), its output goes high, clocking the D Flip-Flop, which in turn causes the output to change states and open the switch (\"Fuse\")! (The switch is then latched in the open state, as no more current can flow and thus there's nothing to trip the comparator and toggle the tit-flop again.)The switch and RC network in the bottom right are responsible for pulsing the reset line of the D Flip-Flop once during startup. 5V goes across the switch to the R input of the flip-flop, the RC network at the control node of the switch is set to open it a few microseconds after power up. Thus the R input of the flip-flop sees a 5V pulse a few uS wide.You could actually make an electronic fuse with a real circuit like this. You'd need to add a current sense amplifier in place of the dependent voltage source and use either a relay (for a slow acting fuse) or beefy MOSFET (fast acting) for the main switch, but it would work!The more you know! ~~~*"
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 15, 2017, 09:01:02 pm",
"content": "Thank you Tim,It is ingenious way of solving the fuse problem.For sure i will get Icircuit for windows and start playing with it.It looks more user friendly than Proteus."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 15, 2017, 10:30:53 pm",
"content": "Actually LTspice has digital parts: INV, BUF, AND, OR, and XOR, with the last four having complementary outputs, SRFLOP and DFLOP. See A devices in the help file."
},
{
"post_id": "",
"author": "Circlotron",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 16, 2017, 12:21:36 am",
"content": "Quote from: igeorge on April 14, 2017, 10:01:20 pmFor this particular kind of circuit:SCR = 1MOSFET = 0--------------SCRs are *hugely* strong and simple and cheap and reliable and will tolerate a \"near enough\" design much better than a MOSFET will. They are very dumb and simple, like a blacksmith's anvil, but that is exactly what you need for this kind of circuit.MOSFETs need all these extra parts around them and can be delicate and fussy if everything is not just perfect. The circuit may only work once because the MOSFET blows just before the fuse."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 16, 2017, 11:58:30 am",
"content": "Thank you ALL for helping me on this tedious task.I still have a dumb question.As i explained through this post, analog for me it is a strange territory.Using basic resistors, capacitors or OpAmp, i did , the rest, is somewhere in the dark.Here is the question:We use the TL431 to trigger the SCR, and a resistor divider to trigger TL.How about using just Resistor divider to trigger the SCR, without using TL ?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 16, 2017, 01:24:43 pm",
"content": "Quote from: igeorge on April 16, 2017, 11:58:30 amYou could but the gate trigger voltage is highly variable.http://www.littelfuse.com/~/media/electronics/datasheets/switching_thyristors/littelfuse_thyristor_sxx20x_sxx25x_datasheet.pdf.pdf"
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 16, 2017, 01:28:52 pm",
"content": "Thank youI found out the hard way.Removed in LTspice.I will stick with the proposed solution.Waiting for next week to get part on my breadboard.Have a nice week end"
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 16, 2017, 02:41:31 pm",
"content": "The minimum parts count circuit is Figure 24. TRIAC Crowbar in the OnSemi TL431 datasheet. Three resistors, one Triac and the TL431. The only reason to go with the Fig 25. circuit is if you need a beefier TRIAC or SCR than the TL431 can directly drive or if using a SCR rather than a TRIAC is going to save you more money than the extra parts cost.I'm wondering what it would take to successfully crowbar a polyfuse, and whether that could be done fast enough to protect a sensitive load.@igeorge,What's the expected peak current consumption on the 5V rail (excluding switchon transients)Its probably worth putting an anti-parallel pair of high brightness red LEDs with a 3K3 series resistor, across the fuse. These fault LEDs would be labelled 'Reverse Polarity' and 'Overvoltage/Overcurrent'. If its possible to use a polyfuse the board would then be far more resistant to idiot installers."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 16, 2017, 03:12:24 pm",
"content": "To make things clear, the fuse it is not polyfuse. It is a one time fast blowing fuse 0.3A.The maximum current on the board is 200 milliamps.All the IC are rated to Max 6VDC.We do not want to use polyfuse for the simple reason, that who made mistake and blow the fuse, has to go to his supervisor and get a replacement (electricians do not like to do that). In this way we can make them to look twice before putting power.Based in fig24, and your choice of Triac, can you please suggest me the value of the 3 resistors and a part number for triac.To test it first on the breadboard i need a through hole version.Later i will find a similar or the same on smd.I read the formula to calculate the Vout, but i do not know what should be.The whole circuit should go on short for 6 VDC.Once the triac start conducting, the fuse will blow and everything will be safe."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 16, 2017, 03:53:05 pm",
"content": "Quote from: igeorge on April 16, 2017, 03:12:24 pmI've already posted that circuit, with appropriate resistor values for 6.5V.https://www.eevblog.com/forum/beginners/2n7000-strange-behaviour/msg1186642/#msg1186642If you want to change it to 6V, then the values for R1 & R2 can be calculated using the site linked belowhttp://www.random-science-tools.com/electronics/divider.htmThe TRIAC part number is not important. Most TRIACs in a TO-220 package will be able to withstand the current pulse for long enough to blow a 300mA fuse at 24V. Here's an example datasheet, I fount by searching for TO-220 TRIAC:http://www.farnell.com/datasheets/1708247.pdf"
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 16, 2017, 04:02:40 pm",
"content": "Thank you Hero999, but you have to understand me.I had so many variants discuses here, and i for got about it being posted.I think i will stop now and wait until i have the parts to test.I put a micro to flash a led on the breadboard on 5VDC and when i have the protection i will supply 24 and pray."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 16, 2017, 04:23:22 pm",
"content": "Quote from: igeorge on April 16, 2017, 04:02:40 pmWhy do that? Simply set up a DSO to trigger at +1V rising, in one-shot mode. One channel before the fuse, one after, with a simple resistive load in place of any delicate parts like MCUs flashing LEDs. For initial testing, as you want the powerup to be clean and sharp to get the worst-case performance of the crowbar, apply +24V via either a Mercury wetted relay with an adequate current rating (at least 10 times the fusing current) or a really beefy P-MOSFET (greater surge current rating than the SCR or TRIAC) driven by a high current gate driver controlled by a debounced switch. If you've got more than two scope channels, put one on the TL431 cathode. Study the resulting traces to see how effective it is at crowbarring the supply. You can probably do initial testing with the fuse shorted out and the PSU set to current limit at a few Amps, but eventually you'll have to blow a fuse per shot to gain some confidence that it will work as expected. Ideally, do about ten shots, downloading the scope traces so you can compare them to see how sensitive it is to fuse variations. It may also be worth checking it with 150mA and 250mA fuses, again to see how sensitive it is to (extreme) component variation.The micro and LED only gets added for the final dog & pony show when you need to convince your boss its worth doing. Or if you have developed 100% confidence, build the crowbar + fuse on protoboard, and feed its output to one of the original boards so you can demonstrate everything except the fuse survives."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 16, 2017, 04:42:02 pm",
"content": "That is exactly what i want to do.Crowbar on breadboard and because the micro is cheap i wanted to put it there too.If it dies, RIP, but if it is still flashing after i replace the fuse, then is OK.Of course i will use a scope also to see it.For power i will just use one of the Omron 24VDC power supply.I will wire it directly and have a switch on the 120VAC. It is limited at 3A. After that it shut down until the short is removed."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 16, 2017, 04:46:10 pm",
"content": "Switching on the AC supply to the 24V PSU will give a relatively slow rising 24V rail with plenty of time for the crowbar to function. If you want to do a worst-case test, you need to switch the PSU output.There's no point in trying to kill a MCU before you are preparing the dog & pony show. Depending on the MCU it may tolerate >>7.5V on Vdd momentarily, but anything over its abs. max. Vdd limit *could* kill it or compromise future reliability, so whether or not it survives doesn't tell you anything - unless you used *exactly* the same type of MCU on the original board."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 16, 2017, 05:10:11 pm",
"content": "Ian, please understand. This is the real plant life.They wire the machine , then they apply power.If the board is wired correctly at 5VDC, it is no way in the world that the power swing to 24.For other applications, i understand. But here, the 5vdc is also a shelf CSA or UL approved supply."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 16, 2017, 05:55:33 pm",
"content": "Fair enough, but you *DO* need to test at a faster supply rise rate than the actual machine's PSU can produce. If the peak voltage before the crowbar fires is acceptable at double the rise rate you can be confident it will always be acceptable (neglecting tolerance variations) in actual installations.I suggest scoping the output of an unloaded Omron 24VDC PSU (if that's what's in the machine) during powerup to get the rise rate, finding its output capacitance, then using a bench PSU set to 24V, + external capacitance equal to the Omron PSU, with the bench PSU's current limit set to charge the capacitor twice as fast as the Omron PSU can, for twice the rise rate. Due to the extra capacitor, you can use a simple switch between the PSU and the capacitor as bounce will no longer be such a critical issue. Scope the result and confirm the rise rate is near to double the Omron's rise rate.Have you considered adding a 'witness' fuse? A separate low current fuse, tapped off upstream of the main fuse, feeding only a 12V Zener - if that fuse is blown >12V or reverse polarrity must have been applied to the 5V rail. That way you can distinguish between board faults that blow the main fuse and bad installation"
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 16, 2017, 06:07:28 pm",
"content": "Thank you Ian.I will do it."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 19, 2017, 06:02:51 pm",
"content": "The great UPDATE/DAY for everybody.I got the parts and tried the simple version with the triac at 24VDC.It did works with no problem.The 300mA fuse blow and the circuit was protected.I have on it and Ti-RS232 chip, and AD8541 and a Pic16F882..None of them was damaged.I replaced the fuse and put 5VDC and everything function normally.After that, i tried my old version with some diodes for reverse protection (started with 3 in parallel and went down to ONE) 1N5819, and a TVS for 24 VDC which break at 6VDC, ST Micro part.I tried the same at 24VDC normal and reverse polarity. Blow the fuse but the circuit was OK.Bellow it is the drawing for the diodes. I believe it is simpler and cheaper this way .I will keep the version with triac for new projects and incorporate it in the price at the beginning.Thank you all of you for the effort and support. It was amazing and i learned a lot.Beside the part number, are the Digikey part numbers also.The one which finish with ND."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 19, 2017, 06:28:20 pm",
"content": "The TRIAC + TL431 is a close tolerance crowbar. Its easy to hold the trip point to 2% tolerance if you use a 1% TL431A and 1% resistors, and fractionally over that for a 2% TL431 and 0.1% resistors, so with the trip point set at 5.8V, you can comfortably stay under the AD8541's abs max supply voltage rating of 6.0V and the PIC16F882's abs. max. supply voltage rating of 6.5V without a significant risk of nuisance tripping due to normal fluctuations of the 5V railHowever your chosen SMAJ6.0CA TVS diode has a breakdown voltage range of 6.67V to 7.37V, so will *NEVER* provide adequate protection for the PIC and the OPAMP as they are guaranteed to see more than 6.6V before the fuse blows. Depending on the peak fusing current, Vdd could easily go over 8V, as the only guaranteed clamping spec is 10.3V @38.8A pulse.It will reduce the probability of failure, but doesn't eliminate it, and because the parts on the 5V rail have been over-stressed, they are likely to have a higher probability of failing in-service."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 19, 2017, 06:49:43 pm",
"content": "Thank you Ian.Maybe i was over excited that it did works.I do not know how it did not blow the AD8541 chip or the PIC.I did it only two times.OK, back to the drawing board.I will present to my boss the triac solution and let him deal with the customer.5.8 volts it is excellent.Thank you for letting me know."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 19, 2017, 07:08:25 pm",
"content": "The next thing you should do is get some dataloggers that can log the maximum transient voltage reached and hook them up to the 5V rail in a few of the machines, so you can see if 5.8V gives you enough margin to avoid unwanted crowbar trips. If the 5V rail is running 5% high and is noisy, you may not have enough safety margin. As you are using a non-resettable SMD fuse, an unwanted trip means the board has to be returned fir rework before it can be put back into service.This may be an argument for using a polyfuse that can be reset by powering down the machine, with a separate witness fuse, Zener and indicator LED for detecting installer idiocy."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 19, 2017, 07:58:06 pm",
"content": "Real plant life sounds strange.If the blown fuse stops the worker from producing and makes him come to supervisor, yes he is more likely to remember that \"this sucks.\" But it doesn't change the fact that he is human and makes mistakes. After the fact, he still doesn't know how/why he made this mistake in the first place. This just increases his anxiety level.If there is mistake which gives instant feedback and it also instantly correctable without major drawback, he gets to make this mistake many times, thus not only learning it is a mistake but also hopefully learning how and why he made it and perhaps know better how to avoid it in the most efficient way.Dog chases a firecracker just once... then he avoids it. You need the dog to keep chasing. So maybe make the stick not explode in his face. If I want to learn how to finish Mario Bros in the fastest possible time without dying, I would learn a lot faster if I could restart that last boss battle instantly, rather than finding someone to restart the game for me and getting a demerit."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 19, 2017, 10:32:03 pm",
"content": "Quote from: Ian.M on April 19, 2017, 06:28:20 pmYes, the TRIAC + TL431 will providefasteraccurate clamping but I question whether it will be as fast as a transient suppression diode. The TL431 isn't the fastest of comparators and experience tells me the SPICE models for it aren't great. It's certainly something that needs to be bench tested.QuoteYou're right there. I think it survived so well because the overvoltage was very brief and I believe manufactures often specify their parts very cautiously. It wouldn't surprise me if a simple MCU can stand around 8V for a few hundred ms with no lasting damage.Another possible problem with this set up is if the power supply doesn't supply enough current to blow the fuse in time. Not only is there a greater risk of destroy the MCU but also the TVS diode, which doesn't form a sharp short circuit. It will sit there a bit over its clamping voltage, passing as much current as the supply will allow, until it overheats. The worst case is if the power supply is current limited to around 300mA, causing the power rail to sit at around 7V to 8V, the TVS diode cooking, failing open circuit, then the MCU being hit by the full 24V.Perhaps combining the crowbar with a transient suppressor diode is a better approach?"
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 19, 2017, 10:56:12 pm",
"content": "Thank you again to all of you.Let me explain again the scenario.A machine builder build a machine where he got 2 sources of voltage; 5 VDC and 24 VDC.He buys boards from a supplier which test them before and guarantee that they are good.The electrician wiring the machine can do one of the mistake:1.Wire 5 VDC in reverse polarity; solved by the reverse Diode on the input AFTER the fuse. Result = blow the fuse, no damage.2.Wire 24VDC in reverse polarity. The solution and result is the same as above.3.Wire correctly 24 VDC. Solution is the proposed TVS (still needs more testing). Result is = Blow the fuse.What ever the electrician do wrong will be discovered on the first test run.Assuming a board is destroyed, it will be replaced and the voltage applied correctly ; 5 VDC.The machine is usually under test for 1-2 weeks before it will leave the shop and go to customer. During that time, what ever can be wrong it might happen, but it will be corrected immediately.The reason do not put a polyfuse, or socket fuse is to prove to machine builder that the boards were destroyed during assembly or tests.In other words the seller of the boards cover his a..During production in the plant, it is no way that somebody will go and reverse polarity or change the voltage supply.Like i said, for future projects, the triac solution will be incorporated on the price. For the existing contract , the TVS is the most acceptable solution."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 20, 2017, 11:35:36 am",
"content": "Quote from: igeorge on April 19, 2017, 10:56:12 pmOh I understand why you need a one shot system which can't be reset by someone who doesn't know what they're doing. You need definitive proof that the electrician is making mistakes. If you went for a PTC fuse, then repeated overvoltage could still damage the components, causing reliablity problems later and you'd have no way of proving it.My concern is the TVS might not always blow the fuse. It worked when you tested it but only because you used a power supply with a high enough current capacity to ensure the fuse opened before any damage was done. If it's connected to a smaller power supply with a lower current limit or via a long piece of thin cable (high resistance) then the fuse might not blow before the TVS and anything else on the board fails.Do you know the current capacity of the 24V power supply the electrician will connect the board up to, the length of the wires and cross-sectional area of the conductors?Are you sure it will be able to supply enough current to reliably blow the fuse before anything else is destroyed?If all of the above is known and you're sure it will blow the fuse, then fine, otherwise you should consider the crowbar."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 20, 2017, 11:50:27 am",
"content": "The power supply is big enough to supply a full 24 VDC to the whole machine.It is in the range of 20-30 A. It is overrated.The wires are usually 16 gauge, big wires with a very low drop.The length of the wire is no more than 30 feet.The supply, provide power radial.From a main terminal strip to each oh the users is one wire.Like i said. The board builder, us, wants to prove to machine builder that the board are damaged during the assembly of the machine.Before, they use to come back to us complaining that a number of boards does not works,WERE delivered defective.In this way we can prevent the complains, and get paid for repairing the board or replacements."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 20, 2017, 05:25:49 pm",
"content": "Quote from: igeorge on April 20, 2017, 11:50:27 amThat's good: you can be sure the fuse will certainly trip very quickly, just make sure the fuse has adequate breaking capacity for the maximum short circuit that beefy PSU can deliver. A ceramic fuse will give better protection than a glass fuse, which would be borderline in this case."
},
{
"post_id": "",
"author": "igeorge",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 20, 2017, 06:50:25 pm",
"content": "Got it.Thanks for suggestion."
}
] |
2025-10-17T18:58:21.697664
| 76
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2n7002-as-a-radio-frequency-amplifier/
|
2N7002 as a radio frequency amplifier - Page 1
|
[
{
"post_id": "",
"author": "AlexRG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 03, 2025, 08:38:06 am",
"content": "Good afternoon. I'm designing a AM receiver (0.5-7MHz). The main purpose of the experiment is to try to replace a two-gate transistor like \"BF998\" type with two single-gate + one bipolar. The scheme works good in multisim. But, I'm confused by the following point.What is the noise level of the 2N7002 transistor? For example, for Nexperia 2N7002AK-Qhttps://www.mouser.com/ProductDetail/Nexperia/2N7002AK-QR?qs=mELouGlnn3ff0hT2G%252Bqyfw%3D%3DI didn't find the noise parameter in the datasheet, so I can't calculate the transistors' own noise level, and hence the receiver's sensitivity. What should I do?Explanation of the scheme:The V2 source is a simulation of automatic gain control. At a voltage of 2.65V, the gain is maximum. At 2.75V, it decreases 20-30 times. This voltage will be supplied from the amplitude detector.Resistors R6 and R11 set the quiescent current of the transistors (19.7mA for Q2 + Q3). The resistor R7 sets the gain. In the diagram, it is now equal to 20 (~26dB). With these parameters, if a 50mV signal is applied to the input of the amplifier, the IMD3 level is -50dB.However, such a quiescent current causes increased heating of the transistors, 43/85mW. This heating, I think, will further increase the receiver's own noise level, which means it will reduce sensitivity.In general, what will be the approximate sensitivity with such transistors? I tried to use the Deepseek AI, it gave a sensitivity of about 30-40uV. I think it's wrong, it's toooo much. Or not?..."
},
{
"post_id": "",
"author": "ahsrabrifat",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "June 03, 2025, 10:18:54 am",
"content": "Have you already implemented the circuit in real life and tested?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 03, 2025, 10:30:57 am",
"content": "The BF999 is a single gate transistor.https://www.mouser.co.uk/datasheet/2/196/bf999-56149.pdfIt has much lower capacitances than the 2N7002.IThe BF999 is designed as a linear amplifier, whilst the 2N7002 is a power switch."
},
{
"post_id": "",
"author": "RoGeorge",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 03, 2025, 10:39:23 am",
"content": "BF999 is probably a typo for BF998https://www.nxp.com/docs/en/data-sheet/BF998.pdf"
},
{
"post_id": "",
"author": "AlexRG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 03, 2025, 10:40:24 am",
"content": "to Zero999I was referring to the BF998 and similar ones from this series with two gates.to ahsrabrifat:No, in reality, I haven't done the circuit yet, because I need to know if it makes sense to use 2N7002 transistors, or if they will have a very high noise level."
},
{
"post_id": "",
"author": "RoGeorge",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 03, 2025, 11:01:26 am",
"content": "When a parameter is not specified in the datasheet, it usually means average to poor performance. If you search for \"noise 2N7002\" the first result is discouraging, but I didn't read all that thread, not sure if the big noise remark there is about 1/f noise only:Quote"
},
{
"post_id": "",
"author": "AlexRG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 03, 2025, 11:47:19 am",
"content": "If we can't find the intrinsic noise level for the 2N7002 transistor anywhere, can you recommend mosfet, which has the noise level indicated? Just not less than the SOT-23 case, otherwise I won't be able to solder it)p.s. And that it should be modern and freely available. That is, accessible."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 03, 2025, 02:00:17 pm",
"content": "Perhaps you could use a J-FET such as the MMBFJ309? The biasing will need to be altered to account for the negative threshold voltage."
},
{
"post_id": "",
"author": "AlexRG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 03, 2025, 02:15:26 pm",
"content": "Quote from: Zero999 on June 03, 2025, 02:00:17 pmCan you draw the changes on the diagram for JFET? Then I'll try to model it. The main thing is to control the gain through the positive voltage of the automatic gain control in the same way."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 03, 2025, 02:32:56 pm",
"content": "The QRM and QRN noise on 500kHz to 7MHz bands is huge therefore any transistor off your junkbox will do well.The \"low noise\" transistors are required for VHF and higher bands usually."
},
{
"post_id": "",
"author": "AlexRG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 03, 2025, 03:36:48 pm",
"content": "Quote from: edavid on June 03, 2025, 02:21:18 pmWell, yea, they are not linear. Watch the simulation at different frequencies. 500kHz is a 4-time gain, 4MHz is an 18-time gain, 7MHz is a 12-time gain.Of course, this is not good, but it doesn't seem to be terrible for the simple AM receiver)). The most important thing is that when I apply a two-tone signal to the input, at a level of 50mV each (this is a huge level for HF frequencies) (1.5MHz and 1.51MHz), the IMD3 level is 50dB. This is much more important."
},
{
"post_id": "",
"author": "TimFox",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 03, 2025, 04:02:17 pm",
"content": "But watch out for 3rd-order IM on crowded bands due to device non-linearity.Of course, the only actual linear device is the vacuum triode.Good MOSFETs and JFETs have predominantly 2nd-order non-linearity, which does not produce 3rd-order IM."
},
{
"post_id": "",
"author": "AlexRG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 03, 2025, 04:16:01 pm",
"content": "Quote from: iMo on June 03, 2025, 02:32:56 pmHowever, I would still like to know the level of the 2N7000 or 2N7002 mosfets' own noise. This is necessary to understand the maximum sensitivity of the receiver. Unfortunately, I don't have the equipment to measure the level of this noise.. And we can't blindly trust any simulators in this matter. I don't trustmaсhineMultisim"
},
{
"post_id": "",
"author": "TimFox",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 03, 2025, 04:24:59 pm",
"content": "Noise characterization is expensive, so manufacturers rarely quantify noise for devices intended for digital operation.Note, as a rule of thumb, that the pink-noise \"corner frequency\", below which 1/fnoise exceeds white noise, is highest for MOSFETs, intermediate for JFETs, and lowest for BJTs.The voltage noise corner frequency for the 2N3631 MOSFET is roughly 1 MHz, maybe 1 kHz for the 2N3821 JFET, and perhaps 10 Hz for the 2N4250 audio PNP BJT.(Old data: feel free to look up newer devices.)"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 05, 2025, 10:54:47 am",
"content": "Quote from: AlexRG on June 03, 2025, 02:15:26 pmFor future reference, please don't use JPG for schematics. It introduces artifacts which make editing a pain. PNG is better, preferably without anti-aliasing on the text. I like to stick to monochrome myself, but that's preference.Perhaps something like this?The gates will now be biased negative, with respect to the source."
},
{
"post_id": "",
"author": "iMo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 05, 2025, 02:47:11 pm",
"content": "This may work with the 2N7002 as well (after minor changes in the 2N7002 biasing).https://w7zoi.net/hycas-pcb.html"
},
{
"post_id": "",
"author": "MariuszD",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "June 07, 2025, 11:54:39 am",
"content": "Quote from: AlexRG on June 03, 2025, 08:38:06 amI found your circuit interesting for analysis. But i don't understand how it is possible for AGC to work with such small voltage/current variation. My simulation shows that it doesn't work at all."
},
{
"post_id": "",
"author": "shabaz",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 07, 2025, 12:07:50 pm",
"content": "His other thread concerns transmission. It seems he's building a transceiver, and who knows for what purpose.Certainly not likely to be legal."
},
{
"post_id": "",
"author": "AlexRG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "June 07, 2025, 12:35:35 pm",
"content": "Quote from: MariuszD on June 07, 2025, 11:54:39 amLet's imagine that the maximum gain of the RF amplifier is 23. The amplitude of the reference voltage is 2.8 V. We increase the reference voltage to 2.85 V, the gain decreases from 23 to 16 times. Then we increase the reference voltage to 2.9 V, the gain decreases from 16 to 2 times.The receiver will have a reference voltage source, by adjusting which you need to set the maximum gain of the RF amplifier. For example, it will be 2.8 V. (In reality, this voltage may be different, depending on the type of 2N7002 transistors).When this voltage is 2.8 V, the RF amplifier gain is maximum. When a constant AGC voltage of 100 mV comes from the amplitude detector, the RF amplifier gain drops to 2 times. The higher the constant AGC voltage, the lower the gain."
},
{
"post_id": "",
"author": "MariuszD",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "June 08, 2025, 08:47:35 am",
"content": "Quote from: AlexRG on June 07, 2025, 12:35:35 pmPreviously, you wrote that a change of 2.65V-2.75V is sufficient, which is why I didn’t observe a significant change in gain in the simulation.Now it works.Quote from: shabaz on June 07, 2025, 12:07:50 pmThe fact that you don't know why he does it is not a crime.Not everyone from Russia is in engaged in war.Not guilty until proven guilty."
},
{
"post_id": "",
"author": "shabaz",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 08, 2025, 09:21:21 am",
"content": "I do not need to prove a thing. People can make their own decisions what to do. It's clear he did try to mislead:https://www.eevblog.com/forum/beginners/tl5001-as-a-audio-pwm/msg5940366/#msg5940366You are acting as his useful idiot, and that's on you."
},
{
"post_id": "",
"author": "Simon",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "June 08, 2025, 03:19:45 pm",
"content": "Quote from: shabaz on June 08, 2025, 09:21:21 amWhy don't you shut up? As you said, people can make up their own minds. Look at the bigger picture. If I am not mistaken what is being made is not the most advanced thing in the world, it's not like many others could not just do this without all this messing about, so what is your problem exactly?"
},
{
"post_id": "",
"author": "shabaz",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 08, 2025, 04:14:35 pm",
"content": "Quote from: Simon on June 08, 2025, 03:19:45 pmYes, youaremistaken.If you had examined more closely before interjecting, you would have seen that the OP is not actually a beginner - he is more than aware about intermods, and his PCB layout shows awareness of how to construct for RF.You should have asked yourself, why then does he need help, if it's as simple as you appear to suggest?The answer is, he is specifically using parts never intended for RF purposes, even though jellybean RF-appropriate parts exist. That then makes it non-trivial because you won't find many online examples, ChatGPT will be less helpful, because there are not as many examples designed in this manner. If it's so easy, let's hear your expert opinions on the subject matter.Then, pile on the fact that AlexRG did mislead regarding frequency of operation, he is squarely targeting within commonly-used military spectrum (there is no indication he is licensed), his transmitter is clearly for a high-power since he needs to feed it from a likely high power PWM-driven buffer, and it doesn't take a genius to figure out that at a minimum this is likely to be illegal, if he has no license.With respect, you can kindly shut up first if you're not going to make the effort to understand what's going on.You could have thought to yourself, here's a person who clearly offers help, has a history of that, and indeed did help AlexRG on his other post, until he realized that the two concurrent threads had warning signs, by indeed looking at the bigger picture, and that surely he must have had a reason to speak up, whether you agree with it or not. I had thought better of you."
},
{
"post_id": "",
"author": "Simon",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "June 08, 2025, 05:09:40 pm",
"content": "we are getting numerous complaints about you from multiple people, if you don't want to help then don't. It is not apparent what the final intentions are so that is that. You are acting like this will win a war, I'm sure that if this is so crucial plenty of others can do it. This is you last warning!"
},
{
"post_id": "",
"author": "shabaz",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 08, 2025, 06:01:45 pm",
"content": "Quote from: Simon on June 08, 2025, 05:09:40 pmMy responses were on-topic. I had to go into some detail simply because you'd incorrectly assumed that the questions were simplistic and that some bigger picture had been missed.I have not been contacted by any moderator to let me know about any complaint, fair or otherwise.If you or others have pent up frustration regarding complaints you have not told me about (and I'm sure I could complain about others), they can't have been all that significant that no-one made the effort to notify me.Your \"final intentions\" comment makes zero sense, I'm not hiding a thing, not even my name, and I'm not going anywhere, I'm here to stay.I don't use a fake name, throwaway e-mail or anything, and I help if I can, and stay out of all the nonsense that some people write. If you're going to choose to interject, how about actually supporting the people who make some effort to provide information, versus those who have demonstrably been misleading as mentioned above?"
}
] |
2025-10-17T16:17:42.058147
| 25
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2nd-more-modern-oscilloscope-choice-or-help-in-the-problem-with-current-one/
|
2nd, more modern oscilloscope choice, or help in the problem with current one - Page 1
|
[
{
"post_id": "",
"author": "Mateusz",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 06, 2022, 11:13:37 pm",
"content": "Hi there.I am not a frequent visitor on this forum, however i thought it would be nice to ask some of more experienced people around here about the current decision i'm about to make. I am sorry to make a big post with wall of text, but i would like to be comprehensive and communicate the most of what's going on in my head.There is more than a good chance you don't remember me so i will reintroduce myself. Couple months ago i was looking for my very first oscilloscope, and i was making some really wide assumptions on what would i like to buy and such. In short, if you don't want to read entire topic (which is here:https://www.eevblog.com/forum/beginners/the-more-i-read-the-more-clueless-i-am-of-which-scope-to-buy/), I personally settled on buying an older scope, i chose digital HP 54645D, which is mixed domain 200MS/s 100MHz scope, that came with additional FFT/storage module on the back. It is really nice, and belive it or not, I actually got a job as programmer/tester in company that assembles battery packs, and i had the reason to use it while i was working HO (home office). In other words - it first helped me got the job (i used that for hobby projects previously), and then helped me IN the actual job. Thus i think investment paid off.I decided now to invest in some more modern choice. The main reason is to actually have some basic modern functionalities, or more bandwidth to explore more things. Modern in sense - connecting to external PC (LAN/USB? maybe some manufacturer has the application to control the scope remotely?), USB stick to screenshot, I2C/UART/SPI decoding that i could observe to troubleshoot designs automatically (i had to manually observe the waveform on the HP before and look what was not right, decoding the protocol in my head), maybe some better sampling rate, and so on. So here are my choices i currently have:1. I got an offer (I was negotiating the price) for R&S RTC 1002, RTC1K-COM2 version, for about $860 (a little bit less, meanwhile official shops has it listed localy at $1300-$1600? idk). It comes with all the necesairy equipment (logic analyzer probe, unfortunately 8bit (i think), 2 other probes, power cord, and ofc scope). It also comes from the seller that is local so no bulls*** with import taxes, expensive shipment and such. Is this the good price?2. I could try to refuse the offer and try to think about the Siglent SDS2xxxX plus (or something), idk how much would the MSO option cost, since it is now not only the software (which there seems to be hacks for), but also the physical logic probe which is worth about $400 alone on ebay (at least)3. I did see very cheap offer for far higher bandwidth scope, in the same price range, but broken, It is a lecroy 7200 (yeah that's quite some leap and quite some absurd comparison to the previous ones, i know, i still did not give up thinking about high bandwidths yet..., i'm just obsessed with oscilloscopes to this day) on ebay (you will easly find it, a lot of observers currently). Long story short, the seller claims most of the stuff \"works properly\" (clocking part, PSU, and one more) but the FPGA unit there isn't working.4. Finally - loking more, to find maybe a scope that is the middle-ground (like idk older scope with 500MHz? there is a Tek TDS7xx (i think) that is around at this price point) and don't bother the modern options (like the USB to PC connectivity, or LAN cable)So here are questions:1. Siglent has some astronomical 200M/ch memory depth and \"120k wfm/s\", meanwhile R&S has like, 2M memory/ch and \"10k wfm/s\". Also Siglent seems to come with the 2M FFT, while R&S has about 128k FFT. Meanwhile R&S comes with the 300MHz BW (and the option for sig i was looking for was 100MHz). What do you think about comparison of these 2? What is the impact of such a big memory/waveforms_update on the capture of the signal, or is this actually \"less\" but the data can be viewed historically (like many aquisitions, and then historical view)?2. How hard is it to troubleshoot such an FPGA problem? I can provide you the feedback (DM) of what the seller replied to me when i asked about the details of this issue.3. On my recent scope i have about 30 MHz ringing while poking around higher frequency signals (for example 400kHz I2C is good, but when choosing really low time/div of about 5-20ns, on test signal rise there is ringing). What could be possible reason to this problem? I tried poking the 24MHz crystal on my FPGA programmer (i got Maximator FPGA, Intel MAX 10, 8k gates, starter borad to get more familliar with logic gates, crystal is on JTAG programmator board) and it is the same. I use Agilent 150MHz passive probes (i belive it is 10074C or something like that, can't remember from the top of my head). I could use the second scope to possibly probe around and diagnose the problem. Or is this something trivial?4. I come from Poland so the prices that i \"tell you about\" are show \"recalculated to USD\" by me and now are changing quickly (4.5PLN to 1USD as of this msg), due to the european situation. Currency value drops heavly and is not stable, which makes purchases from ebay a lot more unsafe."
},
{
"post_id": "",
"author": "FlexibleMammoth",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "March 07, 2022, 12:31:08 am",
"content": "Ok so short version because I really need to get some sleep1. I have owned both the R&S HMO1202 full options (look it up, it's identical to the RTC plus additional 50Ohms input) and the Siglent SDS5000X full options. In 2022, the R&S is only nice if you got no bench space. Siglent is better in almost every other way (yes, even the SDS2000X Plus). Touchscreen, screen size, memory, bandwidth. R&S advantages are component tester, nice XY view with X(t) view, pattern generator. You can hack the Siglent, not the R&S. Personal opinion: I almost never need the big memory, but always need the big screen & touch. More wfms means you'll see more glitches. Numbers are marketing that are only reached in special circumstances.2. Not qualified to talk about that. Most likely complicated unless it's a bad solder joint or you have the tools, and a known good donor board/spare part.3.Try shorter lead lengths, there should be a small spring in the probe accessoires that you can attach instead of the long ground lead. Also, fundamental frequency is worthless, but rise time of the signal is important. A very sharp square wave at 1kHz can have components beyond 500MHz, which eventually hit the resonance of your lead inductance & tip capacitance.4. That will probably be the case for the forseeable future."
},
{
"post_id": "",
"author": "tautech",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 08, 2022, 03:37:31 am",
"content": "Quote from: Mateusz on March 06, 2022, 11:13:37 pmCorrection:SDS2000X Plus use two 2GSa/s ADC's each with 200 Mpts memory support which with 4 active channels divide it down to 1 GSa/s and 100 Mpts max/channel.Thread here:https://www.eevblog.com/forum/testgear/siglent-sds2000x-plus-coming/Comparison thread:https://www.eevblog.com/forum/testgear/functional-comparison-of-rs-rtb2000-siglent-sds2000x-and-keysight-dsox1000/"
},
{
"post_id": "",
"author": "Mateusz",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 16, 2022, 10:29:49 pm",
"content": "Quote from: tautech on March 08, 2022, 03:37:31 amThanks for clarifying thatQuote from: FlexibleMammoth on March 07, 2022, 12:31:08 amThanks for answering that, I'll look into this a little bit more.Quote from: FlexibleMammoth on March 07, 2022, 12:31:08 amok so i did tried this but results are even weirder now, i'll make a video post tomorrow so you will see what i have in mind/what i'm looking at. Basically, with NO GROUND CLIP connected (the aligator clip detached + no \"ground spring\" - what i really have in the 10074C accessories is a plastic shield with metal rigid wire that extends out), i can kind of see the sinusoid from the crystal on one of the 4 legs of the SMD package. When i grab and mount the short ground lead, and connect GND to top of the SMD, waveform becomes a square wave O_o... What is going on? I tried both AC coupling and DC coupling, but at 24MHz i belive, apart from the constant voltage offset, i won't see any meaningful difference.In terms of ringing i wached Alan's (do i remember name right? w2aew yt channel) video about probe compensation but the probe i use is rate to 9-17pF input cap. and the HP54645D has 13 so i guess it is in spec, i noticed i might have some additional interference beacue i keep the scope to many other devices and maybe they interfere? (like for example switching power supplies for some mobile phones that EMI at some freq that causes resonance closely?) Let me know if this could be a potential problem and if i should test this out in some less busy environment."
},
{
"post_id": "",
"author": "Wallace Gasiewicz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 17, 2022, 01:16:08 pm",
"content": "Mateusz:I am not an engineer. I dropped out of eng school after two years. Went into something else. I am a Hobbyist.I have had all sorts of analog scopes and decided to get into the 21st century.You mentioned possibly an older \"middle ground\" scope, so:I purchased an Agilent 54810 500 MHz Scope that had been upgraded to 2 GSa/sec and a solid state drive. Essentially upgrade a 54810 to 54820. Easily done, apparently.The 54815 has four channels vs my two channels, 54820 and 54825 have 2 GSa/Sec.I realize that it does not have any logic capabilities outside of the scope channels.It does have LAN and USB capabilities, connections are on the back, I have never used them.Memory depth is only 32,768 points per channel.I am not impressed with the FFT function. it works but a spectrum analyzer seems to me to be much better.Since you are already using an HP Scope, perhaps it is something worth looking into.Perhaps a stand alone Logic analyzer with one of these scopes would be less expensive and a better, more versatile choice. Maybe less expensive also.I do not have a modern Tek scope, but some people prefer them rather than the HP/Agilent scopes.Anyway, Just an idea......I don't know about the availability of these things in Poland, have not been there in many years."
}
] |
2025-10-17T17:13:20.135713
| 5
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2nd-order-butterworth-as-attenuator/
|
2nd. order Butterworth as attenuator - Page 1
|
[
{
"post_id": "",
"author": "IvoS",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "September 21, 2014, 07:51:28 pm",
"content": "I need to generate clean 1kHz 1mV sinusiodal signal. I am using Arta soft on my notebook using headphone output. I can adjust generator in Arta soft to somewhere -21dB and lower the volume on the notebook and that gets me to 1mV out. The problem is the noise floor and therefore to take accurate measurement of 1mVAC. I have couple of multimeters they have 1uV resolution but the noise floor is a killer.So I was thinking to get 100mV out from my notebook, which produces reasonably clean signal and then use LM49710 in inverting configuration with G=-100 to get me to 1mV.I was trying to use FilterLab soft to make a 2nd order(or higher order) Butterworth low pass filter to reject unwanted noise but the problem is that options are only for gain 1+. Does it mean there is no chance to have low pass Butterworth as attenuator?"
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 21, 2014, 09:20:39 pm",
"content": "1mV / 100mV = 0.01 gain, not -100. Use a resistor divider.If you still need a cleaner signal, you can filter it, but mind you will still be left with the noise in the passband.Also, try the laptop on battery power, AC adapter disconnected. The adapter often adds a lot of noise for some reason.Tim"
},
{
"post_id": "",
"author": "macboy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2014, 02:16:07 pm",
"content": "I would construct a precision 100:1 divider. You can verify the divider by either measuring it with DC or by measuring the resistor ratios directly (99:1). Then send a 100 mV signal into it, and trust that you have 1 mV coming out. Equipment that can accurately measure 1 mV is out of reach of most people. You can measure the 100 mV much more easily. Buffer the output of the divider to prevent voltage sag due to the load."
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2014, 08:05:22 pm",
"content": "Quote from: macboy on September 24, 2014, 02:16:07 pmA simple divider is also easy to capacitively compensate if necessary for a flat frequency response.I have done this exact thing to generate precisely known low voltage waveforms but I used a precision switched RF attenuator which neatly avoids any compensation issues. I calibrated the attenuation at high signal levels were I could accurately measure the input and output and then relied on the now calibrated attenuation to know the miniscule output signal level based on the measured input signal level."
}
] |
2025-10-17T19:54:57.154509
| 4
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2nd-order-sallen-key-lpf-stability-issue/
|
2nd order sallen key LPF : stability issue - Page 1
|
[
{
"post_id": "",
"author": "sdouble",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 17, 2019, 05:51:01 am",
"content": "Hi all,I am trying to design a 2nd order sallen-key Low pass filter. Bessel type. The 1st challenge s that I am requiring a cut off frequency of.. 150 Meg.Second issue, I do need a DC gain of 3. I have big issues with the design : the LPF is basically a very nice oscillator.here is the design.Any help would be highly appreciated."
},
{
"post_id": "",
"author": "awallin",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 17, 2019, 09:55:19 am",
"content": "depending on the op-amp and your board-layout etc. you will have 10pF stray/input capacitances all over the place.better to dimension it so that your caps are >1-10 nF so that stray capacitances don't matter so much?"
},
{
"post_id": "",
"author": "blackdog",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 17, 2019, 10:52:42 am",
"content": "Hi sdouble,What you want to do is very difficult with opamp because you need a lot of bandwidth, think of opamps with a few GHz bandwidth.awallin already indicates that your parasitic capacity of your construction will cause major problems.And then there's the next problem, what's the signal level you're working at.Be aware that e.g. 10pF at 150MHz gives a load of 106 Ohm.I think it's better to build a separate amplifier stage that drives a passive filter and then terminates the filter with the right impedance.You can also take two amplifier stages where the filter is in between, so you have more freedom to choose the impedance on which the filter works.Remember this too, a normal 1:10 probe of a scope will cause a high load when you measure for example at the opamp output because off the probetip capacity.I hope this helps a little.Kind regarts,Bram"
},
{
"post_id": "",
"author": "MaxSimmonds",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "July 17, 2019, 11:24:50 am",
"content": "Regarding the DC gain, I looked into a sallen key filter before, low pass, and I can't exactly remember why, but if you look at the transfer function, if you introduce a DC gain greater than 2 or 3, you get a right hand plane pole, and it becomes unstable. I wouldn't go any more than 1.5, or you'll get a bit overshoot and possible instabilities.I needed a gain of 15, so I just had a unity gain sallen key filter, and then a gain stage at the end - this was sufficient.Hope it helps!"
},
{
"post_id": "",
"author": "ogden",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 17, 2019, 01:24:43 pm",
"content": "Quote from: blackdog on July 17, 2019, 10:52:42 amRight. That's why passive LC filter with separate gain stage is much better choice at those frequencies."
},
{
"post_id": "",
"author": "sdouble",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 17, 2019, 03:21:02 pm",
"content": "Hi guys,thanks for the help.Just a comment about the parasitics. I'm used to deal with very low parasitics. Basically, the routing is such that the parasitic cap is sub pF every where. very small packages (201 and 0402 only) thin and sub mm traces...The AD8045 that I use is supposed to be usable for high gain sallen key LPF. this is clearly stated in the doc."
},
{
"post_id": "",
"author": "blackdog",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 17, 2019, 03:46:25 pm",
"content": "Hi sdouble,The AD8045 that I use is supposed to be usable for high gain sallen key LPF. this is clearly stated in the docThe above does not mean that you can build an active filter with a crossover frequency of 120 to 150MHZ.Let's first look at Figures 48 and 49 in the datasheet.These are the input and output impedance of the opamp from 100 to say 500MHz, this means no ideal opamp values!And now for some horror values, look at figure 46 this is the suppression of interference signals on the power lines.And finally the gain at capacitive load of the opamp output, see figure 10, 18pF load at a gain of 2 gives +5dB gain!I do not mean to say that this is not a good opamp and also that it would not be suitable for filter applications.But the designer will have to take into account at least the properties that I have described above.Kind regarts,Bram"
}
] |
2025-10-17T18:06:47.367248
| 7
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2no-2nc-ssr/
|
2NO 2NC SSR - Page 1
|
[
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 22, 2017, 01:26:38 am",
"content": "I have been looking for something that could serve the purpose of a 2 normally closed / 2 normally open solid state relay for a while with little luck. I want to make one. The device I will be using has 2 separate power sources for the operation. One of them is a constant 12vdc and the signalling voltage will come from a 24vac source. Could I use the 12v as my power on my optotriacs' leds with the 24vac, through rectification and stepping down turning on or off transistors? Or would there be a better way? There would be 4 optos and 4 regular triacs with respective snubbers. I have drawn it up with a zener dropping the 24v after rectification to 12v and then feeding that into the base of some transistors with pull down resistors. I posted my original schematic of this a while ago, but there was little response or help. I know SSRs are better left to the companies that make them, but they don't really have what I am looking for."
},
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 22, 2017, 08:13:55 pm",
"content": "I drew up the schematic."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 23, 2017, 02:06:23 pm",
"content": "It looks like it'll work but there are easier ways to do this, such as a CD4069.R3 to R6 aren't needed. Q1 and Q2 are emitter followers, so the base current will already be limited by negative feedback. R9 & R10 already limit the base current to Q3 and Q4 and their base-emitter junctions will become reverse biased, when the relay is activated and they switch off."
},
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 23, 2017, 09:05:27 pm",
"content": "Will the 24vac need to have a smoothing cap? If I am going to remove the R3 - R6 is there a better value resistor for the pull downs? Just use 10k or something else instead? If I were to use a 4069 would that just replace the transistors and their resistors and feed it the +12vdc as Vdd and Vss is ground?"
},
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 24, 2017, 06:06:13 am",
"content": "Would the 4069 work like this?"
},
{
"post_id": "",
"author": "Paul Moir",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 24, 2017, 06:40:34 am",
"content": "I think a 4069 is not a good idea. It can only source or sink something like 1.5mA while the MOC3041 says it needs 15mA to guarantee a latched output. A 4049 might be just able to do it with no current limit resistors but it's nothing I would want to rely on.(FWIW, maybe with a different optoisolator and using 1 gate output per LED but this doesn't seem easier somehow.)"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 24, 2017, 08:55:49 am",
"content": "Quote from: Paul Moir on March 24, 2017, 06:40:34 amYou're right. The CD4009 should do.Quote from: RyanG on March 24, 2017, 06:06:13 amUse a separate gate for each MOC3041."
},
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 24, 2017, 01:21:52 pm",
"content": "What is the max current source on the 4009? For the The number of pins would work out perfectly for what I need with 4 pins for the NC and 8 pins for the NO. Would the way I drew the circuit up with the 4069 work except with each opto on its own gate? And what resistors would be required?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 24, 2017, 04:39:05 pm",
"content": "Quote from: RyanG on March 24, 2017, 01:21:52 pmPlease read the datasheet and apply Ohm's law, then get back to us if you have any further questions.You should also consider using the, MOC3043, rather than the MOC3041 because it has a lower trigger current and is the preferred device."
},
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 24, 2017, 05:58:58 pm",
"content": "I understand how to use Ohm's Law but I do not understand the datasheet completely. I've not really used an inverter before. I'm assuming the outputs use the VDD so I would use resistors according to +12V, and I am sure that if I use the MOC3043 that the 5ma required would be easily doable. A 2.2kohm resistor would bring it to around that 5ma. I just need a little help understanding this datasheet completely in the sink/source area based on my +12V for VDD and VCC."
},
{
"post_id": "",
"author": "BrianHG",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 24, 2017, 07:50:31 pm",
"content": "When using any ICs, when driving OPTOs, it is better to tie the opto's anode to V12 & have you IC drive the cathode. The logic IC sinks current better than it sources. This means your NO will become NC and vice-versa...Also, for better sink current, if you can change the 12v for 5v, I would use the 74HC14 as it will drive much more current into the OPTO Leds, & for the first input, I would diode protect it by feeding your source through a series 10k resistor + a BAT54S series pair schottky diodes."
},
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 24, 2017, 10:41:00 pm",
"content": "Should I just replace the 12v zener with a 5v and use the 74HC14? Should I use a 7805 on the +12vdc?"
},
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 24, 2017, 11:35:36 pm",
"content": "Changed to include 74HC14. Is it correct? Also, would a 74HC04 do just as well? I have some of those around but no 74HC14."
},
{
"post_id": "",
"author": "BrianHG",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 25, 2017, 12:06:50 am",
"content": "Like this. Note that the 12v always needs to be there unlike the control input which swaps your to relay outputs. Remember, with the NC SSR, it needs power to it's optocoupler to be enabled. That 12v can go anywhere from 7v to the highest voltage the 7805 will allow.Changing the 2 10k resistors at the input will alter the input voltage sensitivity. If you are feeding digital logic into the input, you don't need the resistors or BAT54S."
},
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 25, 2017, 01:45:54 am",
"content": "So, this is the complete thing that I have. What modifications should I make to it? I didn't know how to incorporate the changes you wrote in the last one into this exactly."
},
{
"post_id": "",
"author": "BrianHG",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 25, 2017, 01:59:44 am",
"content": "D5 being 1 watt and R2 being 750 ohm is kind of overkill for a 74HC14 which has almost no input current.I would use a 1/2watt or 1/4watt ZD for D5. Maybe switch the voltage to 4.9v or 4.7v, just to be safe.Change R2 to 10k and add another 10k in parallel with D5. Otherwise, your SSR will take forever to switch off when you remove the 24v AC.You may need to experiment with the value of C1.I think C8 should be at least 10uf so that the 7805's output wont oscillate.Also, you may use 78L05 if you wish since this circuit wont go anywhere near it's 100ma limit.Everything else looks functional."
},
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 25, 2017, 03:35:45 am",
"content": "Alright, I changed the 750 to a 10k and added the additional 10k. I did change the 7805 to a 78L05. I also changed C8 to 10uf. Now I have a few questions about the high voltage side. First, what wattage should the resistors be? Are the caps at 10nf and 1kv enough? And, the neutral of the 120v has to be on pin 1 of the triacs?Also attached is the most up to date schematic. I still have to add screw terminals for the mains to the triacs."
},
{
"post_id": "",
"author": "BrianHG",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 25, 2017, 05:34:17 pm",
"content": "Before we go any further, I assume you 24vac & 12vdc come from isolated sources, I don't want the 5v regulator to recieve a nasty over-voltage surge if the 24vac pushes your GND down by another 24v or more. If you want to be super-safe, we should replace your input stage, diodes and cap, with an AC optocoupler. This will guarantee safe functionality of your circuit under any random circumstances. (It will also make me feel better too since I don't know your complete setup circumstances). For your 24vac input, use the FOD814, see the data sheet:https://www.fairchildsemi.com/datasheets/FO/FOD814A.pdfJust feed the 24vac at the input side through a series resistor. No need for any diodes there. On the output side, just use a pullup resistor & 1uf cap feeding your first input on the 74HC14.First let's clean up the everything to the left of the schematic. All that tracing around the HC14 is giving me a headache following it...For the IC, in your cad, you can mirror it so that the inputs are on the left and the outputs on the right, or, rotate it 180 degrees. This will unscramble all your wires going to the optocouplers and you will should catch a wiring mistake you made when fixing this. Also, for VCC5 and GND, don't be afraid to use labels instead of a wire trace going all around everywhere just to maintain that wired look.1. The resistors on the left should be at least 1/8th watt.2. Except if you want to keep the LED powered from the 24v, make sure R1 is 1/4 watt.3. The 10uf and 1uf are usually polarized.On the HV side:Take a look at my attached screenshot..."
},
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 25, 2017, 08:02:49 pm",
"content": "Alright, thanks for the continued help on this Brian. Sorry about the traces before. I knew that I could rotate the HC14 but didn't really think about it until I had most of the traces on. Should the 1uf cap be on the collector or emitter of the optocoupler? I was thinking the emitter side because of the AC signal, but I put it on the collector side because it was easier in the schematic. I have a bunch of 1/4 watt resistors of a wide range of values so I'll just use those across the low voltage side. For the high voltage side, the picture you posted said to use higher value resistors on the snubbers for inductive loads. This is intended to run AC motors, so should I increase the value of the 47 ohm resistors? Also, what wattage value resistors need to be used on the high voltage side? Looking at some of the other solid state stuff we have around at work, it seems they don't use anything higher than 1/4 watt or maybe 1/2 watt on the triacs/snubbers."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 25, 2017, 08:59:53 pm",
"content": "There should be a pull-down resistor on the emitter of the opto-coupler. The collector can go directly to VCC.LED1 will require some form of reverse polarity protection, as the maximum rated reverse voltage is typically 5V.Probably not what you're looking for but for the normally closed contacts on the SSR, you could use an ordinary opto-coupler with a bridge rectifier and BJT to drive the TRIAC. It won't have any zero crossing but it saves having an auxiliary power supply. The normally open contacts can just use the usual MOC3043 circuit."
},
{
"post_id": "",
"author": "BrianHG",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 25, 2017, 09:21:05 pm",
"content": "Here you go, I fixed the 2 tiny errors.As for the SSR-HV side, if you are using a high inductive load, switch the snubber resistor as describes in the datasheet.1/4 watt is ok.If you want an led right on the 24vac input, place 2 in parallel with opposite polarity through a series resistor right there. Do not connect the other side of these LEDs to your GND, this circuit was designed to totally isolate yourinput 24vac from your logic 5v circuit from all other power sources making it safe to work with any combination of power sources which you might not know where they are coming from or how they are earthed. IE, the 24vac can come from a furnace thermometer control box, or a door-bell button power supply while the 12v/5v can be from a PC power supply while the devices on the TRIACS can be connected to the 120v AC mains without any interference or damage."
},
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 25, 2017, 09:35:04 pm",
"content": "Having the LED there is fine. It is just an indicator of the relay being activated. The 24vac and the 12v are already coming in from the machine I want to place this in, which is why I selected those voltages to work with. I'll up the resistors on the snubbers, and then I think everything is good. Correct?"
},
{
"post_id": "",
"author": "BrianHG",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 25, 2017, 09:50:05 pm",
"content": "Everything looks OK with those 2 final changes.Would anyone else out there following this thread want to comment?"
},
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 25, 2017, 11:08:54 pm",
"content": "Now, I'm trying to look at all the machine information I have to figure out which wires will have to go where on the board. I color coded the wires on the schematic to make it easier to see them. Sorry about the not so good picture quality. It's an original schematic from about 1972."
},
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 26, 2017, 06:43:02 pm",
"content": "I did some figuring out, and I think I got the correct setup for the triacs. The triacs' A2s would be NO7, NO9, NC10, NC3. The A1s would be NO2, NO4, NC5, NC8.(Those are from my 1st picture in my last post) Figured I would show you guys what I am trying to do here if you are interested."
},
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "April 28, 2017, 12:22:23 am",
"content": "So, I finally got the parts to put this all together. It doesn't work. I'm thinking it has to do with the FOD814. I am using the last schematic that BrianHG posted. I think that the C and E of the 5V side are backwards. Is that all that it could be? The NC and NO sides work with just the 12V line connected, but when I connect the 24VAC it doesn't light the LED or swap the closed to open and vice versa."
},
{
"post_id": "",
"author": "BrianHG",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 28, 2017, 06:17:22 am",
"content": "Yup, the C&E are backwards. If the 74HC14 is powered and wired correctly, applying 24v should turn it on.Also check pin1 of the 74HC14, it should be high/5v, then, when you apply 24v ac, or even dc at the input, it should go to GND/0v."
},
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "April 28, 2017, 06:19:20 am",
"content": "Thank you. I tried swapping it earlier and it did work."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 28, 2017, 07:39:32 am",
"content": "Quote from: RyanG on April 28, 2017, 06:19:20 amGood, I'm glad it works but is it safe?Have you left sufficient creepage and clearances between the mains and 24V sides?Is it build on a breadboard, stripboard or proper PCB? What's the minimum distance between anything on the mains side of the opto-coupler and 24V side?"
},
{
"post_id": "",
"author": "RyanG",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "April 28, 2017, 08:26:06 am",
"content": "It's on a PCB with some stuff jumped around for the optocoupler. My creepage and clearance should be good. I used one of the calculators on a website."
}
] |
2025-10-17T18:57:44.797106
| 30
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2psu-same-problem-same-fix-different-results-odd-power-supply-output-_flicker_/
|
2PSU, Same problem-same fix-different results: Odd Power supply output "flicker" - Page 1
|
[
{
"post_id": "",
"author": "EEVPiobee",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "June 14, 2014, 07:19:30 pm",
"content": "Hello there!Today I fixed two small power supplies, same model, same design, same batch on manufacture production run... (SMPS, 12v, 4a, rated, classic Chinese design) that broke down two years ago (don't say I'm slacker, I just reallly busy and those were not a priority at the moment)The problems on these two turned out to be the PMIC that went bad for some reason and the output diodes (2x 3amps in parallel argh!) were heating up, even without load on them...So here is what I've done...I changed:PMIC for new ones, same model (and added a socket for serviceability) (CR6853T)output diodes (cheap generic) for a Schottky TO220 pack 10 amps (B10150CTG)andChanged the opto-couplers used for feedback for new ones if ever this was the reason PMIC didn't work properly. (PC817C)This trick WORKED on both, (at least nothing blows up, and now passes the finger test) but...One of the two power supplies gives me a \"flicker\" on the output voltage... I'd say it's some sort of a sawtooth every 0.3-0.5 seconds or so...for that purpose, let's call them PSU1 and PSU2...As PSU1 outputs a perfect steady 11.89volts (good enough to me for a 12v supply and what is powers)PSU2 Reads from 11.86 and drops down to 11.6 within a .3-.5 period delay and then instantly raises back to 11.86v (the led on the board flickers as well)Any ideas??p.s. I haven't tested them with load on them yet, also, I tried swapping the new PMICs between the two but same result... Flicker stayed on PSU2"
}
] |
2025-10-17T20:00:30.992181
| 1
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2s-battery-charger-chip/
|
2S battery charger chip - Page 1
|
[
{
"post_id": "",
"author": "anda3243",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "June 05, 2022, 06:25:48 am",
"content": "Hello ForumI hope everyone is doing great.I am looking for a chip similar to BQ25883. It is a 2S battery charging chip with built in balancing, with 5V input voltage.https://www.ti.com/lit/ds/symlink/bq25883.pdf?ts=1654409288777&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FBQ25883It would be perfect to use, but I have some issues with it.It is quite pricey, and the availability is not great where I am, in ChinaI would prefer a bigger package and footprint. It would make it a tiny bit easier for the manufacturer. 5x5 mm footprint is OK.I dont need that high current, I will max have 1A 5V input voltage.I have spent some hours searching Mouser and the usual places, but with little luck. Most of the components I find are even smaller or more specialized, and they have BGA solder balls instead of pins.Help is much apreciated"
},
{
"post_id": "",
"author": "mariush",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 05, 2022, 07:24:53 am",
"content": "You'll have a hard time finding one because such charger IC would also need to have a built in step-up voltage regulator to boost your 5v to the voltage required to charge the batteries.The charger needs at least 4.2v x 2 = 8.4v to charge the two batteries in series.Probably the easiest would be to have a step-up regulator in front of your battery charger IC.For example MCP73844 of MCP73842 can do 2 cell charging but needs input voltage between 8.7v and 12vHere's the xxx4 version :https://www.digikey.com/en/products/detail/microchip-technology/MCP73844T-840I-MS/593753Here's the xxx2 version (they make them in 2 versions, one that does 8.2v max battery voltage, one with 8.4v set, this one is 8.2v version) :https://www.digikey.com/en/products/detail/microchip-technology/MCP73842-820I-UN/593742MCP73842 just has an extra 2 pins for a temperature sensor otherwise is pin compatible with the x4 version so the same 10pin footprint could have both.So an option would be to boost 5v to around 9.2..9.5v (8.7v plus some margin to account for ripple and voltage drops on traces and temperature variations) and send that to the charger IC.Another example would be MP2615 :https://www.monolithicpower.com/en/documentview/productdocument/index/version/2/document_type/datasheet/lang/en/sku/MP2615GQ-Z/document_id/1423It has a built in step-down regulator to produce the voltage sent to batteries unlike the above Microchip IC which uses a linear regulator, so it can handle a much wider input voltage, it works from 8.75v all the way to 18vAnother option you may have as a work around to adding your own step-up regulator would be to implement charging only with QuickCharge compatible chargers and add an IC that signals the charger to switch to 9v or 12v when you want to charge.You can also do it without an IC by setting some voltages on the data lines to some specific voltages (ex for 9v you need to have d+ in 0.325v...2v range and d- disconnected or tied to ground (below 0.325v) for at least 1.25v then you need to connect d- to that voltage between 0.325v ... 2v, that will signal the charger that you support QuickCharge 2.0 and more precisely the 9v level. For 12v, D+ must go above 2v when D- goes up."
},
{
"post_id": "",
"author": "anda3243",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "June 05, 2022, 02:11:36 pm",
"content": "Thank you for a good answer!I think I will go with MCP73844 and boost the voltage to 9.5 V from the USB 5V.What would be a good way to do cell balancing? It is only 2 cells. How critical is it to balance these?I am a little surprised that there are not more chips for balancing and charging 2S battery cells."
},
{
"post_id": "",
"author": "tooki",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 05, 2022, 03:51:56 pm",
"content": "I think that for a great many applications, it’s just as easy to use a 1S battery and then buck/boost the output as necessary. That has the added advantage that changes in the battery voltage don’t pass through to the load. And you eliminate the need for balancing altogether."
},
{
"post_id": "",
"author": "mariush",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 05, 2022, 07:59:12 pm",
"content": "Yeah, I agree.You could have the 2 batteries in parallel instead of series, and have the voltage regulator AFTER the batteries, configuring the voltage to whatever your circuit needs.This way you can power the battery charger directly with 5v and charger IC can easily charge up the batteries to 4.2v.There are even charger ICs with load sharing features or you can add your own load sharing feature easily, here's an example :https://blog.zakkemble.net/a-lithium-battery-charger-with-load-sharing/Microchip also has an application note about load sharing which is quite detailed :http://ww1.microchip.com/downloads/en/AppNotes/01149c.pdf"
},
{
"post_id": "",
"author": "Peabody",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 05, 2022, 08:40:31 pm",
"content": "I agree with putting the two batteries in parallel, using a cheap-ass TP4056 charger module, and an MT3608 boost converter, to get your 5V. Then you don't have to balance anything. And you might even find that you don't really need 5V, and can use a buck regulator to get 3.3V, or if you really get lucky, you might be able to power your circuit directly from the batteries.I think the reason there aren't more 2S modules available is because balancing adds a level of complexity that can be avoided most of the time by just using a 1S configuration with a boost converter.Also ditto on load sharing if your circuit is 1S. It just adds a mosfet, a schottky diode and a resistor, and can head off a safety issue depending on the project's current draw."
},
{
"post_id": "",
"author": "anda3243",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "June 08, 2022, 01:16:58 am",
"content": "Thank you for all the replies.I am aware off all the advantages of a single battery design. The main reason going for 2 batteries is that we will need to drive a motor, we need 6V and peak current at 2.5A. The peak is very short, but we need to be able to provide that current.Our single cell battery was barely able to deliver this current, and if we step up the voltage to 6 V, the current would be even higher.My thinking is that 2 batteries in series will be able to deliver the current at the needed voltage in a better way.The downside is that the charging circuit is more complex. The cell balancing being the main problem at the moment."
},
{
"post_id": "",
"author": "mariush",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 08, 2022, 04:26:01 am",
"content": "Shouldn't be a problem with the right boost/step-up dc-dc converter.A standard 18650 lithium battery has around 2200-2500mAh capacity, and usually the recommended continuous discharge current is around 2A, but they can do more for short bursts.In parallel the current pulled from batteries will be even so each battery will supply half the current.Let's say peak 6v 2.5A - that's 15w.When fully charged at 4.2v , you'd have 15w / 4.2v = 3.5A or 1.75A per cell.When discharged down to 3v, you'd have 15w / 3v = 5A or 2.5A per cell.The step-up regulator will not be 100% efficient, but can be above 90% so not a problem."
},
{
"post_id": "",
"author": "anda3243",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "June 08, 2022, 04:31:13 am",
"content": "You are making a very good argument.However we also have some size constraints. so there is no way to fit a 18650 or more than max 1000 mAh. We are kinda pushing the limits on this.Quote from: mariush on June 08, 2022, 04:26:01 am"
},
{
"post_id": "",
"author": "wizard69",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 10, 2022, 09:45:36 pm",
"content": "If you are using two batteries in series of the same type as the single cell, how would you get more current? You would get more power but that is not the same thing.Quote from: anda3243 on June 08, 2022, 01:16:58 am"
},
{
"post_id": "",
"author": "tooki",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 10, 2022, 10:00:03 pm",
"content": "They’re saying that the cell used can deliver the necessary current, but is at its limit. Boosting the voltage would require even more current. By not needing to boost the voltage, the current available is sufficient. At least, that’s their reasoning. I think there should be headroom for current, since the current capability of the cell when less than full will also be lower."
},
{
"post_id": "",
"author": "anda3243",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "July 09, 2022, 07:22:24 am",
"content": "Yes, this is the issue. We believe that 2 batteries in series will keep us on the right side of the right side of the current limitations. We spend the volume that a boost circuit would take up on batteries instead. And waste some of it on battery charging and balancing circuit.Quote from: tooki on June 10, 2022, 10:00:03 pm"
},
{
"post_id": "",
"author": "anda3243",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "July 09, 2022, 07:43:08 am",
"content": "Hello EveryoneThank you for the previous answers!I have finished what I think can be a decent charging and balancing circuit. Battery capacity is 400 + 400 mAh. Fast charging is desired. Any kind of suggestions for improvement would be great. I am restricted to chips that are available in China.I use a HT7991 chip to boost the voltage from 5V to 9Vhttps://item.szlcsc.com/252182.htmlI use MCP73844-840I/MS chip for charging. As suggested by mariush.It has been difficult to find a good alternative to this chip. Its a good chip, but the availability is not great where I am. I have looked at TP5100 but I am not convinced. Has anyone used this chip?https://voltiq.ru/datasheets/TP5100-datashhet.pdfI use 2 pcs HY2213 chips for balancing. These are commonly used in many of the shelf balancing circuits.As mentioned, please let me know if I have made some mistakes or if there is anything that can be improved."
},
{
"post_id": "",
"author": "anda3243",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 29, 2022, 05:42:20 pm",
"content": "Anyone has experience of the MP2639A chip? Seems this chip can make the design much easier.https://www.monolithicpower.com/en/mp2639a.htmlThe bidirectional charging can be disabled."
}
] |
2025-10-17T17:03:56.792739
| 14
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2s-battery-charging-ic-recommendation-request/
|
2S battery charging IC recommendation request - Page 1
|
[
{
"post_id": "",
"author": "junaid",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "May 13, 2024, 07:29:37 am",
"content": "Hey everyone! We're working on a project where we need to charge up 2S li-ion battery with a charger/charging IC that can handle different types of power sources like USB, solar panels, and even a water turbine!Basically, we need a charger that can pick the best power source available and keep our batteries safe while charging. If it already has safety features, great! But if not, we'd like suggestions for how to add them.Here's what we need:1- It should be able to use a USB 5V Input.2- It should also work with solar panels. We found one we like [https://www.digikey.com/en/products/detail/anysolar-ltd/SM351K09TF/14311422].3- And it should work with a water turbine like this one [https://www.amazon.com/gp/product/B095P35MZC/ref=ppx_yo_dt_search_siln_title?ie=UTF8&th=1].Please someone expert let us know a charging IC that fit these needs, or if have any schematics or guides that could help us out, we'd really appreciate it! Thanks a bunch!"
},
{
"post_id": "",
"author": "aliarifat794",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "May 13, 2024, 08:33:08 am",
"content": "you can consider using the BQ24650 charging IC from Texas Instruments."
},
{
"post_id": "",
"author": "mariush",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 13, 2024, 11:12:37 am",
"content": "I like MP2672 / MP2672A from MPS (the A version is newer) :MP2672A :https://www.digikey.com/en/products/detail/monolithic-power-systems-inc/MP2672AGD-0000-Z/13572801orhttps://www.digikey.com/en/products/detail/monolithic-power-systems-inc/MP2672AGD-0000-P/13572796MP2672 :https://www.digikey.com/en/products/detail/monolithic-power-systems-inc/MP2672GD-0000-Z/13159530It has i2c to set some parameters but also works in standalone mode, storing in internal memory the settings.It takes 4v to 5.75v and boosts it to the voltage you'd need to charge 2 cells in series (maximum voltage configurable to 8.4v/8.6v/8.7v/8.8v through a resistor, or in 0.1v steps from 8.3v to 9v through i2c, and saves setting internally) and charges the batteries making the charge voltage also available to system output pin (if batteries are fully discharged, you'd get around 6.7v) and when input is disconnected, the battery voltage is put on the system out pin.For the water turbine, you would have to either use the 5v one or you'd have to use a step-down / buck regulator to convert the 12v to something within the 4v to 5.75v supported range.or if you want something more fancy that supports a wider input voltage range, see MP2760 :MP2760GVT-0000-Zhttps://www.digikey.com/en/products/detail/monolithic-power-systems-inc/MP2760GVT-0000-Z/17142225MP2760GVT-000A-Zhttps://www.digikey.com/en/products/detail/monolithic-power-systems-inc/MP2760GVT-000A-Z/22119781-000A means it factory defaults to 2 cells in series, but you can change the setting through i2c . **** “-010A” is the factory default for 1-cell applications. “-030A” is the factory default for 3-cell applications. “-040A” is the factory default for 4-cell applications.It's buck - boost driver , it can take 4v to 22v in, and can charge up to 4 cells in series, voltage configurable down to 3.6v per cell so it can also do LiFePO4"
}
] |
2025-10-17T16:35:45.862350
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2s-life-charger/
|
2s Life Charger - Page 1
|
[
{
"post_id": "",
"author": "Dave Wave",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 09, 2020, 09:38:22 pm",
"content": "I have a project that uses a 1500 mah 2S Life battery for power (A hobby battery with leads for power and a balance lead).I want to be able to charge it in the device through the balance lead.I was hoping to find a board I could build into the device that would charge and balance the device.I found a couple TP5000 charger boards, 1S chargers so I assume if I try to run two in parallel, it will lead to isolation issues? Would it make a difference if I powered each Tp5000 from and individual buck/boost supply?https://www.ebay.com/itm/TP5000-3-6v-4-2v-Charger-Module-3-7v-Lithium-ion-3-2v-LiFePO4-Battery-Charging/143482390497?epid=2305263656&hash=item21683787e1:g:46oAAOSwA-VeAyMhI also found a BMS board that is supposed to balance the boards and do protection, but does not have an integral charger.https://www.ebay.com/itm/2S-3S-4S-18650-Lithium-Li-ion-LFP-LiFePo4-Battery-BMS-Protection-Board-W-Balance/312772150203?ssPageName=STRK%3AMEBIDX%3AIT&var=611500761627&_trksid=p2057872.m2749.l2649Any ideas how to put this all together with something that can safely charge a Life battery?Thanks,-Dave"
},
{
"post_id": "",
"author": "aix",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "February 10, 2020, 07:35:23 am",
"content": "I'll let someone more qualified chime in on the balance charging aspect, but I wanted to mention that TP5100 natively supports 2S batteries (as well as 1S). There are plenty of boards on eBay, AliExpress etc."
},
{
"post_id": "",
"author": "mvs",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 10, 2020, 07:54:29 am",
"content": "TP5100 is a Li-ion charger with 4.2/8.4V cutoff, a bit to high for LiFePO4 battery.CN3722 should work fine."
},
{
"post_id": "",
"author": "beanflying",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 10, 2020, 08:58:54 am",
"content": "Most BMS boards are not chargers as well. The basics of them is they are simple voltage protection for each cell that breaks the circuit using a fet. So they are only a protection device and not an appropriate method to charge cells with as their is no multistage or current control.With using seperate 1S charge boards I have used theseeBay auction: #371947835700and providing you don't need high charge rates they work fairly well. Just pay attention to the datasheet and give yourself some head room."
},
{
"post_id": "",
"author": "Dave Wave",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 12, 2020, 02:12:15 pm",
"content": "With using seperate 1S charge boards I have used theseeBay auction: #371947835700and providing you don't need high charge rates they work fairly well. Just pay attention to the datasheet and give yourself some head room.I'm confused. My understanding is that the 1S boards can only do 1S, there is now way to set them up to do 2S (using two modules, due to common ground issue). Not true or did I just misunderstand you are using 1S board and 1s battery?Thanks,-Dave"
},
{
"post_id": "",
"author": "beanflying",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 12, 2020, 04:31:23 pm",
"content": "3am here and just had a visit on the roof by some very noisy Possums in heavy shoesbut I Re found an old thread I made using the Mornsun modules and in that case LiPo 1S boards but LiFe boards would sub in just the same.https://www.eevblog.com/forum/projects/multi-cell-lithium-charger-from-a-single-5v-supply/msg1454259/#msg1454259The Mornsun modules are effectively isolated power supplies because of this you can power them ALL from a common low voltage supply to power the 1S boards. The outputs of the 1S charge boards are then all isolated electrically from each other. Because of that you can gaisy chain these outputs and charge each cell by hooking up to them when the cells are in series. That is hook the positive of one 1S board into the ground of the next and so on.If this doesn't make sense I will sketch up a wiring diagram of some sort when I wake up after hopefully some sleep."
},
{
"post_id": "",
"author": "Dave Wave",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 19, 2020, 06:21:30 pm",
"content": "In terms of hooking the 1s boards in a daisy chain....are you talking about the outputs?I would appreciate a diagram if you have time.I found the part on ebay and ordered up a couple.Thanks for the help!-Dave"
},
{
"post_id": "",
"author": "beanflying",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 19, 2020, 09:31:25 pm",
"content": "What you are creating is two floating power supplies with chargers attached to their outputs. So if you used just te Mornsun modules without the chargers you could create a 10V output from a single 5V supply by hooking the positive of one with the negative of the other like a conventional dual power supply.So after adding the chargers Negative Charger board 1 goes to pack negative and positive goes to the positive of the first cell which is also the junction with negative of cell 2. The Negative of Charger board 2 goes to the junction between the cells and then the positive goes to pack positive or the positive of cell 2."
},
{
"post_id": "",
"author": "Dave Wave",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 20, 2020, 11:24:19 pm",
"content": "Got it.Thanks for the help.Ill give it a go when the parts come in.-Dave"
},
{
"post_id": "",
"author": "beanflying",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 20, 2020, 11:54:25 pm",
"content": "No probs. Handy modules for all sorts of jobs"
}
] |
2025-10-17T17:55:18.354437
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2sc5200-fake-or-original/
|
2SC5200 fake or original? - Page 1
|
[
{
"post_id": "",
"author": "kingofthevua",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "October 14, 2018, 01:43:53 pm",
"content": "Hi all!I'm a new member, please help me.I have some kind of transistor 2SC5200. I don't know it is fake or original (I think left is original and right is fake)? I had took some pictures about it. Please help me!"
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 14, 2018, 01:57:07 pm",
"content": "ebay might sell fake Toshiba ones. Why guess if it is fake? Simply buy genuine ON Semi ones at Digikey."
}
] |
2025-10-17T18:23:34.627164
| 2
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2sd870-question/
|
2SD870 Question - Page 1
|
[
{
"post_id": "",
"author": "OpenCircuit",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 09, 2020, 01:59:00 am",
"content": "Faulty?"
},
{
"post_id": "",
"author": "floobydust",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 09, 2020, 02:14:31 am",
"content": "It doesn't look promising.Why aren't you using diode-test? I have no idea of ohms test current and voltage on UT-61E.There are six possible readings to look at when testing a tranny.2SD870 has a built-in EB resistor, and CE damper diode, so those readings would be unexpected."
},
{
"post_id": "",
"author": "OpenCircuit",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 09, 2020, 02:21:59 am",
"content": "Sorry I updated the images. With ohm test I was diagnosing a blown fuse."
},
{
"post_id": "",
"author": "floobydust",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 09, 2020, 05:53:29 pm",
"content": "That's pretty much dead shorted, all the readings way too low. 2SD871 also works."
},
{
"post_id": "",
"author": "OpenCircuit",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 09, 2020, 09:50:03 pm",
"content": "I sent the seller images on ohms settings showing dead short while removed from circuit and they stated it was functioning normally.I am no EE, but I know a place...."
},
{
"post_id": "",
"author": "floobydust",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 10, 2020, 01:40:01 am",
"content": "I would hacksaw off the top and peek inside. Might be good for a laugh. Where was the seller, so we can avoid them."
},
{
"post_id": "",
"author": "ArthurDent",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 10, 2020, 02:25:43 am",
"content": "When I click on the images above I get a 'malicious link' warning from Kaspersky Internet Security."
},
{
"post_id": "",
"author": "OpenCircuit",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 10, 2020, 06:06:13 am",
"content": "Quote from: ArthurDent on February 10, 2020, 02:25:43 amBeen posting images there for years.Quote from: floobydust on February 10, 2020, 01:40:01 amChop it up...sounds like fun- if I do I will post what I find.Sorry, I'd rather not say. I don't think this person actually looked at the ohm reading images I sent and just assumed based on historical information. I'm curious as to how many of those are new defects."
},
{
"post_id": "",
"author": "OpenCircuit",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 11, 2020, 09:09:24 pm",
"content": "Let down was all I found... not even a laugh inside."
},
{
"post_id": "",
"author": "wraper",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "February 11, 2020, 09:26:25 pm",
"content": "Blue glass seals are a dead giveaway of fake Chinese crap."
}
] |
2025-10-17T17:55:54.884016
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2sk117-replacement-for-a-curiously-low-noise-amplifier/
|
2SK117 replacement for a Curiously Low Noise Amplifier - Page 1
|
[
{
"post_id": "",
"author": "mycroft",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "January 22, 2020, 03:55:05 pm",
"content": "Folks,I want to build a couple of these Curiously Low Noise Amplifier from Charles Wenzel site (http://techlib.com/electronics/audioamps.html#curiously%20low%20noise) but the input JFET is no longer available. I intend to use them to measure power supply ripple and noise and some low noise sensors. Any suggestions on a suitable replacement?Thanks."
},
{
"post_id": "",
"author": "andy3055",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 22, 2020, 03:59:48 pm",
"content": "Here is a source:https://www.digipart.com/part/2SK117"
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 22, 2020, 04:08:39 pm",
"content": "The SK209 is relatively similar, just in SOT23 case. To92 or similar case JFETs are becoming more and more difficult to get.Anyway also keep an eye on the sub-group (e.g. color code) for Ids."
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 22, 2020, 04:30:08 pm",
"content": "If the LSK189 from Linear Systems is not suitable, then I am sure they have a part which is. Or a dual part like the LSK389 could be used in parallel. Interfet should have something suitable."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 22, 2020, 04:41:20 pm",
"content": "Usually the choice of JFETs from a more local supplier is relatively limited and especially TO92 parts are often NOS or similar - so it really depends on the source where you get the parts. One may still get the 2SK117 (at least in Germany). Otherwise check the usually limited list that is available.Modern JFETs usually come in SOT23 or similar."
},
{
"post_id": "",
"author": "MasterT",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 22, 2020, 05:53:37 pm",
"content": "My thoughts:1. input cap 0.01u has impedance 15.9k at 1kHz.2. input bias res. 47 meg, certainly is not noise free part.Q: where noise generated by res. would flow?This is definitely not \"low noise\" design, but rather exactly opposite."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 22, 2020, 06:05:07 pm",
"content": "The 47 M resistor only contributes significant to noise at frequencies below the lower cross over, which is at some 0.3 Hz.At higher frequencies the noise from the resistor is shorted by the source (unless that is higher than 47 M). One would hear the noise with an open input.The capacitor impedance does not mean it would produce the corresponding amount of noise. The capacitor does produce a little noise but this is only from the loss part, which is something like 0.1 - 1 % of the impedance.So the design can be low noise, but I would not expect it to be low distortion."
},
{
"post_id": "",
"author": "MasterT",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 22, 2020, 06:23:43 pm",
"content": "Quote from: Kleinstein on January 22, 2020, 06:05:07 pmHow come it would be shorted, capacitor is essentially 15k resistor in between, so doesn't matter how low output impedance of the signal source, amplifier sees noise out of 47 meg loaded by 15k (at 1 kHz, input shorted to ground for simplicity)."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 22, 2020, 06:42:14 pm",
"content": "47 M loaded with the 15 K impedance is only 1/3000 the noise of the 47 M resistor. This is considerably less than the FET noise. As the FET has 1/f noise this is also true for the lower frequencies."
},
{
"post_id": "",
"author": "MasterT",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 22, 2020, 06:54:04 pm",
"content": "According to this pagehttps://www.daycounter.com/Calculators/Thermal-Noise-Calculator.phtmlat 25C 47meg res. has 27.8118 uV just for 1k bandwidth. Even it goes down by 3000, 9nV is still pretty high value"
}
] |
2025-10-17T17:57:15.468428
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2sk118-transistor-alternative-what-are-most-important-parameters-to-look-for/
|
2SK118 transistor alternative, what are most important parameters to look for? - Page 1
|
[
{
"post_id": "",
"author": "HMS",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 19, 2024, 04:59:21 am",
"content": "Hello,i have an old microphone and found a TOSHIBA 2SK118 transistor. so, i want to replace the PCB and buy new components but could not find an alternative to this 2SK118 FET transistorthere are many parameters in datasheet, I have strong feelings that the Gate to source voltage also the very low current drain both are unique, but which parameters or (main parameters) i should be careful about to achieve similar or better results. have no ideafor an electret microphone, what would be the best alternative for this one? or better.thanks."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 19, 2024, 08:12:51 am",
"content": "Which fets work can depend on the circuit it is used in. A problem with JFETs is that the threshold voltage and thus Idss is quite scattering. Most circuits are made to work with a certain range - some care more about the current and others more about the threshold voltage. With Electret microphone the additional problem can be that the gate leakage can matter - they may use it to set the DC biasing.Most electret microphones are a closed system with essentially no way to exchange the 1st critical FET. If the JFETs is used in a later stage so with a separate capsule that alread contains a FET things are easier. Than its only a more normal amplifier stage and it really depends on the ciruit and target (low noise, low power or wide voltage range). For audio amplifiers one usually prefers low threshold types, so maybe SK209 or SK3557 for low noise but with higher current, mmbfJ201 or SK208R for not so high current. For a later stage there is not real need to go overkill with the noise, as the capsule itself has quite some noise."
}
] |
2025-10-17T16:41:52.246248
| 2
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2x-electrolyte-capacitors-on-nvidia-gt7300-graphics-card-for-macpro/
|
2x Electrolyte capacitors on Nvidia Gt7300 graphics card for Macpro - Page 1
|
[
{
"post_id": "",
"author": "vinlove",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "September 24, 2016, 12:49:49 pm",
"content": "hi AllI was checking the capacitors on the Nvidia gt7300 graphics card from my macpro 2.1 because the display went dead on it.2x of the Electrolyte capacitors on the card are being read on the Meter as resistors of 0.2 ohms rather than capacitors.Would I be right in thinking these caps are gone off, and causing the display go dead? The macpro tries to boot, but after displaying the Mac logo for a few seconds, it just goes blank. The monitor loses signal from the graphics card.If it is right assumption, would it be ok to replace them to new ones? I am asking this because having a close look on the pcb of the gt7300, solder is not visible on the parts. It looks like soldering is done in special way, or maybe it is a kind of pcb, normal soldering is not possible?I will try to get the photos of them later to show what I mean. cheers."
},
{
"post_id": "",
"author": "Ammar",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "September 24, 2016, 01:36:15 pm",
"content": "Are you measuring correctly? Are you sure you are not measuring the case? To be sure, you could de-solder them and measure. They are likely decoupling capacitors, so measuring 0.2is certainly problematic.There is no reason why you can't replace them. Make sure the voltage rating of the caps you replace them with is equal or greater than that of the current ones. Otherwise, Good luck!"
},
{
"post_id": "",
"author": "wraper",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "September 24, 2016, 01:54:33 pm",
"content": "If you are measuring them in circuit, then you are measuring not capacitors. It is extraordinary rare case for electrolytic capacitor to fail short. If those are on GPU Vcore, 0.2 ohm probably is fine."
},
{
"post_id": "",
"author": "vinlove",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "September 24, 2016, 02:46:18 pm",
"content": "The first photo - the one on the right black 2x el. caps are reading as resisters of 0.02 ohms.The lone one on the left reads as capacitor as normal.https://flic.kr/p/M6Q4wJThe second photo shows how the soldering on pcb is barely visible. It looks more clear on the photo, but on bare eyes, they look as if not existent.https://flic.kr/p/MnLF3YThe third photo shows the meter reading the caps as resisters.https://flic.kr/p/MnLF4EAs you say maybe they need to be taken out before measuring, but why the one on the left read as normal cap?cheers."
},
{
"post_id": "",
"author": "wraper",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "September 24, 2016, 02:57:05 pm",
"content": "Are you using in component type auto detect mode?"
},
{
"post_id": "",
"author": "wraper",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "September 24, 2016, 03:05:48 pm",
"content": "Such meter unlikely to use DC for measurement. But at high frequency capacitor will appear almost as resistor. Basically what happens, meter measures ESR of the capacitor and shows it. But it cannot detect it as capacitor because of parasitic resistance in the circuit in parallel to the capacitor. You shouldneverexpect component type detection to work properly in circuit."
},
{
"post_id": "",
"author": "jitter",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 24, 2016, 03:10:15 pm",
"content": "Yeah, indeed. Desolder the caps you suspect and measure again.Looking at the pics, the caps look healthy. Bad caps show pronounced bulging of the tops and, in even worse cases, electrolyte leakage.BTW, did you try to measure the voltage across those caps during the brief moment it works at power on?Edit: the soldering of the caps leads looks normal, except for the right most pin. Either there's too much solder on it, or it did not wet properly. My guess is that there's a groundplane connected to that pin. If not designed properly (using thermal reliefs around the pin) soldering that properly can be very difficult. Bad wetting could lead to a weak joint that easily cracks."
},
{
"post_id": "",
"author": "wraper",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "September 24, 2016, 03:22:30 pm",
"content": "Quote from: jitter on September 24, 2016, 03:10:15 pmIt looks like manual touch-up with a soldering iron at factory after the reflow soldering. And thereisthermal relief. Nonetheless even with thermal relief present it is difficult to hand solder parts on multiplayer boards when they are connected to heavy power plane on multiple layers."
},
{
"post_id": "",
"author": "rob77",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2016, 03:39:46 pm",
"content": "Quote from: vinlove on September 24, 2016, 02:46:18 pmif you measure in-circuit , then the circuit does affect the readings... that 3rd cap is apparently in a different circuit and therefore the circuit affects the reading differently. de-solder the caps and measure them with a correct LCR meter.btw.. the 0.02ohm might be a short on that power rail not the capacitor itself (e.g. shorted mosfet or diode)"
},
{
"post_id": "",
"author": "vinlove",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "September 24, 2016, 04:16:06 pm",
"content": "Thanks for great advice.Will de-solder them and measure again.yeah the meter is in auto mode, and it detects components types very well.But components in circuit - it is first time I tried with the meter.As you suggested, maybe the caps may be ok.The gt-7300 had died before this summer, and been resurrected by baking inthe oven for 11 minutes, and it has been working great until it decided to die againthis week.Due to this event, I am on my ipad. I hate using the ipad, so the macpro needs to comeback to life again soon."
},
{
"post_id": "",
"author": "jitter",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 24, 2016, 05:14:08 pm",
"content": "Baking in an oven temporarily resurrects it? Hmmm...I know next to nothing about Apple products but I've heard this before somewhere, probably in a Louis Rossman video.Is this perhaps a model with known issues? Does it by any chance have tantalum caps?"
},
{
"post_id": "",
"author": "wraper",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "September 24, 2016, 06:12:51 pm",
"content": "First of all, electrolytic capacitors shouldn't be baked ever. Secondly, as baking helped, it's 99% chance that it's faulty GPU chip itself."
},
{
"post_id": "",
"author": "vinlove",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "September 24, 2016, 10:09:55 pm",
"content": "Quote from: blueskull on September 24, 2016, 08:23:00 pmI saw them. I was actually going to get a used Quadropro FX4500 with 512mb for £79.But they are all ancient, likely to have been pulled out of dead macpros, or resurrected by baking in the oven. Only God would know how long they will work.BTW, baking the dead gt7300 in the oven worked. It came back to live from non working dead card to a perfectly working and running like new card. I was stunned by it. Only problem is that it died again within 2 months."
},
{
"post_id": "",
"author": "Monkeh",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2016, 10:20:44 pm",
"content": "Quote from: vinlove on September 24, 2016, 10:09:55 pmBecause it didn't 'work'. That's like claiming taking some paracetamol cures a cold.. You relieved the symptoms briefly, nothing more."
},
{
"post_id": "",
"author": "jitter",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 25, 2016, 07:50:06 am",
"content": "Your baking the card only alleviated some symptoms that now have become prominent enough for it to stop working again.Baking in an oven, I'm guessing you were expecting a torn solder joint and attempted to reflow it. It did work for two months, but it's died again.You only live twice, so now the real problem solving starts and you will need to trace the fault.What does Dave always say? Oh yeah: \"thou shalt measure voltages\". Good luck!"
},
{
"post_id": "",
"author": "wraper",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "September 25, 2016, 08:38:07 am",
"content": "Quote from: jitter on September 25, 2016, 07:50:06 amThis has nothing to do with solder joints under the chip. This is because of internal bump fail under the silicon die in the chip itself."
},
{
"post_id": "",
"author": "vinlove",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "September 25, 2016, 09:48:51 am",
"content": "Quote from: jitter on September 25, 2016, 07:50:06 amAt the time when it died first time, I tried everything to get it working, but it didnt work at all. So I was going to toss it in the bin. Baking it in the oven was the last measure. I really didnt expect it to work. But when it did, I realised that most of the used ancient graphic cards for sale on ebay could be from the oven resuurected by 11 miniutes of baking. Thats why I didnt buy them.But yes, I should have done some measuring at the time. Then I had no meters and no knowledge about these things. Now I am learning and reading about Electronicss and fault findings, this is a good opportunity to learn something.If it came back to live another time, I would be overjoyed"
},
{
"post_id": "",
"author": "brabus",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 25, 2016, 10:15:05 am",
"content": "This remembers me of a friend wanting to buy an used TV for pennies, and demanding a two-year warranty for it.The only way you have to relief you ancestral, human fear of being scammed is buying a brand new card - if you find one.On the other hand, thinking that every used board on ebay is being sold because it was defective and has been processed with 11 minutes in the oven, well... it doesn't really work like that.Having bought plenty of used stuff, I have been seldom disappointed. Keep in mind that you get what you pay for. Original package is missing, sometimes the board is sent in a box without protection at all, sometimes it' a DOA. You can ask for a refund or another item to be sent; in general, buyers are supposed to be right - I am a lot more worried when I sell something!Of course, if you still like the idea of a piece of paper that screams \"warranty\", you can bring the whole thing to an authorized repair store."
},
{
"post_id": "",
"author": "vinlove",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "September 25, 2016, 11:00:06 am",
"content": "Quote from: brabus on September 25, 2016, 10:15:05 amI think there is big difference between demanding 2 years warranty for used electrical item and deciding not to buy it."
}
] |
2025-10-17T19:11:20.252710
| 19
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/2x-single-rail-psu-to-make-a-dual-rail-psu/
|
2x single rail PSU to make a dual rail PSU. - Page 1
|
[
{
"post_id": "",
"author": "@rt",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "January 25, 2017, 06:38:49 am",
"content": "Hi GuysAny problem with that?Basically to use a pair of identical single rail variable bench supplies plugged into the same mainswith their output grounds tied together to provide a dual rail output?I can’t think of a problem, but maybe I’m not considering something.Cheers!"
},
{
"post_id": "",
"author": "jeroen79",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 25, 2017, 09:03:36 am",
"content": "No problem at all.Mind that if you tie the grounds (-) together you will have two positive rails.For a symmetric supply you need to tie one's + to the other's -."
},
{
"post_id": "",
"author": "tron9000",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 25, 2017, 09:12:42 am",
"content": "connect negative of supply 1 to positive of supply 2the positive of supply 1 will by V+the negative of supply 2 will be V-the voltage measured between V+ & V-, should be twice the output of each supplyuse the connection made in 1. as your 0V for your circuit.measuring from V- to 0V you should see a negative voltage and from V+ to 0V and positive voltage"
},
{
"post_id": "",
"author": "@rt",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "January 25, 2017, 01:22:50 pm",
"content": "Dual rail might suggest one supply is negative, I don’t know. In my case both are positive.Didn’t think there was a problem.+12V, +5V, 0, for retro computing. A number of computers that have no -12V supply needed, and a distribution block with all the fuses.It just appears I can go a little higher quality for cheaper if both supplies are single rail.Cheers"
}
] |
2025-10-17T19:04:30.804545
| 4
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-12-digits/
|
3-1/2 digits? - Page 1
|
[
{
"post_id": "",
"author": "Axtman",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 15, 2014, 04:26:29 pm",
"content": "What is meant by 3-1/2 digits when describing a multimeter? What is a 1/2 digit?"
},
{
"post_id": "",
"author": "Falcon69",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 15, 2014, 04:29:04 pm",
"content": "it's where you will have 4 digits, but will read 115.6. that period stays."
},
{
"post_id": "",
"author": "Falcon69",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 15, 2014, 04:30:39 pm",
"content": "sorry, i was wrong, take a look at thishttp://www.london-electronics.com/digitresolution.php"
},
{
"post_id": "",
"author": "PedroDaGr8",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 15, 2014, 04:31:54 pm",
"content": "Not true.It refers to the first digit in say a 4000 count meter. On that first digit it only goes from 0-4 so it only goes halfway up. It's a half digit. Colloquially anything that isn't a full digit 0-9 is called a half digit.Sent from my EVO using Tapatalk"
},
{
"post_id": "",
"author": "codeboy2k",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 15, 2014, 04:37:43 pm",
"content": "They've started doing other wonky stuff too, like 5-3/4 digits ... I guess that means it goes to 750000 counts?I dunno.. why don't they just give the damn counts...Counts!! I need counts!!! focus dammit.. echen... where are you?"
},
{
"post_id": "",
"author": "AG6QR",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 15, 2014, 05:09:50 pm",
"content": "The counts should be related to the digits by a logarithmic/exponential relationship.A 1 digit meter can measure anything from 0 to 9, or 10 ^ 1 counts.A 2 digit meter can measure anything from 0 to 99, or 10 ^ 2 counts.A 3 digit meter goes to 10 ^ 3 counts.A 4 digit meter goes to 10 ^ 4 counts.You can see the logarithmic trend. We have the following equations, which should, in theory, be extendable to fractional digits.counts = 10 ^ digitsdigits = log10(counts)A 3 1/2 digit meter, therefore, ought to have about 10 ^ 3.5 counts. That's pretty close to 3000 counts.A 2000 count meter ought to be called a 3.3 digit meter or maybe 3 1/3 digits.5 3/4 digits should be 56243 counts, which would be rounded to 50000 or 60000.I realize that I'm approaching this from an engineering mindset, while many in the marketing department people don't understand logarithms and/or try to play fast and loose with the numbers to push them to whatever they can get away with. So don't take these too literally. In practice, you can't trust the fractional number of digits claimed; you've got to ask for the counts."
},
{
"post_id": "",
"author": "Rick Law",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 15, 2014, 05:39:17 pm",
"content": "Quote from: AG6QR on February 15, 2014, 05:09:50 pmIt is the marketing kind that changed 1GB to 1 million bytes - just to show a larger number. Prior to that, it is always 2^10 meaning 1GB=1024MB. Some even has 1MB=1000KB making the X.xGB or X.xTB very misleading.I am still confused with disk sizes and rely on raw LBA count or other means."
},
{
"post_id": "",
"author": "PedroDaGr8",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 15, 2014, 05:58:22 pm",
"content": "Quote from: Rick Law on February 15, 2014, 05:39:17 pmPersonally I like the new definition better. Yes it short changes the consumer, but the fact is, it's correct. I hated that kilo meant one thousand expect with computers where it was 1024. These modern definitions are true to the sense of the SI prefixes.Sent from my EVO using Tapatalk"
},
{
"post_id": "",
"author": "sync",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 15, 2014, 06:18:57 pm",
"content": "Quote from: Rick Law on February 15, 2014, 05:39:17 pmThis urban legend will never die.Hard disk sizes are traditionally measured with 1M=10^6 and so on. Way before the PC existed. But the half digit is probably a marketing invention. On early DMMs it was not used, e.g. a 120000 count HP 3450A was named a 5 digit meter."
},
{
"post_id": "",
"author": "bronson",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "February 15, 2014, 09:52:56 pm",
"content": "Yes, \"1/2 digit\" doesn't really make sense... It's from the bad old days when the 7 segment display was a big part of a device's cost. The manufacturers added two vertical bars to the left to display 199 instead of just 99, then claimed that double the range means you received another 1/2 digit.Counts makes more sense and is easier to compare but it's a bit unwieldy to talk about 2e6 count multimeters. And what on earth does \"display count = 1000\" mean for the 6 1/2 digit 34401?http://www.newark.com/agilent-technologies/34401a/multimeter-digital-bench-6-1-2/dp/91F3030So it's hopeless."
},
{
"post_id": "",
"author": "Monkeh",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 15, 2014, 10:18:50 pm",
"content": "Quote from: sync on February 15, 2014, 06:18:57 pmIt and the confusion will never die so long as people insist on being stubborn, ignorant, and illogical."
},
{
"post_id": "",
"author": "Rick Law",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 16, 2014, 02:43:37 am",
"content": "Quote from: sync on February 15, 2014, 06:18:57 pm"
}
] |
2025-10-17T20:08:02.695392
| 12
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-15a-fuse-in-a-100w-psu/
|
3.15A fuse in a 100W PSU - Page 1
|
[
{
"post_id": "",
"author": "9Rune5",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "October 01, 2022, 03:19:09 pm",
"content": "This week my Synology DS918+ NAS fell quiet. Its 100W PSU had given up the ghost and tripped my circuit breaker.It is beyond my current skill level to repair. But I was curious about what I found rattling around inside: The cover of a 3.15A 250V fuse. Looks exactly like the one found here:https://www.centiot.com/solid-state-square-body-t2a-250v-slow-blow-miniature-fuse-392-series-lcd-tv-power-boardIf I found the right specs, this is a slow blow fuse. Which I can kind of understand since the NAS contains four hard drives. OTOH, the NAS powers up the hard drives in sequence, thus keeping the power spikes to a minimum. But 3.15A? That hints at an input of 787W? Is that fuse not a tad too big for this PSU?Sidenote: This was a PGB branded PSU. Later models are adorned with Synology's own logo and I found a forum post claiming that there had been issues with the old PSU. In any case, since Synology's PSU cost four times more than an ATX PSU, I simply bought an ATX PSU that can easily supply 200W+ on its 12V rail. It handles my NAS without breaking a sweat."
},
{
"post_id": "",
"author": "wraper",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "October 01, 2022, 03:31:55 pm",
"content": "Fuses rarely blow up by themselves. You have severe burn marks on the bottom side of PCB. As to why fuse is oversized, it's due to high inrush current when device is plugged into mains socket."
},
{
"post_id": "",
"author": "madires",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 01, 2022, 04:19:15 pm",
"content": "There are tons of 12V power bricks with a reasonable price-performance ratio to choose from, e.g. Meanwell."
}
] |
2025-10-17T17:05:07.646563
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-3-24v-gt-3-3-1a-power-supply-reference-design/
|
3.3-24V -> 3.3V 1A Power supply reference design - Page 1
|
[
{
"post_id": "",
"author": "gcardinal",
"author_rank": "Unknown",
"is_op": true,
"timestamp": "January 04, 2022, 02:49:54 pm",
"content": "I'm looking for a power supply reference design. Requirements are as follows:- Vin 3.3-24V- Vout 3.3V or 5V with at least 1A- Compact with small component count- Small footprint > priceI originaly considered TPSM63603 from TI (https://www.ti.com/product/TPSM63603) - however it requeres 3.95V to power up.It should be possible to power finished device from 1 cell LiPo and from a domestic LED driver power supply - usually 24V in Norway.Thanks!"
},
{
"post_id": "",
"author": "drdm",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 04, 2022, 03:21:10 pm",
"content": "You either need a SEPIC, or a buck with a \"100% PWM\" option like this one:https://www.ti.com/lit/ds/symlink/tps629210-q1.pdf?ts=1641275301565&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTPS629210-Q1That is if your output does not go higher than the input.Also the LiPo battery cell is 3.7V at 10% charge, which makes it possible to use a regular Buck, if you so wish.In general, one of the more \"fancy\" Bucks that can transition between PWM and PFM modes and is optimized to work at low loads would be fine, but that's a Mouser search, that you shall embark on alone"
},
{
"post_id": "",
"author": "Terry Bites",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 05, 2022, 01:53:45 pm",
"content": "https://www.ti.com/design-resources/design-tools-simulation/webench-power-designer.htmlopen an acount and have a go."
}
] |
2025-10-17T17:17:09.069969
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-3-volt-regulator-output-on-external-connector/
|
3.3 Volt regulator output on external connector - Page 1
|
[
{
"post_id": "",
"author": "rakeshm55",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "May 11, 2019, 12:17:16 pm",
"content": "Hi,I have a 3.6V rail available on my board.I have a GPS module (XM1100) which needs an active antenna . I plan to have an LDO (LP5907MFX-3.3) to generate 3.3V.Now the antenna port is mounted on external chassis. So the LDO should be hardened enough to handle handling abuse short,Surge,etcIs there a suitable LDO for such applications??"
},
{
"post_id": "",
"author": "t1d",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 11, 2019, 04:17:56 pm",
"content": "Well, as a general answer...1) You need to know if...- The PSU can supply the additional needed amperage, which shouldn't be very much- The rail trace can handle the extra loadAs you are likely to need various components to round out a PSU sub circuit, you may want to make an independent sub PSU board and tap directly to the supply (transformer, etc.). But, again, can the supply handle the extra load? Is the supply the proper type; not a buck converter, for certain types of sub circuits, etc...More information as to the host unit, its supply, etc. and the the GPS power requirements would help.Are you making a GPS time discipline? If so, look at existing DIY project modifications. Skullcom has one on YouTube. There are many others."
}
] |
2025-10-17T18:10:59.170930
| 2
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-3v-(700ma)-from-a-24v-dc-source/
|
3.3V (700mA) from a 24V DC source - Page 1
|
[
{
"post_id": "",
"author": "ppTRN",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 05, 2023, 07:17:40 pm",
"content": "Hi everyone,I need to design a board with an ESP32, powered from a 24V source. I am looking for a swiching regulator but there are so many that I am worried that i might take the wrong one. First things first, I guess that the best way to get 3.3V from a 24V supply is a switching regulator, not an LDO. Secondly, won't the power loss be huge with such a gap between input and output voltages? Did anyone faced such problem, and found a suitable solution?Thank you.PS: till now the best option seems to be a regulator based on the MC34063 or the LM2596"
},
{
"post_id": "",
"author": "wasedadoc",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 05, 2023, 07:33:31 pm",
"content": "1. LDO means Low Drop Out. Only necessary when the input voltage is close to the output voltage. For example 5v in and 3.3v out. 24 in and 3.3 out does not fall into that category. Not saying you cannot use an LDO, just that you would not need to discount a regulator which was not a LDO type.2. When dropping significant voltage in a linear regulator the dissipation needs careful attention. Every volt dropped with every milliamp of current means 1 mW of heat. So heatsinking may be needed and be an additional reason with efficiency for opting for a switching regulator. For some moderate currents you could reduce the heat in a linear regulator by using a series resistor to drop some of the voltage.700 mA times 20.7 Volts is about 15 Watts so you should certainly be thinking of a switching regulator. A side benefit is that the 24 Volt supply will only need to provide about 120 mA."
},
{
"post_id": "",
"author": "mariush",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 05, 2023, 08:16:39 pm",
"content": "While MC34063 and/or LM25x6 would work, they're kind of bad choices because they switch at low frequencies, which means they require big inductors and capacitors to output a smooth voltage, and that means higher costs and more pcb space used.MC34063 is also fairly basic, with minimal protections, but it's indeed very cheap.I'd suggest looking for something that can work at least 200kHz or more (but not too much, as the higher the frequency the more important it is to do proper layout on the pcb and the higher the frequency usually the efficiency goes down a little)A bonus would be synchronous rectifier step-down regulators, which allow you to skip on a diode making circuit cheaper and smaller.For example, some suggestions :AP63201 :https://www.digikey.com/en/products/detail/diodes-incorporated/AP63201WU-7/9858425See figure 10 in datasheet (page 9) and the recommended values chart on page 13 and the example layout on page 15.AP63203 :https://www.digikey.com/en/products/detail/diodes-incorporated/AP63203WU-7/9858426(fixed 3.3v output version of the above, so no resistors to set output voltage required)AOZ1282 :https://www.digikey.com/en/products/detail/alpha-omega-semiconductor-inc/AOZ1282CI/3973644If you want through hole (but NOT breadboard friendly, you must solder to some prototyping board or pcb), well, not much besides the classic MC3x063 BUT you could go with packages like TO-252 that are very easy to solder , and even bend the leds to make it through hole.For example see BD9870FPS (900 kHz) :https://www.digikey.com/en/products/detail/rohm-semiconductor/BD9870FPS-E2/1816644or BD9870FP (300kHz) :https://www.digikey.com/en/products/detail/rohm-semiconductor/BD9703FP-E2/1957242"
},
{
"post_id": "",
"author": "ppTRN",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 05, 2023, 08:30:57 pm",
"content": "Quote from: wasedadoc on February 05, 2023, 07:33:31 pmOf course, my bad, I ment linear regulator.Quote from: mariush on February 05, 2023, 08:16:39 pmSpace on the board is actually not a problem. Thank you for your suggestion, i will go through them!"
},
{
"post_id": "",
"author": "langwadt",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 05, 2023, 08:35:32 pm",
"content": "for a few prototypes or one-ofs it doesn't get much cheaper and simpler than something like this;https://www.ebay.com/itm/224151690136"
},
{
"post_id": "",
"author": "dobsonr741",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 05, 2023, 09:41:48 pm",
"content": "Look at this TI part - no external inductor needed, has a built in one! I’m using one and totally happy how simple to design it in.https://www.ti.com/lit/ds/symlink/lmz14202.pdf"
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 05, 2023, 09:45:42 pm",
"content": "Yep, that's a nice part."
},
{
"post_id": "",
"author": "langwadt",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 05, 2023, 10:57:12 pm",
"content": "Quote from: dobsonr741 on February 05, 2023, 09:41:48 pmit is also expensive and out of stock"
},
{
"post_id": "",
"author": "dobsonr741",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 06, 2023, 12:37:13 am",
"content": "My next runner-up is from XP power:https://www.digikey.com/en/products/detail/xp-power/VR05S3V3/13147710Tried and proven as well.Or, if 0.7A is a hard limit:https://www.digikey.com/en/products/detail/xp-power/SVR10S3V3/13147726"
},
{
"post_id": "",
"author": "AnalogTodd",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "February 06, 2023, 01:59:50 am",
"content": "Quote from: ppTRN on February 05, 2023, 08:30:57 pmLinear regulators are basically controlling a transistor to give a constant voltage at Vout as long as Vin is higher than Vout plus the regulator dropout. They dissipate huge amounts of power based on the equation Pdiss = (Vin - Vout) * Iout. As already pointed out, 24V to 3.3V at 700mA is 15W of power dissipated, basically just becomes wasted heat.Switching regulators operate by moving electricity through from input to output only part of the time. They will turn on a switch to build energy in an inductor, then turn off that switch and the inductor then sends that energy to the output through another switch. For a buck regulator (switch from high voltage to low) going from 24V to 3.3V, the switch turns on less than 15% of the time. The capacitor on the output smooths the output voltage to keep it close to where you want. I know many purists are going to point out that there are a lot of equations and details that I'm not covering, but this is meant to be a basic concept.Because the switching regulator only pulls power from the input part of the time, wasted power is minimized. For a buck regulator, 3.3V output at 700mA is a little over 2.3W of power delivered, and the input is going to be 24V delivering 700mA, but only 15% of the time. So while it can be taking 16.8W of power at a given instant when the switch is on, the average power needed is only 15% of this, a little over 2.5W. Instead of 15W wasted, it's only 0.2W."
}
] |
2025-10-17T16:59:24.005507
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-3v-for-accelerometers/
|
3.3V for Accelerometers - Page 1
|
[
{
"post_id": "",
"author": "cksa",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 23, 2010, 12:22:20 am",
"content": "So I'm designing this portable device that incorporates accelerometers and gyros for inertial measurement purposes. This of course requires a precise and stable voltage supply to these components. However, I am stuck in thinking of how to achieve this whilst not using too many batteries.For example, I could use one AAA and boost it up to 3.3V, but will this be stable enough? Could I boost it up to say 5V and use a linear regulator to regulate it down to achieve less ripple? Since there are other devices on the 3.3V rail, would it be a good idea to use TWO separate 3.3v regulators, with one directly dedicated to the ADC and the accelerometers and gyro?I could also use one li-poly, but that requires a buck-boost or sepic DC-DC converter, again, switching regulators, will there be too much vout ripple?Thanks,"
},
{
"post_id": "",
"author": "Mechatrommer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 23, 2010, 03:27:16 am",
"content": "the is no such thing as accuracy in navigation terminology unless u stick with GPS system... satellites & beacons = man made.... stars & landmarks = god made. i dont see the point of trying harder to design a bulletproof electronics hardware if its for the sake of accuracy, but if its for reliability,durability and quality... then yes! for me... a battery and a bypass caps will just do fine. no offense, but i'm a navigation system designer as well.... not professionally though, just hobbyit is for navigation isnt it? or positioning of some sort?"
},
{
"post_id": "",
"author": "cksa",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 23, 2010, 03:31:50 am",
"content": "Oh lol. It isn't for outdoor applications, so GPS wouldn't work. It's for a sports application very much indoors"
},
{
"post_id": "",
"author": "Mechatrommer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 23, 2010, 03:34:12 am",
"content": "once you are done with the electronics part, the mechanical aspects will come into your way... then it goes to programming part, or circuit tuning part... and it will go merry go round and round until u satisfy... i think"
},
{
"post_id": "",
"author": "marianoapp",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "July 23, 2010, 04:06:48 am",
"content": "and when you finish and get something like this you know it was worth it"
},
{
"post_id": "",
"author": "Mechatrommer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 23, 2010, 04:25:15 am",
"content": "hell! thats aggressive! last time i dealt with browned out mcu and motor kickback issue, several config of caps will do the trick, other than that, i only accept what gyros gave me. just keep focusing on what voltage level you are referencing at. and if its the voltage accuracy for the gyros you are worrying about, i suggest you wire it directly to the main power supply (with superb noise suppression of course!), with the stepped down/up voltage will feed the rest that dont need the accuracy. just my limited knowledge tells."
}
] |
2025-10-17T20:42:43.951187
| 6
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-3v-from-pir-amplify/
|
Amplify PIR 3.3V? - Page 1
|
[
{
"post_id": "",
"author": "almamater",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "January 22, 2021, 12:49:32 pm",
"content": "Hello Everyone!I want to make a simple circuit but now i have one question\\problem. I want to control one LedStrip (40Leds \\~450mAcurrent consumption) with one sensor PIRlike this oneand control one 5mm LED at same time, when LEDstrip is ON the LED is OFF and vice versa.This PIR have3.3V (Hight)at the Output Pin when motion is detectedSo, i made this circuit and works very well with myATX power supply(for simulate the 3.3V input):But now when i test with the PIR Output the circuit don't work, probably i have to amplify some how the 3.3V from the sensor, can you please help me with this? Probably i must put another transistor between the PIR and this circuit (BD139).. but what the best way to do it?Thank you."
},
{
"post_id": "",
"author": "Terry Bites",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 22, 2021, 01:38:58 pm",
"content": "Most of these little PIRs can only source 100uA or less from their output.The BD139 has a beta of ~20 so you will barely turn it on.Change it for alogic level mosfet. For example an NTR4501NT1G, it will handle 2A with very low drive requirements."
},
{
"post_id": "",
"author": "cavac",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 22, 2021, 02:01:57 pm",
"content": "Something like this should work, at least i think it should without actually building the circuit:"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 22, 2021, 04:41:48 pm",
"content": "Quote from: cavac on January 22, 2021, 02:01:57 pmThe MOSFET's drain and source connections are reversed and why use two BJTs, when one will do?"
},
{
"post_id": "",
"author": "cavac",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 22, 2021, 06:36:59 pm",
"content": "Quote from: Zero999 on January 22, 2021, 04:41:48 pmWhoops.Copied the MOSFET design from a recently finished project. Switched the pins on my PCB around after an ElectroBOOM moment but i guess i forgot to update my hand-drawn schematic. Well, uhm, it's good thing that the error popped up here in discussion, i would probably have just copied the design for my next project... and looked in wonderment at another smoking crater in the midst of my PCB...Quote from: Zero999 on January 22, 2021, 04:41:48 pmTerry Bites mentioned that the PIR can only source a tiny current, so i figured i'd better double up on those transistor to get better amplification of that tiny signal."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 22, 2021, 06:42:13 pm",
"content": "MOSFETs have a truly massive, almost infinite, current gain. One BJT is sufficient. The only reason to add more is to improve the switching speed, which isn't necessary in this instance."
},
{
"post_id": "",
"author": "cavac",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "January 22, 2021, 06:46:30 pm",
"content": "Thanks!"
},
{
"post_id": "",
"author": "almamater",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "January 22, 2021, 11:29:04 pm",
"content": "Thanks for the responses!! I will try and test the suggestions"
}
] |
2025-10-17T17:35:02.161175
| 8
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-3v-gpio-controlled-switch-for-high-dc-voltage-(42v-)/
|
3.3v GPIO controlled switch for high DC voltage (42V +) - Page 1
|
[
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 08, 2024, 04:17:12 pm",
"content": "TLDR Version:I'd like some help with a circuit that is controlled via an Arduino (3.3v) to switch on a BLDC motor (700W) and other components powered by a 4.4AH battery that will fluctuate between 42V and 32V depending on battery charge level.Hi All,I'm trying to design/build a power control circuit but I've got to the point where I need a little help.Essentially what I need to do is turn on/off a high voltage battery power source via an Arduino nano (3.3v).I'd prefer not to use a relay because they can run into issues in the long term with contacts fusing and general reliability.Due to this I figured using a MOSFET might be a good solution but I'm open to alternate points of view.I'd also prefer if possible that initially the circuit is in a normally off state, until the Arduino turns it on using GPIO High.It's worth mentioning that amongst other things this will be used to indirectly turn on/off BLDC motors (via external motor Driver circuits) so there may be a chance of Back EMF.I found a schematic online that I've been trying to adapt to work with a higher voltage source. However, I later found out that apparently the original circuit has some issues with reliability or components blowing.At the moment I'll be using a 4.4AH battery pack that will fluctuate between 42V when fully charged and 32V when flat. However, in the future I may decide to upgrade the battery (anywhere up to 55V 20Ah) to get longer run times etc... for this reason I'd really like to better understand how to calculate resistor values used in the circuit and other considerations to adapt the circuit again later if required.Because this is a battery powered circuit it would be great if was somewhat energy efficient.I will have some expensive components attached to the Arduino so any advice in regard to safeguards in the case of component failure when working with a circuit like this would be appreciated!I've read lots of articles and watched a bunch of videos researching this but unfortunately I still feel like I have more questions than answers (I'm not an EE so some of this stuff is a little over my head at the moment).To a lesser extent I suppose it's also worth mentioning that the circuit will be subject to vibration and used outdoors (in an appropriate waterproof enclosure) so it will be subject to temperature fluctuations 6°C to maybe 80°C (Australian summer in the sun).I'll be adding a TO220 Aluminum heat sink to the MOSFET (20 x 15 x 10mm)This is what I have so far but i'm not attached to it, if someone has a better suggestion in regard to component selection or the general design I'm open to ideas.Q1: NPN - BC547Chttps://datasheet.lcsc.com/lcsc/2304140030_LGE-BC547C_C713614.pdfQ2: P Channel MOSFET - IRF9540NPbFhttps://au.mouser.com/datasheet/2/196/Infineon_IRF9540N_DataSheet_v01_01_EN-3363104.pdfD1: Schottky Diode MBR1060https://datasheet.lcsc.com/lcsc/1810301841_SMC-Sangdest-Microelectronicstronic--Nanjing-MBR1060_C260256.pdfD2, D3: Schottky Diode SBX2050https://diotec.com/request/datasheet/sbx2020.pdfR2: 4.7K .25W 1% metal film resistorR1: 2.2k .25W 1% metal film resistorR3: 4.7K .25W 1% metal film resistorC1: 100uF Electrolytic Capacitor 50V Polarhttps://www.rubycon.co.jp/wp-content/uploads/catalog-aluminum/TXW.pdfF1: Fuse 10AI also tried simulating this in LTSpice before coming here but it didn't seem to work the way I expected (I'm new to LTSpice). I suspect that it may be have been due to the resistor values, the way I tried to simulate the load or how I how I tried to run the simulation.See attached LTSpice simulation attempt"
},
{
"post_id": "",
"author": "BennoG",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 08, 2024, 06:45:44 pm",
"content": "I think you will blow jour mosfet with this schematic.The G-S voltage can be 40V in your solution the specs say max 20V.You can use a totempole schematic or a specified chip to drive the P-Fet.Benno"
},
{
"post_id": "",
"author": "Siwastaja",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 08, 2024, 06:54:17 pm",
"content": "The design will be somewhat non-trivial. A 700W BLDC inverter will have significant amount of capacitance on its input, so you want precharge to not exceed the SOA curve of your MOSFET. For different corner cases, current monitoring / \"e-fuse\" type, at very least one utilizing the Rds_on of the MOSFET like a \"desaturation detection circuit\", would be an excellent idea. Also at this current level (especially with your efficiency concerns) you might want to avoid diodes and instead use two back-to-back MOSFETs.There are so called load switch ICs which do all of this integrated (current limiting, precharge, active SOA protection with die temperature sensing), so you might want to look at this. Last time I had a similar case though I had to do complete custom discrete solution because all of those ICs had significant off-state quiescent current which was not acceptable (I was also having a battery as an input).Are there some kind of safety requirements? I mean, the failure mode will be that it fails as short circuit i.e. stuck ON. If this causes a risk of injury or similar then even more care is needed."
},
{
"post_id": "",
"author": "pcprogrammer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 08, 2024, 07:17:11 pm",
"content": "Add a 10V or so zener diode from source (S) to the gate (G) and an extra resistor in between the gate and the collector of the transistor to limit the current through the zener and this will limit the source gate voltage to be below 20V.Another option is to look for a beefy enough N channel mosfet with a gate threshold below 3.3V. This way you only need the one transistor to get it working. Small series resistor between the gate and the GPIO of the arduino. Or use a 5V nano and an IRFZ44N. Gate threshold is 4V max and 2V min, so might even work with the 3.3V version. Id is 49A so plenty for your purpose. Vds is 55V so some head room on your 42V supply.As long as there is no other connection to your BLDC motor driver that relies on ground the low side control is no problem.I would not bother with the additional diodes in the setup, unless there is a real risk of reverse connection of the battery. They have a voltage drop and will dissipate more power then you might like. With a 700W motor on 42V the current is 16.6A which is near the maximum current of the SBX2050 and with .6V drop it will have to dissipate ~10W.But like Siwastaja wrote the turn on current might be very high and an other approach might be needed."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 08, 2024, 08:56:56 pm",
"content": "Why the extra Schottky diodes?The second series one isn't needed. The one in reverse parallel should be after the first one and it only needs to be big enough to pass the leakage.Add an emitter resistor so it forms a current sink, thus limiting the voltage across the collector resistor."
},
{
"post_id": "",
"author": "shapirus",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 08, 2024, 09:22:45 pm",
"content": "Quote from: pcprogrammer on March 08, 2024, 07:17:11 pmBeware, however, that at this load current we want to look not only at the gate threshold voltage, but also at the voltage at which the minimal value of Rds(on) is reached. Resistance at threshold voltage may still be high enough to quickly fry the transistor."
},
{
"post_id": "",
"author": "JustMeHere",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 09, 2024, 01:10:32 am",
"content": "Look at an optocoupler."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 09, 2024, 09:10:36 am",
"content": "This statement in the video the O.P. linked from the schematics is incorrect:https://youtu.be/tePft-bm9mw?t=501The seventh (last) 'method' of implementing a constant power load using a BI source doesn't! The problem is, within the +/-1V region its not resistive due to misuse of the limit() function 'hiding' the if() that is supposed to make it resistive. It becomes the fixed current Imin, so is inherently unstable, resulting in the observed large negative voltage at MOTOR_OUT.Also, most types of DC motor are *NOT* a constant power load so simulating one as a constant power load is almost certainly inappropriate."
},
{
"post_id": "",
"author": "Siwastaja",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 09, 2024, 11:17:13 am",
"content": "Quote from: pcprogrammer on March 08, 2024, 07:17:11 pmGate threshold voltage is completely wrong parameter to look at. It is defined such that MOSFET conducts some micro to milliamps, which is orders of magnitude too little. IRFZ44N specifically needs at least 7-8Vgs."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 09, 2024, 02:16:05 pm",
"content": "Quote from: JustMeHere on March 09, 2024, 01:10:32 amThat would work (put the phototransistor in the place of Q1 in my schematic and increase R1 to 10k) but why? 42V is not that higher voltage? Isolation isn't required, unless perhaps the connections between the MCU and driver are very long."
},
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 11, 2024, 06:19:55 am",
"content": "Quote from: Siwastaja on March 08, 2024, 06:54:17 pmI've not built it yet so I cant say for sure what would happen if there was a failure occurred and it was stuck in the on statePower alone wont cause the motors to turn - as the motors will be controlled via VESC motor controllers controlled via UART connections.Best case scenario if it got stuck in the on state it would eventually run the batteries flat or maybe overcharge the batteries if the BMS in the battery pack does not handle that.Worst case if somehow the motors continued to run while stuck in the on state it's plausible that it might have a chance of causing injury. As the intention of this circuit is a power control for an automated robot.There will be an emergency off button (master power switch) but it might not always be supervised when in use."
},
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 11, 2024, 06:35:24 am",
"content": "Quote from: Zero999 on March 09, 2024, 02:16:05 pmSo I could use an optocoupler instead of the NPN for a gate driver?I've seen optocouplers used for limit switches on CNC machines to prevent issues with EMF feedback.How long is very long?I think the longest wire harness would be around 30cm, I'll use twisted pairs of wires for any data lines and keep any high voltage power harnesses separate to the low voltage stuff."
},
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 11, 2024, 06:40:43 am",
"content": "Quote from: Ian.M on March 09, 2024, 09:10:36 amHi Ian,Thanks very much, I was stumped as to why the negative voltages were so high!I don't suppose you know of any good examples for simulating load in LT spice? Initially I planned to just use a resistor however I read that approach had it's own issues.I'm not concerned about emulating motor speed or anything fancy like that.It might be handy if it was possible to simulate back EMF however at this stage I just want a simple solution that works - one problem at a time"
},
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 11, 2024, 06:45:05 am",
"content": "Quote from: JustMeHere on March 09, 2024, 01:10:32 amAre optocouplers more resistant than BJT NPNs in a situation where the mosfet fails?I've seen optocouplers used for limit switches on CNC machines to prevent issues with EMF feedback."
},
{
"post_id": "",
"author": "BennoG",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 11, 2024, 06:54:34 am",
"content": "A complete different approach would be to use a Smart High-Side Power Switch e.g. BTS724G you can put all 4 output in parallel and get a switch current of 8A.I think there are more beefy versions of this and you can directly switchy them with 3.3VBenno"
},
{
"post_id": "",
"author": "radiolistener",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 11, 2024, 07:09:52 am",
"content": "I think using some small mosfet as a driver to control relay is more reliable way. You can switch even mains voltage with relay."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 11, 2024, 07:10:33 am",
"content": "I'm not saying this is a good idea vs the alternatives that have been offered above, but at least I've got your sim behaving sensibly + fixed up some poor design choices in it.N.B. the SBX2050.asy and SBX2050.lib must be in the same folder as the sim. Other .lib paths are unchanged."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 11, 2024, 07:18:21 am",
"content": "To simulate a PMDC motor, you need an inductance in series with a resistor (winding resistance, determines stall current) and a controlled voltage source proportional to the motor speed (modelling the back EMF from the coils moving in the magnetic field), scaled so that it draws the correct no load current at its no load speed. Modelling the motor speed and acceleration under load is a whole other issue . . .Note this simple model doesn't include torque or current ripple or the effects of commutation."
},
{
"post_id": "",
"author": "pcprogrammer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 11, 2024, 08:27:27 am",
"content": "Quote from: PhoenixAU on March 11, 2024, 06:19:55 amAre you referring to one of these in thevesc project?If so these will take care of a lot of the issues. When power is connected the MCU in it has to startup before any action on the motor will take place, so current when switching on will be low.The main issue with your original design is the to high Vgs which will kill the MOSFET, and the needless additional diodes. For protecting against reverse battery connection you can add the same P-MOSFET in series, but with reversed source and drain connection. Also needs a zener to protect against to high Vgs. Seeherefor more info about this."
},
{
"post_id": "",
"author": "sparkydog",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "March 11, 2024, 08:18:03 pm",
"content": "Quote from: PhoenixAU on March 08, 2024, 04:17:12 pmSo, you say \"I'd prefer not to use a relay\"... but then explain why you'd prefer to not use amechanicalrelay.Have you considered a SSR?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 11, 2024, 10:02:34 pm",
"content": "Quote from: PhoenixAU on March 11, 2024, 06:35:24 amIf you want to go for an opto-coupler, then change to an N-channel MOSFET and use a photovoltaic opto-coupler.It's not so much as length but impedance, i.e. resistance and inductance. When the gate voltage rises, causing a high current to flow, the source voltage will also rise, causing the potential difference between the gate and source to fall. If the source is connected to 0V via a very low impedance, then this increase in source voltage will be very small and have no effect. In the other hand if the source connection is a higher impedance, say a long wire, with some resistance and more importantly inductance, the source voltage will rise more, which will try to turn the MOSFET off a bit, remember it's the potential difference between the gate and source, which cases it to turn on. An opto-coupler, connected between the gate and source, very close to the transistor eliminates this problem because its negative side is connected directly to the source, so the positive side will also increase, if the source voltage increases.I'll post a schematic with simulation it the above explaination is too difficult to follow."
},
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 13, 2024, 04:42:45 am",
"content": "Quote from: Zero999 on March 11, 2024, 10:02:34 pmThat would be great"
},
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 13, 2024, 05:06:07 am",
"content": "Quote from: sparkydog on March 11, 2024, 08:18:03 pmTo be honest I hadn't - but from what I can see anything suitable is going to be around $48USD and I'd require 2 of them (I only had a quick look though).That's getting fairly expensive compared to using a MOSFET + BJT or a MOSFET + optocoupler.Do you have any SSRs in mind that are suitable?"
},
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 13, 2024, 05:11:56 am",
"content": "Quote from: Ian.M on March 11, 2024, 07:10:33 amThanks very much for taking the time to do that Ian! Hopefully I'll get a chance to tinker with it on the weekend!"
},
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 13, 2024, 05:29:17 am",
"content": "Quote from: pcprogrammer on March 11, 2024, 08:27:27 amI'm actually probably going to use a hacked hoverboard as a motor controller that uses UART for communication instead of a VESC but you get the general idea ( see linked video below )It is possible that I might also use a BLDC motor driver such as JKONG Motors JKBLD300 (https://www.jkongmotor.com/Product/JKBLD300-Brushless-DC-Motor-Driver.html)paired with a BLDC motor such as JK57BLS02 (https://www.jkongmotor.com/Product/JKM-57BLS-Round-BLDC-Motor.html).None the less, yes the motors should not be turning until told to do so by the MCU."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 13, 2024, 05:42:20 am",
"content": "Beware: the constant power load still isn't quite working right. The problem is the transition between resistive and constant power, which has a discontinuity, which causes the sim to hang if you add any series resistance to C1 (the presence of which prevents infinite dV/dt at the transition, allowing the solver to pass it more easily).Personally I'd recommend finding a more realistic model for an ESC as a load or using LTspice's native constant power load."
},
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 13, 2024, 05:50:56 am",
"content": "Thanks Ian - at the moment something simple will do, initially I just want to verify the circuit works as expected. So the native constant load approach sounds good.I'll worry about trying to simulate Back EMF once i've tackled the basics.I'd imagine that i'm going to have a hard time finding something that is identical to what im using so near enough will have to be good enough."
},
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 13, 2024, 05:57:29 am",
"content": "Quote from: pcprogrammer on March 11, 2024, 08:27:27 amI suspected that might have been the case when I initially posted the schematic (thanks).Quote from: pcprogrammer on March 11, 2024, 08:27:27 amI can't quite picture that. Is there any chance you could draw a rough circuit diagram showing how that might work, please?"
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 13, 2024, 06:32:29 am",
"content": "You should probably readhttps://ltwiki.org/index.php?title=B_sources_(complete_reference) for details of LTspice's native constant power load, and alsohttps://ltwiki.org/?title=Undocumented_LTspice"
},
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 13, 2024, 06:40:34 am",
"content": "Quote from: Zero999 on March 08, 2024, 08:56:56 pmI believe the intention for the second series resistor (D3 in the original post) is to protect against reverse polarity in the instance where the BLDC is manually turned causing the motor acts as a dynamo or perhaps its an attempt to protect against Back EMF when the motor turns off?It's also my (limited) understanding that if a motor is under heavy load (torque slowing the motor down) then it can also cause some issues due to back EMF.Although from what I've seen online usually a Schottky diode in reverse polarity across the motor terminals as Flyback/Snubber/Suppressor Diode, I've also seen capacitors across the terminals of brushed DC motors to help filter the noise from the Back EMFTo be honest I don't totally understand why D1 is there although once again I suspect it's also to help tame Back EMF."
},
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 13, 2024, 06:45:22 am",
"content": "Quote from: BennoG on March 11, 2024, 06:54:34 amThanks for the suggestion Benno, I do remember reading somewhere that they are meant to be more efficient than than using a MOSFET.Do you know if they are more tolerant to Back EMF than a MOSFET? Apparently if a MOSFET fails due to Back EMF/reverse voltage over current it can cause it to feed voltage through the gate (frying the Microcontroller) or cause the MOSFET to turn on when it's meant to be off"
},
{
"post_id": "",
"author": "pcprogrammer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 13, 2024, 08:00:54 am",
"content": "Quote from: PhoenixAU on March 13, 2024, 05:57:29 amSee attached picture. To protect against voltage spikes I added a TVS with 47V rating at the output. The IRF9540 might be to weak for the task with a Id of 19A. Not a lot of head room with a load of 16A. And with Rds on of 0.2 Ohm you still loose 3.2V per MOSFET. There are beter MOSFETS with lower Rds on out there for sure. Power dissipation will also be around 50W per MOSFET. So in this case a schottky diode for the reverse voltage protection might work out better.The first IRF9540 is to protect against wrong battery connection, and the second IRF9540 is to switch the power on and off. The zener diodes might need a bit more current to work properly, but it gives you an idea of what the circuit looks like.Edit: I forgot to add a pullup resistor for the second MOSFET, that needs to be parallel to the zener diode."
},
{
"post_id": "",
"author": "radiolistener",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 13, 2024, 03:21:19 pm",
"content": "Quote from: PhoenixAU on March 08, 2024, 04:17:12 pmUsually mosfet lifetime is much shorter than relay, especially when they are working at high voltage. You're needs to have a dozen of replacement mosfets for repair, while relay can work for ten years with no issue"
},
{
"post_id": "",
"author": "sparkydog",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "March 13, 2024, 05:07:22 pm",
"content": "Quote from: PhoenixAU on March 13, 2024, 05:06:07 amAh, yes, I was forgetting the little $2 ones are only rated for ~0.1A. Unfortunately, Octopart hates me right now, but based on what I could find before it quit working, I would guess you can probably find something for closer to $20. Certainly there are SSRs rated for... hold on, you said you're driving an18Amotor? That's a honking lot of current.In any case, it's not obvious why you'd need two? (You might need a $2 SSR tocontrola bigger SSR; the larger ones seem to want higher \"coil\" voltages.)On further consideration, I suspect, as others have noted, that there's a way to just \"talk\" to whatever is driving the BLDC that would make your life ever so much easier. (Even if that means replacing the driver.)That said, I also suspect you underrate mechanical relays. Unless safety is a critical consideration (in which case you shouldn't be squawking at the idea of paying $50), a suitably rated EMR from a reputable manufacturer shouldn't be terribly expensive and willprobablylast for years without trouble."
},
{
"post_id": "",
"author": "Siwastaja",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 13, 2024, 05:22:54 pm",
"content": "Seeing that VESC apparently is open-source, then the obvious solution is to integrate everything onto that one piece of hardware and software. The motor controller itself already consists of transistors. All you need to do is to not enable the the motor control and put the microcontroller and all relevant circuits in some low-power state. I don't know if that is possible without hardware modifications, but it would be simpler than cutting the high current path and managing high inrush currents to the capacitors without blowing up these extra power switches.Only if you need bi-directional switching i.e. prevent back-EMF generated by rotating motor going through the diodes of the VESC's existing bridge, only then you would need to add another power switch."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 13, 2024, 07:18:08 pm",
"content": "Quote from: PhoenixAU on March 13, 2024, 06:40:34 amThere is no need for another diode, because it's impossible for there to be any reverse voltage, with a BLDC and drive.The motor is a BLDC type and driver. BLDC is a misnomer, it's really a type of three phase AC motor. The driver will have diodes connected between each phase and both of its supply rails, forming a three phase full bridge rectifier. If the motor is manually turned, it'll generate an AC voltage, which is rectified to the same polarity as the driver, hence no further reverse polarity protection is required.Quote from: PhoenixAU on March 13, 2024, 04:42:45 amAttached is a simulation. The inductor represents a long cable. The MOSFET is being switched at a high frequency. The yellow plot shows the load current and red the source voltage. The increase in source voltage, due to the long, inductive cable, greatly slows down the switching speed. Connecting an optically isolated MOSFET driver between the gate and as close as possible to the source, would increase the switching speed.In your case, you're only switching slowly and at a much lower current, so it's unnecessary. The only reason why you might want to use an optically isolated driver, is so you can use an N-channel MOSFET and switch the high side.Come to think of it, why are you switching it at all? Is it possible to send the BLDC driver a disable command? That would make much more sense, than switching the power."
},
{
"post_id": "",
"author": "Siwastaja",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 13, 2024, 07:24:37 pm",
"content": "Quote from: Zero999 on March 13, 2024, 07:18:08 pmUsual reasons for switching the power:* Prevention of rectified BEMF voltage (generated by the motor when manually turned un-powered) running into the battery/supply* Extra safety layer* Powering off drivers that do not have the enable feature at all, or consume too much power in disabled state, and can't be modified"
},
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 14, 2024, 02:28:15 pm",
"content": "Quote from: radiolistener on March 13, 2024, 03:21:19 pmQuote from: sparkydog on March 13, 2024, 05:07:22 pmThat's food for thought - thanks very much guys!I didn't realise that relays had a longer lifespan than mosfets.(I'd heard lots of bad press about fusing/failing contact due to arcing - which I figured would be an issue with the power i'll be using)I suppose that most cars utilise relays and mechanical light switches have a fairly long service life.One pro for relays is that they don't have drain leakage current.Although I'll have to compare how much power is required to power the coil for the magnet - compared to the alternate solutions.(If I went with relays I'd be using the Normally Open configuration so the coils would be drawing power while it was turned on.)"
},
{
"post_id": "",
"author": "shapirus",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 14, 2024, 02:38:38 pm",
"content": "Speaking of mechanical relays, I use a Powercom KIN-1000AP UPS for my desktop PC, and it's been in service since 2005 -- that's almost 20 years!It uses relays to switch between line power and batteries and also to activate AVR, and these events are far more frequent than I'd wish them to be.It still works (at least, for an external observer) like new."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 14, 2024, 02:39:29 pm",
"content": "Quote from: radiolistener on March 13, 2024, 03:21:19 pmWhat makes you think that?There is no reason why a MOSFET will have a shorter life time, compared to a MOSFET. It depends on the application. A relay will have a finite number of on,off cycles, which will depend on the current and voltage. A MOSFET has infinite on, off cycles. A relay will be more robust, when it comes to over voltage and ESD, which will easily kill a MOSFET."
},
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 14, 2024, 03:02:14 pm",
"content": "Quote from: Zero999 on March 13, 2024, 07:18:08 pmThanks very much for taking the time to do that Zero999, I really appreciate it!!In regard to the inductor representing the long cable - have you got a rough idea of how long a cable needs to be before it starts to cause issues? At this stage I can't foresee any wiring harnesses being much longer than 30cm (12\") - I'll use twisted pairs for data lines and keep the higher voltage harnesses separate."
},
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 14, 2024, 04:56:47 pm",
"content": "Quote from: Siwastaja on March 13, 2024, 07:24:37 pmExactlyQuote from: sparkydog on March 13, 2024, 05:07:22 pmHi guys,yep I suppose there has been a little bit of obfuscation.The circuit in my original post was supplied to keep things easily digestible - the design below essentially uses two of the circuits from the original post and is coupled with an INA169 module for power monitoring, I understand the basics of what was going on, however like many of you I had a few questions to regarding design choices - before my initial post I had tried to simulate it it hope that would answer my questions but the simulation didn't work as I expected - which only led to more questions. I also asked the guys who designed the original circuit, but they didn't seem to know themselves.The circuit in my original post was derived from the following designs:https://github.com/HoverMower/Ardumower_PCBswhich was derived from:https://github.com/Starsurfer78/Ardumower_PCBs/blob/main/Charging_PCB/charge_pcb.pdfThe schematic above performs the following:Turns on/off charging to ensure batteries do not get over charged via Q1 + Q2Q3 + Q4 controls power to J4, J5, J6, J7, J9 - this could be used to turn off the device to prevent battery undercharge or just to turn off the device when requiredMonitors charge current via an INA169 ModuleMonitors Charge Voltage, Batt Voltage via Voltage dividersJ8 is a Normally open switch (momentary) used as a start button to turn on the robotHowever the original schematic (https://github.com/Starsurfer78/Ardumower_PCBs) above was designed for use with a 29.4V battery.Initially I'll be using a 42V 4.4AH battery (10S2P) from a hoverboard - the battery has a built in BMS but it's pretty basic.However there's a high chance I'll upgrade the battery at some point in the future to get longer run times (anywhere up to 55V 20Ah) although that all depends on how it performs with the battery I have.Connected to this \"Power PCB\" via J4, J5, J6, J7, J9Meanwell DDR-30L-5 30W 5V DC/DC converter (to power all 5V devices incl. Arduino Nano and Nvidia Jetson)hacked hoverboard motor driver + BLDC motors (for driving robot)Additional motor driver + BLDC motor (for cutting grass)Arduino Nano @3.3v (controls Power PCB and some other peripherals)Nvidia Jetson Nano 4GB B01 (main MCU - controls Arduino nano via USB cable)Stereo depth cameraIMURTK GPSI'll also have include an emergency stop so that it kills power to all motors but not the computers - that way it can resume what it was doing if the \"emergency\" has passed (like a pause button).So yeah one of my main concerns I suppose was if the mosfet fails, I don't want it surging through the gate pin and frying everything via the connection to the Arduino GPIO however obviously that can be prevented via isolation such as by using an optocoupler, capacitive isolated gate driver, relay etc..."
},
{
"post_id": "",
"author": "sparkydog",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "March 14, 2024, 05:15:02 pm",
"content": "Quote from: PhoenixAU on March 14, 2024, 02:28:15 pmIt's true that contact weldingcanhappen, but so far as I know it's more of an issue with relays being abused beyond their rated capacity. There are also various ways to manage arcing.Elsewhere you said \"BLDC is a misnomer, it's really a type of three phase AC motor\", but we also seem to be talking about disconnecting a battery. What's theactualload current that the relay needs to interrupt? My understanding is that AC is usually a lot less problematic than DC as far as contact welding. (Basically, it's hard to sustain an arc with AC because the voltage drops to zero 120 times per second.)\"Battery\" also implies a portable, possibly hand-held application. Is that the case? I ask because, if you are highly space-constrained, I'm told you can get someseriousindustrial contactors (e.g. the kind used to control air conditioners) for $20 or less. These arenotsmall components, but they can handle significant loads with high reliability.Quote from: PhoenixAU on March 14, 2024, 04:56:47 pmThis suggests that your goal is more electrical isolation than needing toswitcha very large current. Specifically, if you can \"soft stop\" the motor before opening the relay, such that the relay needs tocarrya lot of current but never needs tointerrupta lot of current... then you can definitely be a lot less paranoid about contact welding. Arcing happens when you try tointerruptlarge currents. If you're using the relay for physical isolation (in which capacity an EMR is far superior to a FET), but you can arrange to only open/close it when the load current is low, that willgreatlyimprove reliability."
},
{
"post_id": "",
"author": "PhoenixAU",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "March 15, 2024, 05:33:54 am",
"content": "Quote from: sparkydog on March 14, 2024, 05:15:02 pmIt was Zero999 that was talking about AC motor. It's a battery powered project - I'll be switching DC (either on or off).However, it might be possible that there could be some AC current introduced into the system if the BLDC motor was manually turned while unpowered or via Back EMF or if the motor was turned off/stopped suddenly or is under heavy torque loads (https://www.portescap.com/en/newsroom/whitepapers/2021/12/running-a-brushed-dc-motor-as-a-generator) - I'm not sure what safegaurds (if any) have been included in the design of the Hoverboard driver PCB or the the other BLDC motor controller - if they have sufficient safegards in place it might not even be something I need to consider.In saying that if those circuits were isolated properly that would be less of an issue - Only the motor drivers, the Meanwell DC/DC stepdown and the battery BMS would be on the 42V circuit (And the INA169 power monitor). I'm sure the Meanwell stepdown would shield the low power circuits.Quote from: sparkydog on March 14, 2024, 05:15:02 pmThat could be done - it could easily be handeld by software for shutdown sequences.Quote from: sparkydog on March 14, 2024, 05:15:02 pmYes, I'd like to be able to turn it on or off via an Microcontroller (on 3.3v GPIO OUT) - for system start up, system shut down and battery charge management.I have no need for high speed switching for these switches, I wont be using PWM - they will either be on or off.However, I'd prefer for it to be in a normally open (off) state if it looses power.The charger that I have at the moment is a 42V 2A charger. The charge current would at most be 7A at 50.4V - that's if I upgraded the battery and charger.The only time that I'd need to actually switch a very large current while the motors are running would be via the the emergency kill switch however that would be handled by a mechanical switch - I could use a DPST switch there for extra safety. Tripping the emergency kill switch would not effect the current state of the Relay/Contactor/Mosfet etc..Note: Drain leakage current from a mosfet probably wouldn't be an issue due to the frequency that the robot would be in use - grass grows year round where I am. However, knowing that the batteries are always fully charged would be helpful.Quote from: sparkydog on March 14, 2024, 05:15:02 pmYep it's battery powered - a robot mower.Size, weight and electrical efficiency are all considerations.Weight and electrical efficiency will eat into run time.Obviously I don't want it to be too bulky - but I'm flexible and I'm open to ideas!How big are these industrial contactors? Have you got any examples?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 15, 2024, 08:13:15 am",
"content": "Quote from: PhoenixAU on March 15, 2024, 05:33:54 amAs I said before, any AC generated by the motor, will be rectified by the driver.The output stage has six transistors, each containing a body diode, forming a three phase bridge rectifier. Any AC or back EMF will be rectified and fed into the power supply.https://www.digikey.com/en/articles/how-to-power-and-control-brushless-dc-motorshttps://www.electronics-tutorials.ws/power/three-phase-rectification.html"
},
{
"post_id": "",
"author": "sparkydog",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "March 15, 2024, 09:12:30 pm",
"content": "Quote from: PhoenixAU on March 15, 2024, 05:33:54 amMmm... I'm not actually seeing much thatisn'tlisted as a contactor (and $50+) that's rated forDCvoltage above 24V-30V. Interrupting DC is hard. 🙂 (Finding $2 relays rated for 250VACis a piece of cake.) That said, after much digging, AZDC105 might work but it's still ~$25.It looks like you can find some automotive contactors that are not much bigger than a \"D\" battery, but most general-purpose ones are a few inches on a side. Maybe a little larger than a typical Rubik's Cube. Some DIN-mount models are about the size of a household circuit breaker. Not necessarily a deal-breaker on a mower, but bigger than you'd want in most hand-held tools (at least until you start talking about something more like a chainsaw or leaf blower)."
},
{
"post_id": "",
"author": "Siwastaja",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 16, 2024, 06:48:34 am",
"content": "Quote from: Zero999 on March 14, 2024, 02:39:29 pmIt's radiolistener. He has usually pretty good advice, you just need to run absolutely everything he says through an inversion filter. This transforms his 0% correctness rate to near 100%. For example, when he says that relays have longer lifetimes than MOSFETs, you obviously negate that --> relay has shorter lifetime --> correct!"
},
{
"post_id": "",
"author": "BennoG",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 16, 2024, 09:43:22 am",
"content": "Quote from: Siwastaja on March 16, 2024, 06:48:34 amYes I also find that mosfet has a far longer lifetime than mechanical relais.I have burned mechanical reilas controlling 3 phase AC motors in 1 month switching over 100 times a day.Replaced it with an inverter MOSFET based and it is running for 8 years now without problems.Benno"
}
] |
2025-10-17T16:38:55.220399
| 48
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-3v-serial-with-2-tx-and-1-rx-line/
|
3.3V Serial with 2 TX and 1 RX Line - Page 1
|
[
{
"post_id": "",
"author": "mribble",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 15, 2017, 05:33:13 pm",
"content": "I have a system where micro0 has a TX line, micro1 has a TX line, and mirco2 has RX line. These 3 lines are connected. I know that micro0 and micro1 won't be transmitting at the same time, but just hooking all these lines together won't work because when they aren't communicating they pull the line to 0V. So you would end up with a single between 0 and 3.3V when one wasn't transmitting and the other was. Basically I want a way to change that 0V to high impedance. Which you could obviously do with the micro, but I don't have control over the code for one of the micros. So I though I could put a schottky diode on each tx pin so that they couldn't pull the line low if the other micro was pulling pushing the line high. I thought that would work as long as the forward voltage drop in the diode was within limits for the bus (which it is). However, it's not working reliably.How do you experts suggest I solve this?Thanks in advance!"
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 15, 2017, 05:45:30 pm",
"content": "Are you sure you are describing it correctly?*most* logic level serial signals using RS232 framing idle high.You can combine two such non-overlapping signals with an AND gate.If it actually idles low, use an OR gate."
},
{
"post_id": "",
"author": "mribble",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 15, 2017, 06:11:12 pm",
"content": "I'll need to double check my low and high signals, but your solution is good. That makes perfect sense. I must have been trying to over think things."
},
{
"post_id": "",
"author": "FrankBuss",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "March 15, 2017, 06:11:46 pm",
"content": "If you use 2 diodes, the signal can only be pulled down (or pushed up, if both diodes are the other direction). You need a pullup resistor at the RX pin (or pulldown resistor). I wonder why it works at all. But even with a pullup resistor, it would be not a nice sharp edge, and if the resistor is too low, it would be a problem for the TX pin drivers. So better use an AND gate. Doesn't need to be a big 7408 quad AND, but you can use a modern small 5 pin SOT-353 chip like the NC7SZ08P5X (same chips are available for OR gates)."
},
{
"post_id": "",
"author": "macboy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 15, 2017, 06:12:53 pm",
"content": "In addition to the diodes, put a resistor from the Rx pin to ground. As it is, due to the diodes, there is no conduction path to pull the pin low. Its capacitance will keep it high for a short period of time until enough charge leaks out (through the leaky Schottky diodes) to register as low. The resistor solves this. I'd start with a few kohm, like 3.3k and go from there. Viewing the Tx pin and Rx pin waveforms on a scope would be highly beneficial.Edit: FrankBuss beat me to it, and I forgot that TTL level UART idles high, so you want a pull-up resistor (as Frank said) not pull-down,"
},
{
"post_id": "",
"author": "mribble",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 15, 2017, 09:03:00 pm",
"content": "I didn't mention it but we do have a 10K pullup resistor.I do think the and gate is a better idea so I think that's the way I'll go. Thanks for the pointer to the NC7SZ08P5X."
},
{
"post_id": "",
"author": "dml1333",
"author_rank": "Newbie",
"is_op": false,
"timestamp": "March 15, 2017, 09:16:09 pm",
"content": "(working with mribble on this) Thanks for the quick replies and the proposal to use an AND gate does seem like a much better solution. I do however have a couple of followup questions. The full circuit that mribble was originally describing is in the schematic below. We did have a 10K pull-up on the RX line. Along the way, we added 1K resistors on each RX line based on recommendations in some Arduino forums, presumably for current limit protection.1)do these 1K resistors make sense on the RX lines, or are they likely a contributor to the unreliability? Are they advised or better without?2)If we go with the recommended AND gate, then would the output be directly connected to RX (no pullup and no load resistor needed)?3) Is anything needed or recommended for the 2-RX -> 1 TX (other direction)? do the 1K current limit resistors make any sense here?"
},
{
"post_id": "",
"author": "langwadt",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 15, 2017, 09:42:16 pm",
"content": "Quote from: dml1333 on March 15, 2017, 09:16:09 pmThe 1k resistors doesn't make much sense, and the 10k should probably be smaller to make it reliable at high speed"
},
{
"post_id": "",
"author": "pigrew",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 15, 2017, 10:03:09 pm",
"content": "I sometimes put series resistors in order to damp high-speed signals, but in those cases, I'd use 22 or 33 ohm, and the resistors should be located close to the transmitting side of the line.1 kOhm is likely way too high for this use."
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 15, 2017, 10:05:05 pm",
"content": "Quote from: langwadt on March 15, 2017, 09:42:16 pmWell, the 1k resistors make sense if the MCUs are not powered up at the same time. But I agree, 10 kohm pullup is a bit high, but making it much smaller with the 1k resistor there also won't wash. Perhaps 4.7k.Regarding damping: hey, we're talking UARTs, not GB-Ethernet here."
},
{
"post_id": "",
"author": "dml1333",
"author_rank": "Newbie",
"is_op": false,
"timestamp": "March 15, 2017, 10:05:27 pm",
"content": "I should have mentioned that the speeds are typically 74,880 or 115,200 baud, such as for programming the ESP8266."
},
{
"post_id": "",
"author": "mribble",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 16, 2017, 09:16:26 pm",
"content": "When we switch to an and gate that will clean up that line's resistors.I know the sam3x GPIO pins are protected against over current so if the esp8266 is then we can remove the 1K resistors. If we want to keep them we could at least reduce them to something like 100 ohms which would be 33 ma. They are just there for protection and I'm not sure if they are even needed for that."
}
] |
2025-10-17T19:00:46.688484
| 12
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-3v-to-5v-logic-level-converter-simple-or-is-it/
|
3.3V to 5V logic level converter - Simple - or is it? - Page 1
|
[
{
"post_id": "",
"author": "matt_c",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "July 17, 2020, 11:03:41 am",
"content": "I have a 3.3V microcontroller (SparkFun SAMD21 Mini) I would like to interface with the 5V logic inputs on a motor controller boardhttps://electromen.com/en/products/item/motor-controllers/brushless-dc-motor/EM-347A/The motor controller board inputs state they require 4V minimum. Plus these inputs have 10kΩ pull down resistors on some of them except speed and torque control which have 100k.I plan on using PWM for the speed and torque control.Which voltage level conveter would be most suitable?Originally I was going to go with a bidirectional MOSFET level shifter, with 1k pullup on the 5V side, however it's a lot of seperate components for the 4 channels I need (start, direction, speed, torque). So a single chip would be more convenient.I was thinking a 74HCT244 Buffer/Line Driver may work in one direction.Or perhaps txb0104 or txs0104, but I'm not sure would be able to drive the motor controller input above 4V with the 10k pull down resistors.What does everyone think?"
},
{
"post_id": "",
"author": "Siwastaja",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 17, 2020, 12:24:08 pm",
"content": "Any 74HCTyou have around. A buffer obviously, or an inverter if you swap the polarities in software, and so on.These parts use 5V supply, and output 0V and 5V levels, being CMOS parts. T in the part name means TTL-compatible input levels, and with TTL input levels, 3.3V is reliably '1', which is exactly what you want.Special level shifters offer features like bidirectionality which you do not want here.For the analog inputs, you can RC filter the PWM, but the response won't be fast. I'd assume they filter the inputs on the motor controller, as well, though, to prevent torque ripple caused by noisy inputs."
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 18, 2020, 12:34:51 am",
"content": "74HCT logic would be the simplest although technically any 5 volt TTL logic should work with a pull-up on the output. A common base bipolar transistor with pull-up would also work fine. I have sometimes used optocouplers for level shifting which has the advantage of galvanic isolation."
}
] |
2025-10-17T17:46:09.445724
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-3v5v-npn-transistor-pwm-switching-issue/
|
3.3v/5v NPN Transistor PWM Switching Issue - Page 1
|
[
{
"post_id": "",
"author": "NotionalLabs",
"author_rank": "Unknown",
"is_op": true,
"timestamp": "July 09, 2018, 10:20:17 pm",
"content": "Hey everyone,I'm struggling to understand the behaviour of a little circuit I'm playing with and was wondering if someone here could help explain it to me. I'm looking to control a set of 5 super bright LED's via PWM from a Raspi Zero W. I envisioned using an NPN transistor (currently using a 2N2222) with the base connected to my PWM pin (3.3v), the Collector connected to the 5VDC power rail on the Raspi, and the Emitter connected to a current-limiting resistor (100 ohm) and subsequently the 5 LEDs in parallel). The forward voltage drop on my LEDs is 3v, with peak brightness at 20mA.I've mocked up the circuit in the browser simulator here:http://tinyurl.com/yam4zfhtThe issue I'm having in real life (and in the simulator) is that the voltage on the emitter is capping out at ~2.5/2.7V, less than the forward voltage drop of the LEDs, so they are very dim and are drawing very little current.It was my understanding that as long as I saturated the B, the voltage drop between C and E should be small (0.2V or so) and I should be able to realise the required 3v to the LEDs without issue. I've checked the PWM signal which is clean and as-expected, the 5V rail is strong (it's tied directly to the 5V USB input, a 2.4A iPad charger), and trying multiple current-limiting Base resistors makes little/no difference to the Emitter voltage.Does anyone know why this is? The voltage drop between CE seems really high, and I don't understand the relationship between BE voltage and CE voltage (in the simulator, changing the base logic voltage level to 5V yields a better voltage on the emitter, but still higher drop than I would have imagined).Thanks!"
},
{
"post_id": "",
"author": "JustMeHere",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 09, 2018, 10:24:10 pm",
"content": "You are missing your gate resistor."
},
{
"post_id": "",
"author": "JustMeHere",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 09, 2018, 10:28:39 pm",
"content": "Also your transistor should be below the LEDs if you're using a NPN transistor. And make sure you're not overloading your LED current limiting resistor."
},
{
"post_id": "",
"author": "NotionalLabs",
"author_rank": "Unknown",
"is_op": true,
"timestamp": "July 09, 2018, 10:31:54 pm",
"content": "Thanks for the replies!Re: the Gate resistor: in the sim - yeah, although I have one in the real circuit (I calculated the Base resistor value as ~8.6k to guarantee saturation, and I've tried 10k, 4.7k, and 1k with no difference). I've updated the sim to include it to avoid any confusion:http://tinyurl.com/yanu9wsfRe: the position of the load, I didn't realised that mattered (I assumed that when saturated, the CE path was effectively a short (minus the CE voltage drop) so it wouldn't really matter which side. Could you explain why this is the case?Best, Jim"
},
{
"post_id": "",
"author": "JustMeHere",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 09, 2018, 11:02:03 pm",
"content": "To turn on, your base pin has to be higher than the emitter. Let's say about 1.4v.If the emitter is connected to GND then the emitter pin is 0v and it's easy to get the base 1.4v higher.In your circuit, the emitter probably around 3v. That means you need your base voltage at 4.4v.(Google low side vs high side switching. For a better explanation.)"
},
{
"post_id": "",
"author": "NotionalLabs",
"author_rank": "Unknown",
"is_op": true,
"timestamp": "July 09, 2018, 11:21:02 pm",
"content": "That's perfect, I'll read up on that now. Moving it around solved my issue in my test circuit too - really appreciate the help!"
}
] |
2025-10-17T18:29:25.164702
| 6
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-3vin-1-15vout/
|
3.3Vin 1-15Vout - Page 1
|
[
{
"post_id": "",
"author": "kcs",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "December 01, 2014, 07:35:22 am",
"content": "I am looking for a solution how to get adjustable voltage by 1V increments in a range of 1 to 15V that is going to be done with a microcontroller.Requirements:- Vin = 3.3Vdc- Vout = 1-15Vdc- Isw = 20mA- Iq <= 2mA- Efficiency >= 50%I was searching for step-up/step-down DC-DC converter with I2C control. However, could not find anything that matches my requirements. So, I am thinking of doing the following:1. Use fixed step-up DC-DC converter to get ~18V from 3.3V2. Use adjustable step-down DC-DC converter to be able to get 1-15V out of 18V3. Use digital potentiometer that is controlled over I2CIs there any more elegant solution that anyone could recommend me? And by \"elegant\" I mean something that has better efficiency, less external components and is less complicated."
},
{
"post_id": "",
"author": "wraper",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "December 01, 2014, 08:34:26 am",
"content": "Quote from: kcs on December 01, 2014, 07:35:22 amSepic converterhttp://www.ti.com/lit/an/snva168e/snva168e.pdf"
}
] |
2025-10-17T19:51:36.269432
| 2
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-5-mic-to-usb-conversion/
|
3.5 MIC to USB Conversion - Page 1
|
[
{
"post_id": "",
"author": "vidarr",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 15, 2025, 11:51:18 pm",
"content": "After searching around for some time, I cannot find a way to convert my external mic with a 3.5 jack to USB. There are many other options and versions, but not like what I have.Essentially, I just want to cut the end of the mic cord (cut the 3.5 jack off) and re-wire it to a usb connector so I can plug it into my laptop.I know the pinouts for the USB, but I don't know which wires of the mic go where.In the pic, you can see the 3.5 jack for the microphone. It just has one band, so it must be the audio and a ground? But, the mic also has an on/off switch. How does it get its power?Sorry if this is super newbie, but I never worked with mics before. (I did do research before posting this. I just don't get it.)Thanks!edit: Mic is aiwa DM-H15 IMP600 OHM"
},
{
"post_id": "",
"author": "special_K",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 12:10:29 am",
"content": "You can wire anything to anything, doesn't mean it will work...USB is a computer bus. At each end something \"smart\" exists, be it a full computer or some microcontroller, who can hold an intelligent conversation. \"Hello I exist\", \"what are you?\" \"I'm a keyboard\", \"okay, I will listen for typing from you, and sometimes I will tell you to light up one of your LEDs when capslock is on\".A microphone with a 3.5mm plug is nothing like that. It cannot say hello in USB language, it has no brain inside.What you want is a USB sound card. You plug your microphone into that box, then plug the box into the computer."
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 12:34:41 am",
"content": "At $10 for this one, it doesn't get much cheaper or smaller:https://www.amazon.com/QianLink-External-Headphone-Microphone-Mic-Supported/dp/B0DDCCC7RH/ref=sr_1_20?sr=8-20No affiliation."
},
{
"post_id": "",
"author": "vidarr",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 16, 2025, 04:14:34 pm",
"content": "I cannot order parts right now, I am in the middle of Brazil. But, my laptop also has a 3.5 audio, headphone/microphone jack* that I can use (was in use for speakers, but I can use BT instead to free up the jack).The laptop 3.5 jack definitely works for speakers/headphones, but *I don't know for sure if it supports a mic in. Usually, I can find a decent video on YT, but all I find are junk videos lately.Thanks!"
},
{
"post_id": "",
"author": "abeyer",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 06:50:14 pm",
"content": "The vast majority of modern laptop 3.5mm connectors are of the TRRS variety to support headsets with microphones... I'm sure there are exceptions to that, but they are exceptions.So, it most likely supports microphones, but you can't typically just plug a plain microphone in without an adapter, it's designed for headsets with both mic & speakers. The adapters to do this are easy to buy... but if you really can't and need to wire it yourself, the TRRS wiring is standard, but depending on the type of microphone, though, that side is more variable. You'll need to adapt whatever your mic output format is to the TRRS mic connections."
},
{
"post_id": "",
"author": "vidarr",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 16, 2025, 07:03:50 pm",
"content": "Excellent! This is good news. The mic is an aiwa DM-H15, but I haven't been able to find a pinout for it. I have the pinouts for all the 3.5 jacks already (TRRS, TRS..), just not the mic.I have an old headset with mic that I can cut the cord and rewire to this mic. Then, I can keep my amped speakers by using the headphone wires, and rewire the new mic to the mic wires.Man, I hope this works.THANK YOU!"
},
{
"post_id": "",
"author": "themadhippy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 07:17:42 pm",
"content": "Quotetip is signal and the sleeve is the ground."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 09:24:20 pm",
"content": "If I remember rightly, you need an electret microphone to work with a sound card. A dynamic microphone won't work."
},
{
"post_id": "",
"author": "Analog Kid",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 09:31:25 pm",
"content": "Quote from: Zero999 on January 16, 2025, 09:24:20 pmI don't believe that's correct, but I could be wrong.Sound card don't supply phantom power, so the electret would have to supply its own."
},
{
"post_id": "",
"author": "SteveThackery",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 09:51:56 pm",
"content": "Quote from: Analog Kid on January 16, 2025, 09:31:25 pmIt does - if 5V counts. The PC standard microphone jack is mono with 5V on the ring."
},
{
"post_id": "",
"author": "Analog Kid",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 09:56:49 pm",
"content": "Quote from: SteveThackery on January 16, 2025, 09:51:56 pmAh, so. Sure, 5V counts, even if it's not 48V.Pretty sure either dynamic or electret mikes would work.Heck, maybe even a crystal mike*, depending on the mike input's impedance.*not very well, though."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 09:59:46 pm",
"content": "I've tried a dynamic microphone with a sound card and it didn't work. My current microphone is just an electret capsule on the end of a piece of cable, connected to a 3.5mm connector."
},
{
"post_id": "",
"author": "wasedadoc",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 10:01:45 pm",
"content": "Quote from: Analog Kid on January 16, 2025, 09:31:25 pmRight and wrong!You do not need an electret mic to work with sound cards. The vast majority of consumer sound cards do not supply \"phantom power\" in the true sense* but the vast majority do supply \"plug in power\".* phantom powering uses three wires. One is ground. The other two have balanced audio and (both) have +48 Volts (or sometimes lower such as +24).Plug in power needs just 2 wires. One is ground. The other is a few volts (typically between +3 and +5) from the card and audio from the mic."
},
{
"post_id": "",
"author": "themadhippy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 10:14:36 pm",
"content": "Quotetry raising the gain,used a 58 many a time on a pc"
},
{
"post_id": "",
"author": "Analog Kid",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 10:17:11 pm",
"content": "According toSteve Thackery's post, the tip is the input to the sound card without any power, so that should work for a dynamic mike."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 10:31:57 pm",
"content": "Quote from: themadhippy on January 16, 2025, 10:14:36 pmI tried that and it didn't work. Even with the gain all the way up, I had to put the microphone right near my mouth and shout for it to work. I did think about using a transistor amplifier powered from the electret mic bias provided by the sound card, but decided it was much easier and simpler to get an electret mic."
},
{
"post_id": "",
"author": "Analog Kid",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2025, 11:41:35 pm",
"content": "Sure it was a dynamic mike, and not a piezo (crystal) one?Or maybe the plug wiring was wonky?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 17, 2025, 09:31:25 am",
"content": "Quote from: Analog Kid on January 16, 2025, 11:41:35 pmYes, I know it was a dynamic, because I had opened it up. I would have expected a piezo to have worked because it has a higher output.The wiring was fine because I tested it."
},
{
"post_id": "",
"author": "SteveThackery",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 17, 2025, 09:42:55 am",
"content": "Quote from: Zero999 on January 17, 2025, 09:31:25 amExcept piezo microphones require a very high impedance input. The PCB standard microphone input is very low impedance for a piezo mic."
},
{
"post_id": "",
"author": "magic",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 17, 2025, 10:01:04 pm",
"content": "Quote from: Zero999 on January 16, 2025, 10:31:57 pmYou do realize these statements are mutually exclusive?It works, but sensitivity may be unsatisfactory. Make sure to crank up the gain and enable \"mic boost\" (more gain).In reality, even common dynamic headphones work as a mic if you plug them into a mic jack.Regarding wiring, there are two options:1. If the laptop has TRS jacks, connect the dynamic mic between T and S.2. If the laptop has a TRRS jack for HP/MIC combo, connect the dynamic mic between R2 and S because T and R1 are HP outputs."
},
{
"post_id": "",
"author": "Nominal Animal",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 17, 2025, 10:29:45 pm",
"content": "Quote from: magic on January 17, 2025, 10:01:04 pm(Or, to put another way, the tip is left audio output, first ring right audio output, second ring is ground, and sleeve is microphone signal.)"
},
{
"post_id": "",
"author": "magic",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 17, 2025, 11:26:52 pm",
"content": "Or vice versa and R2 is MIC and S is GND. Welcome to the wonderful world of TRRS headsetsI suppose the laptop jack may be hardwired one way or another, but often both lines are routed to a special chip which tries to guess what sort of thing is connected and ground the appropriate terminal. Some audio \"codec\" chips maybe even have the functionality built-in. And if you get it wrong, you have no ground in your headphones and both sides play the difference between L and R."
},
{
"post_id": "",
"author": "Analog Kid",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 17, 2025, 11:35:10 pm",
"content": "I think my old MacBook is like that; if you jiggle the headphone plug or pull it out and replug it in, it takes a second or two for the audio to come back, so some kind of automagic stuff is going on there."
},
{
"post_id": "",
"author": "themadhippy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 17, 2025, 11:50:34 pm",
"content": "Quotehafler headphones,cool."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 18, 2025, 04:47:38 pm",
"content": "Quote from: magic on January 17, 2025, 10:01:04 pmPedantry aside, I didn't wire the dynamic microphone up. I just used the pre-wired connector and it was unusable, so I swapped it for an electret and it worked perfectly."
},
{
"post_id": "",
"author": "vidarr",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 19, 2025, 01:56:31 am",
"content": "Well, I am still working this out. Why oh why do Mics have to be so simple and complicated at the same time... Seems like mics are a pretty hot topic.So, I actually went back to EEV YouTube video where he talked to the mic designer/engineer that I can't remember his name. He drew some really good mic and op amp circuits.Someone is bringing me one of those tiny USB soundcard with 3.5 jacks.Thanks Guys for All your Input!"
},
{
"post_id": "",
"author": "special_K",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "January 19, 2025, 05:02:39 am",
"content": "Your link does not work. It just sends us to a login page that also advertises a sale or promotion of some sort."
},
{
"post_id": "",
"author": "vidarr",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 23, 2025, 04:02:57 pm",
"content": "My friend brought me this external soundcard that I thought would allow me to use this mic with my laptop, but it isn't working.The laptop recognizes the device; I can play audio through it just fine; it sows up in the Win10, so-called \"Sound Control Panel\"; the mic does not work.I tried my headset with mic and it works.Could it be because of this 3.5 jack? It only has two rings, tip and sleeve. Most of the 3.5 mic jacks I see online are TRS. (I know what the rings are for. TS, TRS, TRRS..., I just don't know what else the problem can be. This should work.)Any ideas? Thank You!"
},
{
"post_id": "",
"author": "magic",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 23, 2025, 04:47:48 pm",
"content": "It's possible that the tip and ring are shorted internally, so this plug shorts them both to ground. This appears to be the case in my \"GeneralPlus\" USB audio dongle - the dongle records in mono and when I plug headphones into the mic jack, both sides work equally so they seem to be shorted.You could take the dongle apart and cut this connection. Or make a cable with TRS plug and TS or TRS socket and leave the ring floating. Or reterminate the mic with a TRS plug with floating ring."
},
{
"post_id": "",
"author": "vidarr",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 24, 2025, 12:22:53 am",
"content": "The tip of the mic jack appears to be the mic audio and the single sleeve is the ground. I'm going to make a homemade adapter where I send the tip of the mic cord to the 2nd ring of a TRRS jack, and the ground to the sleeve.From what I have read so far, computers and phones have TRRS jacks. So, this is what I have to wire the mic to conform to. Not really a problem, just so ridiculous to have to do.Let's ditch the 3.5 jacks and go with USB. Professional audio can keep the 1/4 jacks and XLR; audiophile equipment can keep their RCA and banana jacks; everything computer/phone related should be USB. 3.5 jacks are ridiculous. Really stupid at this point.Thanks!"
},
{
"post_id": "",
"author": "magic",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 24, 2025, 12:55:18 am",
"content": "Hmm, if your dongle's tip and ring contact are shorted, things may also work if you insert the plug halfway:Code:socket: T R Splug: T S"
},
{
"post_id": "",
"author": "radiolistener",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 24, 2025, 01:23:31 am",
"content": "Quote from: SteveThackery on January 16, 2025, 09:51:56 pmThere are two mic pin-out standards for 3.5mm connectors and they are not compatible:PC microphone:Phone/Camera microphone:Headset connectors also have two standards:"
},
{
"post_id": "",
"author": "vidarr",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 24, 2025, 08:40:22 pm",
"content": "OK, so I salvaged some 3.5 jacks and wires and am going to attempt to make this mic work on the laptop.You cannot see the red wire on the mic cord, but the red wire of the mic goes to that red wire on the cord with TRS jack.The black wire of the mic will go to the ground wire of the cord with TRS jack.The jack is wired such that the tip and ring are going to the red wire.The sleeve is going to the ground.Then, the TRS gets plugged into the external soundcard/dongle, which plugs into the laptop via USB.Will this work? IDK... I hope so.Thank You!edit: I was trying to make this simpler radiolistener. LOL."
},
{
"post_id": "",
"author": "vidarr",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 24, 2025, 08:46:03 pm",
"content": "Quote from: magic on January 24, 2025, 12:55:18 amI tried this but it didn't work. Fortunately, the mic screen easily unscrews so I could check its wires. The only thing I don't know is if the mic needs 5v on the red wire from the usb dongle, or if the 5v is even provided. I don't know how the laptop jack is wired. I did not open up the soundcard/dongle either."
},
{
"post_id": "",
"author": "Analog Kid",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 24, 2025, 10:27:20 pm",
"content": "Since the mike clearly says \"cardioid dynamic\", it definitely doesn't need any power, assuming there's no circuitry in the handle (and there shouldn't be). So you just need to find the right connections."
},
{
"post_id": "",
"author": "vidarr",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 25, 2025, 11:20:51 pm",
"content": "Well, it works. I cut off the mic's TS jack and soldered on a TRS jack. Then, that plugs into the USB soundcard to the laptop. Everything turned out to be pretty straightforward in the end.The sound is really good too. There is no noise, or background sounds. Just very clear vocals coming thru. I will do some EQ adjustments to fine tune it, but I am happy with the outcome.Now, my next questions are coming ----> The DAC hookup.Thanks Everyone for your help!"
},
{
"post_id": "",
"author": "vidarr",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "January 25, 2025, 11:21:54 pm",
"content": "Yep, it was pretty simple in the end. Thankfully."
}
] |
2025-10-17T16:24:05.592364
| 37
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-5inch-display-with-good-viewing-angles/
|
3.5inch display with good viewing angles - Page 1
|
[
{
"post_id": "",
"author": "symbianas",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "May 17, 2020, 06:39:23 pm",
"content": "Hi, I bought this3.5inch TFT Arduino UNO Display, but its viewing angles are relly bad if I put display horizontaly, I think its viewing angle is 12oclock and I guess I need 9oclick viewing angle, since I plan to add it to car horizontaly. Is there any better display with same dimensionsions? Oled? Or 9oclock viewing angle?"
},
{
"post_id": "",
"author": "Raj",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 23, 2020, 07:30:59 am",
"content": "Oled and e paper have good viewing angles... But do know, oled might have problem with Sun glasses"
}
] |
2025-10-17T17:49:27.070967
| 2
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-5mm-audio-jack-disconnect-pins/
|
3.5mm Audio jack disconnect pins? - Page 1
|
[
{
"post_id": "",
"author": "trevorford",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "August 18, 2015, 04:42:05 pm",
"content": "I am trying to figure out what all the pins do on these audio jacks, this is the best answer i can find (https://www.adafruit.com/products/1699) but I'm still unsure on what it means or what the pins do. Any help would be appreciated.Thanks,Trevor"
},
{
"post_id": "",
"author": "tooki",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 18, 2015, 07:16:05 pm",
"content": "Quote from: trevorford on August 18, 2015, 04:42:05 pmBasically, it means that the jack is capable of routing the sound to a speaker when nothing is plugged in, and then disconnecting the internal speaker when you insert a plug. Think of it as having 5 pins:GroundL inR inL outR outWhen no plug is inserted, sound comes out the Out pins. When a plug is inserted, the Out pins are disconnected.There are jacks that actually have independent insertion detection switches, but I don't think that's the kind you're likely to encounter as a hobbyist."
},
{
"post_id": "",
"author": "matseng",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "August 19, 2015, 03:25:58 am",
"content": "Audio jacks are evil. Or at least I'm too stupid to read the datasheet right...After being burnt by using the wrong pinsin a few PCBs when I just looked at the datasheet and symbol in the schematics I've vowed to only use audio jacks that I have in stock in my lab where I can verify which pin that goes where and exactly how the disconnect/connect functions work."
},
{
"post_id": "",
"author": "Richard Crowley",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 19, 2015, 04:39:45 am",
"content": "The schematic diagram in the cited PDF seems quite clear. Not sure what all the confusion is about?The diagram shows:(1) Sleeve(2) Ring(3) Ring switch(4) Tip switch(5) TipThe pins (1) Sleeve, (2) Ring, and (5) Tip connect directly to the plug.The ring switch (3) counects to Ring (2) when there is nothing plugged in.And the tip switch (4) connects to Tip (5) when there is nothing plugged in.In traditional circuits, the ring switch (3) connects to the internal right channel speakers,and the tip switch (4) connects to the internal left channel speakers.That way the speakers are automatically disconnected when you plug in the headphones/earbuds or whatever."
},
{
"post_id": "",
"author": "tooki",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 19, 2015, 09:24:36 am",
"content": "Oh for crying out loud, how did I miss the datasheet link?So yeah, replace my answer with Richard's perfect description."
}
] |
2025-10-17T19:35:14.870219
| 5
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-5mm-cable-hum-and-satic/
|
3.5mm Cable Hum and Static - Page 1
|
[
{
"post_id": "",
"author": "DW1961",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 27, 2021, 05:47:00 pm",
"content": "I had two 3.5mm cables bad at the same time.The first cable was creating static over my speakers when moved slightly. The cable connects the DAC to the AMP's AUX port. (It wasn't the wire going into the jack itself. I tested for that by immobilizing the jack pin and manipulating only the wire.)So I replaced the 3.5mm cable with a new one, and didn't have the static issue. However, when there was no input from the DAC plugged into my amp, I got low frequency humming sound from the speakers.So, I unplugged the 3.5mm cable from the DAC leaving only the cable itself plugged into the amp, and the hum was still there. When I unplugged the cable from the amp's 3.5mm jack, the hum stopped.I performed the same tests with a 3rd cable, everything was silent.What would cause a cable and a cable jack to create static when lightly touch or moved a little or cause hum simply by being plugged in to an amp's 3.5mm AUX port? Is there any easy way to test cables for that sort of defect?"
},
{
"post_id": "",
"author": "JustMeHere",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "October 27, 2021, 06:41:38 pm",
"content": "Sounds like a ground loop. All of your power for all of your audio gear should come from the same wall outlet."
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 27, 2021, 07:16:10 pm",
"content": "Sounds more like really cheap, low quality unshielded cables to me."
},
{
"post_id": "",
"author": "DW1961",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 27, 2021, 09:55:55 pm",
"content": "Quote from: JustMeHere on October 27, 2021, 06:41:38 pmIt is."
},
{
"post_id": "",
"author": "DW1961",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 27, 2021, 09:57:42 pm",
"content": "Quote from: Benta on October 27, 2021, 07:16:10 pmOne of them had no hum, but produced the static when moved a little while plugged into the jack. Maybe the jack pin just wasn't manufactured with the correct tolerances?How would you go about testing for poor shielding?"
},
{
"post_id": "",
"author": "DW1961",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 28, 2021, 07:46:33 pm",
"content": "Quote from: Benta on October 27, 2021, 07:16:10 pmHey Benta,I actually had another one of those 3.5mm cables that looked exactly the same as the one that produces that low hum when plugged into the back of my amp's 3.5mm jack. Both came from some audio products. Anyway, this new cable that came with an audio product looked EXACTLY the same as the one that produces hum. Sure enough, I plugged it into my amp's 3.5mm jack, and got the same low hum sound. If the problem were ground loop, then wouldn't it persist no matter what cable? I think these cables are just cheapass bad cables. Other 3.5mm cables I plug in don't make the noise."
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 28, 2021, 07:57:43 pm",
"content": "If you have an open-end 3.5 mm jack cable hanging out of a amplifier input, you can expect a bit of hum. You'll need to short the open jack to see where the problem is. Wrap some tin foil around the jack to see if it gets better."
},
{
"post_id": "",
"author": "DW1961",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 28, 2021, 09:14:31 pm",
"content": "Quote from: Benta on October 28, 2021, 07:57:43 pmI just tested it. After wrapping the jack pin in foil, it went dead silent.The problem is that even when plugged into the amp and another device, such as a DAC, it hums.I just received an Amazon basics 3.5mm cable and plugged in with nothing on the other end, and it produced zero noise. My other 3.5mm cables don't make noise when plugged into the amp with nothing on the other end, either.Also, when I touch the open end of the noisy cable, while plugged into the amp, the hum get 10x louder. Touching the end of the Amazon Basics 3.5mm cable pin does nothing.So, what's up with these 2 humming cables that go silent upon grounding the bare pin?"
},
{
"post_id": "",
"author": "magic",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 29, 2021, 06:25:32 am",
"content": "Some audio cables use coaxial constructions where the signal wire(s) are hidden inside grounded shield and don't pick up mains electric field in the first place.Other cables use simple three-wire construction and they do pick up electric fields. Shorting the terminals shunts the picked up signal to ground and kills hum.If a cable makes noises when moved, it typically means it's broken inside and makes intermittent contact."
},
{
"post_id": "",
"author": "DW1961",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 29, 2021, 05:35:14 pm",
"content": "Quote from: magic on October 29, 2021, 06:25:32 amExcept when plugged into the amp the hum doesn't go away. Is that just the way the simple three wire cables are?"
}
] |
2025-10-17T17:20:32.837456
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-5mm-jack-ir-remote/
|
3.5mm Jack Ir Remote - Page 1
|
[
{
"post_id": "",
"author": "D_K99",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "February 18, 2016, 09:46:00 pm",
"content": "Hello Guys,I want to build an IR Remote, that connects to your Smartphone via the headphone jack. I thought it would be a simple project by connecting an IR Led to the wires of a Jack, but it wasn't working. I turned the volume up and downloaded a siganlgenerator app, so I can change the signal and the frequency. But nothing worked. So can someone please say what the best waveform and what the best frequency is? Or do I need special low current Led's. (I know you can't see IR so I looked at them through a camera, and I tested the led's with a battery and they worked)"
},
{
"post_id": "",
"author": "Skimask",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 18, 2016, 09:52:58 pm",
"content": "How about a schematic?How about a bit of a reference as to what 'signal generator' and what sort of 'waveform' and 'frequency' you used?How about a bit more information?"
},
{
"post_id": "",
"author": "Maxlor",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 18, 2016, 10:02:45 pm",
"content": "Quote from: D_K99 on February 18, 2016, 09:46:00 pmWhat you did won't work for two reasons. First, if you want to interface with existing equipment, you'll need to generate an 38kHz carrier onto which you modulate your signal. 38kHz is not something you can generate with your phone's audio output, unfortunately.Second, the voltage on your audio out will be a few hundred mV at best, so you won't be able to even light up the LED. The available power is rather low as well, so even if you upconvert the voltage, your range will be in the cm rather than meters.What you need to do is add a microcontroller (or at least a timer) that generates the carrier frequency and modulates it, and an additional power source, and then you can use the audio output as a mere communication interface. You could forgo the power source if you used energy harvesting techniques to store and save up the bit of energy you get from the audio port, but I'm thinking that might be something you should investigate at some later time."
},
{
"post_id": "",
"author": "Pavle",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "February 18, 2016, 10:08:12 pm",
"content": "You can make IR remote for android with 2 IR Leds and stereo audio jack:http://www.instructables.com/id/DIY-Infrared-transmitter-for-iPhone-iPod/And you must set volume to the max on android and inside Zaza remote app: uncheck auto recognoze device,select SMART ZAZA and in advanced settings set Zaza max volume to 100%If that does not work you can make other ir remote from here:http://everycircuit.com/list/keywords/ir%20remote"
},
{
"post_id": "",
"author": "mstoer",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "February 18, 2016, 10:14:05 pm",
"content": "I am am guessing you might want a TV remote? I 'built' a IR remote for my smartphone to trigger my Canon camera. I say 'built', but really it was just soldering two IR LEDs together on a jack. It worked fine (using the DSLR Remote app) on a Samsung S2, but it will not work on a Nexus 5. The LEDs light up, so I could say they \"work\", but not enough I guess. You may have a similar problem. What works with one phone may not work wither another."
},
{
"post_id": "",
"author": "Pavle",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "February 18, 2016, 10:17:28 pm",
"content": "With Zaza remote you can control all ir devices.I made ir remote and I have tried and it's working with all devices."
},
{
"post_id": "",
"author": "Pavle",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "February 18, 2016, 10:23:23 pm",
"content": "Solder two IR leds in opposite way to left and right channel not ground.You must turn volume to max.You can use Zaza Remote or you can record ir signal in audacity:http://forum.samygo.tv/viewtopic.php?t=76892 IR LEDS are used to double frequecny.Ir carrier frequency can be between 30-60 kHz and most common ir carrier frequecny is 38 kHz."
},
{
"post_id": "",
"author": "macboy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 19, 2016, 04:09:45 pm",
"content": "The way that the simple two-LED headphone jack IR transmitter works is by creating two 19 kHz signals on the left and right outputs, but 90 degress out of phase. Each LED will only light when forward biased, and only when > 1.5 V or so, so only for a small part of each cycle, so it turns out that they will alternately blink at 19 kHz, creating an effective 38 kHz IR signal. This is simply on/off modulated to create the modulated IR signal. Amazingly, apatent was grantedfor this obvious nonsense."
}
] |
2025-10-17T19:24:22.934297
| 8
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-5mm-rc-bananabullet-connectors-female-pcb-mount/
|
3.5mm RC banana/bullet connectors, female PCB mount? - Page 1
|
[
{
"post_id": "",
"author": "Infraviolet",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "February 25, 2024, 07:24:31 pm",
"content": "Does anyone know if these exist? Female PCB mount through hole connectors to accept Remote Control vehicle style banana/bullet 3.5mm male connectors?This sort of thing exists for the (longer, narrower aspect ratio) 4mm connectors used on multimeters and bench power supplies (examplehttps://uk.farnell.com/multicomp/24-243-1/banana-socket-20a-4mm-pcb-red/dp/1698982), but I can't seem to find it for the short stubby 3.5mm type connectors.I'm setting up a testing board to attach to BLDC motors wich come with the 3.5mm banana/bullet connectors already on the wires, and want to be able to attach them in a removable way, without having to solder the male connectors in to wide plated holes in the board, or having to chop the ends of the motors' wires to it alternative connectors.Does anyone know if 3.5mm female pcb mount jacks are made? And if there's any sellers of them easy to order from in the UK?"
},
{
"post_id": "",
"author": "trilerian",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "February 25, 2024, 09:11:45 pm",
"content": "I just make 7.5mm x 7.5mm solder pads on my pcb’s and solder standard female 3.5 bullets to them. You can make the pads smaller, but you will need at least 5mm wide."
},
{
"post_id": "",
"author": "Infraviolet",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "February 26, 2024, 12:15:38 am",
"content": "You mean SMD mounting those tubular female connectors designed for crimping to wires? A banana/bullet connector has quite a burst of force when pushed in or puleld out, would soldering a female to a pad survive repeated connections/disconnections?"
},
{
"post_id": "",
"author": "coppercone2",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 26, 2024, 12:17:27 am",
"content": "can you use a mini banana plug instead?"
},
{
"post_id": "",
"author": "Jwillis",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 26, 2024, 03:20:34 am",
"content": "SMD mounting is not the best for heavy mechanical connections without some type of anchor to the PCB. The traces simply can't take that type of repeated mechanical use. So you will find that all mechanical connections that require constant force will have some kind of through hole structure. It's not uncommon nor against any rule to mix SMD with through hole components and connectors. Even binding posts can be bolted directly to a PCB."
},
{
"post_id": "",
"author": "trilerian",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "February 26, 2024, 06:19:37 am",
"content": "Quote from: Infraviolet on February 26, 2024, 12:15:38 amNo, the solid brass female connectors. Amass 3.5mm female connectors. I have pushed and pried on them without issues. I use pads and solder XT60 and XT90 connectors on them too. And XT90 connectors can be a pita to pull apart sometimes."
},
{
"post_id": "",
"author": "Infraviolet",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "February 26, 2024, 06:23:25 pm",
"content": "You mean like the females in this sort of set?https://www.amazon.co.uk/Gold-plated-3-5MM-Banana-Connector-Battery/dp/B0BK68CQ5G/I've seen pictures of \"ESC power distribution\" boards which appear to have just soldered these females to large square pads, they also look like they have aligned the little side hole on the female with a hole in the PCB pad, though I'm not sure if it is just solder in there or if they pushed some little piece of wire through the holes before applying solder."
},
{
"post_id": "",
"author": "MarkT",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 26, 2024, 08:28:30 pm",
"content": "Quote from: Jwillis on February 26, 2024, 03:20:34 amThrough hole or peg-and-paste."
},
{
"post_id": "",
"author": "trilerian",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "February 27, 2024, 02:08:29 am",
"content": "Quote from: Infraviolet on February 26, 2024, 06:23:25 pmI always align the little hole down as well. And yes, those are what I use.However, other more experienced people are saying to do something different, maybe that is what the hole is for, some sort of anchor. I've also seen it where the pcb is cut around the part and the pad goes to both sides and you solder it in between. For me, I via stitch the pads together on both sides."
},
{
"post_id": "",
"author": "trilerian",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "March 30, 2024, 02:58:40 pm",
"content": "I wanted to revisit this thread in case the OP was still looking for ideas. I have found through hole XT60PW connectors that sever the purpose here. I have moved my designs using XT60 and XT90 to the PW versions. However the XT90PW are hard to get, I was able to get a hold of the XT60PW rather easily through Amazon. The female XT60PW is just the tubular 3.5mm connector in a plug. The footprint was already in Kicad as well. Granted for the BLDC motor you would need 2 connectors, which would be 4 plugs to it may not be the most elegant solution, but it fulfils the requirements of having a post going through the board that other posters were recommending."
},
{
"post_id": "",
"author": "Infraviolet",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "April 13, 2024, 06:56:51 pm",
"content": "Here's the two ways I came up with in the end:Way 1 uses a through hole sized to be wide enough to take the entry end of the connector, but narrow enough to catch on the wider back section of the connector. The connector is slid in 1A/1B, with solder applied to one side, allowed to cool, then to the other side, and a blob of bluetack to hold it steady before the first side's joint is done. Pretty messy overall, some solder leaks down the space between the connector's brass body and the sides of the through hole, and it seems that when one uses as much solder as is needed for things this big then truly cleaning off all the flux residue afterward is impossible.Way 2 uses a >7mm x 7mm pad with two holes in it. Two stripped singe core wires are looped through the hole in the back section of the 3.5mm female banana/bullet connector and pushed down through the two holes in the PCB pad (2A/2B). The wires are twisted together below to tighten the connector down, 2C/2D. Then apply solder above (2F) by heating both the pad and the connector. Then cut off the wire ends and solder below (2E) heating both the cut off wire ends and the underside pad. Again, couldn't clean all the flux of (rosin, normal sort not activated or super-activated, flux being from the core of leaded 60/40 solder reel, no extra flux added) however hard I scrubbed with a brush and IPA (99%) or water (tried both alternately).The top left image shows the board with 3.5mm banana wires plugged in to those method 2 connectors.I think method 2 is more promising, and could be strengthened by adding some extra holes in the pad for further wire loops run in other directions (like over the top of the main barrel of the connector) to be run and twisted tight before soldering.EDIT: forgot the image attachement, here it is now"
}
] |
2025-10-17T16:37:24.006616
| 11
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-6-v-li-ionli-po-battery-switching-and-charging-circuit/
|
3.6 V Li - Ion/Li-Po battery switching and charging circuit - Page 1
|
[
{
"post_id": "",
"author": "RPBCACUEAIIBH",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "May 18, 2013, 03:29:44 pm",
"content": "I'm trying to design a circuit which switches my other circuits between adapter and battery power, without interruption, charges the battery, and also stops when it is charged, and I came up with this.It will be probably be used with some Li - Ion/Li - Po battery(a bigger one, that can supply about 1 A for a few hours). This is the lowest cost smart charger that I could came up with so far... I have made one more with an ATTINY microcontroller, but that's a little overkill I think... This should do what I need it's simple, cheep, and doesn't require any program to work.Switching: When the Adapter is connected R2 set 4.8 V to the Q1's base which is normally pulled down, causing Q3 to turn off, while the IC1starts to supply the necessary current for the circuit.Charging: IC2 Supplies current to the charger circuit so that is not powered when the device is powered from battery R7 sets the upper limit which stops the charging, R8 sets the lower limit under which the charger turns on. Between the 2 limit the battery is full. The 555 timer is used to switch the charging on and off. For setting the charging current the R4 should be changed.The circuit is not tested yet, but I thought I share it. I'll replay when I test it, but that will be a little further, because I already have a charger, this just came to my mind while I was working on another project."
},
{
"post_id": "",
"author": "Crockett",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "May 18, 2013, 04:00:46 pm",
"content": "This is more the direction I was looking at for my 9-Volt charger/supply. I like the LED circuit posted there, but question I have on that is whether it cuts off charging when the battery is fully charged.Thanks for posting this thread."
},
{
"post_id": "",
"author": "Paul Price",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 18, 2013, 04:25:56 pm",
"content": "The 9v LED regulated charger stops charging when the battery if fully charged, at which point it will give the battery a tiny trickle charge(a few mA at most)."
},
{
"post_id": "",
"author": "Crockett",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "May 18, 2013, 05:25:09 pm",
"content": "Thanks, Paul.Now I still want to see what else I can do with this; I'll return to my thread for that."
}
] |
2025-10-17T20:22:31.879705
| 4
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-6v-6v-700kv-high-voltage-generator/
|
3.6V-6V 700KV High-voltage Generator - Page 1
|
[
{
"post_id": "",
"author": "Kedar264",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 08, 2015, 06:59:10 pm",
"content": "I saw these modules on ebay,http://www.ebay.com/itm/DC-3-6V-6V-700KV-Boost-Step-up-Power-Module-High-voltage-Generator-New-ES-/361127289318I bought one & it works! but if you use carfully . it gives arcs of 3-4 cm and sound ver loud too!!! so i decided to test it whether i can make an emp jammer with it ,it worked fine when i kept output wires near to each other to arc over but when i put them aprt i've noticed ionization process for a minuite and i heared crackling sound which i guess arcing inside between the cock cork walton multiplier stage of it which damaged it ,i can hear the humm noise but not getting any outputi've tried to take it apart but it is as hard as stone which ruined my cutter and screw driverIve bught another and here it is"
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2015, 07:01:41 pm",
"content": "Quote from: Kedar264 on February 08, 2015, 06:59:10 pmAh, eBay. Don't you just love it?"
},
{
"post_id": "",
"author": "electr_peter",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "February 08, 2015, 07:09:37 pm",
"content": "eBay description says not to power for longer than 1 minute. So device meets it's specs."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2015, 07:13:19 pm",
"content": "I doubt it can really give 700kV. It if did then you wouldn't be able to stop it from arcing.If you read the description, you'll find it does warn you that operating it open circuit can cause damage to the module, albeit in very poor English:QuoteThis is to be expected as these sorts of high voltage generators are not designed to be operated open circuit."
},
{
"post_id": "",
"author": "Christopher",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 08, 2015, 07:16:04 pm",
"content": "I am conducting pre-compliance spike tests, wondering if I can use something like this to charge a capacitor (through a series resistance). Using an appropriate switch and series resistor to discharge quickly into the load?"
},
{
"post_id": "",
"author": "Kedar264",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 08, 2015, 07:18:24 pm",
"content": "is there any way to generate high voltage without damaging generator circuit?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2015, 07:24:11 pm",
"content": "There's no need to use a resistor to limit the current. It behaves more like a constant current source, rather than a voltage source. It needs to be protected against open circuit/over voltage rather than short circuit/over current.Add a spark gap to ensure it can't be operated open circuit. Unfortunately the specification doesn't say what the maximum safe voltage is (700kV my arse). A 25mm spark gap would limit the voltage to under 30kV which seems reasonable."
},
{
"post_id": "",
"author": "Kedar264",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 08, 2015, 07:28:59 pm",
"content": "spark Gapgood idea but i dont want to generate pulsating output"
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2015, 07:31:39 pm",
"content": "Quote from: Kedar264 on February 08, 2015, 07:18:24 pmYou have to read the specifications and operating instructions carefully and stay within the limits. Make sure the generator is properly connected to a suitable load before powering it up so that the output current has somewhere to go."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 08, 2015, 09:05:56 pm",
"content": "Quote from: Kedar264 on February 08, 2015, 07:28:59 pmThere won't be any pulses, so long as the resistance connected to the output is low enough that the voltage drop doesn't exceed the spark over voltage. Look at a spark gap as a protection device, not something which operates continuously."
},
{
"post_id": "",
"author": "lapm",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 09, 2015, 09:57:35 am",
"content": "700KV from small ebay device? Highly dought it...That starts to be enough voltage that insulators need special materials (not cheap)... Old thumb rule i was given that 1 KV will jump 1 mm air gap. So that 4 cm sound more like 40 - 60 KV...How ever actually designing one that can generate 700KV would be fun challenge i think. Mainly because extreme high voltage electricity field and effects its brings into play when design and building one.."
},
{
"post_id": "",
"author": "Stonent",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 09, 2015, 10:10:04 am",
"content": "Thanks for helping rebuild our Earth's ozone layer."
},
{
"post_id": "",
"author": "Kedar264",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 09, 2015, 03:50:47 pm",
"content": "bought smaller version of it and it works very good"
},
{
"post_id": "",
"author": "BurningTantalum",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 11, 2015, 09:33:15 am",
"content": "When I first started work in 1974 we had immense fun with high voltages. Those were the days when one could not be sacked for doing silly things. We built a Marx Generator, under the bench, which had capacitors made from lengths of PVC drainpipe covered in baking foil. We made a trap for the rats with it but forgot about Gerry, the security guy, who did the rounds at night...!We used to charge up military metal case capacitors and toss them to each other with a shout of \"Catch...\". One was placed in the boss's jacket pocket and his car keys swapped to the other pocket. We crowded the window as he walked across the car park, then fumbled for his keys... I swear his hair stood up as in a Tom & Jerry cartoon, and both his legs opened like a ballet dancer. Anyway, what was I doing...?"
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 11, 2015, 09:45:13 am",
"content": "yep, it wont be 700KV that would be large tesla coil territory and be jumping 50-100 cm4cm sounds like 50KV maxThis is a TV flyback and tripler being pushed to within an inch of its life (Tripler died after a few minutes)It's 30kv rated and probably producing 40kv or so."
},
{
"post_id": "",
"author": "Kedar264",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 12, 2015, 04:45:15 am",
"content": "yes ,i think its not 700kv but certainly in range of 100-200kv.anyway i need to generate sufficient high voltage so that it can ionize the water , to clean it ,so probably trippers doubler wont work (unless we use higher rating components) also they will take lot of space ,so i need to use higher rating component also they need to be separated to prevent internal arcing between the multiplier stages."
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 12, 2015, 04:47:03 am",
"content": "Quote from: Kedar264 on February 12, 2015, 04:45:15 amOK, you may want to take a chemistry lesson or two..."
},
{
"post_id": "",
"author": "Kedar264",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 12, 2015, 06:01:08 am",
"content": "Yes ,sure. Do you know any better source for it? And what do you think \"does ionization can clean water?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 12, 2015, 08:45:33 am",
"content": "The short answer is no you can't clean water just by passing electricity through it: look up electrolysis which uses much lower voltages.One way to kill bacteria in water is with UVC light from germicidal lamps."
},
{
"post_id": "",
"author": "bktemp",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 12, 2015, 09:05:52 am",
"content": "Quote from: Kedar264 on February 12, 2015, 04:45:15 amI doubt it is even near that.If you look at other stuff that works at 100kV or more, most of it will be filled with oil. Otherwise you need a large distance and round edges on every conductor.The insulation of those small output wires does not look like anything that can handle more than 50kV.Quote from: Psi on February 11, 2015, 09:45:13 amIt died because of the high currents flowing during each spark. I have killed some tripplers the same way. Adding a esistor to limit the current to <1A helps a lot. Neither the caps nor the diodes used in those multipliers are rated for high peak currents."
},
{
"post_id": "",
"author": "Kedar264",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 12, 2015, 10:07:30 am",
"content": "OK but take a look at commercially available ionizers which claims that \"it can kill bacteria clean water etc....."
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 12, 2015, 03:26:24 pm",
"content": "You can ionize air with a high voltage generator, but you can't ionize water the same way. Water is already full of ions. Ordinary water is conductive and will simply short out any kind of high voltage generator and neutralize it.You can sterilize water using UV light from germicidal lamps as Hero999 said.You can also sterilize water with ozone, which can be obtained from an ozone generator. Ozone generators do in fact use high voltages, but there is a bit more involved than just sticking high voltage electrodes in the water."
},
{
"post_id": "",
"author": "katzohki",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 12, 2015, 03:34:52 pm",
"content": "There are some companies that make high voltage power supplies professionally. Emco High Voltage, Ultravolt, HVM etc. A lot of them are used for photo multiplier tubes and some other interesting stuff."
},
{
"post_id": "",
"author": "Kedar264",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 12, 2015, 07:01:19 pm",
"content": "Quote from: IanB on February 12, 2015, 03:26:24 pmAfter reading few things and thishttp://www.epa.gov/iaq/pubs/ozonegen.htmli would say that actually ozone is harmful to health and not effectively clean either air or water."
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 13, 2015, 03:01:24 am",
"content": "Quote from: Kedar264 on February 12, 2015, 07:01:19 pmReading and researching to find facts is good!However, there is more to discover, and air and water are different cases. Here are a few other references to look at:http://water.epa.gov/scitech/wastetech/upload/2002_06_28_mtb_ozon.pdfhttp://www.water-research.net/index.php/ozonationhttp://www.lenntech.com/library/ozone/drinking/ozone-applications-drinking-water.htmThat said, the process of disinfecting water is not as simple as just adding ozone. The ozonation process has to be carefully controlled so that the right amount of ozone is added and also that the ozone is effectively dissolved in the water. Secondly the ozonation process produces solid byproducts that normally should be filtered out of the water afterwards.On the other hand, the needs of industrial processes and home chemistry experiments are different. By all means, once you are aware of the dangers of breathing in high concentrations of ozone (don't do that!), do some experiments. Here are a couple of links on simple ozone generators:http://www.bigclive.com/ozone.htmhttp://www.bigclive.com/oz.htm"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 13, 2015, 08:53:26 am",
"content": "Quote from: Kedar264 on February 12, 2015, 07:01:19 pmThe same is true for chlorine which is also used for disinfecting water, both for drinking and in swimming pools. The ozone/chlorine levels are carefully monitored so they're not harmful to health."
},
{
"post_id": "",
"author": "tiltit",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "February 14, 2015, 01:12:37 pm",
"content": "Those little modules look really nice for the price.Does anyone know if they could be used to build a small Jacob's ladder? My guess is that they would not provide enough current to sustain an arc. But I could be wrong.I once tried to build a small HV transformers around small a toroid but after an afternoon winding wire, seeing it short out after a minute of use was disappointing. But it did work, sorta..."
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 14, 2015, 01:32:22 pm",
"content": "Small neon sign transformer works a lot better at that.A quick one I whipped up one afternoon using just the old NST and some brass brazing wire."
}
] |
2025-10-17T19:47:23.695009
| 28
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-7v-16340-battery/
|
3.7v 16340 Battery - Page 1
|
[
{
"post_id": "",
"author": "nicksydney",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "October 15, 2016, 11:28:03 am",
"content": "Hi,I got a 3.7v 16340 (2500mAh) battery like this onehttp://www.ebay.com.au/itm/New-3-7V-2500mAh-TR16340-Li-ion-Rechargeable-Battery-for-LED-Flashlight-GO-GO-/371581173088and tested with Arduino and WS2812 LED strip (30 LED) and when the battery went below 3v the whole thing stops. The question that I have will it be possible if I use some kind of step up boost converter (not sure if it is the right name) to keep on using the battery and push 3v and above to the circuit ?. The plan is to keep on using the battery to the lowest possible way.Thanks"
},
{
"post_id": "",
"author": "nicksydney",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "October 15, 2016, 11:31:53 am",
"content": "Does something like thishttp://www.ebay.com.au/itm/DC-DC-Boost-Converter-Step-Up-Module-1-5V-to-5V-500mA-Power-Module-New-IT-/161879487895will work ? and suitable for the circuit ?"
},
{
"post_id": "",
"author": "sleemanj",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 15, 2016, 12:22:46 pm",
"content": "LIthium Ion cells should under no circumstances be \"used all the way\", it is dangerous (increasing chance of smoke and flames and running and screaming as your house burns down when you charge that deeply dischaged cell).3v is already regarded as empty, it is not generally advisable to discharge a typical lithium ion cell below this, even 3.2v could be regarded as close enough to empty for useful purposes."
},
{
"post_id": "",
"author": "PA0PBZ",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 15, 2016, 12:40:03 pm",
"content": "On top of that, it is probably the cell protection that is kicking in and shutting down at 3V, so there is nothing you can do to discharge it further."
},
{
"post_id": "",
"author": "CraigHB",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "October 15, 2016, 01:41:20 pm",
"content": "There are many safety considerations with Li-Ion batteries. It's really not something to mess around with due to the potential for fire or even explosion in some cases. I'm not going to get into it too heavily since it would be a book of a post. Here's an article to start with;link.There are a couple points regarding safety with flashlights you might not see right away in researching it. Firstly you should make sure your flashlight has some kind of pressure relief or vents. There have been instances of flashlights becoming pipe bombs due to pressure buildup when a Li-Ion battery fails. Gasses are released from a Li-Ion battery failure at a very high rate.There are many unscrupulous sellers on eBay passing off poor quality batteries with greatly exaggerated capacity ratings. These batteries are the lowest of quality and may tend to fail in a catastrophic manner. The reason I say that is the highest capacity name brand 18650 is rated for 3600mAh and a 16340 is less than half the size of an 18650. Anything over 1200mAh for a 16340 is BS. Likely that battery is fake with a bogus label on it making it of untrustworthy quality and safety. Many people are fooled by this by looking for a Li-Ion battery listed with the highest capacity. That's what these unscrupulous sellers are banking on. Always use a trusted brand from a trusted vendor. There's really no exception."
},
{
"post_id": "",
"author": "CraigHB",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "October 15, 2016, 02:36:07 pm",
"content": "Quote from: nicksydney on October 15, 2016, 11:28:03 amIt is possible to use a boost converter to increase voltage as required, though it calls for higher input currents which may exceed a battery's drain limit. In most cases it's better to use a series pack and buck convert down to the required voltage. Efficiency is better, input currents are lower, and there's a much wider selection of buck converters compared to boost converters.As already stated you can't drive a Li-Ion cell much below 3V or it will cause damage to the cell. The operating range for a standard Li-Ion battery is typically 4.2 to 2.7V, but limits can vary somewhat depending on the particular make and model. For example the LiPo type cells used for powered models have a 3.0V lower limit. High drain 18650s can have a 2.5V lower limit. There's also high voltage Li-Ions that have a range 4.35 to 3.0V.Li-Ion cells may or may not have protection built-in. When they have it, a small round protection PCB is encased under the shrink wrap typically on the negative side. The protection PCB limits voltage and current to safe levels. A protected battery will disconnect and drop out when limits are exceeded. When they don't have protection it's up to the circuit to ensure limits are not exceeded. Any Li-Ion battery must have protection either built-in to the cell or externally via the circuit it powers."
}
] |
2025-10-17T19:10:11.859909
| 6
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-7v-battery-charging-module/
|
3.7v Battery Charging module - Page 1
|
[
{
"post_id": "",
"author": "sairfan1",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 12, 2024, 03:48:51 pm",
"content": "I'm attaching a very common available batter charging module picture here,I want to know if anyone has study it and found it quite safe to use??I'm looking to charge 3.7v (between 1 to 3Am) Lithium battery"
},
{
"post_id": "",
"author": "tunk",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 12, 2024, 04:04:03 pm",
"content": "There's a review here by EEVblog member HKJ (without the protection part):https://lygte-info.dk/review/Review%20Charger%20TP4056%20UK.html"
},
{
"post_id": "",
"author": "sairfan1",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 12, 2024, 04:42:14 pm",
"content": "Thanks for sharing but that modules is a bit different."
},
{
"post_id": "",
"author": "Peabody",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 12, 2024, 05:19:15 pm",
"content": "The module is different in that yours includes a protection circuit (DW01) that prevents over-discharge, etc. But the charger chip - the TP4056 - is the same on both, so the HJK analysis will apply to your module. HJK's module is used when the battery has its own protection circuit. Does your battery have protection built-in?Your module is very widely used, and as far as I know it is reliable and safe. By default the charge current setting resistor is 1.2K, which produces 1A of charge current, which is the maximum the chip can deliver. For smaller batteries, you may need to change that. The TP4056 datasheet has a table showing the current produced by various resistor values.I think the modules now come with a variety of USB connectors, including USB-C. So you would need to decide about that, and whether you want the protection circuit in the module."
},
{
"post_id": "",
"author": "Kim Christensen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 12, 2024, 05:36:21 pm",
"content": "I've used what looks to be the exact same one as yours. They work OK with no problems.The only thing I noticed, and this has nothing to do with the little PCB itself, is that the voltage drop in the USB cable is a limiting factor on max charge current.ie: Even though the charge current setting resistor is 1.2K, you won't get the full 1A charge current due to voltage drop in the USB cable. This is especially true as the battery voltage rises.Picture of one I used:"
},
{
"post_id": "",
"author": "kjr18",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "November 12, 2024, 05:54:10 pm",
"content": "Quote from: Kim Christensen on November 12, 2024, 05:36:21 pmIt depends what you use as power supply, some usb chargers put out a little higher voltage when loaded with higher currents, to minimalise voltage drop. Also TP4056 datasheet mentions small value resistor just before chip, probably to reduce heat."
}
] |
2025-10-17T16:27:47.878350
| 6
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-7v-li-battery-(x2-series-configuration-teclast-t-51-dap)/
|
3.7v Li battery (x2 series configuration Teclast T-51 DAP) - Page 1
|
[
{
"post_id": "",
"author": "13hm13",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 25, 2022, 04:41:44 pm",
"content": "I have a Chinese branded Teclast T-51 DAP (digital audio player) which is the same as the Nationite s:flo2 model.Looks like an early iPhone. This model is from 2010.Inside are TWO batteries apparently in series (balanced) config. I have not taken the protective wrapping off the batts to see the exact wiring config. or the protection PCB. I'm going to assume each battery has its own PCB. I can measure the voltage to about 7.2v when fully charged (which isn't long). The unit charges via std. micro USB (5.0 v).Yes, they lasted 12 years in fairly regular (daily) use for about 10 years. But now, time to replace the battery!Dimensions: 25x90x5mm for EACH battery.I can find NO info on the OEM batt., so no clue as to mAH capacity, etc.Ali and ebay have several options.Please suggest something given the parameters I have provided.Photo below of interior of DAP with batt:Photo below of exterior:"
},
{
"post_id": "",
"author": "ledtester",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 25, 2022, 11:48:49 pm",
"content": "Quote from: 13hm13 on October 25, 2022, 04:41:44 pmSo you have lipo cells in a \"2S\" configuration. Lipo cells come in all shapes and sizes so it is a matter of finding a supplier for the dimensions you need.If you search for \"2S lipo\" you'll get a lot of listings but the two cells are usually stacked on top of each other. One of those could work if the two cells are not glued together and only held together by tape. I'd ask the seller for confirmation of that.Performing a search on aliexpress for \"lipo cell\" yields a lot of hits for largely unprotected cells.I would contact this seller which has a pretty high rating:https://www.aliexpress.com/store/1101115656and say you're looking for two lipo cells which will fit in a 5mm x 50mm x 90mm space. This leaves open the possibility of using cells of dimensions 5mm x 50mm x 45mm as well as 5mm x 25mm x 90mm. Of course, you can always use smaller sized batteries.(You may have noticed that the \"model number\" of the battery is basically an indication of its dimensions -- e.g. a \"755590\" battery is 7.5mm x 55mm x 90mm.)Once you find suitable cells, I would transfer the protection board from the old pair of cells to the new pair. The yellow tape that you see wrapped around the protection board is called \"Kapton tape\". It's a thin, high-temperature resistant tape and it's a useful to have around when repairing electronics. The green tape holding together your old cells is also probably Kapton tape."
},
{
"post_id": "",
"author": "13hm13",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 26, 2022, 04:32:59 am",
"content": "Quote from: ledtester on October 25, 2022, 11:48:49 pmGood, useful info!That Lanzhd Ali seller seem ideal. Ali's English search is atrocious. They could sell a lot more stuff out of China/HK if they invested more time in other languages.Didn't know the sizing code, either. What about that second code next to \"+\"? Could it be the capacity and voltage?"
},
{
"post_id": "",
"author": "ledtester",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 26, 2022, 11:29:34 am",
"content": "Quote from: 13hm13 on October 26, 2022, 04:32:59 amThe voltage of a single lipo cell will always be \"3.7V\".In this pic:https://www.aliexpress.us/item/3256802569830553.htmlthe \"20200101\" next to the \"+\" is likely a date code."
}
] |
2025-10-17T17:03:55.775107
| 4
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-and-5-phase-stepper-motors/
|
3 stepper motors - Page 1
|
[
{
"post_id": "",
"author": "waspinator",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 16, 2017, 03:37:41 am",
"content": "Hi,I'm looking at using 3 phase stepper motors, but I can't find much information about them. How much harder are they to drive? I've only found $100 CNC type drivers online, but they're not mentioned much in hobby community. Allegro makes a SI-7600 3 phase stepper driver, but there doesn't seem to be stock or breakout boards. Where should I be looking to find more information?http://www.alldatasheet.com/datasheet-pdf/pdf/38283/SANKEN/SI-7600.htmlhttps://en.wikipedia.org/wiki/Stepper_motor#Higher-phase_count_stepper_motorsThanks"
},
{
"post_id": "",
"author": "ebclr",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2017, 04:35:54 am",
"content": "Driverhttp://www.onsemi.com/PowerSolutions/evalBoard.do?id=STK673-010GEVB"
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2017, 05:08:56 pm",
"content": "Stepper motors come in a lot of sizes and one thing that distinguishes them is motor current. You didn't say which motor you are using so it is impossible to help select a driver. There's a reason that large commercial drivers tend to be used on CNC milling machines. The motors are drawing somewhere between 5 and 10 amps and we also want a bunch of microsteps.OTOH, if microstepping isn't required and motor current is modest, you can drive the motor with some MOSFETs hung off the side of an Arduino. Or maybe just an L293D driver chip (or similar):https://learn.adafruit.com/adafruit-arduino-lesson-16-stepper-motors/overviewhttp://arduino.stackexchange.com/questions/20503/can-an-l293d-motor-driver-shield-do-microstepping"
}
] |
2025-10-17T19:04:58.464614
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-axis-cnc-router-project/
|
3-axis CNC router project - Page 1
|
[
{
"post_id": "",
"author": "ulfh2012",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "July 07, 2013, 11:50:07 pm",
"content": "Hi.I am new to this forum, and new to the world of CNC routers, but have some electronic background.I have been gatehering parts for a 3-axis CNC router project. I have got most of the mechanical stuff, but I don't understand all consepts about stepper motors. I have found a controller on ebay using th TB6560, and have read articles about how to modify this Chinese unit to make it work. This unit can supply 1-5 to 3 A, and does not support lower current than 1.5 A. Don't understand why, but that's another story.When I look at stepper motors, I find that they mainly specify current, and not voltage. This controller will support 12 - 24 volt input voltage. My project will have a working area of about 10\" x 12\" (may be a bit less) and I want to use it for making PCBs and maybe small parts of aluminium.My main problem now is to find a stepper motor I can use and hopeflully not blow the motor (or controller) by supplying wrong voltage. I have found some motors at Chinatown in Bangkok (I'm in Thailand on a vacation), but they are 24 volt .21 A, and thus cannot be used with this controller. Maybe they also have to litle power? They are incredible cheap, but that does not help, if I cannot use them.Can someone give me advice on what motors to use?Best regardsUlf"
},
{
"post_id": "",
"author": "GeoffS",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "July 08, 2013, 01:22:32 am",
"content": "Welcome to the forum.You need to choose motors that have the same, or higher, current rating as your drivers. In your case 3A.Driving at the maximum rated current will ensure maximum torque from the motor.Voltage on the other hand can be a LOT higher than the rated voltage. A good rule of thumb for maximum voltage is32 * ?L = VMAXwhere L is the inductance of the stepper in millihenries. Any voltage lower than VMAX means your stepper is not running as fast as it could. Other factors will limit the maximum speed.For a good overview of steppers and power supplies, take a look atGecko's website. No connection with them other than as a customer."
},
{
"post_id": "",
"author": "cthree",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 08, 2013, 03:00:52 am",
"content": "I love dealing with a vendor that knows what they are doing and doesn't mind helping you be a well educated customer. It makes me WANT to buy from them! Great link"
},
{
"post_id": "",
"author": "GeoffS",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "July 08, 2013, 06:36:12 am",
"content": "I have a number of their drives. They work great and are almost un-killable.If you do manage to destroy one, they will repair/replace it, no questions asked, at no charge.** First time only."
},
{
"post_id": "",
"author": "Kremmen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 08, 2013, 06:50:44 am",
"content": "Gecko is a reasonably good motor controller for hobby use, but if you get the 540 (the quad motor unit), then one caution: You _must_ solder the current limit resistors in the specified pins of the D9 connectors for individual motors. The documentation indicates the resistance vs desired current. Failure to do that will most likely cause the individual motor driver module(s) to blow inside the unit.I was asked some time ago to fix just this problem and turns out the problem module had wasted half of the H-bridge fets and both half-bridge drivers so there is little or no internal protection in the modules themselves. The motherboard does have protection features but they won't help if you forget the limit resistor."
},
{
"post_id": "",
"author": "poorchava",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 08, 2013, 08:37:44 am",
"content": "Price of Gecko drivers is absurd for a hobby machine. Especially if you live outside of the US.As for the chinese TB6560 driver boards I have analyzed a few types and built my own 1-axis drivers based on that. All chinese boards I have seen have an ihnerent problem: power supply sequence. TB6560 datasheet states clearly that you should connect the logic power supply before any voltage is applied to output bridge supply pins. What chinese do is that they route the high power supply straight to the bridge, feed a 5V regulator from that supply and then use it to power logic. It creates a situation, where you can get a H-bridge shoot-through during power-up and the chip blows up.Also, the TB6560 is not that good for rapid movement, because it's specified only up to 13kHZ of step frequency. With typical drive arrangement being a leadscrew with pitch of 4 or 5 mm, and typical motor having 200 steps/rev, at 1/16 microstep rate you will be getting about 4 rotations per second, which translates into roughly 16-20mm of travel. Even less (~6-10mm) when you use ordinary threaded rods with 1-1.5mm pitch. With normal 4-5mm leadscrew you will get up to travel speed of 1200mm/minute. And that is slow.Those chips can run much faster, but this depends on particular specimen. I've tested like 20 of those and some would go all the way up to 29kHz or so, and some would crap out at 15kHZ. And when operating outside of specification you will occasionally get missed steps which completely ruins the precision of such machine.I would consider using something like A3986 or A4989 as they operate at much higher frequencies.As for the voltage, Geoffs is right - the higher voltage you supply, the faster your motor will go. On the other hand TB6560 goes up to 35V only (normal operation, maximum taring is 40V iirc). For most small motor this should be fine. This is because a motor winding is an inductive load and it will make current ramp up. Current rise rate is proportional to voltage applied, so the higher the voltage the more times a second you can rise the voltage to the max and back again. On the other hand higher voltage requires faster control logic to keep up with current changes."
},
{
"post_id": "",
"author": "KuchateK",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "July 08, 2013, 02:42:16 pm",
"content": "For stepper theory I recommend this FAQ:http://homepage.cs.uiowa.edu/~jones/step/If you want to buy something better than TB6560 or Allegro based drivers but not as expensive as Gecko I suggest this:http://www.leadshine.com/productdetail.aspx?type=products&category=stepper-products&producttype=stepper-drives&series=M&model=M542Ebay clones go for less than $40. They are usually marked as 2m542 (I have clones) and they also work very well.Single supply, built in opto-isolation, current and microstep selectable with dip switches (no G540 resistor crap), quite fast, rated at 200kHz."
},
{
"post_id": "",
"author": "KTP",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 09, 2013, 02:28:31 am",
"content": "Go brushlessI picked up these Adept linear robot slides on ebay for $100 each including a 300 watt brushless motor. I bought a few EN-204 or EN-208 industrial drives that happen to take step/dir for $20 to $30 each and threw together this gantry router that can move a 50 pound Z axis at over 2000 IPM.I do like the cleaness of the Geckodrive stuff for steppers though. They sometimes put the 4 axis unit on sale for $225 on cnczone"
},
{
"post_id": "",
"author": "ecat",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 09, 2013, 05:05:12 am",
"content": "Quote from: KuchateK on July 08, 2013, 02:42:16 pm+1 for the Leadshines.I have three M752s (good for 70V I run at about 50V) and so far they have performed without fault, this includes continuous runs of 16 and 20 hours. They are not the cheapest but, and this is where many people go wrong in my opinion, while there is nothing wrong with saving a bit of money on your CNC build it is a big mistake to skimp for the sake of 10% or 20% on the basics.At the end of the day your main costs will be tooling, materials and time. How much will a couple of lost steps cost you? At £5 to £10 for the tool, about the same for the material and say 5 to 10 hours lost time it soon adds up.Anyway, just my 2c."
}
] |
2025-10-17T20:19:49.271147
| 9
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-bit-address-dual-port-memory/
|
3 bit address dual port memory - Page 1
|
[
{
"post_id": "",
"author": "fabiodl",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 04, 2021, 03:17:54 am",
"content": "What is the easiest/cheapest way to realize a 3 bit address, 8 bit data dual port memory? Actually one port only does writes,and the other only reads.The first thing which comes to mind is using a cpld, but I wonder if there are more specialized parts / tricks commonly used."
},
{
"post_id": "",
"author": "fabiodl",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 04, 2021, 03:50:20 am",
"content": "Indeed, an ice40 may be a nice idea. However, since anything else is 5V, I'd need level translators though (let's say some 74HCT245 or SN74CB3T16211).(this was recently discussedhere)"
},
{
"post_id": "",
"author": "CaptDon",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 05, 2021, 02:17:46 pm",
"content": "It may seem wasteful, but there are 1kbyte dual port memory devices and they are not very expensive. They are a bit big having the data and address lines on both sides, I think maybe 48 pin DIP. It is a bit tough to get true 'write while read' or 'read while write' but I have done it. I had a pc board with 8 8-bit latches. The outputs were always enabled as was the chip selects. The write line was decoded by which latch I wanted to write to (write enable feeding the 'gate' pin and latch address feeding the normal address pins of a 74154) and the data input side of the latches were common. On the output side of the latches the outputs were always enabled and the 8 data lines went to a one-of-eight decoder. There were 8 decoders, one for each bit. All eight D0's to one decoder, all D1's to a decoder, etc. etc. Then I would feed the 3-bit 'read' address to the decoders to select which input data line was placed on the output of the decoders. This is nearly identical to what you are trying to accomplish and probably could be programmed into a CPLD but I would wonder about the synchronicity of the data transfers through the VHDL layout? I never got beyond Xilinx 'Schematic Capture' and all my CPLD work was done as if I was using TTL building blocks. In many cases you can pick-and-place actual TTL part numbers into your layout. I seldom got bad data readouts on my homebrewed dual port system. If there was an exact instant where you were reading as the bits were toggling from a write to the same latch you could get a cross sampling of old and new bits but the coincidence had to be so close since the bit toggle happened so quickly. I can't really say I ever saw a corrupted read!!!"
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 05, 2021, 03:30:45 pm",
"content": "Quote from: fabiodl on February 04, 2021, 03:17:54 amSounds more like a FIFO to me."
},
{
"post_id": "",
"author": "Druzyek",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "February 06, 2021, 03:49:49 am",
"content": "How about chaining some 74HC670s?"
},
{
"post_id": "",
"author": "fabiodl",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 10, 2021, 08:36:16 am",
"content": "Not a fifo, because each port can access in any random order.Druzyek's part is perfect,thank you!"
},
{
"post_id": "",
"author": "RoadRunner",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 10, 2021, 02:00:01 pm",
"content": "Quote from: Benta on February 05, 2021, 03:30:45 pmQuote from: fabiodl on February 10, 2021, 08:36:16 amThey are called pseudo dual port ram in lattice documentations"
},
{
"post_id": "",
"author": "jmelson",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 10, 2021, 04:59:38 pm",
"content": "Quote from: fabiodl on February 04, 2021, 03:50:20 amXilinx 95xxXL are 5V tolerant. You probably need more than the smallest version, as you need 64 FFs. But, this can all fit in one package.Jon"
},
{
"post_id": "",
"author": "CaptDon",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 10, 2021, 05:52:05 pm",
"content": "The Xilinx solution is probably a good way to go and even more so if you can do VHDL/Verilog. I do the clumsy Schematic Capture but it works for me. I would suggest you go with CPLD and not FPGA. A CPLD knows what it wants to do on powerup with no delay, an FPGA is usually supported by a serial EEPROM or flash part and the FPGA must 'educate' itself on power up. It is just a dumb brick until the program/load cycle is complete. I love the flexibility of CPLD's over hardwire but there can be synchronicity problems if the data stream is not related to the master clock and you are trying to steer short transitional pulses or very short random pulses."
},
{
"post_id": "",
"author": "fabiodl",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 11, 2021, 01:27:56 pm",
"content": "Actually now, as I have no parts at hand, I am using a lattice cpld.The code is trivialCode:module dpram(aa,ad,awr,ba,bd);input [2:0] aa;input [11:0] ad;input awr;input [2:0] ba;output [11:0] bd;reg [11:0] storage[0:7];always @(negedge awr)storage<=ad;assign bd=storage;endmodule"
}
] |
2025-10-17T17:33:46.502681
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-build-projects-plus-harvesting-16580-cells/
|
3 build projects, plus harvesting 16580 cells - Page 1
|
[
{
"post_id": "",
"author": "TheBossUT",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "May 07, 2016, 02:01:33 am",
"content": "Hi All,I have a few projects lined up that I want to do, trying to figure out if it is cost effective. looking for input and suggestions.Project 1: Battery pack for x2 16ft Cool White LED lights running at 12v 2.40 amps = 57.6watts hours, I am looking to run the lights for 3 hours for SUP.Project 2: Same as above but for a kayak.Project 3: Cpap battery backup for 16 hours for camping. its 24v @ 3.75amp hour or 90w, I am figuring the amp hour will at least be half since this is for a heated humidifier and heated hose I won't be using these while camping. so maybe 1.875 amp hour ?Tools for the job = Limited.* I will need to get a new 60w solder iron* different gauge wires, I most likely have this.* 16850 salvaged unprotected cells, recharging and discharging to calculate mah from salvaged laptop batteries. Was looking at this for the charging system and maybe discharge test as wellhttp://goo.gl/AqEX3spaired with thishttp://goo.gl/q49ITRto calculate the discharge rate using a 1amp load. to build the charging system is cheap as I have spare PC PSU I can use, the discharge test a bit more expensive looking to do a few batteries at a time.* Pretty sure I am going to need to get a SKYRC iMAX B6 and watch out for the knock off clones as well.* better solder* pretty much unlimited supply of used laptop batteries, talked to a E waste recycling center, they collect a few 100 pounds a month, I have 40 packs now to dismantle.* some way to balance the batteries, BMS, individual charging* buck or boost converter, I will need to either step up / down to 12v 2.4 amp for the LED project and step up or down 24v roughly 2amp for the CPAP project.* lipo firebag, I know the risks of lipos even more so with unprotected cells. most of the work is done outside, or next to the front door for a quick toss.* could I salvage a BMS from one of the dismantled laptop batteries ?I am going to be spending about $40 as it is just to get the charger and most likely another $20 - 30 for remaining supplies. Is it even worth it ? do I just by RC packs and be done with it ? I know I will still need a charger. Once I invest in the initial setup building my own packs might be worth it. figuring I can get at least 1500mah out of used cells taking them down to the 2.7v area.I know soldering the batteries is a risk as well since I won't be tack welding. 60w iron is recommended ? when pulling packs out of laptops maybe it is best to try and keep the tabs on the cells.salvaging the cells from laptops packs, I have sparked a few nothing happened other then the spark, the pack was tossed outside after, is there a major risk from a quick spark ? I know shorts are a issue. I am guessing if anything is going to happen the battery is going to get hot before thermal runaway happens.on to the project specs.Project 1 & 2 are pretty much the same, just one is a SUP the other a Kayak. I know there are already pre done kits for $200+*building the battery or buying it ? if building I was thinking of just a simple 16850 battery holder and load them in like you do the do AA batteries, depending on mah I can get from the cells I will need between 10-14, then when I am done I individually charge each cell, I am hoping this eliminates the need for balancing.Step up or step down ? to keep things simple it would be nice if I can just do 3.7 high mah pack and step it up to 12v using a protected boost converter, really looking for input here,I know I could just run the LED strip off a straight pack, but now I am pushing 16.8 volts to the strip, and they really did not like it when I was pushing 20vwires and strip started to get to hot. then everything will have to go into a waterproof box with a waterproof DC barrel connector.Project 3 CPAP battery backup, ResMed S10 elite 24v @ 90w or 3.75amp max, looking for 16 hours run time 2 8hr nights. I am figuring it will run at 1.8ap to 2amp, have not tested yet, this would be with the heated hose and humidifier off .build or buy a pack ? if can salvage cells that are at 1500mah I will need about 22, or 32 if at 1000mah, again I would like to do the style of a battery holder, but this might add to the weight and build and may not be feasible, so if I build a pack it would need a balance system or BMS. again is it best to Step up or step down, I will need to have some sort of discharge protection, think of taking the cells down to 2.7vlooking for suggestions, thanks for the comments and help."
},
{
"post_id": "",
"author": "sokoloff",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 07, 2016, 09:35:28 am",
"content": "I've tried many times to solder to batteries and finally gave up and bought a tack welder. That makes things wildly easier. You could do the battery holder design or a tack weld pack design, but I'd plan around not being able to solder them."
},
{
"post_id": "",
"author": "TheBossUT",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "May 07, 2016, 10:15:30 am",
"content": "Quote from: sokoloff on May 07, 2016, 09:35:28 amYes that could be an issue as well, along with shorts, Tack welder is not worth the investment to build my own pack, if I was always building pack it would be, but I see this as maybe being a 1 or 2 time. if the pack goes bad then I would have to rebuild. I have seen a few youtube videos of them soldering to the batteries, sandpapering might be best before hand.If I could find battery holders in the configs I need and not singles it might work better. maybe 5 or 10 cell holders then stacked on each other. The more I think about it, the more I think it might be worth just buying even if packs are not cheap.... i have already has some cells short that I was trying to salvage.... Tossed outside they went, nothing happened other then they got a bit warm."
},
{
"post_id": "",
"author": "sokoloff",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 07, 2016, 11:09:12 am",
"content": "I suspect you might be able to find an RC club nearby and someone is bound to have a battery spot welder. A well equipped hackerspace also might.Lastly, if you by chance happen to be in/near Cambridge MA, I can do it for you for just a handful of spare, used cells. It's not worth the hassle of mailing the batteries back and forth, of course."
},
{
"post_id": "",
"author": "TheBossUT",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "May 07, 2016, 05:51:32 pm",
"content": "Quote from: sokoloff on May 07, 2016, 11:09:12 amNever thought to look for RC groups. Thanks. And I live in Tampa FL."
},
{
"post_id": "",
"author": "TheBossUT",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "May 08, 2016, 05:39:03 am",
"content": "wow at a181 views and only 2 replies ? do I have this post in the wrong section ?"
},
{
"post_id": "",
"author": "CJay",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 08, 2016, 06:46:22 am",
"content": "Quote from: TheBossUT on May 07, 2016, 05:51:32 pmIf you're harvesting cells from laptop batteries you'll find the interconnects are spot welded onto them and can be soldered to very easily.Cut them carefully and you have a tagged cell."
},
{
"post_id": "",
"author": "TheBossUT",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "May 08, 2016, 07:54:43 am",
"content": "Yea, currently I have been ripping them off carefully while trying not to short the cell, the tack marks are left behind and i am sure they can still be solder to, the other thing I have been thinking about is I most likely don't need a driver buck /boost converter for the LED strip lights. or under voltage for that matter, since I am shooting for a total run time of about 3 hours for the LEDs I think once the voltage starts getting low, I will be able to tell by the dimming of the Led, tho a boost buck converter would keep the Leds bright all the time, but I need to get the BMS system worked out. unfortunately I am not getting alot of help on forums or crawling the web."
},
{
"post_id": "",
"author": "CJay",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 09, 2016, 03:39:58 pm",
"content": "Quote from: TheBossUT on May 08, 2016, 07:54:43 amWell you may be able to solder to the tack marks but what I meant was cut the thin sheet material that's used to interconnect them so you have a length of that still spotwelded to the cells. Then you can solder to that.I'd not rely on an LED getting dim as a reliable indicator of state of charge, depending what current you want to draw from the LiIon cell I would definitely consider adding a protection bord that will safely disconnect the cell when it's discharged.As for charging, I recycle cells from 'dead' laptop battery packs and use the cheap TP4056 boards to charge them."
},
{
"post_id": "",
"author": "TheBossUT",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "May 11, 2016, 12:53:04 pm",
"content": "looks like I might be soldering the 16850's I cant seem to find anyone one with a spot welder near me, there is a local shop that does batteries but they wont touch them, I understand why."
}
] |
2025-10-17T19:18:53.054857
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-channel-led-driver-mosfet-overheating/
|
3-channel LED driver MOSFET overheating (intermittently) - Page 1
|
[
{
"post_id": "",
"author": "paw",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "July 20, 2015, 06:41:14 pm",
"content": "Hi all. As always I plead ignorance and beg forgiveness for anyone who I may offend by posting this.I replaced a cheap and dodgy IR LED RGB driver with my own at least as flawed and dodgy version (although infinitely better in some respects). I found that on two occasions the lights started flickering and the FETs would show signs of overheating (>160 deg C). Interestingly they would work for hours at a time with no problem on other occasions (at various PWM duty cycles).My limited understanding is that FETs are great while ON and OFF even at very high currents (as per data sheet) but while switching the impedance is unfavourable and due to junction(?) capacitance duration of the switching (while charging) might be longer than desired. I started wondering if for whatever reason my FETs were not completely switching ON or OFF.I've used NTD5804NT4G 40 V, 69 A, Single N?Channel, DPAKI am switching ~ 8A at 12V which is not nothing I realise that. I just hoped that at 1kHz PWM and relatively low R the FETs would cope with board dissipation and air cooling... Which it does every time but twice so far (70C max normally). I provisioned for pull-down (10k) but left it off as it doesn't make them any happier.The Micro PWMing the FETs is running at 5V. The VGS (th) is 2.0V-3.5V. There is a 11k resistor for driving the gate from the micro. Isn't 11k a bit high?I would have liked the switching characteristic to be cleaner but I don't really know what to expect. I'm attaching CH1 (Yellow) Gate, CH3 (purple) Drain without load.Any suggestions appreciated.P.S. Allow me to add that the layout attached is my very first. I would have done few things differently today (decoupling, trace thickness, ground plane etc). I welcome any comments still but would love to understand my FETs better.EDIT: I din't hope hope. Back of the envelop calculation of Vdrop (at 5mOhm or even 25mOhm) and 8A load at 12V gave me under 1W each dissipated on each FET."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 20, 2015, 06:52:54 pm",
"content": "How can you expect to be able look at the waveform on the drain without a load up pull it up to 12V?Yes, 11k does sound on the high side. At 8A the conduction losses shouldn't exceed 768mW but if it's taking a long time to switch, the switching losses will be higher."
},
{
"post_id": "",
"author": "paw",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "July 20, 2015, 06:59:33 pm",
"content": "Ignorance and lack of fundamental understanding?I'll pull the drain up to load it a bit and check. Will see what the switch on looks like with 11k and 1k.Attached 11k and 1k. I like the 1k better. The FET should be fine with 1k right? I'm not going to burn the gate?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 20, 2015, 09:01:27 pm",
"content": "Why would it burn up the gate?A MOSFET's gate is a capacitor. The faster it can be charged and discharged, the better. You could even remove the resistor and it'll probably work but this isn't recommended. Try some low value such as 100R."
},
{
"post_id": "",
"author": "paw",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "July 21, 2015, 07:19:12 am",
"content": "Ah so we are protecting the MCU pin peak current rather than protecting the MOSFTET right?"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 21, 2015, 11:27:13 am",
"content": "Yes, connecting a MOSFET's gate can directly to an MCU output can cause problems due to the current surges.There will also be some inductance which can cause ringing.The voltage on the magenta trace looks wrong to me. Are you sure you didn't have the switch on the probe set to x1 and the oscilloscope set to x10? One tenth of those voltage readings seems more sensible.Notice how the voltage on the yellow trace briefly stops rising/falling, just as it turns on/off and that's it's more noticeable when the gate resistor is higher?It's because the capacitance of the MOSFET's gate increases just as the threshold voltage passed and it starts to turn on/off. This is due to the Miller effect: the parasitic capacitance between the drain and gate form a negative feedback path. When driving MOSFETs it's often more helpful to use the gate charge figures listed in the datasheet, rather than the gate capacitance.See links below:http://www.vishay.com/docs/73217/73217.pdfhttp://www.onsemi.com/pub_link/Collateral/AND9083-D.PDFhttp://www.irf.com/technical-info/appnotes/mosfet.pdf"
}
] |
2025-10-17T19:36:54.480574
| 6
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-chip-microcomp-1/
|
3-chip microcomp-1 - Page 1
|
[
{
"post_id": "",
"author": "Simon123",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "August 24, 2011, 12:30:27 pm",
"content": "can somebothey please send me schematic for 3-chip?picture (bw):http://www.rebelhosts.com/tt/te/images/p101.jpg"
},
{
"post_id": "",
"author": "EEVblog",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "August 24, 2011, 12:34:46 pm",
"content": "Colin Mitchell at Talking Electronics has all the info, and can probably still sell you the mags and a kit maybe.www.talkingelectronics.comTell him I sent you.Dave."
},
{
"post_id": "",
"author": "joelby",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "August 24, 2011, 12:38:35 pm",
"content": "Ha! That brings back memories. I'm sure I have a copy of that magazine issue stashed away somewhere. I've got a Tek-1B in the shed."
},
{
"post_id": "",
"author": "joelby",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "August 24, 2011, 12:55:04 pm",
"content": "Anyway, is there any particular reason why you'd want to build one of these? They are very simple, and there should be dozens of comparable Z80 single board computer designs kicking around on the Internet.From memory it was a simple oscillator (either using inverters or a transistor multivibrator), a 2732 EPROM, and 74LS374 latches for I/Os. The Tek-1 also used a 74LS138 to decode ports - the Microcomp might not have bothered with the latter for simplicity."
},
{
"post_id": "",
"author": "Simon123",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "August 24, 2011, 02:44:34 pm",
"content": "i want build it beacuse its cool (i watched demo of this comp)"
},
{
"post_id": "",
"author": "Simon123",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "August 24, 2011, 02:45:52 pm",
"content": "Quote from: EEVblog on August 24, 2011, 12:34:46 pmi just wana sch. not the mag."
},
{
"post_id": "",
"author": "Simon123",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "August 24, 2011, 02:50:27 pm",
"content": "Quote from: joelby on August 24, 2011, 12:38:35 pmcan u send me the scan of sch and descr. if you find the mag. ?"
},
{
"post_id": "",
"author": "joelby",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "August 24, 2011, 03:11:21 pm",
"content": "It'll be somewhere at my parents' house, and I'm currently in a different state.. so maybe, but it'll take me a while to get around to it. I don't think the code for the EPROM was printed in the magazine, so you might have to ask Colin Mitchell about that regardless. Without this, it will literally do nothing."
},
{
"post_id": "",
"author": "Simon123",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "August 24, 2011, 03:25:09 pm",
"content": "tnx"
},
{
"post_id": "",
"author": "EEVblog",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "August 25, 2011, 05:14:00 am",
"content": "Quote from: Simon123 on August 24, 2011, 02:44:34 pmThen the schematic ain't going to help you unless you have the firmware to go along with it. The articles are excellent, they are worth getting.And it's only fair to pay a few bucks to Colin for his work. he might even have a kit (or the PCB) to make it easy for you to build.Dave."
}
] |
2025-10-17T20:38:30.756463
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-digit-7-segment-help/
|
3 digit 7 segment help? - Page 1
|
[
{
"post_id": "",
"author": "algorithm",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 10, 2021, 03:20:25 am",
"content": "So im perplexed by how the 7 segment display works with digits. I want to power the 7 segment with batteries, manually and statically wiring what segments. But grounding each respective digit results in the same segment on all 3 lighting. Also some pins for segments are used by 2 digits. I know normally the display is visually tricking the user by rapidly cycling. Does anybody know of the best way i would go about wiring each segment seperately off battery without 3 separate battery compartments lol? Maybe a virtual ground? Any ideas are appreciated."
},
{
"post_id": "",
"author": "retiredfeline",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 10, 2021, 03:32:29 am",
"content": "Those displays are intended to be multiplexed to save pins. If you can't manage that you'll have to get a non-multiplexed display.Assuming you are trying to display 3 static digits, if you think about it in information theoretic terms, you are trying to send 21 bits of information into 10 pins. The channel has to be enlarged and this is done by time multiplexing."
},
{
"post_id": "",
"author": "Terry Bites",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 10, 2021, 05:04:33 pm",
"content": "This should make sense of it.https://fsimdeck.wordpress.com/electronics3/led-7-segment-multiplexing/Why: massive power saving, simpler wiring/ PCB, easy dimming, lower cost."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 10, 2021, 06:07:38 pm",
"content": "For modern LED the power savings are a myth. Most LEDs are relatively linear in output power versus ouput power. It deviates unsually to lower output at low (for modern LED often < 1 µA) and high (e.g more than rated current) current. The main point is easier wiring and less pins at the chip/µC - so cost saving.It may have been an issue with the very old LEDs in the 1970s and the LEDs are not regularly tested at very low current - so the intensity may scatter more at a low current than with multiplexed segments."
},
{
"post_id": "",
"author": "emece67",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "March 10, 2021, 07:06:21 pm",
"content": "."
},
{
"post_id": "",
"author": "Terry Bites",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 10, 2021, 09:02:41 pm",
"content": "Explain myth- have LEDs got less efficient?"
},
{
"post_id": "",
"author": "tooki",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 11, 2021, 11:45:25 am",
"content": "Quote from: Terry Bites on March 10, 2021, 09:02:41 pmLEDs have become vastly more efficient. LEDs’ efficiency is lower at higher currents (i.e. doubling the current doesn’t quite double the light output), at least above a certain point. (That’s why lighting LEDs get so hot: they’re usually being run well beyond their range of highest efficiency.) So in theory, having an LED display where each LED (when on) was driven at a constant low current would be more efficient than multiplexing it at a higher current for less time. But I suspect the current needed by all the extra control electronics would more than negate any savings in the LEDs.In terms of raw efficiency, modern (emerald) green and white LEDs are insane. With traditional green LEDs used as indicators (or display segments) you really needed the 20mA per LED. With a modern green one, 1mA is more than enough. I often run them at less than that!!"
},
{
"post_id": "",
"author": "MikeK",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 12, 2021, 12:49:12 am",
"content": "I had to test the \"myth\":I have a clock module with a 4-digit 7-segment display. I tested two methods: 1) Turn on all segments in each digit and multiplex the digits and 2) Turn on each segment and multiplex the segments and digits (turn on seg a, digit 1...seg g, digit 1...segment a, digit 4...segment g, digit 4). I had it switch between the two methods and could not see any difference in brightness, and no flickering.Using my Korad KA3005P power supply set to 5V it showed 23mA with method 1 and 21mA with method 2. Not a huge difference, but not nothing either. And messing with the duty cycle and refresh rate could bring both of those numbers down."
},
{
"post_id": "",
"author": "rdl",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 12, 2021, 03:10:40 am",
"content": "LEDs have gotten vastly more efficient. Thirty years ago it took 10-20 mA for reasonable visibility. There are some LEDs today that will leave serious afterimages at less than 1 mA. I have some old Panasonic 7-segment displays that barely light at 10 mA, while some newer ones I have from China made good reading lights at under 6 mA . Using 4 of them in a clock I had to crank the current way down at night.Here is photo of an older green LED next to a modern InGaN green LED. The newer LED is running at only a tiny fraction as much current as the older LED (320uA vs. 15 mA). In this photo the InGaN LED is actually badly over-exposed (blown out). If the exposure had been correct the older LED (actually all of the other LEDs) would have barely been visible."
},
{
"post_id": "",
"author": "MikeK",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 12, 2021, 01:24:28 pm",
"content": "Nobody's doubting that modern LEDs are more efficient."
},
{
"post_id": "",
"author": "brucehoult",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 13, 2021, 12:56:48 am",
"content": "Quote from: algorithm on March 10, 2021, 03:20:25 amYou've got no choice but to somehow send Vcc and GND each to three different wires in sequence, with each GND connected to one digit and each Vcc connected to the segments you want to light for that digit -- with diodes from the Vccs to the segments to prevent cross-leakage.But it's just as easy to use 10 outputs and do it properly. With a small chip such as a $1 8 pin ATTiny85 with only 5-6 outputs (5 if you don't want to complicate reprogramming it) you could use three outputs for the digits and two outputs to drive a '595 shift register."
}
] |
2025-10-17T17:31:55.702369
| 11
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-ghz-pll/
|
3 GHz PLL - Page 1
|
[
{
"post_id": "",
"author": "slashguitar",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 01, 2012, 11:00:19 pm",
"content": "Hello,I have to test if a 3 GHz PLL is working (ADF4118). I probed the output with a 200Mhz Tek but there is nothing. Is there a way to see if the circuit is working without expensive spectrum analyzers?Thanks"
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 01, 2012, 11:08:09 pm",
"content": "Depends what exactly you want to test.You could buy 4x 3Ghz flip flops and make a 4 stage div/2 frequency divider.That would give you 187Mhz that you could see on the scope.Looking at digikey 3Ghz flip flops cost NZ$6.50EDIT: Actually, it would be cheaper to use two of these div/4 chips, which cost NZ$5.66http://search.digikey.com/nz/en/products/SY100EL33LZG/576-1354-ND/771946"
},
{
"post_id": "",
"author": "slashguitar",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 01, 2012, 11:38:29 pm",
"content": "It looks like it might do the job.thanksUnfortunately the shipping will take a week or so"
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 01, 2012, 11:44:05 pm",
"content": "What about electronic suppliers near you?You could always build 4 flipflops out of 3ghz+ transistors if you wanted to get crazy.And if 3ghz+ transistors are easier to source locally. (they usually are, being more basic components than div/4 chips)"
},
{
"post_id": "",
"author": "Rufus",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 02, 2012, 12:26:58 am",
"content": "Quote from: Psi on February 01, 2012, 11:08:09 pmThen he can post asking how to test if a 3GHz divider is working."
},
{
"post_id": "",
"author": "mikeselectricstuff",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 02, 2012, 01:04:00 am",
"content": "If all you want to test is whether or not the 3GHz is present, a simple diode detector on a scope probe would do it.You may be able to do something clever by mixing the outputs of two PLLs to produce a difference signal with a more manageable frequency."
},
{
"post_id": "",
"author": "ejeffrey",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 02, 2012, 08:39:24 am",
"content": "If you make a frequency divider you have to watch out. If you AC couple the input (which is often convenient) they will usually oscillate at a few GHz if there is no signal."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 04, 2012, 11:47:29 am",
"content": "You're using the wrong tool for the job. You need a frequency counter not an oscilloscope which isn't much use here. Fortunately 3GHz frequency counters are quite common and cost the same as a low end oscilloscope."
},
{
"post_id": "",
"author": "Fraser",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 04, 2012, 12:28:15 pm",
"content": "Simple SHF monitoring tools may be built....1. A simple diode detector probe with suitable diode for 3GHz use. Works with a multimeter or oscilloscope to provide a dc level when RF is present. Frequency cannot be determined.2. Prescaler for oscilloscope or low frequency frequency counter. SHF prescalers are now more available since the advent of satellite TV. They are cheap and can divide a frequency down to that which you equipment can display. Division factors of 64, 128 and 256 are common and cost a few dollars. Just search for prescaler on ebay. Hittie do lots of SHF prescalers.3. A downconverter to convert an SHF frequency down to one that your equipment can cope with. A simple unit will consist of a cheap SHF VCO connected to an SHF mixer. The product of the mixing process must be less than 200 MHz in your case so a VCO in the frequency range of 3000 to 3200MHz or 2800 to 3000MHz would be good. VCO's are self contained little modules and just require a supply and control voltage to get them going. Again search on ebay for VCO. Frequency accuracy will be appalling but you will see if a 3GHz carrier is present in your PLL and what it is doing. RF filtering on the output of the mixer would normally be used to select only the desired IF frequency but you may get away without this in your case.The above are fun little projects that are cheap and cheerful, yet provide a useful tool that may be used in the future.RegardsAurora"
},
{
"post_id": "",
"author": "Neganur",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "February 04, 2012, 05:36:31 pm",
"content": "Quote from: slashguitar on February 01, 2012, 11:00:19 pmDo you have a schematic by chance? I use the ADF4118 in one of my spectrum analyser's local oscillators. It is connected to a VCO through a loop filter and an ultra low distortion opamp. You would want to probe for DC voltages there, not RF."
},
{
"post_id": "",
"author": "slashguitar",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 04, 2012, 09:01:49 pm",
"content": "thanks for all your replies@Neganur it's the ADI's demo boardhttp://www.analog.com/static/imported-files/user_guides/UG-166.pdf"
}
] |
2025-10-17T20:36:20.075512
| 11
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-input-buzzer-fgm-question/
|
3 input Buzzer FGM question[solved] - Page 1
|
[
{
"post_id": "",
"author": "typematrix",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 16, 2019, 04:52:35 pm",
"content": "HiI found this buzzer in a carbon monoxide alarm I was throwing out.Must be 10 years old or so It was powered by 3-4 AA batteries.Its has 3 pins marked F G MMarkings (Made IN Korea by SUN JIN) no part number.I am trying to make itbuzz, want to add to an alarm i am making.I been doing a bit research and found this circuit, I set it up but nothing happened.https://electronics.stackexchange.com/questions/18212/whats-the-third-wire-on-a-piezo-buzzerAny links or ideas here , The buzzer in the alarm was working before I took it apart.thankslinks to image of buzzer."
},
{
"post_id": "",
"author": "Wimberleytech",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2019, 05:00:29 pm",
"content": "Quote from: typematrix on January 16, 2019, 04:52:35 pmThat is the correct circuit. It should work. Once wired, have you varied the power supply to see where oscillation starts? Show us your circuit...Also try increasing the collector resistor to, maybe, 2k or so."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "January 16, 2019, 05:00:57 pm",
"content": "I googled three terminal buzzer and foundhttps://electronics.stackexchange.com/questions/18212/whats-the-third-wire-on-a-piezo-buzzer"
},
{
"post_id": "",
"author": "typematrix",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "January 16, 2019, 05:31:05 pm",
"content": "I got it working by changing the resistor values as suggested.Thanks"
}
] |
2025-10-17T18:18:15.374122
| 4
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-legs-sot23-4kal-markings/
|
3 legs, sot23, 4KAL markings - Page 1
|
[
{
"post_id": "",
"author": "u666sa",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 04, 2023, 10:14:43 pm",
"content": "What is it? Most important thing is how to test it.Marking is 4KAL."
},
{
"post_id": "",
"author": "Dan123456",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "October 05, 2023, 12:55:07 pm",
"content": "What’s the application for this one?I had a quick look and am getting a couple of possible hits but doubt they are relevant(?).One is on 80’s military electronics (which is like 400 pages long so didn’t want to go digging through that without knowing I am looking in the right spot) and the other 2 are declassified CIA documents (I’m not even joking)!!!I didn’t end up clicking all the way through on those ones to check them out as figure I am probably on enough watch lists as is"
},
{
"post_id": "",
"author": "wofritz",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "October 05, 2023, 01:15:19 pm",
"content": "Closest I found is this:http://www.union-ic.com/Upload/Datasheet/Datasheet_UM1431,UM1441_Rev01.pdfThat's a linear voltage regulator (4KA: 2V)Does that make sense?"
},
{
"post_id": "",
"author": "u666sa",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 05, 2023, 02:11:26 pm",
"content": "Quote from: wofritz on October 05, 2023, 01:15:19 pmYes, this hit makes perfect sense. Though I still wonder what is that L at the end, more precisely for the next time, do I drop the L and search for 4KA without L to get a proper hit.Anyway, I've already tested it by removing it and powering up and making some measurements, without it PSU did not work, hence it must be alive. I wonder how one would test this using digital multimeter? Let's assume it is out of circuit.."
},
{
"post_id": "",
"author": "cortex_m0",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "October 06, 2023, 12:00:17 am",
"content": "On small IC markings, often they have a letter for a date code, lot code, or manufacturing site. That's probably what the L is here."
},
{
"post_id": "",
"author": "Shonky",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "October 06, 2023, 01:55:12 am",
"content": "Quote from: u666sa on October 05, 2023, 02:11:26 pmNot a huge amount you can do with just a meter. Maybe compare against a known good if you had one.You could assume it is the regulator you think it is. Put a current limited supply and measure its output.Or just put it back in the board and test input and output voltages make sense. Perhaps measure input side on the board without refitting and see if that makes sense for the pinout."
}
] |
2025-10-17T16:47:19.811882
| 6
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-or-4-18650-batteries-to-get-precise-12v/
|
3 or 4 18650 batteries to get precise 12V ? - Page 1
|
[
{
"post_id": "",
"author": "wwwill",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "September 20, 2016, 11:31:47 pm",
"content": "Hello everybody,This is my first message here, I hope I do everything right. Tell me otherwise.My question may sound silly to you, but I can't really figure.I want to create an autonomous device and one of the boards onboard needs a 12V 4A power supply (I am pretty sure the 4A is for another configuration, 2A is probably more than enough).I plan to reuse some 18650 batteries found in old laptop batteries.But the question is \"how to get precisely (enough) 12V no matter how charged the batteries are ?\"The batteries are each 3.7V as regular voltage.So, 3 in series would be 11.1V when charged.And, 4 in series would be 14.8V when charged.So the logic would be 4 in series with a DC step-down to 12V.But does a 3-pack with a DC step-up to 12V would not waste less energy ?I cannot really figure...Thanks a lot everybody !Guillaume"
},
{
"post_id": "",
"author": "danadak",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 20, 2016, 11:34:21 pm",
"content": "You can use a buck/boost regulator to handle a battery over its dischargecycle.Several vendors offer them, TI, NSC, Micrel, ON.....Regards, Dana."
},
{
"post_id": "",
"author": "wwwill",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "September 20, 2016, 11:40:41 pm",
"content": "Quote from: danadak on September 20, 2016, 11:34:21 pmSo for you I should use 3 batteries in series and a boost regulator.Thanks."
},
{
"post_id": "",
"author": "danadak",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 20, 2016, 11:55:34 pm",
"content": "Depends on design requirements. For same batteries as you raisethe # of batteries you can get longer service out of a charge,but sacrifice volume/size constraints.Also can be an impact on regulator efficiency, consult datasheet.Regards, Dana."
},
{
"post_id": "",
"author": "Rick Law",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 21, 2016, 12:25:57 am",
"content": "You can never get precise voltage with the lithium 18650 since the battery's voltage changes as it discharge.Fresh charge, it would be around 4.2V, but as it discharges, it will drop to 2.6V where most battery protection circuit cuts in and disallow further discharge. So, with 4x18650, you are over 12V with fresh batteries (4x4.2V=16.8V) and near end of discharge at 2.6V each, you have 10.4V. Your voltage depends on the state-of-charge.If you do want to keep it at around 12V, boost/buck is your best bet."
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 21, 2016, 12:44:17 am",
"content": "The battery protection circuit is not in each cell, it is in the battery pack that you do not have. If a cell is discharged lower than about 3.2V then it is ruined or destroyed. You MUST have a circuit to measure each cell's voltage and disconnect the load when the voltage gets below about 3.2V per cell.How will you charge the battery so each cell receives a balanced charge and so the battery does not explode or catch on fire?"
},
{
"post_id": "",
"author": "ebclr",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 21, 2016, 12:45:07 am",
"content": "This little baby will do 12V with any battery combination you want, ( need do adjust trimpot )https://pt.aliexpress.com/item/LM2587-DC-DC-Boost-Converter-3-30V-Step-up-to-4-35V-Power-Supply-Module-MAX/32379182065.html?spm=2114.02010208.3.11.NvAp8a&ws_ab_test=searchweb201556_0,searchweb201602_3_10057_10065_10056_10068_10037_10055_10054_10069_301_10059_10033_10058_10032_418_10073_10017_10070_10060_10061_10052_10062_10053_10050_10051,searchweb201603_2&btsid=3a7a9150-cc51-4ddc-9dcf-c6dc4a1e5843"
},
{
"post_id": "",
"author": "eventhorizon",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "September 21, 2016, 03:55:04 pm",
"content": "I have almost the same one as shown above as a buck converter and if I connect it to 12.19v supply the best I can get out if about 11.53 volts so loss in the circuit on this design will limit the use of the batteries as they get close to the 12v output on the batteries. I think at least with this buck converter you may only get 50% give or take (no numbers written down or calculators used to get that number) use from your batteries before the buck cant keep you at 12v so I would say with my experience at least with this and limited amount of playing with these things that a buck wont get you the best results."
},
{
"post_id": "",
"author": "suicidaleggroll",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 21, 2016, 04:11:26 pm",
"content": "You need a buck/boost.Boost only with 3 cells will not work when they're fully charged. Buck only with 4 cells will not work when they're nearing empty. A buck/boost will work whether you have 3 or 4 cells regardless of their state of charge, provided you stay within its operational voltage range.You will also need a cell balancing and over/under voltage protection circuit so you don't destroy the cells. Lithium Ion isverytouchy when it comes to under/over voltage or current, and if something goes wrong they can catch on fire or explode.DO NOTskimp on the balancing and protection circuitry."
},
{
"post_id": "",
"author": "Rick Law",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 21, 2016, 05:37:47 pm",
"content": "Quote from: wwwill on September 20, 2016, 11:31:47 pmIt depend a lot on the board you choose. Some are more efficient than others. General rule I've found is, the higher the input voltage, the better the efficiency -- which is kind of basic physics really.Personal experience (aka-not expert opinion but what I discovered by messing around) with a dozen or so boost (LM2577/MC34063..) buck (LM2596/XL1509...) at about 300mA-700mA 12V out:- With buck, you get 90-95% efficiency. When input gets too near output voltage, regulation fails and you have 100% efficiency lost.- With boost, you get a very wide range of efficiency. The lower the input voltage, and/or, the higher the current draw, the worst it gets. For my use (1x18650 to 12V at 300mA), I get Watt-out at about 60% of Watt-in.That said, I am chicken (ie: don't want risk), so I stick with 1x(protected)18650 boost. There is no need to balance cell. There is no need to worry about a good cell feeding the destruction of a bad cell should a failure occurs. Awful efficiency, but absolutely no concern of multi-cell issues.If efficiency is your primary concert, use6x(protected)18650and buck it. But you better make sure your cells are balanced and in good shape. That many 18650 is practically a bomb if you abuse it. In my view, even if you have a current-limit with the board, ahardware-fuse on the cell-sideis an absolute must. If there is any excess current, the hardware fuse ensures that the serialization of the 6x18650 is cut even if there is a protection board failure.Oh, beside protection board failure... there are those cheap cells advertised to have protection board but shown to be without the protection board. The hardware fuse give you some level of comfort at least."
},
{
"post_id": "",
"author": "mariush",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 21, 2016, 05:56:32 pm",
"content": "Most cheap buck or boost regulators you find on ebay using lm2577 or lm2596 or xl15** chips are generally only good for about 2-3A . In addition to that, the people that make them put inductors and diodes on them that would make them work with wide range of input and output voltages, but they're not the best choice. The datasheets recommend specific inductor values if your input and output voltages are within some ranges ... if you don't use the recommended uH value, the chip may overheat or the efficiency suffers.In general, buck regulators are more efficient than boos regulators or SEPIC (buck-boost) regulators, so it would make sense to buy something that regulates the voltage down. Buck regulators can achieve 95%+ efficiency, while some boost regulators may only reach up to 80-85%.Also, you could just go for a ready made pack designed for higher voltage than 12v, instead of using cheap possibly crap 18650 cells. You should check outHobbyking, they have a huge selection of batterry pack. Pick something with 12v+ and capable of 2A+ output and you're set. They also have proper chargers that can balance the individual cells inside such battery packs."
},
{
"post_id": "",
"author": "Rick Law",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 21, 2016, 07:49:05 pm",
"content": "Quote from: mariush on September 21, 2016, 05:56:32 pmBesides the spot-on guide line above from Mariush... Also bare in mind that many cheap boards list the max power under ideal situation and a small-print \"with heat sink\". Many of the cheap boards comes without heat sink at all. A heat-sink-less boost/buck chip at 2-3A could be hot enough cook itself.I use an LM2596 with small heat sink for my \"bench supply\". I have a mini-fan (1 inch) which I turn on at > 1A and I don't fell comfortable using it over 2.5A for anything over a minute."
},
{
"post_id": "",
"author": "ez24",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 21, 2016, 08:26:51 pm",
"content": "Quote from: mariush on September 21, 2016, 05:56:32 pmThe OP is using batteries from laptops, so they are likely good quality like mine are (Dell)"
},
{
"post_id": "",
"author": "Cerebus",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 22, 2016, 01:00:53 am",
"content": "Before plunging into the question of what regulator topology works best there is a more important question to be asked first. What exactly are you powering? Perhaps it will be quite happy with the range available between a fully charged stack and a discharged one - many circuits supply voltage requirements are nominal and they'll happily work across a range of voltages. Only once that question is out of the way can you really decide the way forward."
},
{
"post_id": "",
"author": "Red Squirrel",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 22, 2016, 08:40:42 pm",
"content": "Honestly I would just run it directly off 4 batteries (add fuse), but check datasheet of the devices to make sure they will handle the voltage, but they probably will. If the device is low power draw (ex: micro controller) a simple linear reg might work too. Not as efficient though."
},
{
"post_id": "",
"author": "KL27x",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2016, 10:06:39 am",
"content": "+1 if the board is small and the IC's can be indentified, it might be possible to run it directly from batteries. It might have only a few components getting 12V, and the rest distributed through regulators that drop that voltage anyway.But if 12 V is what you need, I don't see why you need buck/boost. 4 cells and a buck could work. You don't lose too much capacity stopping at 3V under load. The end is near, anyway. And board will most likely work slightly below 12V, if you want to push your batteries.Common cutout voltages go from 2.7 to 2.9, judging from the most available/common voltage detectors on the market, and from my personal experience you don't get much from the difference there, nor between that and 3.0."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2016, 08:35:42 pm",
"content": "How precise does it need to be?What's the specified operating voltage range of the board?It's possible it already has a regulator built-in and will work over a fairly wide range of voltages. Check the datasheet/schematic."
}
] |
2025-10-17T19:11:23.975231
| 17
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-phase-240208v/
|
3 Phase 240/208V - Page 1
|
[
{
"post_id": "",
"author": "tommygdawg",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "June 18, 2016, 12:34:00 am",
"content": "Hi, allI'm struggling to understand conceptually how three phase 240V electricity works, specifically in relation to power distribution on film sets. Tell me if I'm on the right track. You have a big generator, say 500 amps (in film they're labeled by amps and not kW). It provides camlock outputs that you then wire up to a distribution box which has various Bates and Edison outputs on it. Many of these boxes have three phase input and provide 120/240 (208) out. If I'm understanding correctly, when you want to run a load (say, an 18,000 watt light) at 208 volts, you connect both ends of the load to separate hot 120V legs in your 3 phase system, rather than connecting one end to a hot 120V and the other end to your neutral.The other option is to use single phase 240V, which would be connecting one end of your load to a hot 240V leg and the other end to your neutral wire. Correct?Am I on the right track? If so, then we have to get into the whole other topic of load balancing a 3 phase 240/120 setup."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 18, 2016, 12:45:06 am",
"content": "https://en.wikipedia.org/wiki/High-leg_deltaA.K.A. 'wild' leg delta.Needs a 240V Delta wired genset with either a centre tap on one winding or an autotransformer for the 120V loads and the neutral. Not to be confused with 120V Wye, which delivers 208V phase to phase, but cant feed any 240V loads."
},
{
"post_id": "",
"author": "Fank1",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "June 18, 2016, 01:06:43 am",
"content": "Unless it's a very unusual generator or there is a special transformer in the distribution box you don't really get \"240\" only 208 and 120.Divide the line to line voltage by the square root of 3 ( 1.732)."
},
{
"post_id": "",
"author": "tommygdawg",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "June 18, 2016, 01:34:33 am",
"content": "Thanks guys. I'm aware that in Wye configuration you get 208 volts. I don't really understand why in the Delta configuration you get 240 volts. Furthermore, how do you wire up your load in either a wye or delta configuration? Where do you put your neutral in relation to your hot legs?"
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 18, 2016, 02:36:28 am",
"content": "For Wild leg delta, you can run 240V loads between any pair of phases, and 208V lighting loads from the wild leg to neutral. You get 240V between phases because the genset's got windings designed to output 240V each. (if the same genset was wired wye, it would be 415V between phases, 240V phase to neutral)Wyes always have neutral in the middle. Deltas are stranger as there is no natural place t connect a balanced neutral, so you get oddities like wild leg delta or corner grounded delta."
},
{
"post_id": "",
"author": "johansen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 18, 2016, 05:37:24 am",
"content": "Quote from: tommygdawg on June 18, 2016, 12:34:00 amcorrect, if the generator is 120/208wye. if its 240vdelta then you have 240 natively, but you also have 208 available. and you also have 120v available.Neither the 208 or 120v outputs can deliver anywhere near full rated load on a 240v delta, 120/240v, (208v from high leg to neutral) generator.but if the generator is 120/208 wye then you can deliver full rated load into various 208v loads, but you still have to load balance as any single load can only be as much as two thirds of the full load."
},
{
"post_id": "",
"author": "R005T3r",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 20, 2016, 08:55:54 pm",
"content": "Quote from: tommygdawg on June 18, 2016, 01:34:33 amTo understand why you get 240V on Delta config, you need to look at this chart:As you see:N -> is the neutralE -> the 120V generators.The Vector CB, called V3 = -E1 +E2, so, The big question would be, how do you get 240? The main definition of voltage, is actually a potential difference, between two states. In this case , if you take the point of E3 as a reference (let's say it's actually the neutral, even if it isn't the neutral as we understand) and you measure the difference between E3 and E2 is actually |E3|+|E2|, and so, you get 240 V.So, is the current flowing between one live wire to an another, yes. Why? Becasue the wires are shifted by 120°.Delta config:Where R, T, S are the wires coming out the generatorWhere R, T, S are the wires coming out the generator.How do you choose the configuration of the generator? It's simply given by default. Are these two the only two configurations? NO: there's also the zig-zag configuration, that's common in old equipments and it's not used anymore else:This article here explains come things on zig-zag generators/transformers. I bet that if you get a generator that has 120/240/108 V selectable voltages it's probably something like this one. I've seen one in my life, but i've never had a chance to work on it...https://en.wikipedia.org/wiki/Zigzag_transformer"
},
{
"post_id": "",
"author": "johansen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 21, 2016, 09:13:52 pm",
"content": "Quote from: R005T3r on June 20, 2016, 08:55:54 pmVery doubtful. three phase generators are usually 3 coil, 6 wire generators, or they are 6 coil, 12 wire generators. or they are 240/120 with 208 available but not at full rated load.A true, 208/240v three phase generator requires a generator head that is wound with 25% larger copper for the 208 coil as it is for the 240v coil, which requires that the generator head be about 16% larger than it needs to be if it were wound for only one voltage.The alternative is instead of placing that 25% extra copper inside the generator.. you can place it outside the generator, inside a 16/32v transformer and just convert 208 into 240v or vice-versa. such an option however is less efficient than just building a larger generator head."
},
{
"post_id": "",
"author": "R005T3r",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 22, 2016, 11:36:00 am",
"content": "True. There's no point in doing a generator with zig-zags. And, I'm assuming that the machine is a transformer not a generator..."
},
{
"post_id": "",
"author": "johansen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 23, 2016, 01:44:20 am",
"content": "Quote from: R005T3r on June 22, 2016, 11:36:00 amhis original post mentions generators, and in the film industry they are by amps, not kilowatts (i have never heard this before)the whole mess can get confusing when, 120/208/277/377/415/480/600 volts are all reasonable voltages that often co-exist in standard systems."
}
] |
2025-10-17T19:16:18.845730
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-phase-automatic-transfer-switch-(ats)/
|
3-phase Automatic Transfer Switch (ATS) - Page 1
|
[
{
"post_id": "",
"author": "negative_feedback",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 06, 2023, 03:13:03 pm",
"content": "I have to connect 3-phase 230VAC resistive load over ATS (Automatic Transfer Switch) of some sort. Source A and B would be both 230VAC mains, but on different power meters (longest absolute cable run <40m).Heater (12kW) sometimes uses 1 phase and sometimes all 3 and it is wired as 3P + 1N + 1PE.There was a similar discussionherebut it was about single-phase load.Options so far:1) Cheap changeover switch from AliExpress (TOMZN 4P/125A) - if we control primary source with MCB then it would be in semi-automatic mode. This is the only way I would use these uncertificated devices (additionally, On-Delay relay);2) Two 25A 4P contactors, mechanically or electrically interlocked;3) AIO device from SE/ABB/Hager will be installed after initial test run.It would be swell if someone can explain this to me:Q1: Why I have to use 4P switching equipment instead of 3P (can I use two 3P contactors for ex.)?Q2: What should be used for safety/controlling of ATS, 3P MCB or 4P (RCCB, its hard to find 4P MCB) ?Q3: Should I worry about phase sync, one meter is digital and the other is analogue."
},
{
"post_id": "",
"author": "themadhippy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 06, 2023, 03:30:48 pm",
"content": "Quoteuk regs at least require all live conductors to be broken for safe isolation,it also classes the neutral as live conductor.Quotechange suppliers, my local wholesaler has 4 pole devices on the shelf,or will order in anything too exoticQuotenot unless your trying to parallel the 2 supplies up,however best to check the phase rotation just in case someone decides to chuck in a 3 phase motor"
},
{
"post_id": "",
"author": "rogerggbr",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "October 06, 2023, 04:11:07 pm",
"content": "Advantage of dedicated changeover unit (i.e. 8 pole) is the interlocking is built in and power stays on even if your controls are dead, manual changeover still possible. Ditto MCCBs. Contactors have the advantage that they fail safe and both drop out on control fail. You decide which way to go.As pointed out above, it is normal to break the neutral as you may not have control of the upstream supplies and joining neutrals could be bad so 4P switching is safer.For controls the easiest is bias A on, B on if A fails, can just do this with a couple of timers. In industry you would use a phase fail relay to detect loss in any phase as well as voltage drop. It is usual to add timers to the process to ensure no race conditions, there are many dedicated units available of course.The phases would normally be synced, but this is assuming loads with motors. If your load is guaranteed resistive only then of course no need to bother, but it would still be good practice."
},
{
"post_id": "",
"author": "negative_feedback",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 06, 2023, 04:52:39 pm",
"content": "I understand it is more safe to use 4P but discrepancy in availability between 3P and 4P is ridiculous. That's why I thought 3P can do the job. What would be the worst case scenario with resistive loads?I was checking TME.eu but I couldn't find dedicated units from SE/ABB, what supplier you use now in the UK?"
},
{
"post_id": "",
"author": "themadhippy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 06, 2023, 05:03:59 pm",
"content": "Quoteif you mean for 4 pole mcbs either a local independent wholesaler or city electrical factors,https://www.cef.co.uk/catalogue/categories/mcb-s-miniature-circuit-breakers-four-pole-mcb-sboth are electrical wholesalers not an electronics supplier"
},
{
"post_id": "",
"author": "Jeroen3",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 06, 2023, 05:25:02 pm",
"content": "Quote from: negative_feedback on October 06, 2023, 03:13:03 pmCode says (nen1010):You may omit switching neutral if the network operator guarantees the neutral to be reliable low impedance to earth, only in TN-C-S and TN-S systems.In residential or living spaces neutral must always be switched.So.. 4p contactors. 3p may also mess up upstream differential protections.Quote from: negative_feedback on October 06, 2023, 03:13:03 pmSee above, 4p. Andno.Quote from: negative_feedback on October 06, 2023, 03:13:03 pmYou should at least keep the sequence the same. Since you only have loads, and no producers this isn't that much of a concert if your loads can take it.Is this in belgium with a 230V delta system??"
},
{
"post_id": "",
"author": "negative_feedback",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 06, 2023, 05:42:57 pm",
"content": "Quote from: themadhippy on October 06, 2023, 05:03:59 pmI was interested in availability of SE TransferPacT or ABB Compact ATS. For 4P versions I have to place an order and wait.Quote from: Jeroen3 on October 06, 2023, 05:25:02 pmNo, NL. How does Hager compare to SE/ABB?"
}
] |
2025-10-17T16:47:17.154544
| 7
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-phase-bldc-motor-driving-frequency-formula/
|
3-phase BLDC motor driving frequency formula - Page 1
|
[
{
"post_id": "",
"author": "daveatol",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 27, 2013, 01:20:15 am",
"content": "Hi all,I found some 3 phase motors on scrap and was wondering how to work out the rotation speed based on the drive frequency. The motor has 63 coils and 56 magnets.. does anyone know the formula to calculate the number of electrical cycles to attain a mechanical cycle?Also, just showing my ignorance, but what stops an RC ESC being used to drive a larger motor? Is it just the rotation speed? e.g. could a 60A, 25V ESChttp://www.ebay.com.au/itm/160631159669be used to drive a 24V BLDC motor?Thanks.PS I did ask this on another forum a week back but couldn't get the answers I was after."
},
{
"post_id": "",
"author": "peter.mitchell",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 27, 2013, 12:33:29 pm",
"content": "generally, RC based ESCs have a pretty tight frequency range, designed for 2-4-6 pole motors, if you use them on a high pole motor the motor won't spin very fast and the ESC may not be able to accurately judge the position of the rotor form the back EMF.Also, to a certain extent, on BLDC motors, the \"voltage\" doesn't matter; provided you don't overload the motor or go outside its RPM range, it will most likely be fine"
},
{
"post_id": "",
"author": "daveatol",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "March 28, 2013, 09:03:36 am",
"content": "Thanks for the reply Peter. So the problem may be with the drive frequency and feedback at low RPM.Would you happen to know how to calculate the RPM from the number of coil triplets and magnet pole pairs?"
}
] |
2025-10-17T20:24:31.610593
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-phase-earth-test/
|
3 Phase earth test - Page 1
|
[
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "August 25, 2015, 04:35:22 pm",
"content": "Hello,Just discovered that my new house has 380V...It's contracted to be 240V, but the old 380V stuff was left. And is still live!Two phases are combined to make a false neutral 240/250V mains (depends on circuit, 16A=250V, 40A=240V)This is done via an innocent looking module on the electrical panel.Apart from the inconvenience of the phase tester lighting up on phase and neutral, the normal earthing test gives a weird result.Normally, when testing earth, one side should read 1V or less and the other the nominal voltage.Here I get about 130V on each side...Is this normal or should I call the Ghostbusters because ball lighting is going to fly out of the outlets?CHeers!"
},
{
"post_id": "",
"author": "nihilism",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "August 25, 2015, 04:42:35 pm",
"content": "My advice on this one is, if you don't happen to be a ghostbuster yourself, i'd call one in.AFAIK earth should be close if not the same to the neutral potential. May be different for a split phase system in your particular country though, i'm not sure."
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "August 25, 2015, 05:48:25 pm",
"content": "Quote from: nihilism on August 25, 2015, 04:42:35 pmA yes I forgot a detail. There was no earth post. 380V and no earth, what could go wrong? 1950's men were scared of nothin'!So I've sunk a by the rules post to the exact specs to be legal, that's why I was testing the earth...Did some more checks and it's pretty near to split phase potential. It get much nearer with just a small load (40W bulb).I did have a ghostbuster over for two days just making the whole thing safe, but he had never done 380V in the residential context, so he was not 100% sure of everything right off the bat.There is no way that I can pay a ghostbuster to do all the work, the electricals in this house are too crazy, real \"stick a wet finger and see if it tingles\" crazy, it would cost a literal fortune to get someone to do it all.So I have made little to no attempt at fixing, I'm simply replacing line after line starting from the fuse box making fresh furrows with new legal wiring each time."
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 25, 2015, 06:20:03 pm",
"content": "Good to do that, and rip out the old wiring asyou go. that way you can spend a weekend or a few nights with a stanley knife and get a lot od copper to sell as scrap. Might help defray the costs a little."
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "August 25, 2015, 06:54:48 pm",
"content": "Quote from: SeanB on August 25, 2015, 06:20:03 pmThe old wiring is not pure copper, it's kinda orange when freshly cut but turns to a stainless steel colour after a while. The gauge is also about 65% of what's legal today.Another weird thing is that the insulation has two layers: an off-white centre and a coloured PVC outer. Any humidity makes this last layer crumble.If there was any value, I would stick it in the burn off oven at work - too easy."
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 25, 2015, 07:07:05 pm",
"content": "So it is tinned copper wire with a PCB filled PVC outer insulation. Put the lot in the burn off oven ( here they just light a fire next to the road somewhere to burn off copper wire) and then wash it, it will be pure copper wire inside."
},
{
"post_id": "",
"author": "TheElectricChicken",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "August 25, 2015, 11:49:26 pm",
"content": "Quote from: gildasd on August 25, 2015, 06:54:48 pmQuote from: SeanB on August 25, 2015, 07:07:05 pmThe wiring may not be as old as you think, there are places with even older kinds of wiring than pvc...Burning off the cable is the worst idea ever.It creates and then distributes all over the places you walk around and live and eat, the worst poisons you can imagine ! It all comes back down and gets all over peoples gardens including yours, or as a dust throughout the neighbourhood. Please guys, just use a knife and do it in front of the TV and you won't even notice the effort at all."
},
{
"post_id": "",
"author": "Delta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 25, 2015, 11:59:22 pm",
"content": "I am struggling to get an idea of your 3 phase installation, could you post some photos please? Do you have 3 phases AND A NEUTRAL coming in?A line voltage of 380v (phase to phase) gives a phase voltage of 220 (phase to neutral), not 240.Connecting two phases together cannot \"create a neutral\", it creates a short!Some photos could really help here! 😃"
},
{
"post_id": "",
"author": "JacquesBBB",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "August 26, 2015, 08:31:54 am",
"content": "Normally, from what I know, you should have 230V between a phase and neutral, and about 400 V between two phases.If you have no Earth, the neutral may be floating. You should have an Earth pole installed and the neutral connected to Earth at theelectric board.Another inconvenient may exist in old installations, which is common neutral.In modern installation, each circuit has three wires starting from the electric main board.: Phase, Netral and Earth.In old installations, there may be just a Phase from the main board, and the neutral is taken from any circuit.The problem is that if you cut the circuit at the main electric board, there may still be power coming from the neutral through another circuit.Is your installation of this kind ?If it is, I would suggest to gradually replace these circuits by modern circuits starting from the main electric board."
},
{
"post_id": "",
"author": "vk6zgo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 26, 2015, 11:16:47 am",
"content": "Quote from: JacquesBBB on August 26, 2015, 08:31:54 am3 Phase&a Neutral is very common in \"all-electric\" homes in Western Australia (I'm not sure about the other States).Kitchen stoves are often operated on two Phases,and some Electric Hotwater systems use all three Phases.I have a \"honking big\" 3 Phase socket in the carport---I have no idea what the previous owner operated off it!"
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "August 26, 2015, 02:16:36 pm",
"content": "Quote from: Delta on August 25, 2015, 11:59:22 pmThe first pic is an idea of what I find here and there... Blue and Brown for 240 mixed with Grey+Grey and black of 380. In the same box...The four black boxes (starting from top right) are; day meter, general cut off, night meter, 380V thing.This is a detail of the 380V box.The electrical panel.The magic box that converts 380 into 240...An idea of how I'm installing the new circuit."
},
{
"post_id": "",
"author": "M. András",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 26, 2015, 05:26:10 pm",
"content": "that \"electrical board\" is a mess where are the incoming wires? the 5 core cable have only the phases connected no earth and neutal where the hell is that going?"
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "August 26, 2015, 05:49:06 pm",
"content": "Quote from: M. András on August 26, 2015, 05:26:10 pmThe incoming wires are in the lower left.The neutral and the ground are connected to nothing.If you think this is a mess, you should have seen it when I arrived; \"bombed out multicolored spaghetti factory\" would be fair description.All the earthing you see is mine, there was NO earth at all..."
},
{
"post_id": "",
"author": "128er",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "August 26, 2015, 05:53:00 pm",
"content": "What an electrical nightmareQuote from: gildasd on August 26, 2015, 02:16:36 pmThat's an RCCB. But it's totaly useless in your case. It's hard to see it from the pictures. But it seems, that there is a separate Earth conductor going to the PE bar at the top right of your panel, maybe 16mm². You practicaly have a TN-C configuration. If you had a real separate Neutral, it should be passed through the RCCB, to protect you from electrical shocks.Edit:Quote from: gildasd on August 26, 2015, 05:49:06 pmWhere does the thick (16mm² ?) PE wire comes from? Grounding electrode? Water pipe?"
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "August 26, 2015, 06:04:17 pm",
"content": "Quote from: 128er on August 26, 2015, 05:53:00 pmI put that ground connector, it's 20 or 24mm² - it's over spec't.Edit: 1.5m earthing spike 0.6 m below surface, moree than 1.5m from the house and the neighbour. It so legal I could offer it a drink.Edit3: Using the water pipes is about as legal as a suitcase of Colombian marching powder.There was NOTHING connected to the earth at all when I started...There are 13 \"spaces\" in this house. So far I've made 3 100% up to norm, 4 partially. It's a battle.With an electrician we cleared out the biggest piece of spaghetti (things that were connected to two differentials, 75% of the house supplied via a single 0.75mm² wire etc).This triphase is a nuisance, but I can work around it for the time being.Edit 2; I'm using the regulation guides from Vinçotte and Belor. I use those as a base line."
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 26, 2015, 06:27:57 pm",
"content": "I want to meet that electrician, I think I have seen his work over here in the Metro side where anything goes. At a minimum that box should have everything stripped out and it should be redone from the meter outlet onwards to some code. Try to do to BS spec aside from the ring mains, it is pretty safe."
},
{
"post_id": "",
"author": "128er",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "August 26, 2015, 06:38:16 pm",
"content": "Quote from: SeanB on August 26, 2015, 06:27:57 pm"
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "August 26, 2015, 06:39:58 pm",
"content": "Quote from: SeanB on August 26, 2015, 06:27:57 pmThat's the plan. But I need all the lines installed to do that.The box is by far not the worst or the most dangerous electrical mess.He untangled the mess that somehow allowed for about 75% or the house to run from a single wire that is only legal for a single light.I can now continue removing things from the old and getting new wires in.When I have that done, I'll run over the box with my car before taking it to the recycling centre, and put a all new one in.\"Getting it done\" would cost 5 to 6000€, mostly pulling wire.Getting the electricity supplier to come rewire the meters and supply (that I or an electrician can't touch) would also be costly, so they are coming when it's ready within the general inspection - they are not coming twice.I also fitted 3 good quality (German) fire alarms."
},
{
"post_id": "",
"author": "cs.dk",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "August 26, 2015, 06:40:03 pm",
"content": "Quote from: JacquesBBB on August 26, 2015, 08:31:54 amI don't know how many european \"standards\" there is..Our system seems like yours, but the neutral wouldneverbe floating - It is actually the starpoint in the nearest transformer-station, which is grounded safely - And the generators starpoint at the plant to. (TT)Measuring between a phase and neutral should give the same reading as between a phase and ground (PE). = ~230VTN-C and TN-S is not very populated here.Belgium must be must like the rest of the EU - But again, differences appears."
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "August 26, 2015, 06:47:35 pm",
"content": "Quote from: cs.dk on August 26, 2015, 06:40:03 pmThat's what I've seen in commercial installations.My system was barely legal in 1954 and totally illegal now. I can't even connect the neutral because it's in a box with seals..."
},
{
"post_id": "",
"author": "Delta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 27, 2015, 12:10:47 am",
"content": "Wow, what a mess!But you CANNOT get 240v from a 380v three phase supply! Phase voltage = line voltage / 1.73220v 1p from 380v 3p230v 1p from 400v 3p240v 1p from 415v 3pWhat is the nominal single phase supply voltage in your area? (can you measure it at a friends house maybe?)Where do the three cores supplying the consumer unit (breaker panel) connect to at the meter board?Is that a jumper connected on the top of each RCCB?Is there an unused terminal (marked N maybe) on each RCCB?Could you get some photos of the incoming cable and first termination into the house?What you have sounds more like a split phase supply....."
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "August 27, 2015, 08:05:57 pm",
"content": "I will measure all that tomorrow... I'll go to the neighbour's to read the mains there."
},
{
"post_id": "",
"author": "M. András",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 27, 2015, 08:08:42 pm",
"content": "Quote from: gildasd on August 26, 2015, 06:39:58 pmjesus christ... how big is that property? thats an insane amount of wire to be 6k euros or is it mostly cost of the workmanship?btw three phases, its simple you have single phase to everything with 3 core cables, phase/neutral/earth, for 380/400 2 or 3 phase loads motors, stoves, heaters, you need atleast 2 phase wires neutral and earth, for 3 phase stuffs 3 phase wires and earth"
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "August 28, 2015, 04:17:36 am",
"content": "200m2 (of which170m2 are living spaces).It's hard to get an electrician for 32€ an hour, a good one costs about 50€... So I'm rewiring myself, this is a lot of cutting up brick walls (no wood structures here) because the old tubes are too thin and the old wires break if I try to pull anything bigger than lights wiring.Thusly, I only call the cavalry when I get stuck or for the final check before inspection."
},
{
"post_id": "",
"author": "bills",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "August 28, 2015, 04:42:11 am",
"content": "Wow I did not know that 3 phase was used in a home? Is this common in your country?In the US industrial plants we would use a transformer to convert 3 phase to 120/240v for the offices low voltage.and use 277volt for lighting as long as the load is balanced.is this a 4 wire system? and where does the neutral come from? It is not common to have a 4 wire system here (just 3 hots and a common ground 480v.) no neutral. Each leg of the 480v to ground is 277v.I wish I could be more helpful but after reading this thread I am confused. (that is easy to do with me)I have seen some industrial setups with a separate single phase service 120/240v."
},
{
"post_id": "",
"author": "MarkF",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 28, 2015, 05:12:44 am",
"content": "I don't pretend to understand the 3-phase configuration used in your country. Here in the states are delta-wye and a delta-delta configurations I captured about 2014 NEC - Transformer Electrical Code. Maybe it will help understand what you have."
},
{
"post_id": "",
"author": "vk6zgo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 28, 2015, 05:50:41 am",
"content": "In Australia,the 3 phase house wiring is \"Wye\" or as commonly said here, \"Star\" configuration.The 230v (nominal) supply to the wall power sockets is connected between Neutral & Phase.The Phase to Phase voltage is \"the square root of 3\"(or approx. 1.732) times 230v.(my calculator has \"gone walkies\",& I am too lazy to work out the exact value on paper.)"
},
{
"post_id": "",
"author": "Towger",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 28, 2015, 07:14:48 am",
"content": "Quote from: vk6zgo on August 28, 2015, 05:50:41 amSo that's were the the phase to phase 220 is coming from, I think most of us assumed it was delta.Many of the older houses in Dublin city have 3 phase, dating back to when they were first converted from gas lighting 100+ years ago. Not that common in a more modern house, unless it is huge or you have a particular reason to want it. Electricity is distributed in (most areas) as 3 phase. The conected phase alternating between every few houses along a road. If you want 3 phase you fill up the paperwork and pay cost to connect up the other 2 phases."
},
{
"post_id": "",
"author": "German_EE",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 28, 2015, 03:44:41 pm",
"content": "We have three phase here in deepest Germany. The reason for that is the cooker and that's the only three phase connector in the apartment however I also know that the lights are on one phase and the sockets are on another. The incoming cables to the apartment are as thick as my thumb, the incoming cable to the building is thicker than my arm.Chunky German electrical engineering"
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "August 28, 2015, 04:29:12 pm",
"content": "The neighbours house is exactly 230V.My house has 229v.Measured at a plug: phase to ground is 113.5 and 113.8.But another plug is 227.8 but the phases are 131 and 133And there is 50V between the \"unconnected\" earth and the \"unconnected\" neutral... WTF?Also 30V between either of these two \"unconnected\" wires and my new earth...There is 50 amp limit, but that's still a shitboat full of energy.The installation and wiring is from 1954 but the box and the differentials are 10 years old max.I'll look around for the name of the electrician of the previous owner and report him, this is ridiculous.\"Angrier than this emoticon;\"I will now switch off the electricity and go cap those faaaackin' wires."
},
{
"post_id": "",
"author": "M. András",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 28, 2015, 04:52:49 pm",
"content": "pull everything out of the walls cos thats a whole lot off broken or burnt trough cables in those walls if you measure that insanity, get a wall chaser hilti makes good ones and i guess you can rent them too in your country to cut up the walls for the plastic tubing for the cables you dont need anything more then the chaser and a good industrial vacuum for it then you can use even a srewdriver to break out the the brick from the cut channel"
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "August 28, 2015, 05:47:37 pm",
"content": "Quote from: M. András on August 28, 2015, 04:52:49 pmThe old system is disconnected at the room and the fuse box.Straight lines are drawn with the wiring as per regulation. If I find old wires I rip them out, but I don't go out of my way to find them.The old PVC tubing is macerated cow excrement in material and disposition, so it's not worth pulling new wires in them.I'm only concerned in not cutting water pipes with the 350mm grinder/wall cutter while laughing maniacally."
},
{
"post_id": "",
"author": "M. András",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 28, 2015, 05:56:02 pm",
"content": "Quote from: gildasd on August 28, 2015, 05:47:37 pmget a wall scanner or some kind of metal/wire detector that can work over 10cm to find the water pipes.if those are measured with new wiring from the distribution panel something is oddly wrong still. and i highly doubt you have a split phase system"
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "August 28, 2015, 06:13:09 pm",
"content": "Quote from: M. András on August 28, 2015, 05:56:02 pmThe pipes are connected to nothing, no earth, nothing.I follow the pipes (they are in steel 5cm deep max, a magnet is sufficient) and mark them with a red spray.The position of the now wiring is in green.The old wiring, well, I don't care about the old wiring when I'm sure there is no juice in it."
},
{
"post_id": "",
"author": "Delta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 28, 2015, 09:35:52 pm",
"content": "Your supply is seriously fucked up mate!From your figures, the first set of measurements indicate a split phase supply on that circuit, but the second set indicate two phases of three phase star connected supply (with the star point earthed).I can only guess that the distribution network uses some form of high leg delta (high leg star?), but I've only ever heard of the Yanks using such a daft system."
},
{
"post_id": "",
"author": "vk6zgo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 29, 2015, 02:15:13 am",
"content": "Quote from: gildasd on August 28, 2015, 04:29:12 pmIf you are measuring at a normal domestic power socket,(what we call a General Purpose Outlet,or\"GPO\"in Oz),229 volts between the two\"non-Earth\" pins is about right for a European system.(you are usually on the low side of \"nominal\"--we are on the high side).Remember,those pins of aGPOare not \"Phase to Phase\"------they are \"One Phase & Neutral\".\"Phase to Phase\" would be around 400v.It is not common in Domestic situations in Australia to bring 3Ph out to any sockets,it is usually used for stoves,hotwater systems,etc.or to feed two or more runs of GPOs,or light circuits.I would suggest normal practice in your country would be similar.It looks like you do not have a connection between Neutral & Earth at your Entry PointMany of your funny results are because of this,AND the fact your DMM has a 11MegOhm input impedance-------------Google \"Phantom Voltages\",,"
}
] |
2025-10-17T19:34:38.636481
| 36
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-phase-generator-circuit/
|
3 Phase Generator Circuit - Page 1
|
[
{
"post_id": "",
"author": "Windows9Professional",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 20, 2020, 05:38:28 pm",
"content": "For testing of an three phase induction motor I would need a powerful three phase generator (120° phase shifted).Is there a simple circuit for this job?I was thinking of an SPWM sine generator with just 3 lookup-tables for sinewaves which are simply 120° out of phase, but that seems a bit of overkill."
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 20, 2020, 07:59:03 pm",
"content": "How powerful? Voltage? etc., etc. My crystal ball is in the workshop."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 20, 2020, 08:10:51 pm",
"content": "I wouldn't bother designing one, unless it was for purely educational purposes. What you're after is known as a variable frequency drive and is an off the shelf module."
},
{
"post_id": "",
"author": "Windows9Professional",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 20, 2020, 08:43:51 pm",
"content": "Since I only want to experiment with (self made) induction motors I better keep the voltage down for now and after some research it seems to me that Variable Frequency Drives are mainly available for mains voltages, for which I could also use the three phase mains here in Europe, but ist far too dangerous.I'm looking for an Low Voltage, three phase generator with reasonable current capability or for an DIY alternative"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 20, 2020, 08:45:28 pm",
"content": "Then use a VFD with transformers connected to the output?"
},
{
"post_id": "",
"author": "Windows9Professional",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 20, 2020, 08:55:18 pm",
"content": "That brings me to the next point:(After my research on them) they are all around 100€ or more and even if I use a transformer to step the voltage down there will still be mains voltage involved (and a transformer also limits the current to a small extend)and I need three transformers"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 20, 2020, 09:05:08 pm",
"content": "Quote from: Windows9Professional on February 20, 2020, 08:55:18 pmThat doesn't seem like a lot of money to me. How was I supposed to know? You made no mention of the power output or budget. My psychic powers are failing me.You're wrong about the current. If a transformer steps down the voltage, it will boost the current. If you don't want to use mains, then how else are you going to power this thing?"
},
{
"post_id": "",
"author": "grifftech",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 20, 2020, 09:23:23 pm",
"content": "brushless ESChttps://www.amazon.com/s?k=brushless+esc&crid=34O7PU84BWWJ7&sprefix=brushless+%2Caps%2C167&ref=nb_sb_ss_i_5_10"
},
{
"post_id": "",
"author": "Windows9Professional",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 20, 2020, 09:58:59 pm",
"content": "Yeah I didn't provide much information at first and since I'm only a hobbyist I think I will go with the SPWM method, which fits my budget better.I don't think that ESCs for brushless DC motors will work since these are usually meant to operate with synchronous motors instead of asynchronous induction motors"
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 20, 2020, 10:24:20 pm",
"content": "You still didn't reply to the questions in reply #1 (from me).If this is the quality from a \"Windows9Professional\" (whatever that is), then I can only say"
},
{
"post_id": "",
"author": "David Hess",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 21, 2020, 01:17:20 am",
"content": "Quote from: Windows9Professional on February 20, 2020, 05:38:28 pmAnalog and digital logic 3 phase oscillators are pretty easy to make but output power stages are not."
},
{
"post_id": "",
"author": "Windows9Professional",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 21, 2020, 11:11:56 am",
"content": "Quote from: Benta on February 20, 2020, 10:24:20 pmLike I said: I'm looking for an Low Voltage, three phase generator with reasonable current capability or for an DIY alternative"
},
{
"post_id": "",
"author": "Windows9Professional",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 21, 2020, 11:15:11 am",
"content": "Quote from: David Hess on February 21, 2020, 01:17:20 amI was thinking of an H-Bridge with a low pass filter on the output for every phase, would that work?"
},
{
"post_id": "",
"author": "Dave",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 21, 2020, 12:03:02 pm",
"content": "Electric motors are inductive, they don't need any filtering of the excitation voltage.Quote from: Windows9Professional on February 21, 2020, 11:11:56 amLow voltage and reasonable current. Gotcha. Now we know exactly what you need."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 21, 2020, 12:10:00 pm",
"content": "Quote from: Windows9Professional on February 20, 2020, 09:58:59 pmI don't see why a brushless motor driver won't work. The simpler and dumber the drive, the greater chance it stands of working. Try a cheap one, they're not expensive.Quote from: Dave on February 21, 2020, 12:03:02 pmWell mains is low voltage, so a standard variable frequency drive, would meet his requirements.https://en.wikipedia.org/wiki/Low_voltage#IEC_DefinitionAC RMS voltage (V): 50 to 1 000"
},
{
"post_id": "",
"author": "Windows9Professional",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 21, 2020, 01:22:26 pm",
"content": "I'm going to try a cheap brushless motor driver and mabye realise the H-Bridge-extra low voltage inverter.Thank you all for your time"
}
] |
2025-10-17T17:55:16.880315
| 16
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-phase-generator-problem/
|
3 phase generator problem - Page 1
|
[
{
"post_id": "",
"author": "ching90",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "August 04, 2016, 10:30:29 am",
"content": "I bought a new 3 phase generator from online shop.It is used to transform 220V 50Hz to 3 phase output.However, it dosent work on my household electrical product.Then, i use my CRO and found out below phase to phase voltage like below.Is it a correct traditional 3 phase waveform of phase to phase?"
},
{
"post_id": "",
"author": "Jeroen3",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 04, 2016, 02:03:18 pm",
"content": "That is a 3-phase motor drive. What are you powering?Yes, that waveform looks normal. Especially open circuit. You're having some common mode noise though. Is your scope properly isolated?"
},
{
"post_id": "",
"author": "ching90",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "August 05, 2016, 01:16:17 am",
"content": "Quote from: Jeroen3 on August 04, 2016, 02:03:18 pmThanks, Jeronen!My purpose is used to drive a 3 phase motor, but the motor seems not work. I checked the motor is work on my friend home.I am a totally a newbie of 3 phase. You are right! The Phase to Phase waveform measured under open circuit. It is interesting and difference to my 3 phase concept~ And i cant find any 3 phase waveform from online website like thisThe scope is handheld type, so i think it should not a common mode reject problem. Am i right?Do i need to set anything of the generator? Because there is some parameter called Center voltage, center frequency."
},
{
"post_id": "",
"author": "Jeroen3",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "August 05, 2016, 05:25:52 am",
"content": "Quote from: ching90 on August 05, 2016, 01:16:17 amWhen you buy a real motor drive. The unit will ask, or the manual will tell you to complete at least the basic operation parameters:- Nom speed, and there the speed ref comes from. (ext 4-20ma, 0-10V or front pot)- Nom current.- Non voltage.- Non cosphi.And thing like that you can read from the plate.RTFM.There area lotof parameters in these things. And therefore I highly recommend not to buy them from a random eBay seller.Does the motor make any audible screeching noise, since that would indicate current is flowing. It will use somewhere between 4 to 16 KHz as switching frequency, probably 4 by default (least derating, maximum audible screeching noise)."
}
] |
2025-10-17T19:14:03.188555
| 4
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-phase-induction-motor-and-their-failure/
|
3 phase induction motor and their failure - Page 1
|
[
{
"post_id": "",
"author": "aiq25",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "December 07, 2014, 06:00:56 pm",
"content": "Hello. Recently I been doing some research on 3 phase induction motors and I had a question. In the 3 phase system if one of the stator windings breaks, will it still be possible for the motor to run? I would think you could make the motor run by making some hardware changes. I think using two of the stator windings you could create a magnetic field in 2D space in any direction, so you could use this magnetic field to move the rotor."
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 07, 2014, 06:41:21 pm",
"content": "Yes it will run, but will be noisy, and the remaining 2 windings will carry excessive current and heat up considerably, until they eventually have insulation failure and either go short circuit internally ( normally a lot of smoke comes out, or a lot of black goo) or short out to the case and blow the leads open. with an open winding it may not start under close to full load, and will sit there and rapidly overheat till it fails.That is why it is pretty standard for 3 phase motor overload relays to have current imbalance protection built in along with overload protection."
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 08, 2014, 04:27:40 am",
"content": "Ya know, I don't think it would be that bad. Just one winding failing means the motor still sees a full circle magnetic field each cycle. It's a little imbalanced, but you still have three connections at work. The remaining two windings would see on the order of 2/sqrt(3) times more current I think, which -- if the first winding failed due to thermal overload and burnout, the other two won't be far behind, especially now -- but under reduced ratings rather than a fault condition, I see no reason why it should be destructive.Saturation is not a concern, because each winding must tolerate the line voltage, period, whether driven in full three phase or not. You can drive an induction motor with just one winding powered (as a single phase unit), if you give it an initial starting direction (it will spin just fine in either direction). The third terminal basically serves to provide directional information and smooth torque output.Point in case, there is a two transformer three phase connection called 'open delta': the advantage is only needing two transformers (instead of three independent transformers or one three-legged type), while the disadvantage is extra required capacity, and a load dependent droop between the output terminals (because, the third transformer acts to balance it).Tim"
},
{
"post_id": "",
"author": "kolbep",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "December 08, 2014, 05:56:12 am",
"content": "In some cases, when a Winding fails on a 3ph motor, or if one of the supply phases fails,then the motor runs backwards!!!But the previous comments are right,the motor will buzz and overload,it will draw a lot more current on the existing phases,overheat, and eventually burn out (unless the protection device / breaker trips out first)...At some sites where I am, if the overload on the contactor keeps on kicking out (because of failure of a phase or winding),then they just get one of the lesser paid guys to stand there, holding the contactor in with a stick,Until the whole thing is completely messed (smoke pouring out of the motor), by then the Contactor, Overload and Motor all need to be replaced."
},
{
"post_id": "",
"author": "johansen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 08, 2014, 07:05:01 am",
"content": "the motor will run on two out of three windings when WYE wired, but it won't start very well, if at all, and it will spin in either direction.many folks run a three phase motor on single phase, but the third coil is supplied with starting and run caps to ease the load.some people have a separate motor belted to the idler for startup to solve that problem.i think the general rule is the motor could still deliver half the rated output. 57% i think, but i can't recall exactly."
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 08, 2014, 07:26:06 pm",
"content": "Open Delta is used with very large derating on the transformers. The most common use of a 3 phase motor is in a larger air conditioner, where it will be driving the compressor and will be running at full load all the time. Loss of phase there means that the motor will burn out in a very short time. Running a fan will also do it, but there it might take longer as the motor will have higher slip and thus will deliver less power, so it will draw less from the supply so it might only run at 150C core temperature instead of 200C."
},
{
"post_id": "",
"author": "aiq25",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "December 10, 2014, 03:41:43 am",
"content": "Thanks for the replies. I don't think I'm going to experiment with running an induction motor with 2 windings but it's good to know. Man it's been a while since I have heard of OPEN DELTA transformer connection. I used to work for a utility company, and we had a lot of open delta connections, as well as WYE connections."
},
{
"post_id": "",
"author": "johansen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 10, 2014, 08:51:05 pm",
"content": "re-reading your question, it is rare for a single winding to fail open without burning up and destroying one or both of the other coils.in the case of a wye motor where you have the floating neutral point grounded (which is rarely the case) you can run the motor at about 2/3rds load and it will also start, because there is a rotating field. same way for the open delta with one winding failed.. you still have three phase connected.in the case of a 9 lead dual voltage motor, when wiring the motor for the lower voltage, you have access to the wye neutral point of one of the sets of windings. if you connect that node to neutral, then a loss of any single coil will still allow for the motor to start and depending on which coil is lost you'll either have 16% derating or 33% derating. (unless you bring out all 12 leads, then any single coil will cost you 16% derating) --provided you connect the wye neutral to neutral.most everyone will tell you its a really bad idea to ground the neutral of a wye connected motor to the neutral of your three phase supply... I don't think there should be any serious problem.. might even get more power out of it at full load, at the cost of higher no load draw due to circulating third harmonic currents. -it really comes down to who built the motor."
}
] |
2025-10-17T19:51:02.055194
| 8
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-phase-inverter-with-scr/
|
3 phase inverter with SCR - Page 1
|
[
{
"post_id": "",
"author": "miso156",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 06, 2020, 04:36:56 pm",
"content": "Hello,I would like to build a 3 phase inverter from old SCRs to control 12V car alternator running as a motor.My expectation is to use typical 3 phase inverter:With waveforms:Are SCRs able to handle frequency from 30 to 100Hz and current about 50A?If I connect more SCR parallel, can imbalance couse some problem, or do i need to put some serial resistance for every of them?What is the typical way how to turn SCRs off?Is possible to use some LC tank to force current to zero and turn the SCRs off?Do I need to maintain V/f ratio? Means when the phases are swithed with lower frequcency I need to apply lower Voltage.Can be lower voltage obtained by shorter pulses?Thank you."
},
{
"post_id": "",
"author": "Ground_Loop",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 06, 2020, 08:34:08 pm",
"content": "How will you turn off the SCRs"
},
{
"post_id": "",
"author": "miso156",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 06, 2020, 08:59:23 pm",
"content": "Quote from: Ground_Loop on February 06, 2020, 08:34:08 pmLC resonant circuit in series or in paralell to SCR will decrease the current under holding limit and turn it off. Or by adition SCR and discharging capacitor. See comution classes of SCR turning off."
},
{
"post_id": "",
"author": "jmelson",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 06, 2020, 09:08:45 pm",
"content": "How do you commutate those SCRs? You can apply a gate pulse to turn them ON, but you can't turn them off until some combination of input waveform and output voltage/currentallows each SCRs current to pass through zero. I can't see anything that would turn them off with a DC input.Jon"
},
{
"post_id": "",
"author": "james_s",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 06, 2020, 09:19:20 pm",
"content": "Is there a reason you want to build something with 1970s technology instead of just buying one of the many cheap and readily available brushless DC motor controllers that are available?"
},
{
"post_id": "",
"author": "miso156",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 06, 2020, 09:54:47 pm",
"content": "Quote from: james_s on February 06, 2020, 09:19:20 pmYou are of course right, but first I want something to learn, I have nothing to do during nights. And second, its easy to make something from very good components like Mosfets, but i preffer more \"softer swithing\" where the fining tune has to by applied."
},
{
"post_id": "",
"author": "schmitt trigger",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 06, 2020, 10:32:57 pm",
"content": "I applaud your desire to do power electronics the hard way. Meaning with SCRs.The only three phase SCR bridges I built in the early 80s were all naturally commutated. Force commutated bridges I only built single phase, and they are tricky.My recommendations, based on a lot of sweat and tears (and some nasty explosions):-SCRs are commutated by having its current decrease to zero. This means that the LC tank, pilot SCR or whatever you are using to force commutate the device, has to be able to provide the full load current magnitude, for the turnoff period.-For reliable commutation, you have to use inverter grade SCRs. Regular phase control SCRs have widely variable commutation times. Back then, I would only use SCRs from Semikron.-The commutating capacitors will see extremely large dI/dt pulses. Regular capacitors tend to fail prematurely. Back then General Electric made some oil filled caps suitable for inverter purposes.-Fuse each SCR individually, THIS IS A MUST, with a fuse capable of quenching large fault currents. You want to limit the damage when a SCR fails or misfires.-The gate driver should be very robust, and provide good insulation. Back then Coilcraft had some excellent SCR gate drive transformers.-Speaking of gate drive, use a picket fence waveform. Don't ever rely on a single pulse for the SCR to latch."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 06, 2020, 11:22:57 pm",
"content": "Sorry this is a bad idea. SCRs are not ideal at such a low voltage, because they have a high voltage drop, compared to MOSFETs and a car alternator will give a rubbish efficiency anyway. A good old brushed motor will give a higher efficiency than this and is much easier to control."
},
{
"post_id": "",
"author": "miso156",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 07, 2020, 12:03:14 am",
"content": "Quote from: Zero999 on February 06, 2020, 11:22:57 pmI know. When I look at KTxxx thyristors they say 1.4V, but BJT like BD911 are also high 1-2V and when hfe is 20 the base current is also not neglibigle from losses point of view.The car alternator is only temporary solution, next i will buy some motor with higher voltage rating.Thx anyway."
},
{
"post_id": "",
"author": "miso156",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "February 07, 2020, 12:42:03 am",
"content": "Quote from: schmitt trigger on February 06, 2020, 10:32:57 pmNaturaly commutated, do you mean using AC supply voltage where do you can expect zero cossing for sure?Where do you see problems in forced comutation?What happend if SCRs in bridge have variable commutation times? - If I use LC network for comutation, I can expect much higher tolerances in LC components.Thank you."
},
{
"post_id": "",
"author": "MosherIV",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 07, 2020, 07:54:25 am",
"content": "QuoteYes.SCRs can be turned on by the control gate but not turned off.The way to turn off SCRs is for the supply voltage to reach 0V, zero switching as you refer to. Hence they are mainly used to control AC circuits.Your suggested circuit may work with transistor or mosfets BUT you will not be able to get negative part of AC waveform."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 07, 2020, 09:20:02 am",
"content": "Quote from: miso156 on February 07, 2020, 12:03:14 amApart from the fact that the BD911 is far too small to drive an alternator, BJTs are also unsuitable for this application, hence why I mentioned MOSFETs, which have much lower on losses.A quick flick through the RS-Components catalogue gives the IRFS7430, which has a maximum on resistance of 0.75mΩ, so hardly any voltage loss even at hundreds of Amps.https://docs.rs-online.com/cba3/0900766b813c79c2.pdfWhat voltage are you eventually going to be running the motor at? If it's over 600V, then you can consider IGBTs, which have similar on losses to SCRs, but are much easier to switch off."
},
{
"post_id": "",
"author": "Circlotron",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 07, 2020, 11:45:16 am",
"content": "This is the kind of project that separates the men from the boys!The fact that the car alternator is being used as a synchronous motor means that if the motor has sufficient rotor excitation it will present a leading power factor to the inverter. That means extra commutation components are not needed. The SCRs will commutate naturally. I have never built one like this. My experience was with DC choppers some 35 years ago.https://www.google.com.au/search?source=hp&ei=60w9XouhJrfFz7sPjou82AQ&q=scr+inverter+synchronous+motor&oq=scr+inverter+synchronouis+motor&gs_l=psy-ab.3.0.33i22i10i29i30.950.11839..13552...0.0..0.247.5682.0j26j5....2..0....1..gws-wiz.......0i131j0j0i22i30j0i333j33i160j33i21.WnFEcZpJnx8"
}
] |
2025-10-17T17:56:14.686322
| 13
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-phase-isolating-transformer-shorted/
|
3 phase isolating transformer - shorted? - Page 1
|
[
{
"post_id": "",
"author": "sebdehne",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "September 13, 2015, 10:30:45 am",
"content": "Hi guys,I bought a used 3 phase isolating transformer (230V -> 400V) like this one:http://www.noratel.com/produkter/p/3lt-250-1/detail/and when I connect it, then the fuse goes at once.I measured 0,1 Ohm across all three primary terminals. That means that there is a fault somewhere, right? I also measured around 0,1 Ohm on the secondary terminals. The specs says it should have around 300W idle consumption, so there should be some resistance.This is not normal, right?Thanks!"
},
{
"post_id": "",
"author": "Andy Watson",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 13, 2015, 10:41:25 am",
"content": "Quote from: sebdehne on September 13, 2015, 10:30:45 amMeasured with a DC meter? A 36A, 25kVa transformer winding will have very low DC resistance.QuoteYes - but measured with AC.What size is the fuse - have you allowed for inrush/magnetisation current?"
},
{
"post_id": "",
"author": "rob77",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 13, 2015, 10:42:08 am",
"content": "for bigger transformers the DC resistance of 0.1ohm might be pretty normal.what is the size of the transormer ? power rating ? how did you wire it up ?you say idle consumption 300W ? that would mean it's a multi-kilowatt one if the loses are 300W alone."
},
{
"post_id": "",
"author": "dmills",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 13, 2015, 10:44:35 am",
"content": "DC winding resistance on a 25KVA transformer should actually be pretty negligible, 0.1 ohms sounds reasonable to me.What fuse values are you using, and are they slow blow or motor rated?Transformers tend to have massive inrush currents, and a 25KVA unit could well draw 150A or so for a cycle at startup.Regards, Dan."
},
{
"post_id": "",
"author": "sebdehne",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "September 13, 2015, 10:55:47 am",
"content": "It is a 25kVA transformer. Currently there is a 40A type C fuse in front of it. The seller of the transformer said that it is in working condition. So it sounds like I would need a fuse which allows for higher inrush current. Which type? My main fuse for the entire house is of type G."
},
{
"post_id": "",
"author": "Andy Watson",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 13, 2015, 10:59:22 am",
"content": "Download the \"3-Phase installation\" pdf from the page that you originally linked. I believe it recommends an 80A fuse for 230V operation."
},
{
"post_id": "",
"author": "all_repair",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 13, 2015, 11:03:21 am",
"content": "You probably need to startup through resistors and after the inrush period when the coil is energised, then the fuses are cut in."
},
{
"post_id": "",
"author": "thefamilyman",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "September 13, 2015, 11:34:15 am",
"content": "you'll be looking at using a D curve MCB.depending if you have the secondary side also protected will determine what primary side rating you need.if secondary side is protected you'll need a 150A D Curve MCB on the Primary and a 25A C or D (depending on what your load is) on the Secondary side.if just the primary side is protected you'll need a 70A D curve MCB with no protection on the secondary."
},
{
"post_id": "",
"author": "sebdehne",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "September 13, 2015, 11:50:21 am",
"content": "I am not planning to use the transformer to its full capacity. The main fuse for the entire house is 63A and the plan is to use a 50A (or 63A) fuse for the transformer. At startup, there is no load on the secondary side.Would it be enough to use a 50A (or 63A) fuse with D curve or should I be looking at limiting the current during startup, like all_repair suggested?"
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 13, 2015, 12:05:54 pm",
"content": "You will need inrush current limiting for sure, a set of power resistors ( 3 2kw electric heater elements in the line) and a bypass contactor with a 1 second power on delay closing the contacts will do."
},
{
"post_id": "",
"author": "Circlotron",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 13, 2015, 12:38:08 pm",
"content": "Just for the sake of a test, power up the 400V side with 230V. Then there should be almost no inrush current to speak of, depending on where in the AC cycle you hit the switch. You should get about 132 volts out the other side."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 13, 2015, 12:39:01 pm",
"content": "If anything a DC resistance of 0.1R is probably a bit on the high side. The datasheet says the copper losses are 496W which will be 165.3W per phase, so 82.67W per primary and secondary. Use Ohm's law and you'll find the DC resistance should be around 0.064R for that loss at 36A."
},
{
"post_id": "",
"author": "rob77",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 13, 2015, 12:50:05 pm",
"content": "Quote from: Circlotron on September 13, 2015, 12:38:08 pmexactly, and that would also verify whether or not your wiring is correct...furthermore... are you sure you have 230V between phases (delta)? the transformer you linked expects that. just asking because 3 phase outlets in houses are always star configured over here (400V between phases and 230V between phase and neutral)."
},
{
"post_id": "",
"author": "mij59",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 13, 2015, 01:09:03 pm",
"content": "According to Wiki the mains in Norway is 230V/400V, so you are feeding the 230V transformer winding with 400V.Why do you need a isolation transformer for the entire house ?Electricity in Norway must be really cheap, in the Netherlands the idle power consumption of 300W cost about 600 Euro per year."
},
{
"post_id": "",
"author": "sebdehne",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "September 13, 2015, 01:13:40 pm",
"content": "Thanks for all your replies. I connected it on the secondary side and it worksI measured 136 Volts between all three phases on the primary side. I guess that confirms it is in working condition. Thanks for the great tip!I guess I will try a D-type fuse (don't have any available right now) and if that doesn't work then I will have to use 3 heaters with a contactor which bypasses the heaters after 1 sec.(BTW: yes, in Norway you get 230 between the phases and there is no neutral but I want 400V with neutral for faster charging of an EV)"
},
{
"post_id": "",
"author": "rob77",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 13, 2015, 01:19:15 pm",
"content": "Quote from: mij59 on September 13, 2015, 01:09:03 pmi think that will be the problem as well - feeding the 3x230 with 400V... - hence my question in the post abovebtw.. those prices in Netherlands are crazy ! over here it's 0.0575 Eur per kWh - so the 300W idle would cost something like 150Eur per year."
},
{
"post_id": "",
"author": "mij59",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 13, 2015, 01:34:40 pm",
"content": "Quote from: rob77 on September 13, 2015, 01:19:15 pmYes good observation, still wondering about the need for a isolation transformer, bit concerned about earthing.Just wondering, do have very very long extension cord ?"
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 13, 2015, 04:06:46 pm",
"content": "He does not really need the isolation, but needs the 400VAC output, though the isolation is a bonus."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 13, 2015, 04:46:04 pm",
"content": "Quote from: mij59 on September 13, 2015, 01:09:03 pmA primary side switch is essential."
},
{
"post_id": "",
"author": "sebdehne",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "September 13, 2015, 06:52:32 pm",
"content": "Quote from: Hero999 on September 13, 2015, 04:46:04 pmIts maybe around 200 Euro per year. So switch is a good investment :-)Anyway, I will try to draw the circuit with the resistors for the startup time in a simulator and see how that works... LTSpice?"
},
{
"post_id": "",
"author": "sebdehne",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "September 19, 2015, 04:50:03 pm",
"content": "Thanks for all the good advice I got here. I will use a timer so that the transformator is disabled automatically and is not on permanently.I have attached the schematic of how I want to wire it all up. The second contactor's reaction time is around 10ms, which is all I need to filter out the initial peak of inrush current I think.My question is which 4.0 Ohm resistor I could use that would withstand 60A for 10-100ms.I tested one of thesehttp://www.arcolresistors.com/resistors/hs100/(25Watt version) by manually toggling a switch (maybe it was on for 300ms), but the magic smoke got out :-)I found those:http://www.digikey.no/product-detail/en/LPS1100H47R0JB/LPS-47.0D-ND/3125517but they are quite expensive.Any recommendations regarding the soft-start resistors?"
},
{
"post_id": "",
"author": "MagicSmoker",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 19, 2015, 05:42:08 pm",
"content": "Quote from: sebdehne on September 19, 2015, 04:50:03 pmA 200-250W wirewound resistor should take this kind of abuse, otherwise use a \"motor starter\" contactor (probably the easiest and most robust, if not the cheapest, solution)."
},
{
"post_id": "",
"author": "johansen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 19, 2015, 05:43:36 pm",
"content": "I would use 10 ohm resistors or higher, and the cheapest wirewound resistors are appropriate.stove or oven elements are just fine.I'd use at least 1 second for soft start."
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 19, 2015, 06:18:15 pm",
"content": "3 2kW kettle elements instead of the resistors, just in free air. That way even if the contactor fails the elements will survive a few seconds, providing you use a non resettable thermal cutout per element to disconnect the main contactor coil if the elements overheat. You can use a 210C cutout, because the kettle elements are going to survive that easily till the trip.You only really need resistors in 2 of the 3 phases, as that will still limit current in any case. If the 2kW elements do not work use some 6kW immersion heater elements, available at plumbing suppliers or electrical wholesalers. Just buy 2 of the cheapest ones at 6kW they have, it really does not matter the mounting or shape provided you can fit it in a box of sorts."
},
{
"post_id": "",
"author": "sebdehne",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "October 12, 2015, 01:18:41 pm",
"content": "Thanks for all the good help I got here. Here is the result of the project:http://dehnes.com/electronics/2015/10/11/22kW_charger_and_transformer_soft_start.html"
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 12, 2015, 06:11:00 pm",
"content": "Nice to see it all working."
}
] |
2025-10-17T19:32:12.018549
| 26
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-phase-matrix/
|
3 phase matrix - Page 1
|
[
{
"post_id": "",
"author": "midasgossye",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "April 29, 2013, 06:11:28 pm",
"content": "Can anyone help me with the following problem please?Recently, I took an old external CD player apart. I hacked the draw opening system and hooked it up to an arduino with a motorshield.Also I wanted to control the \"spindle\". The motor that spins the CD.After some research I discovered it was a small 3 phase motor.The chip that was driving this used a 3 phase matrix. Chip N° BD7902FS (datasheet in attachment)I don't know what that means.Is it possible to drive this kind of motor with an arduino?Greetings,Midas"
},
{
"post_id": "",
"author": "codeboy2k",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "April 30, 2013, 07:18:59 am",
"content": "These are just DC brushless motors with 3 windings in the body of the motor, and permanent magnets on the shaft. Each winding is driven by a PWM signal, and the PWM signals are out of phase, i.e. one signals leads the next signal which leads the next signal. This causes a rotating magnetic field around the core, which pushes on the magnets of the shaft and cause it to rotate. The speed and direction of rotation are controlled by the pwm and the order in which the windings are energized.The phase matrix is simply a 3-phase full-bridge controller consisting of 6 MOSFETs. This lets the controller provide acceleration torque and deceleration torque in both forward and reverse directions. This is known as 4 quadrant operation.There are many different algorithms for controlling the 6 pwm signals needed. You should read up on 3-phase DC motor control theory and about the PWM algorithms in particular. The algorithms cover the wave shapes, the transition times, PWM frequencies, etc... everything needed to get the motor going in the direction you want at the speed you want with the amount of torque needed.Whether or not you can control this with the Arduino depends on the arduino having a 3-phase full bridge and 6 available pwm outputs. Or a shield for that. I don't know anything Arduino so I can't help there."
}
] |
2025-10-17T20:22:59.744132
| 2
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-phase-motor-in-star-configuration-any-benefit-of-grounding-the-star-point/
|
3 phase motor in star configuration - any benefit of grounding the star point? - Page 1
|
[
{
"post_id": "",
"author": "magic",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "September 09, 2022, 10:05:03 am",
"content": "I hope I am not starting a religious war with thisMost induction motor wiring diagrams I have seen show the shorted ends of the windings simply left floating, on the grounds that phase voltages and motor windings ought to be symmetric, so the center point voltage is approximately zero anyway.On the other hand, there appears to be a minority that insists that the star point should be connected to neutral in order to equalize small current imbalances that do occur.Is this ever a serious concern?"
},
{
"post_id": "",
"author": "Gyro",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 09, 2022, 10:26:38 am",
"content": "A good question. Possible factors I can think of...- Does leaving the star point floating assist in 'balancing' the motor drive in the case of unequal phase voltages?- Does it reduce the risk of motor damage if one phase drops out?- How solid is the Neutral in a particular installation, sometimes it is weak and high resistance.- On the other hand, err..."
},
{
"post_id": "",
"author": "capt bullshot",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 09, 2022, 01:34:28 pm",
"content": "Never seen the motors star point connected to anywhere.It might work (meaning you should get away with \"no magic smoke escape\") if you do so with a regular 3ph mains, but never ever do this with a VFD (inverter) supplying the motor.In a very special case, when one phase is open circuit, the motor might still be able to run if the start point is connected to neutral."
},
{
"post_id": "",
"author": "mag_therm",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 09, 2022, 02:05:53 pm",
"content": "A title edit is suggested because \"grounding\" a circuit galvanically conected to a live source would be a code violation in most countries, however Magic correctly refers to connecting star (Y) toneutralin text of o.p.Anyway:A 3 wire connection is usually preferred because the 3 sources can handle the Negative sequence currents due to imbalance in the motor impedances or torque fluctuatiuons.A 4th wire is not needed to do this balancing.A 4th wire would/could have Zero sequence current in the neutral which is undesirable and might be higher if there is harmonic voltage distortion on the 3 phases which there usually is.An industrial 3 phase distribution board will usually have a neutral bar to get single phase supplies , and it is desirable to reduce neutral currents to be as low as possible in the interest of reducing noise and balancing the loads on the incoming transformer.With all the small phase supplies often having capacitor input DC filters, the neutral currents have a 3rd harmonic component in which the contributions from the 3 phases add instead of cancel.This is a reason why the Power Factor Correction type of small power supplies are needed.( Like the one posted by Tim yesterday : )https://www.eevblog.com/forum/projects/power-factor-correction-discrete-control-circuit-(for-bcm)/"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 09, 2022, 02:16:40 pm",
"content": "Connecting to neutral wouldn't hurt, but it won't make any difference either. Do not connect it to safety earth/ground. That's a bad idea and is against the safety regulations in most jurisdictions."
},
{
"post_id": "",
"author": "coppice",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 09, 2022, 02:20:24 pm",
"content": "It depends. There is no point of grounding the star point of the actual motor. However, you often find there is something associated with the motor's wiring that is running from just one phase. For example the lighting on a three phase machine, or some electronic controller box."
},
{
"post_id": "",
"author": "bdunham7",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 09, 2022, 03:12:43 pm",
"content": "At best it won't matter and at worst you'll get significant startup surges and 5th harmonics on the neutral which may disturb your control circuitry or even stuff in the rest of the building. Or, if this connection is made inside of a unit which is later moved and connected to a corner-grounded delta service (a US thing only AFAIK, so no worries in Poland) you might have a bit of sparkles depending on what you do with the neutral."
},
{
"post_id": "",
"author": "magic",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "September 10, 2022, 04:46:30 pm",
"content": "Quote from: mag_therm on September 09, 2022, 02:05:53 pmWell, I meant grounding in the circuit theory sense. I had a character limit to fit this title inObviously, no one in his right mind advocates for connecting motor windings to safety earth.But once in a while I run into handwavy arguments in favor of connecting it to neutral. For example here, and I frankly have no idea what they are talking about.https://www.allaboutcircuits.com/textbook/alternating-current/chpt-10/three-phase-y-delta-configurations/QuoteAnd there are others, often internet forum users with low post countwho use language like \"balance\" without further elaboration on what exactly should go wrong if said \"balance\" is lacking.I smell BS because wiring diagrams from manufacturers of motors and Y/Δ switches show the floating configuration, but I'm no expert on motors so maybe I'm missing something."
},
{
"post_id": "",
"author": "bdunham7",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 10, 2022, 04:53:32 pm",
"content": "QuoteI can tell you with some certainty that in a system that has a neutral, having your large three-phase motors neutral connected will not prevent a flaming catastrophe if you lose a phase and your breakers don't promptly trip. Your single-phase loads that use the neutral for the lower voltage ((208/120 or 380/230 or similar) will be subject to huge surges as the neutral voltage goes crazy. And yes, they're typically bonded to the ground at the service entrance in the US, but there is no breaker on the neutral!"
},
{
"post_id": "",
"author": "elekorsi",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "September 10, 2022, 05:31:36 pm",
"content": "On 3ph motors you never connect the neutral. Never.It's a balanced loadI am not saying that i had never saw one, but those cases were the result of \"electricians\" who got their eletrical degree from youtube and diy forums..."
},
{
"post_id": "",
"author": "fordem",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "September 11, 2022, 02:26:18 am",
"content": "Quote from: Zero999 on September 09, 2022, 02:16:40 pmI'll just point out that many \"jurisdictions\" REQUIRE the neutral to be bonded to \"safety earth/ground\" at some point in the installation, typically the building entrance."
},
{
"post_id": "",
"author": "langwadt",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 11, 2022, 02:29:23 am",
"content": "Quote from: fordem on September 11, 2022, 02:26:18 amand _only_ at that point"
},
{
"post_id": "",
"author": "elekorsi",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "September 11, 2022, 07:01:05 am",
"content": "Quote from: fordem on September 11, 2022, 02:26:18 amNot really, combining Earth and neutral is only at the source, which in our case is the distribution transformer.In TN-C system you get earth (PE) and neutral (N) combined, designated as PEN conductor from the distributor. Per IEC, PEN conductor is green/yellow. If you need neutral, you seperate them in such way that the PEN is directly connected to the PE bar and then linked to the N bar. At this point you make the TN-C-S type of system.After the point that PEN is seperated into PE and N, they should NEVER be combined again.Minimim allowed cross section of the PEN conductor is 10mm2 for Cu.TN-S: you get seperate PE and N, no joining allowed. You join your own PE with the distributions PE.TT: you get only N from the distribution, PE is yours, no joining allowedIT: only 3 phases from distribution, no neutral, your own PE"
},
{
"post_id": "",
"author": "geggi1",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 11, 2022, 07:56:00 am",
"content": "First of all regarding the cross section of the PEN conductor.The cross section of is different in different countries depending on the regulations used.Here in Norway the regulations basically is that the PEN must be able to handle the same current as the phase conductor.The reason for this is that with a single phase earth fault on a TNC or TNC-S system the full current will run through the N and PEN conductor back to the source.This will ensure the quickest disconnect time at the protective device.Second regarding connecting connecting the star point on a 3PH motor to ground or neutral.Connecting to ground will most likely give you a earth fault trip or alarm depending on how your system is set up.Connecting to neutral is not needed because when looking at the currents on the phases the vector sum is zero. If the protective device for your motor is a smart electronic one it might also nor work properly."
},
{
"post_id": "",
"author": "capt bullshot",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 12, 2022, 05:34:28 am",
"content": "Quote from: magic on September 10, 2022, 04:46:30 pmOK, these circuits look like the stuff you've got to see in \"Energietechnik\" at university. The left hand side star isn't a motor at all, but rather imagined as a generator or secondary of a transformer. And they're talking about having a neutral line or not in transmission systems of electric energy. The three phase motor is a load (a balanced one, as others pointed out too) that never gets connected to the neutral."
},
{
"post_id": "",
"author": "magic",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "September 12, 2022, 08:09:10 am",
"content": "I guess you're rightAlthough I still don't get their remark about neutral connection \"alleviating problems should one element of a 3-phase load fail\".Maybe a reference to something in the earlier articles, but I'm not sure if I want to bother reading them all."
},
{
"post_id": "",
"author": "capt bullshot",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 12, 2022, 08:43:17 am",
"content": "\"Should one element fail\"I guess this is e.g. about a load composed of three independent resistors or whatever. If one fails without neutral, you'll see a series connection of two resistors between two left over phases. In case neutral is connected, two resistors from each left over phase to neutral would remain.In case your load is resistive indeed, this would result in quite different power consumption of the remaining circuit. Pointless for loads that rely on the three phase system, like three-legged transformers or motors (or electrical machines in general)."
},
{
"post_id": "",
"author": "mag_therm",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 12, 2022, 09:00:09 am",
"content": "Yes, that article could be in relation to residential service distribution in country like USA ( note the archaic units) where each user only has access to a single phase.In that case the neutral is rated so that 2/3 of users stay on in event of one line failing.Trees or lightning.Another application is shipboard where some services stay on with partial damage like ground fault on one phase.Industrial services with 3 Phase loads like motors and transformers would want all 3 phases to trip immediately to avoid damage like overloaded motors or cables.Ordinary industrial overcurrent protection devices trip all 3. And some have trip on imbalance."
}
] |
2025-10-17T17:05:59.439801
| 18
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-phase-motor-single-phasing-troubleshooting/
|
3 phase motor single phasing troubleshooting - Page 1
|
[
{
"post_id": "",
"author": "robsims",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "September 24, 2022, 09:58:12 am",
"content": "Hi,I have a question. This is a three phase system(see picture) with line voltages of 380 volts . If a line breaks during operation (when the contacts of the contactor are in closed position), what voltages will i measure at U-V, U-W and V-W ? Will i still measure 380 volts between points U-V, U-W and V-W ? Please, no guessing, i want only experienced members to answer. Many thanks in advance"
},
{
"post_id": "",
"author": "themadhippy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2022, 11:35:34 am",
"content": "0v as the overload will have detected the increase in current and opened the contactor"
},
{
"post_id": "",
"author": "BeBuLamar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2022, 12:11:00 pm",
"content": "The breaker should trip in single phase condition but before it trips the voltage is still full 380V. Some motor actually run in single phase condition for quite some time. The current draw on the 2 legs are very high and the motor gets very hot."
},
{
"post_id": "",
"author": "WattsThat",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "September 24, 2022, 12:56:43 pm",
"content": "Full voltage will be measured across all three measurement points as shown in your diagram.If the motor U phase opens as you suggest, the thermal overload (if set and wired correctly) should trip and remove the control voltage from the coil of the contactor. A very lightly loaded motor may not draw sufficient amps to trip the thermal.If the motor U phase internally shorts to ground and the motor is lightly loaded, it may continue to run without tripping. That’s a maybe and it depends upon where in the coil the turn(s) become shorted."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2022, 01:01:39 pm",
"content": "The reason why you'll still measure a voltage, when a phase is disconnected is because the motor will act as an alternator. This can be done deliberately to create a three phase supply, from single phase, but it's better to just use an inverter."
},
{
"post_id": "",
"author": "BeBuLamar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2022, 02:00:55 pm",
"content": "But then I have the feeling that you asked us to do your quiz. You don't have a motor to take care of."
},
{
"post_id": "",
"author": "robsims",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "September 24, 2022, 02:57:42 pm",
"content": "Many thanks guys for helping me out. I do a lot of self study. Not getting much help from colleagues, everyone is busy. But that doesn't bother me.Answers that were to the point were from WattsThat and BeBuLamar. But okay,.. to summarize things, if the U line is broken and the motor is still running and before the thermal overload trips or the contactor is opened i will measure the full 380 volts across points U, V end W, Am i correct?Part 2If a line is open (like the U line)A And the motor is running, it will still run but will lose power. The current draw in the remaining lines will be higher and the thermal element andcontactor will disconnect. In the worst case the motor will burn.B And the motor is not running, it will not start running when the contactor kicks in i assume.Question: If i'm not aware a line is damaged and situations A or B occur, how do i troubleshoot?"
},
{
"post_id": "",
"author": "Jeroen3",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2022, 03:35:21 pm",
"content": "Source:Measure each phase to eachother or neutral/earth. (viability depends on earthing system)Use your phase sequence detector.Motor:Disconnect the cable on the motor and measure the motor windings.Also perform insulation test of the motor windings."
},
{
"post_id": "",
"author": "BeBuLamar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2022, 04:00:08 pm",
"content": "My troubleshooting is relatively simple. Leave the contactor open, measure the 3 windings resistance. They should read the same. Measure resistance from any of the phase to ground and perhaps with a megaohm meter. If it's OK here. Energize the contactor and verify that you have all 3 phase voltage at the motor."
},
{
"post_id": "",
"author": "robsims",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "September 24, 2022, 04:17:13 pm",
"content": "Many many many thanks BeBuLamar and jeroen3. if there are others who have additional information they want to share please feel free to do so, thank you"
},
{
"post_id": "",
"author": "themadhippy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2022, 05:32:29 pm",
"content": "When measuring the voltage better to use a low impedance meter,you wont be the first to disappear down the wrong rabbit hole chasing a strange voltage thats due to alternative paths"
},
{
"post_id": "",
"author": "rstofer",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 24, 2022, 09:29:10 pm",
"content": "If the motor is lightly loaded, you may not notice.The full load current will increase to 173% of FLA (if the motor is heavily loaded) and the overcurrent device should be set at 125% of FLA so, sooner or later, the thermal devices will open the control circuit and the starter will drop out.Google is always your friend:https://www.cbmconnect.com/three-phase-motors-single-phasing/https://blog.se.com/industrial-software/2019/03/07/motor-protection-three-common-mistakes-and-how-to-avoid-them/When it's really important, you add a phase-loss detector to the control circuit:https://www.mcmaster.com/phase-loss-detectors/Wye-Delta and resistance starters require a bit more thought. Again, a phase-loss detector is helpful.For the truly paranoid, there are fuses with microswitch trip indication that can interlock with the control circuit.https://www.crescentelectric.com/fuses/fuses/cartridge-fuses/600v-4-12a-class-j-td-fuse"
},
{
"post_id": "",
"author": "elekorsi",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "September 28, 2022, 06:32:23 pm",
"content": "I usually dont even measure voltages on the running motors, but only check all three phases with current clamp meterIt tells me almost everything that i want to know. If possible i do a visual check, listen for bad bearings and sometimes take my thermal camera to check the bearing housing if anything is happening there...On a stationary motor: low resistance check of the windings and insulation check (1000V) of windings to ground and if possible also insulation between the windings."
},
{
"post_id": "",
"author": "Seekonk",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 29, 2022, 01:46:14 pm",
"content": "I used to design three phase loss detectors. The very lowest cost el cheapo detector was just a resistor to A and capacitor to B and measure that junction voltage to C. All on the motor side. If I remember right, it is a little better if there is an additional resistor in series with the capacitor. then measure the resulting voltage with an under/over voltage detector."
}
] |
2025-10-17T17:05:09.899329
| 14
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-phase-question/
|
3 Phase Question - Page 1
|
[
{
"post_id": "",
"author": "nick.sek",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "May 14, 2012, 07:01:16 pm",
"content": "If we have a 4 wire wye configuration on a three phase circuit; which has an unbalance load and we add up the phase currents (Ia, Ib, Ic) to find In. And we get a current there must be a voltage; so dictates the wonderful Ohms Law. Is there a way to calculate this voltage? If there is no load on the neutral line?If someone can point me towards a theory I would be really thankful.ThanksNick"
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 14, 2012, 07:22:57 pm",
"content": "When you think about voltages, you must always think about two measurement points in your system. There is no such thing as a \"voltage\" as a point property.So when you ask for the voltage on the neutral wire, you must answer the question \"Voltage relative to what point?\"If you measure the voltage on the neutral wire relative to the neutral wire, then the voltage is always zero by definition.Maybe you can measure the voltage on the load end of the neutral wire relative to the supply end. Now you have a voltage difference along the wire proportional to the current flowing along the wire. So you can use Ohm's law if you know the wire resistance.Perhaps you may ask about the voltage between any of the phase conductors and the neutral wire? Well this will depend on the source characteristics. If you have a perfect voltage source with no source impedance, then the voltage will always be the design voltage.If you have a source with a non-zero impedance, then you can consider how the loads interact with the source impedance and see how the load voltages vary accordingly."
},
{
"post_id": "",
"author": "Bloch",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "May 14, 2012, 07:59:14 pm",
"content": "Quote from: nick.sek on May 14, 2012, 07:01:16 pmThere are some things there don't add upIf Ia, Ib, Ic are not the same then there will be a In. That is ohms lawDid you mean that the neutral line is not connected ?"
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 14, 2012, 08:09:42 pm",
"content": "Quote from: Bloch on May 14, 2012, 07:59:14 pmIsn't that Kirchhoff's current law?"
},
{
"post_id": "",
"author": "ejeffrey",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 14, 2012, 08:20:23 pm",
"content": "You have to add the phase currents including their time dependence. If you have linear loads you can add them as phasors. Remember to use the current phase, not the voltage phase."
},
{
"post_id": "",
"author": "Kremmen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 14, 2012, 09:06:52 pm",
"content": "Quote from: nick.sek on May 14, 2012, 07:01:16 pmThere's lots of theory on multiphase networks but all mine are in books and cannot be bothered to start a net search.Your question has an easy answer though; do as efferjey says and calculate using a phasor diagram. Assuming a resistive load the voltages and curents will be in phase. In case you are just interested in the magnitudes, a static snapshot will do and you don't need to consider the time evolution of the system.So, select one phase (say Ia) and arbitrarily fix its phase angle (theta) to 0. Then the other ones will be (Ib) at 2pi/3 radians (120 degrees) and (Ic) at 4pi/3 radians (240 degrees).The magnitudes in x direction will be Iicos(thetai) and in y direction Iisin(thetai) where i = a,b,c.Next sum all the x magnitudes to get the sum, and same for y magnitudes. The final neutral current will be the vector of these magnitudes, i.e. In = sqrt(Ix^2+Iy^2) at angle atan(Iy/Ix).For example say you have a system with phase currents of 500, 400 and 300 amps respectively. The y axis magnitude would be -86.6 amps and the x magnitude +150 amps. Their vector sum would be 173 amps pointing at -0.52 radians or -30 degrees.This current will pass through the neutral wire. As to the voltage, that would be a voltage loss along some stretch of the neutral conductor and defined by the resistance of said stretch of wire. If you look at a real system, say a star connected heater with connected neutral wire, where some of the elements have e.g. ground faults, then the voltage you see at the star point would most naturally be measured against the local ground wire termination - that providing the closest approximation of true ground potential."
},
{
"post_id": "",
"author": "FreeThinker",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 14, 2012, 09:32:56 pm",
"content": "Try reading thishttp://forums.mikeholt.com/showthread.php?t=93575I think this is for non inductive loads as I seem to recall you would need to take into account the reactive components of each phase, but it is a VERY long time since I did this."
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 14, 2012, 09:44:35 pm",
"content": "A good process when faced with questions like this is to do a few thought experiments on simpler cases.So for instance, instead of the three phase case consider the single phase case with one phase (\"live\") wire and one neutral wire forming a circuit.If there is a load on the live wire the current must be returning on the neutral wire (assuming no ground leaks). If there is current in the neutral wire, what then is the voltage on the neutral wire?After answering this question, it is then possible to extend the insight gained to the three phase case."
},
{
"post_id": "",
"author": "FreeThinker",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 15, 2012, 12:22:32 am",
"content": "@IanB. That will work for balanced loads but is still not a great method. In a balanced load the neutral can be disconnected and still work as normal (ie there is no neutral current flowing), in an unbalanced load the star point will float around zero with respect to each phase dependant on the load imbalance as the imbalance current shares the return paths of the other two phases, this in turn causes the voltage per phase to vary which can cause significant current fluctuations if loads are dynamic. As an apprentice (Many years ago) we had a neutral cable burn off in a distribution board we lost loads of single phase motors because they were getting over 300 volts across them because of the loading imbalance, not nice!"
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 15, 2012, 01:32:40 am",
"content": "Quote from: FreeThinker on May 15, 2012, 12:22:32 amI think you misunderstand the idea of looking at a simpler case and thenextendingthe insight gained. Extend being the operative word.As to the unbalanced load--\"the star point will float around zero\"--what zero, exactly? Isn't the neutral wire the zero reference? How can it float when it is by definition always zero? (If you tie the neutral wire to ground it will be anchored very strongly to ground as well.)I don't doubt the reality of motors burning out, but the cause is not explained in quite the way you propose it to be."
},
{
"post_id": "",
"author": "Rufus",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 15, 2012, 05:29:41 am",
"content": "Quote from: nick.sek on May 14, 2012, 07:01:16 pmOhms law being wonderful tells you that voltage is current multiplied by resistance. Given you know the current all you need is the resistance between where you think 'this' voltage is and where you think the 0v reference for 'this' voltage is."
},
{
"post_id": "",
"author": "Kremmen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 15, 2012, 05:47:18 am",
"content": "Quote from: IanB on May 15, 2012, 01:32:40 amThe problem here is that a single phase case is not directly extendable to multiphase. For single phase you essentially calculate with magnitudes only (yes, the voltage and current phase may differ but that is not the point). For multiphase you necessarily must consider the system from the vector viewpoint. Anything else is kicking yourself in the foot all the time. Now as to the neutral point, the voltage, as indeed the phase voltages as well, are referenced to \"earth\", and that usually means the Earth. The spike driven into ground at the power station(s) generating the voltage in the first place. Using that logic it is entirely possible and reasonable that the neutral point of an unearthed star can sail at any voltage subject to the load asymmetry. Only when you bond the star point with earth using a conductor, a neutral current is possible and then the impedance between the star point and earth comes into play. But to find out the magnitude and phase angles of the neutral current and voltage, you must calculate everything using vectorial representations. In single phase systems currents and voltages are just magnitudes that may have a mutual phase angle. In multiphase systems all voltages and all currents are vectors and their combinations are vector sums and products. Calculating by simple magnitudes gets you nowhere."
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 15, 2012, 06:45:26 am",
"content": "OK, it seems I must explain better.In the single phase case we have a neutral wire with some current in it. Let's say the originating end of the neutral wire is tied to ground at the transformer/generator and this becomes our zero reference. Now with current flowing in the neutral wire the load end of the neutral wire will float at a voltage caused by the resistance of the wire and Ohm's law.In the three phase case we consider the three loads and do the vector sum as you indicate. When we are done we can consider the magnitude of the resulting current flowing in the neutral wire. The load end of the neutral wire will now float at a voltage caused by the resistance of the wire and Ohm's law. Just the same as the single phase case.On the other hand, we may consider the load end of the neutral wire as our voltage reference, which makes it zero by definition. We can do this in the single phase case and in the three phase case.In the single phase case we can consider the voltage difference between the neutral (zero) and the live conductor. It will be what it is according to the conditions. In the special case where the conductors have negligible resistance and the voltage source has zero impedance then the voltage will remain equal to the source voltage regardless of the load.In the three phase case we can consider the voltage difference between the neutral wire and each of the three phase conductors individually (the phase voltages). If the load is unbalanced, each of these phase voltages may be different, but each voltage will be what it is according to the conditions just as in the single phase case. In the special case where the phase and neutral conductors have negligible resistance and the voltage source has zero impedance, then each of the three phase voltages will remain equal and balanced, regardless of the load imbalance. Any \"floating\" of the voltages depends only on the current flowing and the resistance (impedance) of the conductors and the impedance of the power source (transformer, generator).Lastly, we may note that we can use phasors and vector sums equally well in both the single phase case and the three phase case when determining the current in the neutral wire. It is trivially redundant to do so for the single phase case, but it still works. So if we look at the problem the right way, we can see no difference in principle between the single phase case and the three phase case."
},
{
"post_id": "",
"author": "Kremmen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 15, 2012, 07:46:18 am",
"content": "Yes, all true but i don't see what point you are trying to make, exactly.If we are talking about power distribution things then we should use the conventions normally used in that context. For the purposes of the distribution network the load end, whatever node, is not a reference. For the power guys the distribution network is the circuit and that is referenced to planet earth. Only for some special cases is anything else done but this would not be one of those. What we are talking about is a perfectly typical case where you expressly should use the true ground as reference. Othewise you lose sight of the neutral circuit and will miss problems there.Also, for the power guys all conductors are impedances, no such thing as an ideal conductor or source. Additionally, they use their own calculation methods (such as the positive, negative and zero sequence method). A brief intro into that you can find in a technical app note from my previous employer athttp://search-ext.abb.com/library/Download.aspx?DocumentID=1SDC007101G0202&LanguageCode=en&DocumentPartId=&Action=Launchannex B, page 32. All calculations are against the earth.The attachment contains some medium and low voltage distribution network short circuit calculations that i found in my PC archive. Those might be illuminating at least to demonstrate the point that in practice the subject is not without complications."
},
{
"post_id": "",
"author": "ejeffrey",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 15, 2012, 08:27:27 am",
"content": "Quote from: IanB on May 15, 2012, 01:32:40 amZero being the voltage it should be at -- the voltage of the neutral supply you have disconnected from your load or equivalently the average voltage of the three phases. This causes the individual phase-to-neutral voltages to vary anywhere between zero and the phase-to-phase voltage of the supply."
},
{
"post_id": "",
"author": "FreeThinker",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 15, 2012, 11:45:31 am",
"content": "Quote from: IanB on May 15, 2012, 01:32:40 amWhen the neutral is floating the ONLY reference you have is local ground (earth) and indeed the neutral conductor is no more than an Extension of the Generators earth point. Think of it this way as a two phase supply (or dual rail supply) with a voltage divider across the supply(say +- 5v) with a 0v tied to the centre.OK you will have 5v dropped across each resistor and the load currents will be determined by ohms law. Remove the 0v and the resistors become in series across a 10v supply and again ohms law applies. As you can see the ONLY way you would get 5v across each resistor was if they were the same value (balanced load)."
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 15, 2012, 02:19:04 pm",
"content": "Quote from: ejeffrey on May 15, 2012, 08:27:27 amThis is true and logical of course and I get that it's the way engineers think about the problem.But there is nothing to stop you drawing a control envelope around the load for the purpose of analysis and making the star point your reference where the neutral wire connects to the load. In that case each of the phase voltages seen by the load would appear to vary."
},
{
"post_id": "",
"author": "ejeffrey",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 15, 2012, 03:02:24 pm",
"content": "Quote from: IanB on May 15, 2012, 02:19:04 pmTechnically this is true, but it is a weird and potentially misleading way to look at the system. The reason is that the phase-to-phase voltages remain constant. So it isn't that each phase varies. Rather, all three phases vary together relative to the star reference. Once you recognize that, it is much more natural to say that star node is the floating one and the other three remain fixed relative to an imagined reference point which is the mean voltage of the three phases."
},
{
"post_id": "",
"author": "FreeThinker",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 15, 2012, 04:06:48 pm",
"content": "Quote from: IanB on May 15, 2012, 02:19:04 pmThats a bit like tying your boat to a jetty and saying the jetty moves as the tide comes in and out, you need a point of reference and that is earth. Whilst you can use the star point as a point of reference any measurements taken from it must be with regard to earth as this is where the current wants to get to, that is its zero potential point and no other."
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 15, 2012, 05:17:13 pm",
"content": "It seems like lots of discussion here is going at crossed purposes. I think some people have different configurations pictured in their mind to what others have. I'll make a diagram later to clarify what I am talking about, then it should become clearer."
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 16, 2012, 04:33:47 am",
"content": "Quote from: nick.sek on May 14, 2012, 07:01:16 pmOK, here are pictures.Firstly, the 4 wire wye configuration is important. We need to consider the problem as stated.Secondly, I said \"consider the single phase case first\".So here is the single phase case:Note how the neutral wire from the transformer is grounded near to the transformer. This represents our reference point for measuring voltages. The neutral wire may also be grounded near to the load, but this does not materially change the analysis.We can find out from analyzing the circuit what the current in the neutral wire is. A current in the neutral wire causes a voltage drop in the neutral wire and soVNwill differ from the ground reference point accordingly. If the load is disconnected so that no current flows, thenVNwill be at zero potential.Next, we can extend this to the three phase case. We are told we have a 4 wire wye configuration:Similarly to the single phase case we can find out from analyzing the circuit what the current in the neutral wire is. The necessary extension from the single phase case is to consider phase angles when summing the three load currents, as previously described in the thread. But after doing that, the analysis proceeds in the same way. A current in the neutral wire causes a voltage drop in the neutral wire and soVNwill differ from the ground reference point accordingly. If the three loads are perfectly balanced so that no neutral current flows, thenVNwill be at zero potential."
},
{
"post_id": "",
"author": "Kremmen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 16, 2012, 05:25:56 am",
"content": "Yes. These pictures are what i have been discussing the whole time.but when you said:Quote from: IanB on May 15, 2012, 06:45:26 amit got confusing. Yes, there are cases when one would make that measurement. Like when one measures the voltage of an ordinary wall socket. But that is not the way one does circuit analysis, esp. multiphase.QuoteThere is the drawback that in this analysis the phase voltages change magically. Heavily loading one phase will mysteriously raise the voltages of the other phases. If the cause of the loading is itself a multiphase load with cos phi less than unity, the behavior of the voltages and currents gets very confusing. There is no benefit in fixing the reference in this way and that is why it is not done either. It is also a somewhat risky method, since fixing the load side neutral point to zero, we lose the neutral current. We know it is there but to find out what it is, we need to consider the earthed generator ground point floating at a nonzero voltage. Someone already compared this to the jetty moving instead of the boat.Shouldn't we agree that the power guys have got it right and true ground is the reference that creates least extra complications?"
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 16, 2012, 05:32:16 am",
"content": "Quote from: Kremmen on May 16, 2012, 05:25:56 amYes, I see that problem. I stand corrected.QuoteYes, agreed."
},
{
"post_id": "",
"author": "ejeffrey",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 16, 2012, 09:55:16 am",
"content": "Quote from: Kremmen on May 16, 2012, 05:25:56 amNo! Not earth ground. Except in very specialized circumstances earth connections are not supposed to carry any current, not even fault current. The planet earth ground reference is a red herring in 99% of electronics. The resistance of a ground rod is quite large compared with copper wires. The proper zero reference for a 3-phase wye system is the star node of the distribution transformer. That is where the phase currents want to return to by the lowest impedance path. The fact that it is connected to a ground rod is mostly irrelevant.The reason the distribution grid is earthed is for lightning protection and to prevent geomagnetically induced currents from generating large inductive voltages.There are a few exceptions. Single wire earth return power distribution is used for long distance distribution in some places. This requires special grounding rods with low impedance to handle the large currents. I think the old telegraph system used an earth return for the signal currents. These are the exceptions rather than the rule, and by and large referring any electrical signal to the planet earth is at best misleading and at worst wrong.Ground of course matters quite a bit for RF antennas and signal propagation through free space, but not for signals passing through cables."
},
{
"post_id": "",
"author": "Kremmen",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 16, 2012, 11:45:47 am",
"content": "Oh, come on. Could you maybe read through the thread and get the point? This is not about _electronics_, but power distribution.The resistance of a ground rod of some specific installation is a local issue and is largely irrelevant to the general subject.Regarding networks with neutral lines; do the math and you will see in no time why the power companies are not keen to run thousands of kilometers/miles of unnecessary extra conductor. As they do not. The ground is not used as a \"return wire\" just because the (largely) symmetrical load in the network does not especially need it for that. But it _is_ used as a reference.Grounding does not protect air wires from lightning strikes unlike lightning wires that you see above high tension current carrying lines. Those do. Still, lightning strikes where it wants and one just has to live with the consequences of the resulting surges. In premises the fixed wiring _is_ protected from overvoltages provided a good (preferably Ufer type) grounding and proper surge arrestation is in place.I don't know how things are done in your part of the world, but here the practice is that distribution is 3 phase no ground and the final low voltage leg comes from a 20 kV/400V D/y transformer with neutral wire connected to the star point. The neutral wire is grounded at the transformer, again at the entry to premises and circa every 200m thereafter if there is subdistribution from the entry panel. The neutral and PE (Potential Equalization or ground) are separated at the main entry panel and are separate after that to enable proper operation RCD devices. After this separation the code considers the N (neutral) wire a current carrying one and the PE (ground) not. So the low voltage circuit is definitely grounded, and there definitely are neutral wire currents.Just where the grounding turns into a red herring in this scheme i fail to see.That grounding does not matter for signals (and power) passing through cables is just simply dead wrong. Study the subject before uttering such nonsense, would you please."
}
] |
2025-10-17T20:33:58.847849
| 25
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-phase-reversal-detection-logic/
|
3-Φ phase reversal detection logic - Page 1
|
[
{
"post_id": "",
"author": "khatus",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "September 06, 2020, 09:00:20 pm",
"content": "hello guys this the flow chart for 3-Φ phase reversal detection.My question is why they use the logicif captured time(T) in between 3 mesc and 8 msecIs that for (3+8)/2 = 5.5 msec??It is not clear to me.In my country the frequency is 50Hz so what should i take??Can i take 4msec and 9.32 msec?? So that (4+9.32)/2 gives 6.66 msec??"
},
{
"post_id": "",
"author": "ledtester",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "September 06, 2020, 09:31:13 pm",
"content": "Let's consider a 60 Hz system.In one direction the time between the L2 and L3 zero-crossings will be close to 5.5ms.In the opposite direction the time will be 16.66 - 5.5ms = about 11ms.So if you allow a 3 to 8 ms window you will comfortably discriminate between the phases going one way versus the opposite way.For 50 Hz the times are 6.66ms vs. 20ms - 6.66 = 13.3ms. Again, the 3 to 8 ms window allows for some variance in timing while still giving a large margin for telling the difference between the forward and reverse modes."
}
] |
2025-10-17T17:42:58.081246
| 2
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-pin-scanner-inverter/
|
3 pin scanner inverter - Page 1
|
[
{
"post_id": "",
"author": "klayus",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "November 18, 2014, 12:17:43 pm",
"content": "Can anyone help me? I've taken apart a konica copier machine and i salvaged among other things this lamp with its inverter.the problem is the inverter has 3 pins on the input. by following the traces to the capacitor i've found which one is the + and the ground but i cant figure out whats the 3rd (middle) pin and the lamp dosen't start! it dosent draw any current either.i gave it 15V on the + and middle pin, i even put the middle pin to ground, but nothing happens.i didnt try giving it the full 24V as all of my other scanner light inverters start with less than their full voltage.here are some pics:please helpthanks in advance"
},
{
"post_id": "",
"author": "Paul Price",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 18, 2014, 04:30:00 pm",
"content": "Check F1, the fuse."
},
{
"post_id": "",
"author": "klayus",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "November 18, 2014, 06:11:17 pm",
"content": "I bypassed it and it still dosent turn on"
},
{
"post_id": "",
"author": "Paul Price",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 18, 2014, 10:54:18 pm",
"content": "Did you retry grounding or pulling up the center lead again?Was the scanner lighting up before you took it apart, showing the inverter was ok?Try to find a specsheet for the IC.I can see the inverter IC abd it just doesn't look like it requires a special signal on the middle connector pin, there are not enough pins on this chip or the power connector. There are usually other pins used for clock/data/enable functions.Some scanner inverter chips do use a serial bit stream to send control commands to set brightness/on/off. .just a hunch this is the case, the specsheet tells the full story. I cannot make out the IC Mfg. part # to check this, it is up to you.The most common failures of these inverters is HV arc-over that destroys the inverter transformer and this due to failure of the lamp it is connected to.I cannot see on the bottom of the PCB any connection from the connector center wire to any other part of the circuit. The pin's trace seems to end near the fuse."
},
{
"post_id": "",
"author": "klayus",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "November 19, 2014, 05:25:56 am",
"content": "The middle pîn goes to a leg of a transistor but I can't figure out what happens after it. The ic is a 10393 comparator so i'm guessing there should be some voltage on that pin to maybe set the intensity of the light. I'll try with a pot and see where that takes me.I'm pretty sure it was working as I have another one with a similar inverter, 3 pins, and I can't start that one either. That one has a pc494 inverter controller on it.Any other opinion is greatly appreciated.L.E. i tried with a pot the wiper feeding the middle pin and nothing happened. i'll try with pwm on that pin see where that takes me."
},
{
"post_id": "",
"author": "klayus",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "November 22, 2014, 07:50:27 am",
"content": "I got it working! The middle pin has to be put to ground through a current limiting resistor after the circuit starts.http://i62.tinypic.com/1448ozl.jpg[\\img]thanx for your helpbest regards"
}
] |
2025-10-17T19:52:11.799744
| 6
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-port-directional-coupler/
|
3 port directional coupler - Page 1
|
[
{
"post_id": "",
"author": "maxcy",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "July 28, 2020, 08:57:55 pm",
"content": "I'm thinking of buying a directional coupler to connect my signal generator to my transceiver in a way that protects it just in case I accidentally do key the tx. I see 3 port couplers that have an input, output, and a 'couple' port. I am assuming that Ishould connect the signal generator to the output, the transceiver to the input, and really don't know what to do with thethird port. Maybe connect it to a dummy load? Anyone with experience with these units?"
},
{
"post_id": "",
"author": "TimFox",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 29, 2020, 10:17:27 pm",
"content": "A 3 port \"circulator\" should couple power from each port to the next one in order. To protect port 1 against reflected power or on-purpose external power at port 2, the third port should be terminated in a dummy load that can handle the power from the source. Power from port 1 goes to port 2 (not to port 3), power from port 2 goes to port 3 (not to port 1), and the power from port 3 (zero if properly terminated) goes to port 1 (not to port 2). Connected this way, it is called an \"isolator\". Of course, the isolation available (e.g., \"not to port 2\") is finite, and you will get some unwanted coupling, which should be specified by the manufacturer."
}
] |
2025-10-17T17:45:18.486338
| 2
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-port-ethernet-switch-with-self-address-filtering/
|
3-Port Ethernet Switch with Self-Address Filtering - Page 1
|
[
{
"post_id": "",
"author": "Timma",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 05, 2022, 06:00:57 am",
"content": "Hello.For a while have been using switches KSZ8873, KSZ8863, KSZ8463 from Micrel. Self-Address Filtering functionality is useful for HSR implementation. Now some of ICs are not recommended for new designs already.Is there any similar switches, another manufacturer probably?"
},
{
"post_id": "",
"author": "SL4P",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 07, 2022, 03:54:28 am",
"content": "OK, I’ll bite.What is Self-Address Filtering"
},
{
"post_id": "",
"author": "Timma",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 10, 2022, 12:10:56 pm",
"content": "Quote from: SL4P on March 07, 2022, 03:54:28 amProbably I used a wrong term.Here, explanation from the datasheet:"
},
{
"post_id": "",
"author": "TomWinTejas",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "March 10, 2022, 05:56:50 pm",
"content": "Does the Analog Devices fido2100 meet your requirements? The price is significantly higher than the Micrels, but it's the only one I see that has support for device level rings, which might offer the same functionality you are looking for?"
},
{
"post_id": "",
"author": "Timma",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 10, 2022, 06:28:04 pm",
"content": "Quote from: TomWinTejas on March 10, 2022, 05:56:50 pmThanks, seems like FIDO2100 supports HSR.Though it doesn't have internal PHYs, which means 3 separate IC (one of them LQFP-128) instead of one LQFP-64. Will not fit on the board.Modern IC shortage is no jokeI wonder if Realtek chips have something similar?"
},
{
"post_id": "",
"author": "magic",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 11, 2022, 05:20:41 am",
"content": "Some more sophisticated switches have VLAN support which is used by embedded systems like routers to pretend that some ports of the switch are different interfaces.The software would have to use different MACs on different VLANs (VLAN tags are stripped by the switch while forwarding the packet outwards) and in absence of filtering in the switch, it could detect looped packets itself by validating source MAC against VLAN tag added by the switch to ingress packets."
},
{
"post_id": "",
"author": "Timma",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 11, 2022, 07:17:17 am",
"content": "Quote from: magic on March 11, 2022, 05:20:41 amInteresting idea.Would that allow to use VLAN for its intended purpose?"
},
{
"post_id": "",
"author": "magic",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 11, 2022, 09:03:53 am",
"content": "Not 100% sure.Apparently, you can nest VLANs (apply VLAN tags to already VLAN tagged frames).The question is if the switch will handle it normally or act up and if you can get your software to produce and receive such frames.See figure 4https://www.alliedtelesis.com/sites/default/files/documents/configuration-guides/c613-16016-00-a.pdfeditI may add that the whole filtering feature seems like a nothingburger to me, because host software could easily handle recognizing and ignoring packets originated from itself. I suppose what you really want is some ability to send packets through a chosen port and knowing which port the responses are coming through?"
},
{
"post_id": "",
"author": "PKTKS",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 11, 2022, 10:33:08 am",
"content": "suggestion to move this to Networking...IMHO suchfeaturesare arguably cost effective...Paul"
},
{
"post_id": "",
"author": "Timma",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 11, 2022, 11:59:57 am",
"content": "Quote from: magic on March 11, 2022, 09:03:53 amWell, if host takes on filtering all traffic in the net, it will require a lot of computing resources. More convenient when switch filters traffic and send to host only relevant packets."
}
] |
2025-10-17T17:13:40.872752
| 10
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-position-ononon-switch-with-6-terminals-how-to-wire-it/
|
3 position On/On/ON switch with 6 terminals: how to wire it? - Page 1
|
[
{
"post_id": "",
"author": "twingall1",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "October 04, 2023, 09:17:47 pm",
"content": "Hi all,This is my specific switch: 1MD6T1B5M1QE SWITCH, SOLDER TAG, DPDT, ON-ON-ONIt's a toggle switch with 3 positions and 6 terminals underneath and marked 'ON-ON-ON'I hoped to be able to wire it so each position (left , centre, right) would connect a different leg of an RGB led, giving me pure red, pure green, pure blue.But, it seems that there is no way to connect so that at least one position doesn't share a terminal/ crossover, and the best i can achieve is green, blue, bright pink.Can anyone advise if i'm missing a trick here or if i simply need to go and buy some 9 terminal switches.Many thanks,T"
},
{
"post_id": "",
"author": "ataradov",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 04, 2023, 09:31:59 pm",
"content": "If you use pin 2 as a common and connect pins 3 and 5 together, then you will get 3 connections In a position 1, the common would be connected to pin 6, in a position 2 it would be pin 4, and in a position 3, it would be pin 1."
},
{
"post_id": "",
"author": "twingall1",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "October 04, 2023, 10:16:03 pm",
"content": "Excellent, working perfectly. Thank you so so much for your help!All best, T"
}
] |
2025-10-17T16:47:25.676165
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-position-switch-is-on-in-off-position/
|
3 position switch is ON in OFF position - Page 1
|
[
{
"post_id": "",
"author": "Legion",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 06, 2014, 10:03:05 pm",
"content": "I've got a 3 terminal, 3 position switch which I'm trying to use to switch two devices. Center position is off. Positions 1 and 2 should turn on devices 1 and 2, respectively. I can't get it to work though. In the off position, both devices turn on. The problem is there's continuity between all three terminals in the off position. Just a 0.8V drop between terminals.Why would this be labeled off if there's still a connection?"
},
{
"post_id": "",
"author": "lewis",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 06, 2014, 10:11:35 pm",
"content": "Knackered switch"
},
{
"post_id": "",
"author": "What_NZ",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "July 07, 2014, 08:11:26 am",
"content": "Quote from: Legion on July 06, 2014, 10:03:05 pmWhat happens when you push Position 1 or Position 2, is there still continuity between all 3 contacts?"
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 07, 2014, 08:30:00 am",
"content": "yeah, maybe its a 3 postion normally connected switch"
},
{
"post_id": "",
"author": "SL4P",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 07, 2014, 01:04:56 pm",
"content": "How about the idea that the COM terminal is one of the outer pins?hat would mean - if you wired it as though the centre was off - then odd things would happen.Either the printing on the switch body, or a simple test with LED or multimeter ohms range will help you out. Or an oddball switch !"
},
{
"post_id": "",
"author": "jmoreland79",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "July 07, 2014, 06:36:50 pm",
"content": "I'd imagine the switch came from a specific device where the labeling on it matches up with the behavior.It may not be describing the \"On/Off\" state of the device, but perhaps a secondary function. For example, it could function as a dimmer on a lamp. Position 1 is 50%, position 2 is 75%, and \"Off\" means no dimming. If the switch was mounted in fixture and had \"Dimmer\" written above it, it would make sense.Probably not the best example, but you get the idea."
},
{
"post_id": "",
"author": "Legion",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 07, 2014, 07:00:49 pm",
"content": "Sorry to waste your time. It was my fault. I had wired it up in some ridiculous fashion. When it didn't work, I rewired it in other ridiculous ways. It was only when I wrote out the circuit on paper that I saw my mistake. Prior to working on this, I received some bad news of a personal nature and I think I was letting it distract me."
}
] |
2025-10-17T19:59:17.902517
| 7
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-push-onoff-circuit/
|
3 push on/off circuit - Page 1
|
[
{
"post_id": "",
"author": "Jasen",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 09, 2014, 10:46:44 pm",
"content": "Introduction:Howdy all, I'm a novice but can build most anything with some guidance. I'm a residential carpenter by trade for 25 years , woodworker, shade tree mechanic for 35 years and have dabbled in electronics from a few simple circuits, playing with LEDs and repairing burnt component's and broken solder connections.To the point:I recent quite smoking after 35 years and I'm using an e cigarette and it's working. I've decided to build my own box mod using some schematics I got from a e cig forum. This is variable Volt 2.4-4.2v running off two 18650 3.7V 2600mah li-ion or li-ma batteries.Some of the manufactured e cigs have a safety feature where you have to push the power button 3 times quickly to turn it on/off so as to not accidentally activate the unit in ones pocket, once said button energizes the button is then used to heat the coil to produce the vapor.I've googled to no end and have found nothing. I can just use an on/off push button but that's to easy, I'd like to build a circuit like this, any guidance would be greatly appreciated.Jasen"
},
{
"post_id": "",
"author": "Rerouter",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 10, 2014, 06:17:20 am",
"content": "short of using a 6/8 pin micro i am failing to see any non cumbersomely sized circuit options, (possibly a charge pump, you have to press it a few times quickly to turn it on and then every few seconds to keep it on)edit: you could use the charge pump idea with 2 op amps acting as a window comparitor, press it 3 times to pass the lower threshold and latch the device awake, and enable power to a second pole on the switch, which you then use to turn on or off, and if you press it a few more times in quick succession it passes the upper threshold and turns itself off"
},
{
"post_id": "",
"author": "Jasen",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 11, 2014, 02:32:43 am",
"content": "Rerouter,Thanx for the input."
}
] |
2025-10-17T20:06:33.400987
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-rather-old-oscilloscopes-are-any-worth-buying-for-a-few-dollars/
|
3 rather old oscilloscopes, are any worth buying for a few dollars? - Page 1
|
[
{
"post_id": "",
"author": "dentaku",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 28, 2013, 09:51:58 pm",
"content": "Someone in a nearby village sent me some photos of some old oscilloscopes (and a few other things) inherited from his father.It's even older than I was expecting but it might be fun if it works.I've never owned an oscilloscope before and I only want one for audio work (oscillators, filters, synth related stuff)EICO 460 - (quite ancient, not useful for me other than that it looks nice and I love salvaging old knobs and rotary switches along with old pots) It looks like it has tubes in itAdvance OS1000A (pre-Gould I think) - decently modern compared to the EICOI don't know, if it works it could be useful.B+K Precision BK1472c - looks like the best of the three. This one could be perfectly useable.What do you people think?The EICO is a historical curiosity (along with his EICO Model 324 signal generator which would be nice just for the case and retro knobs)The Advance and the B+K might be useful if they work well?I don't think they're each worth more than $45-ish Canadian though???Here's some dark photos I think he took with an iPad (definitely not Nokia Lumia quality)https://app.box.com/s/v71fzgex61g0j1emjm6g"
},
{
"post_id": "",
"author": "Thor-Arne",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "July 28, 2013, 10:40:39 pm",
"content": "I'd go for all three.In my case it could be for learning and poking around in scopes.Perhaps trying to restore.Scopes is rather rare to get cheap here, so I'd happily drive to the next town to pick up a couple.They might be useful for audio work, just go for it, can't have to much gear."
},
{
"post_id": "",
"author": "dentaku",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 29, 2013, 12:36:53 am",
"content": "Quote from: Thor-Arne on July 28, 2013, 10:40:39 pmI know, the EICO has this great look but I can't justify getting more stuff just because it looks good(I'd take if for free just to salvage any rotary switches or pots it might have though)The B+K, on the other hand looks like it could be perfectly useable if it's not broken.That reminds me, I have to go check how big these things are and the date of manufacturing. The Advance OS1000A might take up less space than the B+K Precision BK1472c though."
},
{
"post_id": "",
"author": "edavid",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 29, 2013, 04:36:49 am",
"content": "The Advance is definitely the best scope. It's only 20MHz though, so $45 is pushing it. The Eico would make a good scope clock if you could get it for say $10-15."
},
{
"post_id": "",
"author": "vk6zgo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 29, 2013, 04:54:02 am",
"content": "Don't \"salvage\" the Signal Generator bits if it works---RF Sig Gens,no matter how basic,are extremely useful,especially if teamed with a cheap frequency counter.The EICO may have tubes,but it doesn't really look that antique.-----if it works ,give it to some impoverished EE/Tech/Ham.The other beasties look nice,but try to bargain him down,--say $100 for the lot!"
},
{
"post_id": "",
"author": "dentaku",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 29, 2013, 12:15:14 pm",
"content": "They're for sale as \"make me an offer\" so that's why I'm trying to figure out what they're worth.I'd buy the Advance and the B+K (with 4 probes) together for $80-ishjust because of the convenience of not having to pay for shipping. His father must have had a decent soldering station mixed in with all that equipment so maybe I can buy one of those too.Yup, it looks like you could build that EICO yourself back in the 60's as a kit so it's not exactly antique, but almost. For me it's still not worth the space it would take up even tough it looks good.Oh, and don't worry, I don't need that frequency generator so I won't dismantle itIf something doesn't oscillate in the audio frequency range I really don't have any use for it.Quote from: vk6zgo on July 29, 2013, 04:54:02 am"
},
{
"post_id": "",
"author": "dentaku",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 29, 2013, 05:09:25 pm",
"content": "OK. I think I might end up deciding to get both the Advance and the B+K Precision if he's willing to get rid of them cheap.What, in your opinion, makes the Advance better the the B+K other than the 20MHz versus the 15MHz?I've been having a hard time finding an exact date of design on these things. The Advance looks like it's from the 70's from what I've found on other forums and the manual for the B+K says 1985, but that could just be when that particular revision was printed. They also seem to be selling for a few more dollars on auction sites but those prices are sometimes way off the actual value.Quote from: edavid on July 29, 2013, 04:36:49 am"
},
{
"post_id": "",
"author": "edavid",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 29, 2013, 05:44:57 pm",
"content": "Quote from: dentaku on July 29, 2013, 05:09:25 pmIt seems to have a proper rectangular CRT, instead of the crappy round one in the B+K. It also has 10X magnifier instead of 5X.The OS1000A manual is dated 1974, the 1472C manual is dated 1978."
},
{
"post_id": "",
"author": "dentaku",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 29, 2013, 09:07:21 pm",
"content": "Nice, I didn't notice that the BK only did 5X and even though the Advance might be older it does look more modern. Looking at the manual I can see that he filter that goes over the CRT is round.Thanks for the infoQuote from: edavid on July 29, 2013, 05:44:57 pm"
}
] |
2025-10-17T20:18:53.969876
| 9
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-resistor-voltage-divider/
|
3 resistor voltage divider - Page 1
|
[
{
"post_id": "",
"author": "Christopher",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 01, 2015, 04:31:34 pm",
"content": "I have 3 resistors in series, tapping off two voltages to the inputs of a high-impedance comparator.If I know the output voltages, input voltage, how is best to calculate the three resistors needed in Excel or similar?This is probably more a question for a Maths forum..Here are my equations:"
},
{
"post_id": "",
"author": "JacquesBBB",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 01, 2015, 05:15:34 pm",
"content": "You cannot deduce the values of the resistors. You can only find their relative valuesA solution isR2/R3 = (V2-V1)/V1R1/R3 = (Vin-V2)/V1Any value of R3 will work.(edit : to get the absolute values you need the intensity of the current in the circuit)."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 01, 2015, 05:17:38 pm",
"content": "Yes, find the relative values and search for the combination which gives the best results."
},
{
"post_id": "",
"author": "Christopher",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 01, 2015, 05:23:58 pm",
"content": "Quote from: JacquesBBB on May 01, 2015, 05:15:34 pmLovely clear formulas. This now makes more sense to me."
},
{
"post_id": "",
"author": "German_EE",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 01, 2015, 05:29:07 pm",
"content": "1) Start by considering this as a single voltage divider with Vin, V2 as output, R1 and (R2+R3)2) Assign R1 a nominal value (say 1K ohm) and work out (R2+R3) for the voltage you need.3) Do the calculation again but this time for the second voltage divider. Input is V2, output is V1 and make a best guess for R2 before you work out R3So, let's suppose you have an input of 10V and you want your output voltages to be 7,5V and 2,5VR1 is 1K ohms(R2+R3) needs to be 3K ohms for 7,5V outVin for stage 2 is 7,5VR1 is 2K ohms and R2 is 1K ohms (sum 3K ohms)Edit: JacquesBBB got there before me by expressing this as formulae rather than practical examples, c'est la vie"
},
{
"post_id": "",
"author": "Christopher",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 01, 2015, 05:46:15 pm",
"content": "Great. Thanks. I was getting mixed up in various sim equations earlier which wasn't helping.Now, just say I have two comparators drawing bias current from both V1 and V2. What's the best way to stop the voltage drop across the two resistors? Or will it be so negligible that it doesn't matter?"
},
{
"post_id": "",
"author": "PSR B1257",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 01, 2015, 06:30:13 pm",
"content": "QuoteSure they doQuoteMost likely. Unless you choose resistors in the terra-ohm region, you should be fine"
},
{
"post_id": "",
"author": "Christopher",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 01, 2015, 06:54:38 pm",
"content": "Quote from: PSR B1257 on May 01, 2015, 06:30:13 pmI have a series feed resistor of 27k on my input. With 200nA bias current, that will drop 6mV.Kinda insignificant knowing my input offset maximum is about 6mV, too.."
},
{
"post_id": "",
"author": "PSR B1257",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 01, 2015, 07:17:48 pm",
"content": "QuoteHoly crap, what type of comparator do you use?QuoteRather tight. In this case you also need a stable refevenre voltage. And you should use trimmers in between the resistors, in order to fine tune the voltage."
},
{
"post_id": "",
"author": "Christopher",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 01, 2015, 07:34:23 pm",
"content": "Quote from: PSR B1257 on May 01, 2015, 07:17:48 pmLM2903, which has a max bias current of 200nA over temp range & 15mV offset.QuoteI think i will just use trimmers to set the comparator limit & shut them closed with some red Loctite. Works out easier than trying to fit a load of resistors in series, and trimming becomes a whole load easier."
},
{
"post_id": "",
"author": "PSR B1257",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 01, 2015, 09:47:42 pm",
"content": "QuoteWhy did you use this one, if it is supposed to be aprecisionapplicationQuoteYes, but with the resistor-trimmer-assembly you have a smaler range to adjust the voltage, and therefore you can use more of the trimmer-range."
},
{
"post_id": "",
"author": "Christopher",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "May 01, 2015, 09:53:28 pm",
"content": "Quote from: PSR B1257 on May 01, 2015, 09:47:42 pmI can use any I like, this just happens to be the first I have chose for these basic calculations! In my final project I will use a better specced comparator (the only real specs I need to look at are offset voltage, bias current and response time, right?).Any advice on a decent part to use?Quote from: PSR B1257 on May 01, 2015, 09:47:42 pmGood point. I plan on using 10-turn pots and a 5V reference. I can put some series resistance below the pot to decrease the pot range!"
},
{
"post_id": "",
"author": "PSR B1257",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 02, 2015, 06:44:06 am",
"content": "QuoteYou should not use this one for any calculations, if you know, that it is not suited.QuoteYes, these values should be low.QuoteWho knows? We still don't know, what your application looks like."
},
{
"post_id": "",
"author": "abit",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "May 09, 2015, 04:55:41 am",
"content": "Quote from: Christopher on May 01, 2015, 04:31:34 pmExcel has a function for permutations, so if you care to run all of E variations (not to mention power ratings and tolerances of 0.1% to 5%) you are going to end up with a DATABASE larger than Earth.. There is a reason why the E-standard was designed as such, and to save your sanity - do not ever think about going parallel more than 2 resistors. Even then, the effort is not going to justify the cost.I have nothing to back this up but I have gone insane before along these lines, and the first approximation of the math in bash script was as expected, it ran for days and gobbled up gigabytes of disk space for a loose result.Do not go beyond two resistors paralleled - and go there only when in dire straights for an odd value. Even then, you are going to loose some precision, since the approximation is a logarithm, and when there IS a PERFECT match you SHOULD have a discrete value of E192 of the same.Now, the question is if you need it in:0.125W, 0.250W, 0.500W, 1W, 2W or higher.0.01%, 0.2%, 0.5%, 1% precision or lower.... You got the ideaDo not think about it, do not go there. The variations of all these man-made objects is larger than Earth itself."
},
{
"post_id": "",
"author": "JacquesBBB",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 09, 2015, 12:14:42 pm",
"content": "@abitI am sorry, but I do not understand the purpose of your post.The initial question of this thread is on voltage divider, and it is solved (see above).Then discussion followed on proper resistance values compared to the impedance ofthe opamp that is in the circuit.You seem to answer to a question, but as the answer is confuse, it would at least be nice tostate again which is the question to which your answer corresponds.Apart from that, despite the uncertainty of the question, let me remind you that to solve asimple circuit problem, the best method is not to try all possible values for the components.A simple circuit can be modelized by mathematical formulae that can often be solved,thus providing answer without filling a Earth sized database."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "May 09, 2015, 12:34:36 pm",
"content": "It's possible to minimise the effect of the bias current by making the impedances connected to each input as close as possible, that way the offset due to the bias on each input will be the same."
}
] |
2025-10-17T19:41:01.793807
| 16
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-state-mechanical-switch/
|
3 state mechanical switch? - Page 1
|
[
{
"post_id": "",
"author": "wtoddp",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 20, 2024, 07:24:04 pm",
"content": "I'm hoping to find a very specific type of switch, and don't know if they exist or what they would be called, so my Googling is not producing the results I'm seeking.The switch I'm hoping to find would be:Small, like ~1/4\" or ~6mm push buttonWould work with 2 very simple circuits running on a 3volt battery with 2 LED lights in separate circuitsWould be like a momentary switch, but have/allow for three \"States\"State 1 - Everything is OFFPush once to enter State 2 and a Red LED lights upPush again to enter State 3 and the Red LED goes out and a Blue LED lights upPush a third time and both lights go out (back to State 1)RepeatI can visualize how a mechanical switch like that could work, as each press would cause an interior part to rotate and create a different circuit with each press. I can also imagine a number of reasons why those may not be manufactured now, if they ever were.Any advice would be appreciated!"
},
{
"post_id": "",
"author": "langwadt",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "March 20, 2024, 07:43:11 pm",
"content": "close enough?https://www.adafruit.com/product/1684"
},
{
"post_id": "",
"author": "wtoddp",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "March 20, 2024, 08:05:05 pm",
"content": "Aw, man! Perfect! THANK YOU!!!"
}
] |
2025-10-17T16:38:41.835392
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-terminal-smd-part-labeled-6katj/
|
3 terminal SMD part labeled 6kaTJ - Page 1
|
[
{
"post_id": "",
"author": "georgedone",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "July 02, 2017, 02:46:03 pm",
"content": "Hi !I just received for free an old Packard Bell EasyNote TK laptop (i3 380M) which seems dead. I'm trying to repair and use it. It seems to have a fault close to the power input as there is absolutelly no sign of life when I connect a working power adapter. When I check the motherboard, close to the power connector there are 2 small smd components labeled 6kaTJ(TJ is engraved in larger characters than 6ka), 6kaTJ, one of which is obviously burned (there is a hole in the casing just above the junction). I assume they are some Mosfet transystors but I'm unable to find a datasheet or a replacement part. Anyone knows what could be ?"
},
{
"post_id": "",
"author": "bingo600",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 02, 2017, 07:36:27 pm",
"content": "The only 6ka i can find in the Turuta 2011 book are attached , but none of those are 3-pin (housing is in yellow/greenish)"
},
{
"post_id": "",
"author": "floobydust",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 03, 2017, 04:59:19 am",
"content": "This website is good for SMT marking codes, but it's slow sometimes and Russian language:http://chip.tomsk.ru/chip/chipdoc.nsf/vc1!readform&view=smd&cat=6&start=4001&count=500If you knew the package, you can look for the root marking code. The TJ maybe the date code/plant ID."
}
] |
2025-10-17T18:53:31.036084
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-terminals-on-li-ion-battery/
|
3 terminals on Li Ion Battery - Page 1
|
[
{
"post_id": "",
"author": "Greorge",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "December 06, 2014, 06:24:55 am",
"content": "What is significance of 3 terminals on Li-Ion battery?It is Nokia BL-4 3.7V batteryIt doesn't last long enough in phone, so I repaced it, but I want to use it for LED or something.Is it OK just to find + and - and chage and not worry about the third one?"
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "December 06, 2014, 06:48:00 am",
"content": "The 3 connections are +, - and BSI (Battery Size Indicator, or sometimes Battery Sensor Indicator)It's a resistor which the phone can use to detect the battery size.eg, 5k might indicate 1Ah and 10k might indicate 1.5Ah for example.So yes, you can just ignore the BSI pin."
},
{
"post_id": "",
"author": "Greorge",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "December 06, 2014, 07:21:31 am",
"content": "Thank you very much for help."
}
] |
2025-10-17T19:51:16.725647
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-way-impedance-match/
|
3 way impedance match - Page 1
|
[
{
"post_id": "",
"author": "rahulrahullll",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "November 23, 2017, 05:26:17 am",
"content": "i have---60 w 4 ohm woofer40 w 4 ohm mid30 w 12 ohm tweeter4 ohm 3 way crossover basic type---2 inductor and caps, resistors-------tda 2050 amp---30 w at 8 ohms/ 50 w at 4 ohms--------WHAT IS THE IMPEDANCE OF THIS 3 WAY TOWER SEEN BY TDA 2050 METHOD OF CALCULATION ?"
},
{
"post_id": "",
"author": "Brumby",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "November 23, 2017, 05:50:10 am",
"content": "3 onions and a canary.Seriously, there is not enough information to give a definitive answer. A full circuit diagram of the entire crossover, including speakers would be necessary to calculate an answer - and if you want to get really pedantic, at least the frequency vs impedance characteristics of each of the speakers.With a bit of guessing and assumption, we could offer a ball park figure - but I've not been into crossover network design and it's been years since I've even looked at them that closely.PS. Don't use all caps - unless you want to be interpreted as SHOUTING."
},
{
"post_id": "",
"author": "rahulrahullll",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "November 23, 2017, 06:35:49 am",
"content": "thanks----------i have another doubt--------how measure ac current output of amplifier by dc multimeter(in my multimeter there is only dc current mode) just wanted to calculate powerhttp://www.ashopbd.com/wp-content/uploads/2017/02/Kros-s-Pocket-Digital-Multimeter-SDL326809972-1-97f3b.jpg"
},
{
"post_id": "",
"author": "Brumby",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "November 23, 2017, 07:50:16 am",
"content": "1. Get a resistor to match the amplifier output - 4 ohms, 8 ohms or whatever - with a high enough power capacity to handle the amplifier output.2. Measure this resistance as accurately as possible.3. Connect to amplifier and feed the amplifier with (ideally) a sine wave of no more than 400Hz (limit of your DT830D)4. Turn the volume up on the amplifier and measure the AC voltage across the resistor.5. Use Ohm's law to calculate current.General recommendation: Do NOT run your amplifier at elevated levels for any longer than youabsolutely need to.Any full power measurements are going to stress the amplifier. It will be your responsibility to ensure that such stress does not exceed the limits of the amplifier or you could damage it."
},
{
"post_id": "",
"author": "macboy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 23, 2017, 03:21:35 pm",
"content": "Quote from: rahulrahullll on November 23, 2017, 05:26:17 amIf your crossover expects a 4 Ohm tweeter, then in order for it to work correctly, you need to add a 6 Ohm resistor in parallel with the tweeter. This provides a 4 ohm total impedance, which will make the crossover point correct. Otherwise, the tweeter will produce sound at a much lower frequency than expected. There is usually not much power in the highest couple octaves, so a 5 Watt resistor is quite big enough.Even though you have three 4 Ohm speakers (after adjusting the tweeter to 4 Ohms as above), the load to the amplifier is still just 4 Ohms. The crossover effectively splits the signal between the speakers based on the frequency content. The TDA2050 is rated to drive 4 Ohm loads, so you should be OK. Keep in mind though, that speakers are complex electro-mechanical devices, and the \"4 Ohm\" rating is only \"nominal\" or approximate. The real load may drop to 1/2 of nominal (~2 Ohm) at some frequencies and may go very high (tens of Ohms) at other frequencies. The amplifier might have difficulty if the woofer drops much lower than 4 Ohms.Consider upgrading to a better crossover. A 3-way unit with a 2nd order (12 dB/octave) slopes will have 4 inductors, 4 caps, and maybe some resistors."
},
{
"post_id": "",
"author": "rahulrahullll",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "November 23, 2017, 03:27:59 pm",
"content": "thank you-----Brumby ---actually i dont know how 400 hz sine wave sending , dont have 4 ohm--30 w resistor--quite long process----is there any shortcut method to measure ac current by dc multimeter----any approximate method maybe----http://www.ashopbd.com/wp-content/uploads/2017/02/Kros-s-Pocket-Digital-Multimeter-SDL326809972-1-97f3b.jpg"
},
{
"post_id": "",
"author": "rahulrahullll",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "November 23, 2017, 03:35:37 pm",
"content": "thank you--macboy------so according to you what should be the speaker resistance for woofer,mid,tweeter and crossover for 4 ohm amp and 8 ohm amp-------------"
},
{
"post_id": "",
"author": "Bud",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 23, 2017, 03:42:50 pm",
"content": "BTW you have the dash key stuck."
},
{
"post_id": "",
"author": "jmelson",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 23, 2017, 05:58:52 pm",
"content": "Quote from: macboy on November 23, 2017, 03:21:35 pmFREQUENCY?? No, not possible. Yes, the tweeter will get the wrong amount of power, and possibly the balance of sound would be wrong. I'd suspect the tweeter would be not producing much output, but the LC components in the crosover could do just about anything with this mismatch.Oh, maybe I get your meaning, the tweeter would start getting power from the crossover at a lower frequency than intended. Yes, could be, assuming the crossover just uses a series cap for the tweeter. But, with the 12 Ohm impedance, it might never get much output, compared to the other speakers.Jon"
},
{
"post_id": "",
"author": "macboy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 23, 2017, 08:50:11 pm",
"content": "Quote from: jmelson on November 23, 2017, 05:58:52 pmThe power in the tweeter at any given high frequency (well above the crossover frequency) is the same, with or without the resistor! The problem is that the crossover frequency is shifted down because the resistance of the speaker coil is part of the filter itself. Higher R means lower Fc.\\$F_{c}=\\frac{1}{2\\pi RC}\\$The crossover described by the OP is a 1st order one, and for the tweeter, is just a simple capacitor. It, together with the resistance of the speaker/tweeter (12 ohms) forms a one pole high pass filter. At very high frequencies, the capacitor is low impedance and the speaker sees the full voltage (very little voltage dropped across the cap). At very low frequencies, the capacitor is high impedance and the speaker sees very little voltage (it is almost all dropped across the cap).The shift in the frequency of the crossover point means that the tweeter will be exposed to more musical power and might burn out or be physically damaged by large excursion.(edit)Even if it isn't damaged, there will likely be a hump in the frequency response of up to +6 dB due to the overlap of the mid and tweeter spanning about 1.5 octaves.(/edit)FYI, the woofer has a coil in series with it forming a LR lowpass filter, and the midrange has a coil and a capacitor in series with it, forming a RLC bandpass filter. (A much better 2nd-order crossover would add shunt elements as well, but the OP said his had 2 coils and 2 caps, so it can only be 1st order).Since the OP said the crossover was designed for 4 ohms, it needs a 4 ohm load for the crossover frequencies to be correct. That is why the 6 ohm resistor is added in parallel to the 12 ohm tweeter.(edit:)It does not attenuate the tweeter response at all (a series resistor would). The 12 ohm tweeter might or might not be efficient enough to provide a flat(ish) response in combination with the other drivers. Randomly picking a woofer, mid, and tweeter will not usually yield a 3-way speaker with a good flat response. Usually, one or two drivers need to be padded (attenuated)."
},
{
"post_id": "",
"author": "T3sl4co1l",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 24, 2017, 02:28:26 am",
"content": "Speakers are terrible loads. The impedance is complex versus frequency, making filter design awkward. The best approach is to measure the speaker impedance, with the speaker in the enclosure, and use that to design the filter.On the upside, the flatness spec is terrible, too (a speaker might be +/-10dB, and listeners acclimate very easily to worse), so it doesn't much matter -- how accurate or how well designed the filter is.Tim"
},
{
"post_id": "",
"author": "Brumby",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "November 24, 2017, 02:29:10 am",
"content": "Quote from: rahulrahullll on November 23, 2017, 03:27:59 pm- You can get Apps for mobile devices.- You can use the sound card on your computer and use a program or search for \"sine wave generator\" for an online source, such ashttp://onlinetonegenerator.com/- You can build a simple sine wave oscillator. It doesn't have to be low distortion - just reasonable.The fact of the matter is, if you want to measure the output of the amplifier, you are going to have to feed it a signal. Ordinary audio - like a song - is not steady enough for measurement by a multimeter and would have too high a crest factor anyway. So, if you want to feed a signal that your equipment can measure with any confidence, then a sine wave is the one to use.QuoteGet creative. 30 120ohm 1W resistors in parallel; A long piece of wire; Some nichrome wire; Salvage a piece of the element from an electric heater.QuoteIn all seriousness, this is NOT a long process. However, what do you expect when you don't have the right equipment?QuoteDo you have a diode and a capacitor? Create a simple peak detector. This will give you a maximum volts as a DC value - but you will have to add the forward voltage drop of he diode to get the actual peak voltage. Again, use a sine wave as your signal source and you can divide the peak volts by 1.414 to give you an equivalent RMS value of the AC. To get the current, you will need to divide this by the impedance of the load at the test frequency used.In short, by using test gear that cannot directly measure the quantity, you are going tohaveto use indirect methods and some (simple) mathematics to get an answer."
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 24, 2017, 04:44:29 am",
"content": "Why do you want to measure AC current with a DC multimeter? To calculate the power?Why do you need to calculate the power when the datasheet shows a graph of the power into a 4 ohm load (that you have) with different supply voltages.If your supply is plus and minus 15V (30V total) then the power is a little less than 20 Watts. The output power is 50 Whats (with horrible 10% distortion) into 4 ohms only when the volume control is turned up too high and the supply voltage is the maximum allowed voltage of plus and minus 22.5V (45V total) then the real power is a little less than 40 Watts at a fairly reasonable lower distortion.The output impedance of the amplifier is not 4 ohms or 8 ohms. Its load can be 4 ohms or 8 ohms and the impedance is not matched. The output impedance of a modern amplifier is 0.04 ohms or less so that it can damp the resonances of speakers. A woofer would sound like a one note bongo drum if its resonance is not damped by the very low output impedance of an amplifier. Midrange and tweeters also resonate but at higher frequencies and sound much better when properly damped.EDIT: Here is the graph of power:"
}
] |
2025-10-17T18:44:25.863125
| 13
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-way-switches/
|
3-way switches - Page 1
|
[
{
"post_id": "",
"author": "Mpegger",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "November 23, 2023, 06:02:27 am",
"content": "I'm in the process of replacing some 3-way switches with some combo 3-way & outlet, and just came across a really weird wiring setup that has left me stumped. I should have taken pictures of the wiring before I took everything apart, but I wasn't expecting the wiring that I found after I removed the switch in the 2nd box. Hopefully my description is good enough.There is a light switch at the bottom of the stairs, and 2 light switches at the top of the stairs. The light switch at the bottom of the stairs is a 3-way, and one of the switches at the top of the stairs is a 3-way, which control the lights in the basement. The 2nd light switch is a regular light switch that controls a single light at the top of the stairs.The main 12/2 line from the breaker goes into the box at the bottom of the stairs. In that same outlet box there is a 12/3 line, and another 12/2 line. Seems normal enough, I figured the 2nd 12/2 was to get power to the box at the top of the stairs for the single light switch since its on the same breaker.The 2nd outlet box is a double size, as it has the 2nd 3-way switch and a separate regular switch (no combo switches). In this box, you have the 12/3 line coming into it, a 12/2 line going to the lone light at the top of the stairs, and then another 12/2 line coming in. I assumed that the 2nd 12/2 was the 12/2 from the first box bringing power to this box for the regular switch, and the 12/3 was wired with the lights between the two 3-way switches, so I'd have to break out the multi-meter and verify which wire should be which in the 3-way circuit as no wires were taped to designate Hot/Neutral/Red.Except the 12/3 wasn't feeding any of the lights in the circuit and was just a straight run from the first box, to the 2nd.And that 2nd 12/2 in each box? Turns out that 2nd 12/2 line in the first box is the same 12/2 line in the 2nd box as I assumed, but wired to the lights in the basement.And every light in the basement is wired properly like a normal circuit would be, Hot (Black) to the center pin in the light socket, Neutral (White) to the threads in the socket. This corresponds to the 12/2 in both boxes.Again, I know I should have taken pictures before just tearing everything apart as I wasn't expecting anything out of the norm (still kicking myself for that), but somehow with this wiring, they manged to not only control the lights in the basement with the 3-way switches, but also provide power to the lone light at the top of the stairs separate from the 3-way circuit, with the 12/3 wire run NOT going to the lights (as one would expect with lights BETWEEN two 3-ways). From what I recall, none of the wires were mixed (no Neutrals, Hots or Reds wire nutted together), none of the wires are wrapped with colored tape (which was done on other circuits in the house so the electrician would have done the same here), and every wire was connected to something, no wire was left hanging all alone.I thought this would be a simple job, but I can't figure this circuit out, and I'm at the point I'm just gonna wire everything straight to power and leave the 3-way switches out of the circuit and use smart lights instead, but I'd like to have the switches in play, even if I never actually use them cause of the smart lights (plus why have switches if they don't do anything). Anyone wanna take a crack at this puzzle?"
},
{
"post_id": "",
"author": "donlisms",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 23, 2023, 09:21:50 am",
"content": "Word salad!Draw a diagram of everything you know, as correctly as you can, and let us see it."
},
{
"post_id": "",
"author": "Mpegger",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "November 23, 2023, 05:55:30 pm",
"content": "Very well. I shal bestow upon you the skills and artistry that have brought many a person to weep and bawl."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 23, 2023, 06:23:40 pm",
"content": "The first post didn't make much sense.Here's a schematic showing the internal switching in a 4-way circuit. You can play around with a battery and bulb, or LED and a suitable series resistor.Hopefully that's helpful."
},
{
"post_id": "",
"author": "Mpegger",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "November 23, 2023, 06:44:16 pm",
"content": "The wiring is as I show. It cannot be changed cause I'mnotabout to go making dozens of holes in the walls trying to trace where all the armor cable is running through and attached to pull it out and/or run new romex in its place."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 23, 2023, 07:01:39 pm",
"content": "Quote from: Mpegger on November 23, 2023, 06:44:16 pmI was not suggesting changing any of the wiring. The schematic was posted, with the intention of you studying, so you can understand how it works.How it was wired is anyone's guess."
},
{
"post_id": "",
"author": "themadhippy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 23, 2023, 07:37:31 pm",
"content": "Quotewhilst thats the often seen example of a 2 way and intermediate lighting circuit in real life its often impracticable to have your feed in at one end of the circuit and the switched live at the other,often you'll find it wired like this,both the feed in and switched live are at the same switch."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 23, 2023, 07:59:55 pm",
"content": "Have a look at this. One wire is not needed and is not connected."
},
{
"post_id": "",
"author": "themadhippy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 23, 2023, 08:27:41 pm",
"content": "Quotewhilst it will work it wouldnt be acceptable in the uk,and depending on the local regs else were as your switching the neutral"
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 23, 2023, 09:16:21 pm",
"content": "Sigh."
},
{
"post_id": "",
"author": "Mpegger",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "November 23, 2023, 09:43:09 pm",
"content": "I thought of something similar, but tossed the idea aside because I clearly remember that every wire in both boxes was in use, and most of the neutrals were all tied together in each box. There was no wire left floating in either box, which is why I couldn't think of any way to complete such a circuit with every wire in use. I'll go ahead with your setup though as I dont want to waste more time with the wires hanging out of the boxes, nor no lights available in the basement other then what I plug into the receptacles around the room."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 23, 2023, 09:52:51 pm",
"content": "The circuit posted by soldar is a two way, not a three way switch. Is that what the original poster meant? Correct terminology is very important."
},
{
"post_id": "",
"author": "soldar",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 23, 2023, 09:57:56 pm",
"content": "Quote from: Mpegger on November 23, 2023, 09:43:09 pmDouble sigh."
},
{
"post_id": "",
"author": "themadhippy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 23, 2023, 10:11:05 pm",
"content": "Quotesame thing different language,and a 2 way with intermediate is a 4 way switch"
},
{
"post_id": "",
"author": "MarkF",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 24, 2023, 03:58:37 am",
"content": "This is the about the only way I can figure that doesn't have two colors tied together and all the wires are used. Although a couple wires should have their color taped as black. I can't figure any way with the wire runs you have that will meet code."
},
{
"post_id": "",
"author": "WimWalther",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "November 24, 2023, 04:22:06 am",
"content": "My only advice - Make no assumption so foolish as to think the original circuits met code. You may be forced to work with existing runs that simply cannot be made to meet current codes without sacrificing functionality."
},
{
"post_id": "",
"author": "MarkF",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 24, 2023, 04:51:10 am",
"content": "Or it could have been something like this."
},
{
"post_id": "",
"author": "Mpegger",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "November 24, 2023, 06:08:30 am",
"content": "Nice job leaving no line disconnected.Unfortunetly its all moot as I noticed half-way wiring up the downstairs box, that the extension box I was using to run a new armored 12/2 over the exterior of the wall to the breaker panel, is too narrow to house anything other then those super skinny single-pole toggle switches because of the cable clamp and 12/2 cable protruding too far into the box.So for now I just wired the downstairs box to feed power straight to the basement lights with no switch (they are all \"smart\" lights anyway), and straight upstairs where I swapped the 3-way switch there for a double outlet, and the single-pole switch for a combo single-pole + single outlet (this combo I had originally planned to switch). I don't need 3 outlets at the top of the stairs, but I might as well wire something up instead of leaving a dead 3-way switch in place.Looks like I'm going to need to cut into the drywall anyway and swap that single gang box for a double if I want to place a outlet there, which I do cause theres no outlet near the main panel, nor anywhere around that corner of the basement."
}
] |
2025-10-17T16:44:54.844227
| 18
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-wire-load-cell-no-signal/
|
3 wire load cell - no signal - Page 1
|
[
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 20, 2015, 08:30:47 pm",
"content": "I have been fighting with 3 wire load cells all week and I am in a rut...I am trying to get a measurable signal to amplify out of a load cells found in bathroom scales.There is a wealth of data about 4 wire cells available, but these would cost about 8 times more to employ.Very little is said about 3 wire set up; people usually go from \"here is a Wallmart scale ~blurry lines~ here is the finished project\"...My project needs to measure weight on each cells individually, not wire 4 together.I have measured the cells: unpowered, 1.5V, 3V, 4.5V and 6V. All have no visible movement on a scope in the 5mV scale.Using a bench meter I get about 0.13mV per kilo, but I am starting to see RF signals down there... Boosting it 100x or 1000x with a 741 is getting me nowhere - nearly no shift.To the point I thinking the 0.13mV is my body conducting stray charges...The best result I have to date is measuring resistance and getting 1.002 kOhm unloaded and 1.004kOhm with 15 kilo load between the black and white wire - with no current.As soon as I give 1.5V, the resistance goes into the MOhm range and I can't see variation any-more (not enough digits on a Fluke 175).Am I missing something obvious or should I spend cash on the big alloy cells (these bring a whole host of problems due to their size and heat sensitivity).Here is some data, but the numbers are at least 10x off from what I am getting.https://learn.sparkfun.com/tutorials/load-cell-amplifier-hx711-breakout-hookup-guide?_ga=1.265664391.925322740.1443502696"
},
{
"post_id": "",
"author": "retrolefty",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 20, 2015, 09:24:02 pm",
"content": "I believe a '3-wire load cell' acts like a simple 3 terminal variable pot. If you wire say regulated +5vdc to the red and ground the black you should see a change in voltage measured between the white wire and the ground wire. You should see some change in millivolts output as you very the pressure on the cell. Just maybe 10s of millivolts change so don't expect large voltage changes. That is why they almost always require amplification before wiring to something interesting."
},
{
"post_id": "",
"author": "Paul Moir",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "October 21, 2015, 02:56:56 am",
"content": "Just had a quick look on aliexpress and similar ones are quoted as being half-bridges, with a sensitivity of 1mv/V. So if you complete the bridge with a pair of 1K ohms resistors, excite it with 5v and load it to it's max, it'll develop 5mV across the bridge.You should be able to identify the pinout with a multimeter. You would expect to get 2k between the two excitation wires and 1k between either excitation and the signal terminal.http://www.ni.com/white-paper/4172/en/"
},
{
"post_id": "",
"author": "Dago",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "October 21, 2015, 06:27:29 am",
"content": "The signal levels from load cells like that are extremely small and it is no wonder you don't see anything with an oscilloscope"
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 21, 2015, 07:04:36 am",
"content": "Quote from: Paul Moir on October 21, 2015, 02:56:56 amOk, i get it. I was barking up the wrong tree... Simple now!"
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 21, 2015, 07:09:45 am",
"content": "Quote from: Dago on October 21, 2015, 06:27:29 amIf complete the bridge as Paul Moir suggests, is a simple Op amp amplification valid to get a good signal before the ADC?"
},
{
"post_id": "",
"author": "retrolefty",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 21, 2015, 12:04:23 pm",
"content": "Quote from: gildasd on October 21, 2015, 07:09:45 amMost all load cells are configured in a Wheatstone bridge configuration and utilize an instrumentation op-amp giving the desired gain to match the range of the ADC processing the measurement value. Lots of examples on the web."
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 21, 2015, 12:16:50 pm",
"content": "Quote from: retrolefty on October 21, 2015, 12:04:23 pmThe three wire examples in my possession do not (I wish they did!)."
},
{
"post_id": "",
"author": "retrolefty",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 21, 2015, 12:28:11 pm",
"content": "Quote from: gildasd on October 21, 2015, 12:16:50 pmBut are sure that two were not wired in opposite polarity in a bridge configuration?"
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 21, 2015, 01:23:17 pm",
"content": "Quote from: retrolefty on October 21, 2015, 12:28:11 pmAll four cells made a single sensor, I'll post the skematics when I'll get home, but I was hoping that the white wire was the output of a bridge.It's not.For my use I need the sum of the sensors, not the average, so I cannot wire them as you say."
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 21, 2015, 09:43:36 pm",
"content": "It's working!It was a half Wheatstone bridge!I get nice repeatable results:- 3.66mV no weight- 3.32mV with 2kgThis is very usable once amplified a 100 or a 1000 times - success!I'll post the full instrumentation amplifier schematic tomorrow (based on a Tl084 4xOp amp): I need to redo the values as I was not expecting the variable resistance values to go down with weight...I'll see what kind of value range I can get before choosing an ADC (I2C flavor).Bed time, I'll sleep well!"
},
{
"post_id": "",
"author": "lapm",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "October 22, 2015, 02:13:36 pm",
"content": "Quote from: gildasd on October 21, 2015, 09:43:36 pmAll you need to do now is balance the bridge so it gives 0.00 mV at no load and its even more usable."
},
{
"post_id": "",
"author": "SeanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 22, 2015, 05:29:55 pm",
"content": "Going down with mass added simply swap the power and ground leads of the half bridge, problem solved. Those half bridges only have the 3 colours so the assembler can tell them apart, I have seen a few with the red lead connected to the battery negative."
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 24, 2015, 10:42:17 pm",
"content": "Conclusion: 3 wire load cells suck for my project.I made a full bridge with a normal and a Trim resistor.Next the trim was adjusted to as close to 0mV as possible with no load (I got to -0.2mV).The resulting signal is fed basic Op Amp instrument amplifier (with no gain to start with) to see what amplitude is available to feed to the ADC.However I could not get a logical result out of the amplifier... There was a base signal that should not have been there.Frustrated I went to bed.I have now added a load and ceramic cap on the 3v line and still I got weird results.Thusly I went back to load cell without the Opamp and found this:(Series of measurements)No load _ 2Kg load-1.09mV -1.00mV-1.10mV -1.01mV-1.12mV -1.03mV-1.13mV -1.04mV-1.14mV -1.05mV-1.16mV -1.06mV-1.18mV -1.07mVetc, the load cell is drifting like hell...I tried adding a load to the 3V line, a ceramic cap etc, it changes nothing.This explains why 4 cells are wired together and the scale calibrated at each use.The rig I'm building has to measure wind force non stop for 1 month without calibration, apparently this cannot be done with this sensor type.Edit, going to test if it's not the trim pot that's the issue - but I'm pretty sure it ain't."
},
{
"post_id": "",
"author": "Andy Watson",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "October 24, 2015, 11:28:14 pm",
"content": "Quote from: gildasd on October 21, 2015, 01:23:17 pmI might have missed this in the thread, but, have you actually identified which wire IS the output? Other, similar devices reported on the web suggest that the excitation voltage is applied between white and black - leaving red as the output (contrary to what any normal person would assume!) Measure the resistance between the three possible pairs of wires - this will tell you how the half-bridge is wired."
},
{
"post_id": "",
"author": "Paul Moir",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "October 24, 2015, 11:29:58 pm",
"content": "All load cells drift a lot so there is more to a scale than a load cell and adc. You have to do zero tracking, weight change detection, maybe even temperature compensation."
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 24, 2015, 11:52:05 pm",
"content": "Quote from: Andy Watson on October 24, 2015, 11:28:14 pmIt is the white. I was measuring voltage not resistance as I thought it was the output of a full bridge.QuoteYeah but 100% variation (the loaded value drifts to the no load initial value) after 10 cycles is awful. Simply crap. Even membrane cells do better.In gusty conditions, 10 cycles is a few seconds. I can't put a box over the sensors to reset the null every 5 seconds. It's not feasible.I can live with heat drift because all the cells will drift the same (shade and moving air).The weight will be a constant during the whole campaign.I think I will have to go to 4 wire alloy cells. More complicated but I would only have to do a drift compensation measurement once a week (if I read the specs right)."
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 25, 2015, 07:38:52 pm",
"content": "I've been fooling about all day:From what I've tested, up to 5kg, the cells are imprecise and drift.The 0 moves as much as the loaded value.Beyond 5kg, this goes down. At 10kg, the absolute value repeats quite nicely... And the 0 drift does not matter as much (equivalent to hundreds of grams).The drift actually goes up and down slowly over a period of minutes... Apparently this can be partially cured by using two cells to form a single bridge. This would cost twice a much obviously.However, at this price, I can use alloy bar cells that are for better:https://www.sparkfun.com/products/13329And it's dedicated amplifier:https://www.sparkfun.com/products/13230Edit1; The Amp Hour's latest guest has managed it!I think he avoided most of my pitfalls by using a better scale (thus sensors) and \"preloading\" them with the heavy wooden hive.https://hackaday.io/project/4648-analogio-a-full-stack-iot-platform/log/23345-measuring-the-weight-of-beehivesEdit2; The 0 seems to stabilise after about an hour...mV time0.5 21:14:002.4 21:23:003.0 21:34:004.3 21:44:0032.6 21:54:0029.1 22:04:0028.8 22:14:0028.8 22:24:0028.8 22:34:00"
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "October 29, 2015, 11:00:54 am",
"content": "I've changed the way I generate voltage and set the reference:0kg mV 2kg mV Diff 0kg mV 2kg mV Diff time-1.51 -1.39 -0.12 -2.03 -1.9 -0.13 10:00:00-1.5 -1.38 -0.12 -2.02 -1.88 -0.14 10:05:00-1.52 -1.41 -0.11 -2.04 -1.92 -0.12 10:10:00-1.51 -1.4 -0.11 -2.05 -1.93 -0.12 10:15:00-1.51 -1.4 -0.11 -2.05 -1.93 -0.12 10:20:00-1.5 -1.39 -0.11 -2.05 -1.92 -0.13 10:25:00-1.5 -1.39 -0.11 -2.05 -1.93 -0.12 10:30:00-1.5 -1.38 -0.12 -2.05 -1.93 -0.12 10:35:00-1.5 -1.38 -0.12 -2.05 -1.92 -0.13 10:40:00-1.49 -1.38 -0.11 -2.05 -1.92 -0.13 10:45:00-1.5 -1.38 -0.12 -2.05 -1.93 -0.12 10:50:00-1.5 -1.36 -0.14 -2.05 -1.91 -0.14 10:55:00-1.49 -1.37 -0.12 -2.05 -1.92 -0.13 11:00:00-1.5 -1.38 -0.12 -2.05 -1.92 -0.13 11:05:00-1.5 -1.38 -0.12 -2.05 -1.92 -0.13 11:10:00Much better, the no load voltage is still too high, but I have ideas to solve this."
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 01, 2015, 10:58:55 pm",
"content": "I tried this with PT10 trimmers of 2.5 kOhms, then 100 Ohms, but I had problems getting it to 0.01mV the measured voltage would go straight from +0.1mV to -0.1mV.This was solved by using 100 Ohms Vishay Cermet trimmers.The drift due to the supply, mains, whatever etc was cured by using a 3.3V Zener on the -Vcc.I have 0.02mV drift in a few hours, I think linked to heat changes in the room.In any case, it works but I have to start soldering because the thin pins on the Cermets slowly slip out of the bredboard and change the measurement."
},
{
"post_id": "",
"author": "gildasd",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "November 08, 2015, 06:17:29 pm",
"content": "Well, that did not f#####g work...The soldered circuit became a bloody RF nightmare...It was picking up the earth's magnetic field (tested with a compass), the power supply of my computer and was building up charge (static?)...Not to mention high sensitivity to heat, pressure and noise (FFS).After working on it to remove all the unused traces and putting ceramic caps here and there... It was beginning to be way too complex, no amount of make-up is going to make up for that, and even if it did, it would crack at the slightest provocation.So a bit of potential precision was sacrificed to make the simplest circuit possible:The results a much better, in fact, if I can buffer and sum 4 sensors, I've solved this.Edit: how do I limit the size of the images in the post, but leave them as big in the link."
}
] |
2025-10-17T19:30:41.458223
| 21
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3-wire-usb-adapter-for-connecting-rc-charger-to-pc-for-logging/
|
3 wire USB adapter for connecting RC charger to PC for logging - Page 1
|
[
{
"post_id": "",
"author": "vjekobalas",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "September 16, 2021, 05:12:56 pm",
"content": "I wanted to make sure I'm about to do the right thing and not destroythe RC charger UART. I would like to connect a \"3 wire\" UART signal from a RC charger to USB/PC (further details below).Would it work to connect this RS232/USB cable (which I already own):https://ftdichip.com/products/us232r-100-bulk/with handshake looping as per this example:https://www.airborn.com.au/serial/rs232.htmlOR do I need another type of RS232/USB adapter eg. the Hitec HRC44168 mentioned belowor something cheaper like this which I presume is the same thing: ?https://www.ebay.de/itm/202055184678?hash=item2f0b6d7126:g:55cAAOSwoRBZr25SHere are all the details I have collected:RC charger is Ev-peak CQ3. According to advert on Ev-peak website(which seller is denyingand Ev-peak are not answering) for several chargers including CQ3, communication with pcis supposed to be possible and the pc monitor software + firmware update softwareis on their web page.According to the schematic I found on the web (attached), two pins from the temperaturesensor connector are supposed to be the TX/RX pins.This is the RC charger processor showing onboard UART:https://www.nuvoton.com/products/microcontrollers/arm-cortex-m0-mcus/m051-base-series/m0516ldn/?__locale=enIn the following thread post #46:https://www.rcgroups.com/forums/showthread.php?2589760-Does-anyone-have-experience-with-Ev-Peak-CQ3-charger/page4it is indicated that the USB adapter that could work would be the Hitec HRC44168 - here's a photo showing 3 wires:https://www.rcmodelscout.com/Batteries-and-Chargers/Hitec-USB-Adapter-Cable-X4-X4-X1-HRC44168/329765According to post #1 :https://www.rcgroups.com/forums/showthread.php?1616244-X4-charger-USB-adapter-install-troublethe hitec HRC44168 uses the \"cp2102 usb to uart bridge controller\""
}
] |
2025-10-17T17:22:31.672150
| 1
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/30$-jyetech-scobe-from-ebay-what-can-it-do-measure-mains!!!!/
|
30$ JYEtech scobe from ebay: What can it do? MEASURE MAINS!!!! - Page 1
|
[
{
"post_id": "",
"author": "Beamin",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "July 25, 2018, 12:56:12 am",
"content": "I got a few of these mainly because the first two magically self destructed and the screen just would boot up white. Dave did a video on it and every other electronics youtuber.But not wanting to break my last one:Can I measure things like power supplies with the \"probes\" (alligator clips to BNC) it came with; no A/C filter like putting a cap for protection? Does this act as a low impedance device where it will just short my lab power supply out and kill the scope?Would it be saved if I run a real 10/100X probe on it? Or a 1m resistor in series on it? I have a whole bunch of little power supplies I found and would like to see how clean they are then connect some power resistors and compare. Could be use full for quick and dirty measurement where you don't want to lug around a scope.What the most voltage a scope can take? I never see those specs but I guess it's not a single answer or they just assume you know what you are doing. I'm still hesitant to burn up my tek 3365? scope from the 80's. I did only pay $100 for it, but thats $400+ to replace. If I could learn on this little one it would be perfect."
},
{
"post_id": "",
"author": "lordvader88",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 25, 2018, 09:47:14 am",
"content": "Are you talking about a pocket scope like a DSO138 ? Yeah IDK what the highest input voltage is, but it's not that high, maybe 50V.They work fine with 10x probes on RECTIFIED 169V from 120VAC, I think I used it on 320VDC from the PFC stage of a computer PSU.I never bothered to try probing before the rectifier tho so IDK, but with 10x probes I 'think' it should handle it fine."
},
{
"post_id": "",
"author": "stj",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 25, 2018, 12:43:18 pm",
"content": "most probes only have insulation ratings of 300v btw.and that de-rates as the frequency increases too."
},
{
"post_id": "",
"author": "Beamin",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "July 26, 2018, 12:02:09 am",
"content": "Quote from: stj on July 25, 2018, 12:43:18 pmAs far as the impedance goes: it comes with alligator clip leads. Could I just connect them directly across a <20v power supply like I could a voltmeter?"
},
{
"post_id": "",
"author": "Nusa",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 26, 2018, 12:47:40 am",
"content": "The specs for whichever model you have are listed on the appropriate page on the site:https://jyetech.com/Products/Oscilloscope.phpAlso links to documentation if you don't have it. Some of the counterfeits probably left it out."
},
{
"post_id": "",
"author": "Jwillis",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 26, 2018, 06:00:55 am",
"content": "Those DIY scopes are more a curiosity than a workable tool.I wouldn't trust them over a maximum of 50V DC.Mine starts to clip even at 30 Volts .Basically just toys .Have you considered a High Voltage Differential Isolating Oscilloscope Probe.If your concerned about high voltage that might be the safest bet."
},
{
"post_id": "",
"author": "Beamin",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "July 28, 2018, 09:11:54 pm",
"content": "So I just found the thermostat in my house runs on 24VAC could I use the alligator clips to probe what the different wires do (or rather look at the ac wave forms)? This wont hurt the scope or blow the fuse in the thermostat? Can I assume you can use it the same way you would a multimeter keeping in mind not to probe abouve 50 or 30 volts?If I use the alligator clip leads would it just look like a high impedance source so very little current would pass through it?I hate only having one of something I can't blow up by accident. I want to get comfortable with this device before I start using my tek scope."
},
{
"post_id": "",
"author": "Jwillis",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 30, 2018, 06:08:08 am",
"content": "Why don't you build a simple oscillator circuit with an inductor and capacitor.You can see the varying oscillations by changing the inductor or capacitor. And you can even predict what the resonant frequency is.Frequency in Hertz is f= 1/2pi√L*CYou can run your simple oscillator on a 9 volt battery"
},
{
"post_id": "",
"author": "Beamin",
"author_rank": "Super Contributor",
"is_op": true,
"timestamp": "July 30, 2018, 11:23:36 pm",
"content": "Quote from: Jwillis on July 30, 2018, 06:08:08 amJust the post I was looking for and it gives me an excuse to build something!I think next I'm going to attach the red lead of the scope to the tungsten tip of the TIG welder and the black lead to its ground turn the amps all the way up and see if the waveform distorts right when I turn it on. Or measure how clean the power from the stick welder when it's all the way up. Something tells me I should video tape this."
}
] |
2025-10-17T18:28:01.925812
| 9
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/30-amp-automated-variable-on-off-pulse/
|
30 Amp Automated Variable On Off Pulse - Page 1
|
[
{
"post_id": "",
"author": "itsme1414",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "May 19, 2019, 10:21:32 pm",
"content": "I was able to determine the 30 amp DC power amp I would need to use for my solenoid project.Now I need to find out if there is anything made you can purchase that has adjustable on off timesExample would be a high power adjustable strobe controller.Need to come out of the amp into something that can be an infinite loop timer that could have variable on and off times for each pulse but could handle 30 amps.Does anyone make this or can anyone make this?Thank you"
},
{
"post_id": "",
"author": "pwlps",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "May 21, 2019, 03:53:36 pm",
"content": "A LED lighting strobe controller ? Not sure they can handle such currents, but could be used to drive a 30 amp SSR."
}
] |
2025-10-17T18:10:13.707288
| 2
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3003xiii-power-supply-question/
|
3003XIII power supply question - Page 1
|
[
{
"post_id": "",
"author": "robotic",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "July 10, 2017, 01:04:38 am",
"content": "Hi I am interested in buying the CSI 3003XIII power supply.I'm wondering if I am able to connect 2 of the outputs to combine their current. For example, if I happen to have to use 5A for an LED project.Or should I not buy the 3003XIII and go for a 10A one from ebay. I'm seeing a used for about ~$60. The ebay ones are around the same price but only 1 output, but are at around 5A or $80 for 10A.Thanks."
},
{
"post_id": "",
"author": "alm",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 10, 2017, 01:17:34 am",
"content": "Based on the picturehere: yes, you should be able to parallel the two channels for 30 V / 6A. There is even a convenient 'parallel' button on the front panel, so you can do it without any extra wiring.There has been some discussion on this forum about the cheap eBay bench power supplies (search this forum). Do not expect them to deliver their full rated power continuously."
},
{
"post_id": "",
"author": "robotic",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "July 10, 2017, 01:42:35 am",
"content": "haha thanks. Didn't even notice it. =)That's perfect."
},
{
"post_id": "",
"author": "robotic",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "July 10, 2017, 02:45:27 pm",
"content": "Just got it and don't have anything to with a high current to test it with currently. Hopefully it works like that.Since it was used. It didn't come with any cables.Hope it doesn't need thistype of cableon the left. Or i'll have to make one to get the 6A."
},
{
"post_id": "",
"author": "alm",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 10, 2017, 03:55:29 pm",
"content": "I doubt that you would need to make any special cables. Even if the power supply does not connect the terminals together when you enable parallel mode, then you could just use banana leads to wire the two black and red jacks together. Just make sure to use decent leads at 6 A, for example not those cheap crimped alligator clip leads."
}
] |
2025-10-17T18:53:01.759305
| 5
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/300v-ac-source-needed-for-multimeter-calibration/
|
300V AC source needed for multimeter calibration - Page 1
|
[
{
"post_id": "",
"author": "DrJoe",
"author_rank": "Contributor",
"is_op": true,
"timestamp": "August 09, 2014, 02:36:13 am",
"content": "I'm in the process of restoring an ancient Triplet Multimeter (model 60). I need a 300V AC source for calibration (60 Hz).Any ideas for the most economical way to get there?I was thinking about the voltage multiplier that Dave explained in the Uni-T UT513 Insulation tester teardown (episode #468) but I have no idea what diodes and capacitors to use in the circuit or if special precautions are needed as far as voltage isolation cut-outs on the circuit board.A 120:300V transformer is about $50 and I was hoping to do it cheaper.The only ac source I have besides direct mains is a signal generator that only does 10V peak to peak.Thanks,DrJoe"
},
{
"post_id": "",
"author": "BillWojo",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "August 09, 2014, 03:37:53 am",
"content": "Does it really have to be 300VAC? Small 240 to 120VAC control transformers are cheap, look on ebay. Run it backwards with 120VAC in and you should get 240 out the other side.BillWojo"
},
{
"post_id": "",
"author": "mij59",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "August 09, 2014, 04:31:10 am",
"content": "Quote from: DrJoe on August 09, 2014, 02:36:13 amAn isolation tester uses a dc voltage, so you'll have to convert it to a ac signal."
}
] |
2025-10-17T19:57:26.524779
| 3
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/300v-dc-to-24v-dc/
|
300V DC to 24V DC - Page 1
|
[
{
"post_id": "",
"author": "Sam__",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 03, 2013, 03:13:33 pm",
"content": "I was wondering what the best way of getting from mains rectified 330V DC to a usable 24-36V DC?I'm struggling to find step down transformers via the almighty google.thanks in advance."
},
{
"post_id": "",
"author": "M. András",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 03, 2013, 03:34:08 pm",
"content": "just buy the transformer for your line voltage and with a 24v output then add a bridgerectifier plus some caps then you can regulate it from there"
},
{
"post_id": "",
"author": "Sam__",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 03, 2013, 03:49:26 pm",
"content": "Sorry I should have said in OP that this is a purely theoretical question as I just took apart a computer power supply and saw it used 300V DC and was wondering how it got down from that to a lower DC voltage."
},
{
"post_id": "",
"author": "c4757p",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 03, 2013, 03:53:08 pm",
"content": "A custom transformer. Keep in mind you can't just stick 300VDCup a transformer, you'll blow the shit out of it. The computer power supply is an SMPS - it pulses the 300VDC to make AC at a controlled frequency and duty cycle. If you need to convert 240VAC to 24-36VDC just get a normal line transformer and put the rectifierafterit."
},
{
"post_id": "",
"author": "Sam__",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "February 03, 2013, 04:04:48 pm",
"content": "Quote from: c4757p on February 03, 2013, 03:53:08 pmI knew it was a switchmode I was just confused as to how it got from 300DC to the lower voltages. Thanks a lot for explaining it. I may have to do a bit more reading on the subject, it's quite interesting."
},
{
"post_id": "",
"author": "mariush",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 03, 2013, 04:12:25 pm",
"content": "A switching power supply rectifies the 220-245v AC voltage to 310-350 (220-240 x 1.41) v DC, sometimes there's an Active PFC circuit that boosts the voltage to about 390-400v DC.Then there's a small controller which generates pulses of this voltage up to 50-120 thousands a second (52kHz - 110kHz) that are sent through the small smps transformer. The pulses are then rectified to DC voltage on the other side.On this secondary side there's another chip which monitors the output voltage of the transformer and depending on how low or high it is, it sends a signal to the primary controller to reduce or increase the number of pulses going into the transformer.So overall it's a very complex design.The simpler and easier design is to just use 220-240v AC and a regular transformer, which however will be much heavier and kinda expensive... If you want smooth 24v DC you get 20-24v AC that you can then rectify to DC and get 24v DC or more. Then you need some big capacitors (one or more 3300-4700uF 35v or 50v capacitors) to smooth out the voltage after it's rectified, and maybe even use a linear regulator to get the voltage really steady at 24v DC."
},
{
"post_id": "",
"author": "c4757p",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 03, 2013, 04:20:19 pm",
"content": "I wouldnotuse a 35V-rated capacitor for that. A 24VAC transformer will put out almost 34VDC, and especially if it's meant for a high load, it will easily soar a good bit higher than that unloaded. A 35V cap gives younosafety margin."
},
{
"post_id": "",
"author": "mariush",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 03, 2013, 04:27:12 pm",
"content": "I said 20-24v AC and 35 or 50v... 20 x 1.41 = 28v ... might peak to about 32v depending on your mains voltage.Also, some transformer manufacturers are nowadays listing the voltage for the secondary as it is after rectification, so if you get one on those that says 24v on secondary, it's actually 24-26v rectified, not 24 v AC.35v rated capacitors would be a bit risky, but if they're made by a good manufacturer, they should be OK...Of course 50v or even 63v would be better and safer, and someone should go for those if you can find them cheap and in stock at some good company like Mouser, newark, digikey etcHere's some transformers that will work to get a 24v DC output or slightly more, just for reference :http://goo.gl/bfnbU(goes to Farnell / Newark - their urls are super long and break down on this forum, so shortening them)Some of the transformers on the link above are 2 x 12v or 2x 15v , you can link the secondaries in series to get 1x24 or 1x30 that you can then rectify... There's also a separate section with toroidal transformers that you might wanna check out - those transformers are better for some types of usage but they're also a bit more expensive."
},
{
"post_id": "",
"author": "mikeselectricstuff",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 03, 2013, 04:30:38 pm",
"content": "A switchmode PSU designed for 230VAC should run fine on 300VDC. Two potential issues are if it has PFC, DC may confuse the PFC circuit, but that can probably be disabled quite easily.The other is the internal fuse will probably not be rated for 300VDC - Fuses for DC are a potential problem as if it blows & arcs, they don;t have the AC zero crossing to extinguish the arc."
},
{
"post_id": "",
"author": "IanB",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 03, 2013, 04:42:06 pm",
"content": "Quote from: mariush on February 03, 2013, 04:27:12 pmGotta watch the peak voltage carefully. Inthis postI show measurements of a \"12 V 2 A\" transformer and the unloaded output voltage is 15 V. If we assume a 24 V transformer of similar design would behave the same way we would have 30 V AC unloaded. Multiplying that by 1.41 would give 42 V DC, so the 50 V rated smoothing capacitor would definitely be indicated."
},
{
"post_id": "",
"author": "mariush",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 03, 2013, 04:47:27 pm",
"content": "I forgot to mention that a bridge rectifier has about 0.5-0.7v voltage drop per diode, so about 1-1.5v drop on the rectifier.But I agree with you, 35v may be too close for comfort."
},
{
"post_id": "",
"author": "codeboy2k",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 05, 2013, 04:15:16 am",
"content": "Quote from: mikeselectricstuff on February 03, 2013, 04:30:38 pm... and (I'm sure Mike and many others know this already, but I'll put it out there ..) that's why fuses on multimeters are special, and called HRC fuses (high rupture capacity). They are usually filled with sand to fill the gap and extinguish any high voltage DC arc."
},
{
"post_id": "",
"author": "Psi",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 05, 2013, 06:50:28 am",
"content": "Quote from: Sam__ on February 03, 2013, 03:13:33 pmDepends on the current needed."
},
{
"post_id": "",
"author": "nobody",
"author_rank": "Newbie",
"is_op": false,
"timestamp": "March 11, 2013, 05:05:46 pm",
"content": "best to use is transformer and some caps"
}
] |
2025-10-17T20:25:24.598616
| 14
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/3010d-power-supply-short/
|
3010D power supply short - Page 1
|
[
{
"post_id": "",
"author": "Jane",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 22, 2022, 08:25:00 pm",
"content": "I measured voltage with this 3010D power supply but accidentallyvery high voltagehappend to be on a measuring point. As a result, plus input of that power supply is shorted to ground.Is there a schematic available ? Or anyone already solved a such problem in the past?Thank you for help"
},
{
"post_id": "",
"author": "Jane",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 23, 2022, 08:15:13 pm",
"content": "That power supply is made under different brands e.g. YIHUA PS-3010D.None knows about a schematic or how to repair it?"
},
{
"post_id": "",
"author": "BrokenYugo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 23, 2022, 08:41:08 pm",
"content": "Don't use a bench power supply to measure things, DMMs are cheap. How high voltage are we talking about? What sort of equipment was this?Open it up and look at the power electronics (bigger parts) near the output for signs of damage, check diodes and transistors with a DMM. Pics of both sides of the boards help others follow along.This is a very international forum, it is not uncommon for a thread to not really take off for a day or two, it takes that long just for everyone to have a chance to read it."
},
{
"post_id": "",
"author": "Gyro",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 23, 2022, 08:54:31 pm",
"content": "Looking at the web, the 3010D (30V 10A) is clearly an smps type. There are many potential hazards for an inexperienced person, including primary reservoir capacitors charged to mains peak voltage and the high likelyhood that the damage will be on the primary (non mains isolated) side. As this is the Beginners section, I must advise extreme caution.I am also confused about the details of what you actually did. What is \"very high voltage\" in this context? Detail may be important for diagnosis."
},
{
"post_id": "",
"author": "janoc",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 23, 2022, 10:30:13 pm",
"content": "Quote from: Gyro on July 23, 2022, 08:54:31 pmAlso, there are multiple types of \"3010D\" supply:https://www.amazon.com/3010D-III-Adjustable-Regulated-4-Digits-Alligator/dp/B09VL7ZZJPOr this:https://electrobes.com/product/yihua-3010d-30v-10a-direct-current-regulated-laboratory-power-supply/The \"content\" is unlikely to be the same.It being Yihua, it means that every corner possible has been cut. I am not sure I would even want to touch something like that.These supplies sell for about $50, I would just bin it. Probably the safest (and most economical) option available."
},
{
"post_id": "",
"author": "MrAl",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 23, 2022, 10:41:26 pm",
"content": "Quote from: Jane on July 22, 2022, 08:25:00 pmHello there Jane,It is probably a simple problem but the solution probably cant be found on the schematic anyway because they probably dont show the component you need to replace. It's a simple diode like the 1N5400 series.What they do is connect that diode directly in reverse parallel to the output terminals of the power supply so that if another power supply tries to power the unit in reverse the diode will conduct and sink the current and probably blow out in the shorted condition.It could also blow with a higher voltage input than the diode is rated for. Again the diode would blow out in the shorted condition so it has to be replaced.To replace it you have to remove the internal circuit board, then you can find it. It is mounted fairly close to the output terminals so look there. It is not easy to find without removing the board though you may not even be able to see it without taking out the board.Once you spot it, it will probably be cracked which means it burnt and became a short.It's a simple way to help protect the power supply from blowing out completely if something that provides power to the input gets accidentally connected to it. The same will happen if you connect a large 12v lead acid battery in reverse to the input terminal polarities.I hate to say it, but there could be other things wrong too if the diode didnt catch the fault in time, but the diode is the starting point. You can test it to see if it is shorted then replace it and hope for the best.I have a schematic for a similar power supply the HY3010E if that can help i can try to find it. It does not show the protection diode either but the connection is very simple as explained above.Good luck with it Jane, and i hope you can report back here on your progress with this power supply."
},
{
"post_id": "",
"author": "Jane",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "July 25, 2022, 07:52:36 pm",
"content": "Thank you for your replies particularly MrAl"
}
] |
2025-10-17T17:07:34.463997
| 7
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/304-stainless-steel-electrical-contacts-bad-idea/
|
304 Stainless steel electrical contacts. Bad idea? - Page 1
|
[
{
"post_id": "",
"author": "rickey1990",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 30, 2022, 09:27:25 pm",
"content": "Hi, I am currently working on a project, That involves connecting 40/50A lugs to a PCB. I know there's tin plated copper board connectors. However I was looking trying to come up with cheaper methods.I remember in electronics class that Stainless steel shouldn't be used for battery connectors. Which this isnt however i went on a online calculator to see the power drop for 304 stainless. If I was to use M6 x 18mm square washer with a 1.5mm thickness as a pad for a lug.Work out the area for the 6mm hole and take that from the area of the 18mm square. It would leave me a area of a 19.4mm circle. Which I used for my wire size.Leaves me with these results. Would you say these are acceptable. Or should I really be using Brass or copper.Also wago also uses stainless steel in there connectors."
},
{
"post_id": "",
"author": "Benta",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 30, 2022, 09:41:51 pm",
"content": "Probably not the best idea, but explore it.Stainless is stainless because it builds an oxide layer on the surface by itself. Not because it doesn't corrode. it does, especially in contact with aluminium (galvanic corrosion).Oxide layers are bad for conductivity."
},
{
"post_id": "",
"author": "abquke",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "July 30, 2022, 09:48:58 pm",
"content": "-As I understand it, Stainless is tricky for welders because it doesn't conduct heat quite as nicely as other steels which can affect material properties.-Steels are generally harder than the usual electronics metals so a battery contact can't dig into the material and have a surface to make electrical contact. On the contrary, the steel would scratch up the (likely) nickel plating of the battery.-Dissimilar metals + moisture + electricity usually equals badI'd say \"try it and see\", but I doubt it will qualify as a good idea."
},
{
"post_id": "",
"author": "MrAl",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "July 30, 2022, 10:31:48 pm",
"content": "Quote from: rickey1990 on July 30, 2022, 09:27:25 pmHi,If SS was good it would be widely used but instead they use gold plating because of the resistance to corrosion. Gold isnt as good a conductor as silver or copper but it's still used in a very thin layer and so the extra resistance does not matter as total resistance also depend on the length of the conductor and a thin plating is not very long.So with SS being much cheaper than gold but not used widely, i would think SS is not that good. It does depend on other things too though like the normal movement of the contacts. If they rub that could reduce the resistance.You also have to remember that it may be hard to test without doing a test that lasts for months. It may look good for the first week or two, but then after 6 months start to show signs of a problem with the contact resistance. You might be able to set up a custom test set that checks for this, but it will take patience and unfortunately it may act differently in a different applications. Flashlights seem to be a problem area even regular tin plating doesnt seem to hold up for long and needs to be cleaned. Maybe the humidity gets to it.The \"long term tests\" are always a problem area when you try to design your own stuff that is not normally done it takes time to know if something is going to work out well over months or years.If you are really intent on doing something like this though, maybe you could try to find some papers written on contact testing as sometimes they have tests developed for particular types of components. For transistors for example they elevate the temperature and increase voltages and then can extrapolate the spec's for long term normal use at normal temperatures and voltages.If you find out anything definitive maybe you can get back here and report the findings. Should be interesting.Oh BTW there is a company Air Electro that seems to claim SS has good properties for this maybe you can check with them."
},
{
"post_id": "",
"author": "rickey1990",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "July 30, 2022, 11:00:20 pm",
"content": "Thankyou for all your comments. Well I will be making afew of them.. Also afew PCB manufacturers have 10 (10cmx10cm) boards for $5. Which is why I was looking at larger contacts. If I don't have to pay for the space, I might as well get the most out of my 10 by 10.I have decided on brass 6mm * 18mm round washers. Hopefully that will resolve some of the issues.brass can be more brittle , however 100 washers for £4 makes it a cheap fix."
}
] |
2025-10-17T17:07:23.871540
| 5
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/30a-or-ing-circuit/
|
30A OR-ing Circuit? - Page 1
|
[
{
"post_id": "",
"author": "PeteD",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "June 26, 2015, 03:47:10 pm",
"content": "I'm looking for information on OR-ing circuits.I have a 3D printer that works well for the most part, but it is underpowered when it comes to heating the bed. I'm usually waiting about 45 minutes to an hour for the bed to heat up to 100C, and the wait is irritating me. Others with my type of printer recommend using a 24V 30A PSU and a 100A SSR to get the bed heat up time to less than 10 minutes. Unfortunately, I'm on a budget and don't want to spend the $200+ that that solution would cost.I have a couple of cheap Chinese 24V 15A switching power supplies, but linking power supplies is a little more complicated than putting batteries in parallel. My google-fu has found some information on low voltage, low amp OR-ing circuits, but it has failed me in finding anything for higher currents and voltages.Could someone who knows more about this subject than I (that wouldn't be hard, I've pretty much said it all in this post) point me towards more information on OR-ing design? Also, are there any cheap solutions already out there?Thanks,Pete"
},
{
"post_id": "",
"author": "krish2487",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 26, 2015, 04:25:22 pm",
"content": "Yes.Just use any standard diode bridge (medium to high A rating) and you are good to goPSU1 ---|>---\\_________ TO LOAD/PSU2 ---|>---As simple as that. For your particular application it is not critical about load sharing and such. Just make sure that you put a heatsinkon the bridge. Or if you can also go with a high A rating Schottky diode bridges like MBR20100 and short out the anodes too to get a 20A rated Schottky diode. Use several such to parallel your Power suppliesLike this.|-----|>-----\\|-----|>------\\------------------- TO LOAD|-----|>------/|-----|>-----/"
},
{
"post_id": "",
"author": "macboy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 26, 2015, 04:29:29 pm",
"content": "You basically do just need to connect them in parallel.To ensure current sharing between them, use ballast resistors. The simplest ballast resistor is simply the length of wire between the supply and the load. So, instead of connecting the two power supplies in parallel near the supplies then using a single length of wire to the load, use one length of wire to the load from each supply, making the parallel connection only at the load. The voltage drop across each length of wire helps ensure current sharing. The other important thing is to adjust the two supplies' output voltage to match as close as possible.If you want true \"OR\"-ing of the outputs, you put a series diode on each output. Then you could technically use only one without having the disabled supply see the voltage from the enabled supply. You need really beefy diodes here. I have salvaged several suitable diodes from dead computer power supplies. They are in TO-247 (TO-3P) packages like transistors, but are actually high current Schokttky diodes. One that comes to mind isMBR3060CTMUR3060PT, a 30 A, 60 V (reverse) diode."
},
{
"post_id": "",
"author": "PeteD",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "June 26, 2015, 05:06:59 pm",
"content": "Thanks, Krish, Macboy!It's good to know I was over complicating this. About how much heat should I expect from a couple of parallel MBR20100 diodes in normal operation? Would attaching them to the sheet steel legs of my printer's stand be enough to dissipate the heat, or should I get some heatsinks as well?"
},
{
"post_id": "",
"author": "PSR B1257",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 26, 2015, 05:21:05 pm",
"content": "QuoteDefinenormalAt 15A you get a voltage drop of about 900mV (depending of the tempreatur), therefore 13,5W power dissipation. And this is a lot if you have no heatsink. In fact the diode would go up in smoke pretty soon.QuoteHard to say. It would probably do the job.You should try it first with the method macboy suggested. Additionally you should trim (almost every SMPS has a little trimmer near the output terminal) the output voltage of the supplies to match each other. Ideally you also measure the current of both supplies simultaneously while they are at full load, to make sure, they spread the load current evenly.However a diode bridge (also heatsinked of course), like KBPC5010 for instance, worth also a try."
},
{
"post_id": "",
"author": "krish2487",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 26, 2015, 05:26:07 pm",
"content": "Actually diodes decouple the PSUs from interfering with each others control loop.If there is even a slight mismatch in the output voltage setting or length of the wires then the power supplies willconstantly \"fight\" with each other.The diodes, on the other hand, ensure that each power supplies senses and regulates its own output.13.5 Watts is not really a lot of power to dissipate. It can be managed with a decent sized heatsink.PS: Scratch my suggestion with the MBR20100. The MUR3060 is more likely a better diode to do the job."
},
{
"post_id": "",
"author": "PSR B1257",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 26, 2015, 05:52:16 pm",
"content": "QuoteAs I mentioned"
},
{
"post_id": "",
"author": "tszaboo",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 26, 2015, 06:42:09 pm",
"content": "Any reason not to connect them in series?"
},
{
"post_id": "",
"author": "PSR B1257",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 26, 2015, 07:16:11 pm",
"content": "QuoteThat gives a nominal resistance of 0.8Ohm.At 48V you would get a current of 60A and a power of 2880W.These supplies are not designt to limit the output current, they just switch of, if there nominal current (times a faktor of 1.1 ... 1.5 or so) is exceeded.In general connecting SMPS in series is not more or less critical than connecting them in parallel if they are not designed accordingly."
},
{
"post_id": "",
"author": "PeteD",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "June 26, 2015, 08:43:24 pm",
"content": "OK, I'll stop trying to be too cheap and geek for some heat sinks.Just curious, why do you think the MUR3060 will perform better than the MBR20100? Better Peak Voltage? It's unlikely these diodes will see 100V, let alone 600V, isn't it?"
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 26, 2015, 09:23:58 pm",
"content": "As power dissipation is a major issue here, you want to look for diodes with the lowest possible Vf at a rated current greater than the max PSU output current. I would recommend at least a 20A If rating, preferably 25A, as if one PSU trips out, the other one's current is likely to surge very briefly over its normal max rating before it also trips. The worst case scenario voltage wise is one PSU running and the other tripped with 24V across the tripped PSU's diode, and any diodes with a voltage rating greater than 35V should handle that OK. Avoid diodes with a grossly excessive voltage rating as they usually have a higher Vf as well.Due to the fact that the PSUs cant operate in a current limited mode, its essential to have ballast resistors as macboy described above. The output wires for each supply should be as far as possible absolutely identical, especially the length and both the +ve and -ve wires should be separate all the way to the diodes and build platform for optimum current sharing."
},
{
"post_id": "",
"author": "madires",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 26, 2015, 09:40:59 pm",
"content": "There are dedicated ORing controllers which drive MOSFETs, like the LTC4357 or LTC4359 for example."
},
{
"post_id": "",
"author": "dom0",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 26, 2015, 09:44:16 pm",
"content": "What moron had the idea to heat these things with low-voltage DC?To contribute something meaningful also: get a fat transformer in the right range and do full-wave control with a SSR (on the primary!). Should give you >98 % efficiency, especially with a toroidal (xformer switching relays required then)."
},
{
"post_id": "",
"author": "krish2487",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 27, 2015, 12:59:28 am",
"content": "Not the voltage. The current. The Die itself is rated for 75A for the MUR3060.Quote from: PeteD onTodayat 06:43:24 AM"
},
{
"post_id": "",
"author": "edpalmer42",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 27, 2015, 02:16:16 am",
"content": "Instead of buying diodes and a heatsink and making your own, check at your local automotive supply store. They probably have a battery isolator which allows you to have two batteries that charge together but are discharged seperately. It's typically used when you have auxiliary loads like an inverter. You power the inverter off one battery and start the vehicle with the other one. The auxiliary loads can't drain the starting battery. Electrically, it's nothing more than two diodes and a heatsink!"
},
{
"post_id": "",
"author": "rx8pilot",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 27, 2015, 04:15:36 am",
"content": "Build an 'ideal diode' with a controller and a MOSFET. Wont need a heatsink and can do it with about $15 or so - probably less than the value of the heat sink needed for a normal diode.I have been using LM5050 but there are tons of options out there. Find a low Rds(on) mosfet and a few other parts. It"
},
{
"post_id": "",
"author": "PSR B1257",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 27, 2015, 07:14:12 am",
"content": "QuoteWhat do you get, if you switch the MOSFET on? Basically a piece of wire. Meaning you are shorting out both supplies, which is the exact opposite of what we want here.The topic in this case is chosen rather confusing. He actually wants an ADDing circuit since both supplies are intended to deliver power simultaneously"
},
{
"post_id": "",
"author": "madires",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 27, 2015, 11:07:51 am",
"content": "Quote from: PSR B1257 on June 27, 2015, 07:14:12 amHave you ever read any datasheets and application notes of ORing controllers? They got a reverse current protection, i.e. if current flows the wrong direction, the MOSFET is switched off. Most controllers use the R_DS_on as current sense resistor."
},
{
"post_id": "",
"author": "rx8pilot",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 27, 2015, 04:29:03 pm",
"content": "Quote from: PSR B1257 on June 27, 2015, 07:14:12 amSort of....you are not shorting the supplies - you are putting them in parallel. This will only happen if current is flowing out of each supply. If one supply dies or is a lower voltage the high side supply will not backfeed into it. The only purpose of the diodes (or ideal diodes) is to prevent reverse current that will damage the supply.Quote from: madires on June 27, 2015, 11:07:51 amIt does nothing to help balance the load, which is an additional effort if the load needs to be evenly split. First things first - don't allow one SMPS to feed into another and ideal diodes are designed for that with very little heat dissipation or voltage drop. The title is asking about an OR-ing circuit which is exactly what a diode (OR'ing controller) does. Perfectly matching the supplies is a longer conversation. If it were me, I would use two isolated heaters that each SMPS can handle on it's own."
},
{
"post_id": "",
"author": "PSR B1257",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 27, 2015, 06:17:16 pm",
"content": "QuoteOf course not shorted in terms of shorted from V+ to V- but shorted in terms of a quasi zero ohm connection from V+ to V+ and V- to V-"
},
{
"post_id": "",
"author": "madires",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 27, 2015, 07:28:46 pm",
"content": "Quote from: rx8pilot on June 27, 2015, 04:29:03 pmSharing the load is quite simpleAssuming that both PSUs got different output voltages, the PSU with the higher voltage wins. But if the load is too large for one PSU the PSU's output voltage drops until it's not far off from the output voltage of the second PSU. The second PSU starts providing current. Get a dual-channel lab PSU, add two diodes and a shared load. Then set the output voltages to be 1V apart. Slowly decrease the higher voltage and watch the currents. Yes, it's simple like this."
},
{
"post_id": "",
"author": "rx8pilot",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 27, 2015, 07:35:08 pm",
"content": "I understand how the highest voltage wins. The problem is that each supply is only capable of carrying a partial load. Because of that, you cant have one supply win over the other because it will ve overloaded and possibly shutdown. When it does shutdown, the other supply will also be overloaded and fail."
},
{
"post_id": "",
"author": "dom0",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "June 27, 2015, 07:42:36 pm",
"content": "This can work with OVPd supplies, too, but only if the output resistance of the supplies is high enough to ensure balanced currents before OVP kicks in (or the supply fails). Now, with a good supply output resistance is very small and consists mostly of irreproducible contact resistances...In redundant server supplies they do it with a current-sharing line, which acts as a control line for all supplies. Basically each supply puts a voltage proportional to it's load current via a resistor on that line and an error amp ensures that every supplies load current is about current-sharling-line / n."
},
{
"post_id": "",
"author": "LukeW",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "June 28, 2015, 12:51:20 pm",
"content": "Do you really need 720 watts (30A at 24V) of power to get a 3D printer's heated platform up to an acceptable temperature quickly?I seriously doubt it, unless it's one of those \"print something the size of a house\" things.What kind of bed heater are you using exactly?What voltage is the heating element designed to run on?What is its resistance?"
},
{
"post_id": "",
"author": "PeteD",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "June 29, 2015, 03:09:06 pm",
"content": "Quote from: LukeW on June 28, 2015, 12:51:20 pmThe heated bed is a 12\" diameter plate with the heating element in 1/8 inch thick fiberglass. On top of the heating plate there is a 1/8\" thick aluminum disc, a 1/8\" thick borosilicate glass disc, and a 1/32\" thick disc of PEI. The 100K thermistor is attached to the heating plate.The Onyx heating plate was designed to run with 12V and 24V PSUs. I am currently using a 12V 450W power supply.I haven't measured the resistance of my heating plate, but it is advertised to have a 1.1 Ohm resistance at room temperature. Some users have seen a higher RT resistance on their plates."
},
{
"post_id": "",
"author": "Magicmushroom666",
"author_rank": "Contributor",
"is_op": false,
"timestamp": "July 02, 2015, 05:01:24 pm",
"content": "Hi, I'm running an onyx heated plate for my printer too. I'm using 18V at whever current that takes, not actually measured it recently, but 18V was enough to get good heat up times without needing silly sized cables etc.You could save on the SSR and just use a mechanical relay to save costs, as long as the controller is just off-on. I've used a relay salvaged from a car which happily manages the current."
},
{
"post_id": "",
"author": "PeteD",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "July 06, 2015, 05:46:41 pm",
"content": "Quote from: Magicmushroom666 on July 02, 2015, 05:01:24 pmSomeone please correct me if I'm wrong, but I believe wire gauge is determined by amperage not voltage.I did look into using an EMR instead of an SSR, but too may people who have used EMRs in their printers have had issues with false signals messing up the print when the EMR switches. Avoiding that problem is worth the cost of an SSR to me."
},
{
"post_id": "",
"author": "ruffy91",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "July 06, 2015, 06:57:12 pm",
"content": "Quote from: PeteD on July 06, 2015, 05:46:41 pmThe heated bed is fixed resistance so more volts means more ampere."
},
{
"post_id": "",
"author": "PeteD",
"author_rank": "Newbie",
"is_op": true,
"timestamp": "July 06, 2015, 07:32:52 pm",
"content": "Quote from: ruffy91 on July 06, 2015, 06:57:12 pmThe heated bed is a fixed resistance, so more volts means morepower dissipated, which is the purpose of this exercise.However, the amperage flowing through the wires to the heated bed should max out at 30A, and the wire gauge won't change between 12V or 18V or 24V."
},
{
"post_id": "",
"author": "ruffy91",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "July 06, 2015, 09:40:02 pm",
"content": "No. If the bed is 1.1 Ohm you will get a max. current of 12V/1.1Ohm=11A for 12V or 22A for 24V"
},
{
"post_id": "",
"author": "Riotpack",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "July 06, 2015, 10:42:01 pm",
"content": "big rectangle power resistor bolted to the plate and connected to the mains through a thermostat"
},
{
"post_id": "",
"author": "LukeW",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "July 07, 2015, 03:20:08 am",
"content": "Quote from: PeteD on July 06, 2015, 07:32:52 pmHigher voltage means less current for the same power transfer, meaning thinner wires and less supply current needed, less voltage drop in the wires and less heating,ifthe heating element is designed for the appropriate voltage.Let's suppose that your particular 3D printer design needs 100W of bed heater power. This depends on the area, the materials, airflow, thermodynamics, desired temperature at the surface etc.But I think 100W is plausible - not 720 watts.Suppose you've got a 12V power supply available.So you use a 1.44 ohm heating element, and this gives you 100W of heat power, ignoring loom resistance. And your power supply needs to deliver 8.33A.But you need to watch the loom resistance - suppose your total loom resistance is 0.5 ohms.Now your power delivered to the heating element is only 55 watts, so it won't get hot quickly enough. And you're dissipating about 20 watts in the wires.So suppose you keep the same heating element, and crank the supply voltage up to 24 volts.Ignoring loom resistance, you're now dissipating 400W in the heated bed, so it will get way too hot. The PSU also needs to be able to deliver 4x the power, twice the current it did before - 16.7 amps at 24V.If there's 0.5 ohms of loom resistance then the heater power has dropped to 220 watts - still probably too large.And you're dissipating 77 watts in the wiring loom.One solution is to use thicker cable, but a pound of copper costs a bit.A better solution is to use a higher supply voltage if you can, the highest voltage that is practical, andchoose the bed heater resistance appropriately. And use relatively thick connecting wires.Suppose the supply voltage is 24V and the heating element resistance is 4.7 ohms and the loom resistance is 0.5 ohms. The element resistance should be high relative to the cables.Then you'll have 100W at the heating element, a manageable 10W in the wiring loom, and a supply current requirement of 4.6A which is pretty manageable."
}
] |
2025-10-17T19:37:40.916120
| 32
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/30m-long-mains-extension-cable-trips-fuse/
|
30m long mains extension cable trips fuse - Page 1
|
[
{
"post_id": "",
"author": "vinlove",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 21, 2022, 09:33:33 pm",
"content": "I have this 30m long mains extension cable. It has 13A fuse in the plug, and is plugged into the mains 230V UK socket in the house, and I use it to connect the Bosch power hose. The Bosch power hose / washer is one of the top model from Bosch, and it is very powerful. As soon as it is switched on, it trips the fuse in the mains extension cable 13A fuse.If the power hose is connected directly to the mains socket in the house without the extension cable, then it is OK. The power washer will run all day without tripping any fuse.So what is it? What causes the extension cable fuse to blow? Would it be the length of the extension cable having excess resistance? Or would it be the extension cable is not thick enough to be able to cope with the current required by the power washer?"
},
{
"post_id": "",
"author": "TimFox",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 21, 2022, 09:39:00 pm",
"content": "This sounds like normal behavior of a standard fuse that is marginal for the starting/inrush current of an electric motor.What protects the house outlet that you plug the equipment into? A fuse or circuit breaker?"
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 21, 2022, 09:44:31 pm",
"content": "What is the mean operating power rating of the equipment? Ditto peak startup rating?What is the fuse in the equipment?Excess resistance would reduce the tendency of the fuse to blow."
},
{
"post_id": "",
"author": "vinlove",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 21, 2022, 10:03:36 pm",
"content": "The power hose / washer is this one.https://www.amazon.co.uk/Bosch-06008A7D70-Pressure-Washer-AdvancedAquatak/dp/B07MQ9HHS2/ref=sr_1_4?adgrpid=53916679915&gclid=Cj0KCQiAjc2QBhDgARIsAMc3SqTp9jlTGP9TbczLp2K0WYeZ81hdivybSBrgUZr5OfzAsHSlrSd0z8UaAh_gEALw_wcB&hvadid=259101229342&hvdev=c&hvlocphy=1007330&hvnetw=g&hvqmt=e&hvrand=343638132528553728&hvtargid=kwd-489502856392&hydadcr=5309_1829680&keywords=bosch+power+washer&qid=1645480794&sr=8-4It is rated at 2100W and runs on 230V AC mains.The machine has a 13A fuse in the plug. It is fine, no problems.But the 13A fuse in the 30m long extension cable always blows.Tried with a 10m long extension cable, and it is OK."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 21, 2022, 10:11:23 pm",
"content": "Quote from: vinlove on February 21, 2022, 10:03:36 pmWhat's the crossectional areas of the 30m and 10m cables?If anything the longer cable should be less likely to blow the fuse, because it will limit the current surge."
},
{
"post_id": "",
"author": "tggzzz",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 21, 2022, 10:23:16 pm",
"content": "Are the fuses equivalent?Differences could be slow-blow vs normal, or poor manufacturing."
},
{
"post_id": "",
"author": "rs20",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 21, 2022, 10:24:16 pm",
"content": "Quote from: vinlove on February 21, 2022, 10:03:36 pmYou say \"13A fuse\" as if all \"13A fuses\" are identical, but they are not. Have you swapping the fuses in the machine and the extension lead? Just to eliminate the possibility that the fuse currently sitting in the power washer is on the more tolerant side of the bell curve (or indeed, maybe a slow-blow variety of fuse?) (oops tggzzz pipped me, but I'll still post with the concrete suggestion of how to check)Is the area where the extension lead fuse is located (right near your mains powerpoint I presume?) extremely hot for some reason?"
},
{
"post_id": "",
"author": "vinlove",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 21, 2022, 11:38:30 pm",
"content": "I used to think all 13A fuses are identical. Maybe they are not.Will check them out tomorrow, and update here.Yes, it is a mystery to me. Why the 30m long extension cable keeps blowing its 13A fuse when plugged with the Bosch power washer.With every other devices such as Bosch hedge cutter, work lights (800W), battery chargers, it is fine.The Bosch power washer works OK with the other extension lead which is 10m long (13A fuse in the plug), or when connected directly to the wall socket 230V AC mains in the house on the kitchen wall next to the door to the garden."
},
{
"post_id": "",
"author": "WatchfulEye",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "February 22, 2022, 12:12:30 am",
"content": "This could be due to the resistance of the cable. Increasing the cable resistance can result in an increase in inrush current duration, which can blow fuses or trip breakers. The increased line resistance reduces motor torque, which causes a delay in the motor reaching normal operating speed and normal operating current.Try using an extension cable rated for 32A as this will have larger conductors with lower resistance."
},
{
"post_id": "",
"author": "vinlove",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 22, 2022, 10:30:16 am",
"content": "Quote from: WatchfulEye on February 22, 2022, 12:12:30 amyeah this is what I thought, but wasn't sure. The 30m long extension cable is an old one, and was very cheap. It has 4 sockets on the winding base. The wire looks a bit thinner than the other extension cable."
},
{
"post_id": "",
"author": "MathWizard",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 22, 2022, 10:45:48 am",
"content": "I've ran a 125V 15A compressor of an outlet right next to the panel, on a 10A breaker. And it would run, and drop the mains voltage 1V or so. And not trip the breakerAnd on the same breaker, if I move to the next plug along, the voltage drops another 1-2V, and by the next plug, another 1-2V. On the far end of the house, still on same breaker, the AC is down from 118V to about 108V, and the breaker does trip then.So yeah like another guy said is it just an increased duration of in-rush current, at the lower voltage ?All the plugs and wires are new in my home, IDK what good contact resistance for wire nuts, and plugs that u just strip and insert the mains wires into, some day I better measure some resistances...., I'd love to know what current the compressor really uses."
},
{
"post_id": "",
"author": "nali",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 22, 2022, 10:59:00 am",
"content": "You say \"fuse\" and \"trips\". Is it a fuse or a breaker? If it's a breaker then earth leakage might be your issue, not overcurrent."
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 22, 2022, 11:09:21 am",
"content": "Voltage drop would make sense. Induction motors tend to have a quasi-constant power characteristic. Reducing the voltage, increases the slip, along with the current, which would explain why the breaker is blowing, with the longer extension lead, which would drop more voltage.Using cable with a higher conductor crossectional area (thicker wires) would help. In the UK and Europe the crossectional area is measured in mm2. The minimum size for a 13A flexible cable is 1.25mm2, but you probably need 1.5mm2or 2.5mm2. I doubt you'll be able to go thicker than that because it might not fit a 13A plug."
},
{
"post_id": "",
"author": "vinlove",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 22, 2022, 11:17:58 am",
"content": "Quote from: nali on February 22, 2022, 10:59:00 amIt is \"fuse\". There is no breaker. Sorry. I didn't make it clear.The 13A fuse in the plug of the 30m long cable keeps blowing, and it had to be replaced.It only happens with the Bosch power washer, when it is powered on."
},
{
"post_id": "",
"author": "CaptDon",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 22, 2022, 02:17:25 pm",
"content": "Are the physical sizes of the fuses identical?? Somehow I get the impression the one on the washer unit is an AGC or MDL size and maybe the one on the cord is a GMA or T size?"
},
{
"post_id": "",
"author": "vinlove",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 22, 2022, 09:27:26 pm",
"content": "Quote from: CaptDon on February 22, 2022, 02:17:25 pmyeah, they are all identical in size. I checked the 13A fuses both in the machine plug and the extension plug, and they are just the same 13A fuses. No difference was noticed.I am wondering also - from the 30m long extension cable, only 10m cable is extended from the base, and the rest of the cable is in wound state. Would wound cable exhibit some peculiar characters in resistance or inductance, causing anomalies?"
},
{
"post_id": "",
"author": "wraper",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "February 22, 2022, 09:38:43 pm",
"content": "Device may pull more current due to the voltage drop on the cable to keep the same power. But it still would not explain why the fuse in the socket where the extension cord is plugged in does not blow."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 22, 2022, 10:25:38 pm",
"content": "British ring main wiring! The BS1363 plugs have max. 13A fuses but the ring main feeding the sockets is typically fused (nowadays with a breaker) at 32A. Its also possible to have radial circuits fused (breakered) at 16A feeding BS1363 sockets, but they are far less common. However both are rated for more than a BS1362 13A fuse, which is *supposed* to provide discrimination such that the distribution panel fuse doesn't blow if an appliance shorts out. Nowadays with circuit breakers in the panel, discrimination is much less reliable and near non-existant on 16A circuits, though admittedly its much less of a PITA to reset a breaker rather than having to replace a fuse cartridge or rewire a fuse."
},
{
"post_id": "",
"author": "Monkeh",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 22, 2022, 10:35:39 pm",
"content": "Quote from: CaptDon on February 22, 2022, 02:17:25 pmErr, no, they're going to be the same.Quote from: wraper on February 22, 2022, 09:38:43 pmBecause there is no fuse in the socket?"
},
{
"post_id": "",
"author": "WatchfulEye",
"author_rank": "Regular Contributor",
"is_op": false,
"timestamp": "February 23, 2022, 01:22:08 am",
"content": "Quote from: wraper on February 22, 2022, 09:38:43 pmThere is quite a wide tolerance on fuses. See the attached specification for BS1362 fuses.It is likely that the one fuse that has survived multiple overloads is towards the lower sensitivity end of the population. I suppose that there is always the possibility of a counterfeit fuse, but by the sounds of things the fuse came with the appliance, so this may be less likely than a fuse bought off amazon or alix."
},
{
"post_id": "",
"author": "wraper",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "February 23, 2022, 09:31:38 am",
"content": "Quote from: Monkeh on February 22, 2022, 10:35:39 pmSeems my memory failed me as I recalled UK sockets were fused too."
},
{
"post_id": "",
"author": "nali",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "February 23, 2022, 09:39:11 am",
"content": "No fuse in the socket, but it's still a bit strange as there will be two fuses inline - one in the equipment's plug and one in the extension lead's plug.I'm wondering if it's a heat conduction thing? The fuse is right at the threshold of its I2t rating but the equipment's plug has more substantial contacts sinking just enough of that heat away that it doesn't blow on the startup surge."
},
{
"post_id": "",
"author": "Ian.M",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 23, 2022, 09:43:30 am",
"content": "Quote from: wraper on February 23, 2022, 09:31:38 amSome are:https://www.tlc-direct.co.uk/Products/MKK2737.htmlThat's a triple socket, that for the purposes of the UK wiring regulations, counts as a single socket because its fused. They used to be popular in hotels etc. to limit disruption due to *IDIOTS*!"
},
{
"post_id": "",
"author": "Terry Bites",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 23, 2022, 09:59:32 am",
"content": "Shoving 10A down a 30m lead is asking for trouble. A 13A socket can't necessarily provide 13A safely, see makers advice.Run your washer from a dedcicated RCD/ MBC outlet.Most extension leads are crap"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 23, 2022, 11:10:49 am",
"content": "Quote from: nali on February 23, 2022, 09:39:11 amAnother possibility is the temperature. If the extension lead is plugged in to an indoor socket, it will be much warmer, than the plug on the pressure washer outside.Quote from: vinlove on February 22, 2022, 09:27:26 pmTo answer the question: no. There won't be a significant difference in inductance, because both the live and neutral wires are in parallel, so the fields generated by the current will cancel. The resistance won't change, as long as the temperature rise isn't big enough to significantly affect it. The reason why it's considered a bad idea to use an extension lead, without fully unwinding it is because the heat can't escape as easily and there's an increased risk of the cable overheating. The temperature rise won't affect the resistance much, but it can be enough to melt the insulation, cause a short circuit and fire."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 23, 2022, 11:28:42 am",
"content": "Induction motors may draw more current when the voltage drops. As an additional effect the motor may not even start proper. Especially compressors have this problem with a long extension cord."
},
{
"post_id": "",
"author": "Monkeh",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 23, 2022, 12:33:03 pm",
"content": "Quote from: Terry Bites on February 23, 2022, 09:59:32 amThen it's not BS1363 compliant and can't be on the market. Stop buying garbage from the poundshop.Quote from: vinlove on February 22, 2022, 09:27:26 pmDon't do that. If you don't need the 30m, just don't use it."
},
{
"post_id": "",
"author": "vinlove",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 23, 2022, 05:15:37 pm",
"content": "Quote from: Ian.M on February 22, 2022, 10:25:38 pmyes, I seem seeing it nowwith some parts to delve into more. The most wall mains sockets in UK residential properties are rated at 32A I think especially for the electric cookers, storage heaters and even washing machines. So they will never blow fuses. They don't even have fuses. They can trip the breaker when installed with the breakers."
},
{
"post_id": "",
"author": "bingo600",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 23, 2022, 06:09:25 pm",
"content": "I have a 25m rool/spool of 230v extension cable.When using with high power utils (1000+ Watt) - I always make sure to unrool all of it.Was once told about possible inductive kickback, if not doing that.I'm no EE or Electrician , but i can run my devices wo. fuse blowing (10A).I think 1800W is the max i have loaded it with."
},
{
"post_id": "",
"author": "vinlove",
"author_rank": "Frequent Contributor",
"is_op": true,
"timestamp": "February 23, 2022, 11:23:08 pm",
"content": "Quote from: bingo600 on February 23, 2022, 06:09:25 pmYes, I was suspicious of this effect of the rolled cable inductance play up when used with high current device pulling lots of currents through it.I was not sure how it affects, and why in theory."
},
{
"post_id": "",
"author": "themadhippy",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 24, 2022, 12:26:10 am",
"content": "QuoteRing finals are slowly going out of favor with A2 (4mm cable and 32A breaker )and A3 (2.5mm 20A) becoming more popular.A3 especially so for low demand areas like bedroom and living area sockets ,and keeping the ring for kitchens with its higher demand also no need to buy a drum of 4mm.QuoteA standard BS1363 double socket to is only designed for maximum load of 20A"
},
{
"post_id": "",
"author": "Zero999",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "February 24, 2022, 10:54:26 am",
"content": "Quote from: vinlove on February 23, 2022, 11:23:08 pmThe cable should be unwound before using, especially to the full rating, but I repeat:it's got nothing to do with the inductance. As I said before,the currents in the neighbouring conductors flow in opposite directions, thus causing the magnetic fields to cancel each other out. Even if you put the live through one extension lead and the neutral through another (don't do this, it's a bad idea, it's just a thought experiment), so the fields don't cancel, the inductance would have a similar effect at 50 to 60Hz, as the resistance of the cable: a couple of mH inductance will have an impedance of just under an Ohm, similar to the DC resistance. The reason for this is because there's no magnetic core. This is why all transformers and inductors designed to work at mains frequencies have magnetic cores. Also note that inductance doesn't result an any power dissipation.The reason for unwinding the cable ispurely thermal. A tightly wound coil concentrates the power dissipated due to I2R losses in the cable, into a small space. The cable in the middle of the coil, doesn't have air circulating around it to provide convective cooling and any radiated heat is absorbed by a neighbouring turns, causing them to heat up more. When the cable is unwound, the heat can escape more easily due to better air circulation and the heat is able to radiate out into space more easily.The bottom line is, a tightly coiled cable will heat much more, than an unwound cable, given everything else (current, length, conductor size) being equal. The temperature rating of the insulation will be exceeded, if it's not designed to work at full power, when coiled up, which is the case for all extension leads made.Suppose the total resistance of the cable is 1 Ohm* and the current is 12A, P = I2R, so that's a power dissipation of 144W, more than an old school 60W light bulb and a bit more than a slow cooker. Imagine the difference in temperature rise, when that heat is concentrated in a small area, compared to spread out over a large one.*Based on 60m (the total length of the live + neutral in a 30m run) of 1.25mm2cable rounded up, given it's specified at 20oC and the cable will get heat up.http://www.farnell.com/datasheets/1805062.pdf"
}
] |
2025-10-17T17:14:25.081207
| 32
|
electronics
|
beginners
| true
|
https://www.eevblog.com/forum/beginners/30v-10a-bench-supply-schematic-is-it-any-good/
|
30v 10A bench supply schematic. Is it any good??? - Page 1
|
[
{
"post_id": "",
"author": "FotatoPotato",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 13, 2017, 01:08:54 am",
"content": "Hello everyone,I have been interested in building a bench power supply for a while now and just recently I got a 24v 10A transformer, and I want to put it to use. Because I am new to building power supplies I decided to just look up schematics for power supplies that would meet my requirements. I found this schematic and it looks pretty good. Even though it's only rated at 4A I’m sure that if I just beef up the transistors and power traces/ components then it would be fine for delivering 10A. Let me know if this is a good schematic and if I should build it.ThanksEDIT: I'm looking for 12v @10A for the High current and 30v @ 5A"
},
{
"post_id": "",
"author": "schmitt trigger",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 13, 2017, 01:47:20 am",
"content": "Question yourself: 300 watts output from a 240 VA transformer?Because this is a linear power supply, expect no more than about 170 watts output."
},
{
"post_id": "",
"author": "FotatoPotato",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 13, 2017, 01:59:36 am",
"content": "Sorry, I should have been more specific. Im looking for 12v @ 10A and 30v @ about 5A"
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 13, 2017, 02:04:33 am",
"content": "The schematic is a partially modified Greek kit from at least 13 years ago and Chinese copies are available today. I fixed some of its problems by beefing up many parts and using two output transistors (with emitter resistors) and a 28V/4.3A (120VA) power transformer.When it had a 24V transformer its output voltage could not reach 30V when loaded to 3A, maybe 25VDC.MC34071 opamps in a DIL package are not available anymore but a TLE2141 is available in a DIL package,has the same pin numbers and has the same spec's.For an output of 10A then the BD139 driver transistor might have a heart attack and the opamp driving it might not be powerful enough."
},
{
"post_id": "",
"author": "FotatoPotato",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 13, 2017, 02:10:15 am",
"content": "Would replacing the Drive and Power transistors with a high power Mosfet and adding a mosfet gate driver Ic help with achieving a 10A output?"
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 13, 2017, 02:42:17 am",
"content": "A Mosfet will produce exactly the same heat as a power transistor. But its gate-source voltage is high which will reduce the output voltage of the supply."
},
{
"post_id": "",
"author": "FotatoPotato",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 13, 2017, 02:49:53 am",
"content": "Ah, Ok so pretty much no difference to efficiency and power output between a Mosfet and a power trannie. Would It make more sense to build a Buck-boost converter and feed it 15v @20A so that I can get a higher efficiency? I get the 15v @ 20A from the transformer because it can be configured to output 12v @ 20A or 24v @10A, the 15v is what I get after it goes through a full bridge rectifier and filter capacitor."
},
{
"post_id": "",
"author": "Cliff Matthews",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "November 13, 2017, 03:45:48 am",
"content": "Quote from: Audioguru on November 13, 2017, 02:04:33 amThere's always these cheap helpers (SOIC-8 to DIP-8)https://www.sparkfun.com/products/13655Perhaps the OP hasn't seen this one (using 2 vintage DIL's to control TIP142's)http://www.ve2ums.ca/chasse/Serge/Atelier/Projets/Membres/VE2EMM/alimentation_ang.htm"
},
{
"post_id": "",
"author": "FotatoPotato",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 13, 2017, 03:58:26 am",
"content": "The PSU you linked is a great help and I really appreciate it, I might actually make it because it meets my needs and the components aren't too expensive. Do you think it would be possible to replace the TIP142 NPN Darlington BJT with a N-channel Mosfet for better efficiency?Thanks!"
},
{
"post_id": "",
"author": "Cliff Matthews",
"author_rank": "Unknown",
"is_op": false,
"timestamp": "November 13, 2017, 12:09:36 pm",
"content": "Quote from: FotatoPotato on November 13, 2017, 03:58:26 amhttp://home.earthlink.net/~schultdw/psupply/"
},
{
"post_id": "",
"author": "FotatoPotato",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 13, 2017, 03:24:23 pm",
"content": "Again, another SUPER useful resource, Thanks so much"
},
{
"post_id": "",
"author": "dmills",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 13, 2017, 03:25:25 pm",
"content": "Your 12V @ 10A is actually by far the nastier requirement for a simple linear supply capable of 30V at any current at all.The reason is that for ANY simple linear supply the power dissipated in the pass transistor is (input voltage - output voltage) * current, essentially independent of the pass device technology.For a simple minded linear like your are trying for the input voltage must be greater then 30V (So that you can get 30V at the output), which means that at 12V @ 10A you are dissipating at least 30 - 12 = 18V * 10A = 180W, and it only gets worse as the output voltage drops.The '3055 lacks the safe operating area to do this at temperature, quite apart from being the '741 of the power transistor world (Old and crap, and beloved of a certain generation of hobbiest), I would be looking at a dozen of the things to handle this, and would almost certainly use something else in practise.If you wanted such a supply to supply say 1V @ 10A, you would have at least 290W being dissipated in the pass bank.Yea there is a reason everyone gets clever to a greater or lesser extent when building high current variable output power supplies.One nice trick for example is to use a transformer having a couple of secondary windings and have a 'range' switch which changes the connections from parallel to series as the voltage is turned up.If for example you had such a thing putting out say 18V in parallel mode and 36V in series mode (quite reasonable) then @ 12V, 10A your pass device is now only dropping (18 - 12) * 10A = 60W, a third of the case for the simple minded design.The ultimate expression of this idea is a switched mode preregulator setup to maintain the input to the linear regulator at say a volt above its output, which is what most designers these days seek to do, it trades complexity for a MASSIVE reduction in heat, and components are cheaper then heatsinks.Regards, Dan."
},
{
"post_id": "",
"author": "FotatoPotato",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 13, 2017, 08:21:59 pm",
"content": "I like the points you bring up and I never thought about the fact that I would be dissipating almost 300W of heat stepping down 30V to 12v @10A. I do however think the design will be fine because I can think of only an EXTREELMY small amount of projects where I would actually need 12v @ 10A. I just want that power as a possibility so that if I need to supply something for maybe 30 seconds to a minute with such a large amount of current then I Could. I have played around with building a SMPS but I never got anywhere and it eventually proved to be too complicated for my beginner skills (or lack there of). For now I’ll probably just stick to the more simple linear design."
},
{
"post_id": "",
"author": "dmills",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 14, 2017, 12:07:34 am",
"content": "There is not actually all that much in hobby electronics that needs anything like that much current, personally I would build a supply capable of say 20- 25V @ 1 amp and see if you ever need more (20 or so V chosen to allow a 12-0-12 transformer secondary).This will suffice for most of the little micro sort of projects, and if you were to build a dual output one would also cover most audio projects (+-15V is common there).This is a decidedly easier project in all sorts of ways, and in all probability by the time you really need more then that you will have the skills to cope with building something clever.I have **MUCH** bigger power supplies in the lab, I nearly never use them.regards, Dan."
},
{
"post_id": "",
"author": "FotatoPotato",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 14, 2017, 04:17:12 am",
"content": "That is ture, I have only had a handfull of times when I ever needed more than 5A, mostly with 100W LED's and peltier modules, I'll still build this supply so that it is \"capable\" of delivering more than 5A but I'll probably never use more than 3A. And like you said, by the time I need more than 10A, I'll have the know-how to build a proper switchmode supply that can handle that kind of power."
},
{
"post_id": "",
"author": "ogden",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 14, 2017, 09:30:36 pm",
"content": "Quote from: FotatoPotato on November 14, 2017, 04:17:12 amExactly. When it's about higher power than my small lab supply can do, I just bring out my old 400W desktop PC power supply (and some fuses too). There's quite a lot of information around about using such for loads that are not PC. You can even slightly adjust voltage up or down with simple tweak:http://electronics.pl7.de/power-supplies/converting-computer-power-supplies-psu-to-stabilized-13-8-v-dc-20-a/When you need higher voltage @ high power - just buy it. Today for ~30$ you can get quite decent 24V 20A \"brick\". If you need variable voltage and/or current regulation - add DPS5015 (Dave recently blew such up) and you are quite covered. Rather than having 300W linear lab supply \"beast\" on the table, I put my projects there."
},
{
"post_id": "",
"author": "FotatoPotato",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 14, 2017, 10:53:29 pm",
"content": "I have wanted to learn how to build a completer SMPS, not just a large step down transformer combined with a Buck-boost converter, but a true SMPS that converts the 110v AC directly to my desired output. The only thing keeping me away is the complexity and fact that I would be dealing with 110V AC and somewhere around 230V DC, so if I make one mistake then there goes my face, my room and my circuit breakers. And I'm not too keen on having something like that happening. Maybe one day I'll make a schematic and post it here and have people tell me if I made a bomb or a functional power supply."
},
{
"post_id": "",
"author": "ogden",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 15, 2017, 01:34:19 am",
"content": "Quote from: FotatoPotato on November 14, 2017, 10:53:29 pmYou don't build soldering iron and multimeter, right? Or did you? - Then why do you need to build supply? SMPS design is very complex stuff, only knowledge you can learn while designing SPMS is that you shall not design SMPS, especially while you are beginner. Better build something that is really worth your time and resources."
},
{
"post_id": "",
"author": "FotatoPotato",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 15, 2017, 02:11:50 am",
"content": "Definitely, trying to design one now would be a waste of time, there are many other more useful things that I could work on that would teach me some really useful stuff."
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 15, 2017, 05:19:13 am",
"content": "A TIP142 darlington has a maximum base-emitter voltage loss of 3.5V at 10A. Many Mosfets have a 10V gate-source voltage loss at 10A.So if you use Mosfets then the maximum output voltage is 6.5V less, unless you are lucky enough to find very sensitive Mosfets that have a loss of only 4.5V."
},
{
"post_id": "",
"author": "dmills",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 15, 2017, 04:29:00 pm",
"content": "Yea but producing an isolated gate drive voltage 12V or so above the source terminal is not exactly rocket science....Point still stands that a linear passbank will be horrible efficiency wise a lot of the time, and not just when it is up against the input rail (Which is actually best case).Regards, Dan."
},
{
"post_id": "",
"author": "rob77",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 15, 2017, 05:13:30 pm",
"content": "Quote from: Audioguru on November 15, 2017, 05:19:13 amthere is no such a thing as \"gate-source voltage loss\" , so please don't spread BS.you need a voltage at least Vgs above source's potential to controll the N-chan mosfet. but that has nothing to do with the output voltge drop on the mosfet you can still have a voltage drop Vds of few millivolts while Vgs at 12V! the gate is isolated and you can think of a N mosfet as a variable resistor which needs to be controlled by a voltage higher than the voltage on the source pin. the source pin is usually the output of a PSU so you need higher gate voltage than the output. you can easily solve this by a small dc-dc converter (e.g. MC34063) providing the needed higher voltage for the control circuit of the mosfet and clamping the Vgs with a zener."
},
{
"post_id": "",
"author": "ogden",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 16, 2017, 02:56:59 am",
"content": "Quote from: rob77 on November 15, 2017, 05:13:30 pmNow explain please - supply voltage coming into N-FET linear regulator is 30V and it is only voltage rail of the supply. To open gate, 12V voltageabovesource needed which would be at 29.99V considering few mV drop as you say. But hey - we have single rail which is 30V. How do you open N-mos? IMHO in this case gate shall receive 29.99+12V above groundOr am I missing something here? Ok. Didnt come to hang yourself. In short: introducing switching crap intoregulator chainlike MC34063 and clamping(!) Vgs of N-MOSlinear regulatorwith zeneris worst crime which can be done tolinear lab supply."
},
{
"post_id": "",
"author": "rob77",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 17, 2017, 12:03:40 am",
"content": "Quote from: ogden on November 16, 2017, 02:56:59 ami don't see how a zener used to protect the gate of as mosfet is a crimeand a low current switcher can be easily filtered down to virtually no noise , so i can't see a crime there either.but after your last post i'm pretty sure you have a major gap in understanding of a mosfet as a series pass element... the voltage at the gate is NOT DIRECTLY RELATED to the output voltage , it's not like a NPN emiter follower. with a mosfet you control the resistance of the drain-source path by changing the gate voltage . if the threshold voltage of the mosfet is for example 5V and saturation is at 10V Vgs then you control the whole output range (for example 0 to 30V) of the PSU with that 5V swing (5 to 10V) at the gate."
},
{
"post_id": "",
"author": "dmills",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 17, 2017, 02:12:26 pm",
"content": "The low noise, simple way to get that extra rail is usually to just do a voltage doubler off the main transformer secondary, current is pretty negligible, so the caps can be small.Small isolated switchers can work, but why bother when you can get something usable with a couple of diodes and caps?It has to be said, that I have personally never really seen the virtues of mosfets in this application, the limiting factor if usually more Safe Operating Area then saturated switch efficiency, and jellybean BJTs usually have much better SOA then modern jellybean power mosfets for the simple reason that power mosfets are usually designed as switching devices (There are exceptions mainly aimed at audio, but they are less common then they were).BJTs also usually parallel more easily then mosfets in practise because they do not have that annoying variation in threshold voltage to the same extent so simple emitter resistors are sufficient to get reasonable current sharing out of the things.Regards, Dan."
},
{
"post_id": "",
"author": "Audioguru",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 17, 2017, 05:00:41 pm",
"content": "The original supply was linear, not switching and used emitter-follower 2N3055 output transistors that needed a base voltage of 31.5V max to produce an output of 30.0V at 4A. The question was if a Mosfet would increase efficiency. I replied that the 10V gate-source voltage loss (of a source-follower) would require a minimum gate voltage of 40V then the opamp driving it would need a very high supply voltage that might destroy it. Even a logic level Mosfet would produce a gate-source voltage loss of 4.5V and would push the opamp to its maximum allowed supply voltage limits and maybe destroy the opamp when the load current is low then the transformer voltage is a little higher than its spec."
},
{
"post_id": "",
"author": "Kleinstein",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 17, 2017, 05:38:32 pm",
"content": "Using MOSFETs can reduce the voltage lost in the high current path, but as a source follower it needs an extra higher supply voltage. MOSFETs also have difficulties having them in parallel. There are cases where MOSFETs are a good idea, but there are also cases where they are not.The source follower has another problem: with BJTs the current gain tends to go down at high current. This tends to limit the peak current on a short. With MOSFETs the trans-conductance usually is going up with high current. So peak currents can be rather high. Related to this MOSFET speed also depends a lot on the current: at higher currents they a rather fast, but at low currents they are slow. This can make the design of the regulator more difficult. So often one needs a relatively high bias current to avoid the slow range.The circuit with the power stage as an emitter follower is usually chosen to have a low output impedance and this way allow for a smaller output capacitor and simpler regulator. A source follower (especially with those FETs with a good FBSOA) tends to have a higher output impedance than the emitter follower and this way might not work well in the similar simple circuit. It might take a rather high bias current to make it acceptable."
},
{
"post_id": "",
"author": "ogden",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 18, 2017, 07:49:47 pm",
"content": "Quote from: rob77 on November 17, 2017, 12:03:40 amProtection is not a crime but assumption that mosfet gate voltage can be exceeded inlinear supplyis sign that you do not understand how linear supplies/regulators work. Basically you accused Audioguru of spreading BS w/o proper understanding what actually he is talking about.QuoteWell well. Whole essence of linear supplies and big, heavy mains AC transformers used is to avoid switching noise, bring regulation into low, AC mains 50/60hz frequency domain. If noise can be easily filtered in the regulation circuit, then it can be easily filtered in the power circuit as well - using much smaller inductors than that big heavy transformer. Think about it. Do you even know what is inductor parasitic capacitance and how it affects ability of filter to do actual filtering? Of course it is crime to introduce switching regulator intopure linear supplyunless it is not a part of output regulation.QuoteNo a lot of understanding is actually required to comprehend that MOSFET in linear supply is not used as a switch. Power transistors in linearregulatorsare never widely/fully open because there always shall be some voltage headroom forregulation- in case mains (input) voltage drop. So your \"voltage drop Vds of few millivolts\" when we talk about linear regulator is BS instead."
},
{
"post_id": "",
"author": "FotatoPotato",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 19, 2017, 06:08:55 am",
"content": "So I just finished building the 0-20v 0-10A linear power supply. Everything works flawlessly and it is almost perfect. If you look at the schematic that I linked you can see that the main transistor is a TIP142 Darlington BJT. The original schematic is only rated for 1A but by adding 4 of them in parallel you can obtain a 10A output. So I did that, the only problem is that only 2 of the BJT's work at any given time. Even weirder is that its random. If you look at a pic of the PSU you can see that they are in groups of 2 (2 on the left and 2 on the right) and randomly only one of those pairs of 2 will work. They are all linked together identically and all their bases are connected as well.So I have no idea why this is happening, maybe you do. If you have any advice on changes to make for all 4 BJT's to work please let me know!"
},
{
"post_id": "",
"author": "ogden",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 19, 2017, 09:09:00 am",
"content": "Quote from: FotatoPotato on November 19, 2017, 06:08:55 amFor 2 or more transistors to work in parallel - they shall be identical, but usually they are not. To have better chances of equalizing current between transistors, you shall add small value (0.2 to 0.5 ohm resistor) to emitter of each transistor as shown in article below. Make sure you calculate worst case dissipation and size those resistors accordingly. IMO each transistor shall have it's own base resistor as well (or maybe not). Try just emitter/ballast resistors first:Article:https://www.allaboutcircuits.com/textbook/semiconductors/chpt-4/bjt-quirks/"
},
{
"post_id": "",
"author": "Twoflower",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 19, 2017, 09:53:41 am",
"content": "Make sure you don't exceed the 25mA the VZpin of the 723 can provide. The TIP142 states for the ON-Characteristics IB= 10mA or even 50mA depending on the IC. That's per transistor not for the the four you have."
},
{
"post_id": "",
"author": "FotatoPotato",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 19, 2017, 05:52:58 pm",
"content": "Would something like this work to balance the current between all four transistors? And I do have a 220resistor on the output signal to limit the current, is that ennough or should it be lower?The 5th transistor is a 2N3904 if you couldnt read it (sorry the schematic immage is a bit blurry)"
},
{
"post_id": "",
"author": "ogden",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 20, 2017, 05:34:32 am",
"content": "What exactly 2n3904 transistor is doing there?! Please explain your intention.This 4-transistor power stage operates as emitter follower, no any additional trickery/transisors needed - connect bases of power transistors together, add individual ballast resistor to emitter ofeachtransistor.220Ohm is fine. For starters. The higher value resistors - the better balancing of the power, but higher dissipation/losses. You can use even smaller ballast valuesiftransistors are well matched, but only measurements will tell. Precisely measure resistance and voltage drop on each ballast to estimate current flowing, share your results"
},
{
"post_id": "",
"author": "FotatoPotato",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 22, 2017, 10:31:26 pm",
"content": "OK, so I added a 0.22resistor to the emitter of each transistor to the supply rail. This seems like it has worked to an extent because when I put a large load on the supply, all 4 transistors begin to get hot which to me indicates that all 4 of them are working. This is all fine and well but there is one problem. On larger loads over 1A one of the pairs of 2 transistors still gets WAY too hot. They are hitting 180c at 4A of current draw while the others are sitting at about 65c. I know they should get hot but not that hot! Is this just a case of crappy thermal pads or is something else wrong here?Also it seems like I’m well within the current limit of the 723's Vz pin because I have pulled 8A so far with all 4 transistors and it hasn’t popped. Let’s hope it stays that way!"
},
{
"post_id": "",
"author": "glarsson",
"author_rank": "Frequent Contributor",
"is_op": false,
"timestamp": "November 22, 2017, 10:37:08 pm",
"content": "Measure the voltage drop over each 0.22 ohm resistor. If the transistors share the load equally the voltages should be close. If the voltages are close (i.e. same current, same voltage drop over the transistor, same power dissipation in the transistors) then check if there are differences in cooling, e.g. thermal pads, paste, etc."
},
{
"post_id": "",
"author": "FotatoPotato",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 23, 2017, 02:24:24 am",
"content": "Huh, this doesn’t seem right.... when I pull 500mA at 20V there is a different drop across each resistor. On the first transistor there is a drop of 60mv with a resistance of 0.226, on the second transistor there is a drop of 7mv with a resistance of 0.226again, on the third transistor there is a drop of 3mv with a resistance of 0.227, again, and on the final transistor there is a drop of 27mv with a resistance of 0.229..... I don’t think that is what is supposed to happen. Any advice?"
},
{
"post_id": "",
"author": "ogden",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 23, 2017, 10:51:16 pm",
"content": "Quote from: FotatoPotato on November 23, 2017, 02:24:24 amPerhaps some or all power transistors are already damaged because you said that transistors (their cases?) approached 180oC temp, but at 150oCjunction tempmanufacturer says they are basically dead. I would never let transistors to approach more than 90oC or so.I would derate/downgrade my power supply power plans, leave two most similar transistors and debug circuit with just two, obviously without overcooking them."
},
{
"post_id": "",
"author": "FotatoPotato",
"author_rank": "Regular Contributor",
"is_op": true,
"timestamp": "November 23, 2017, 11:18:00 pm",
"content": "After some more testing I have concluded that it was shitty thermal padsI took them off and replaced it with some nice thermal paste, now all 4 transistors sit comfortably at 50c while pulling 6.5A at 13v. Welp, problem solved!It also seems like the 25W 0.22resistos that I'm using are a bit overkill as they dont even get mildly warm under a heavy load."
},
{
"post_id": "",
"author": "ogden",
"author_rank": "Super Contributor",
"is_op": false,
"timestamp": "November 24, 2017, 07:24:50 am",
"content": "Quote from: FotatoPotato on November 23, 2017, 11:18:00 pmIt is. You really shall use Ohms law *before* you pick resistors.Power_dissipated=Current*Current*Resistance"
}
] |
2025-10-17T18:44:11.130971
| 39
|
electronics
|
beginners
| true
|
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