jay diddy 5 transistor esr meter - Page 1
Forum section: electronics / projects

author: pete g
author_rank: Regular Contributor
timestamp: April 30, 2016, 08:21:43 pm
content: hi all, greetings from s. florida. I just completed the 5 transistor esr meter project. need some help to determine if its working right. at turn on the meter goes all the way to the right. when I short the probes the meter does not go all the way to the left. when I scope the output, I get a square wave at 94khz, vpp of 90mv. has anyone else built this project? should the meter go to the right without shorting the output? I posted this in test equiptment by mistake.

author: EntropyWizard
author_rank: Contributor
timestamp: May 01, 2016, 01:43:49 am
content: Something went wrong. The meter should hold near the left origin. You can use the zero adjust on the meter face to calibrate the left mark (open circuit). When you short the terminals, it should move all the way to the right-most mark. You can calibrate the right zero (0 ohms) with the pot that is specified in the circuit.

author: pete g
author_rank: Regular Contributor
timestamp: May 01, 2016, 12:19:13 pm
content: hi, thanks for your response. I made the smd version, I checked the board, looks ok, the problem must be in the meter circuit? any ideas?

author: Bryan
author_rank: Frequent Contributor
timestamp: May 02, 2016, 10:32:58 am
content: Well other than the obvious, shorts, opens, defective components. I assume the PCB design has been tested by others and is correct by the schematic.

author: pete g
author_rank: Regular Contributor
timestamp: May 02, 2016, 12:52:33 pm
content: hi bryan, to answer your question, I don't know. i'am curious as to whether this design has been proven out by someone. from what I can see, it appears the osc signal is always present at the meter, thus the full scale deflection. I verified this by scoping the signal.

author: dannyf
author_rank: Super Contributor
timestamp: May 02, 2016, 08:14:42 pm
content: QuoteWith the probes open, the meter should not move at all, at its left most position.With the probes shorted, the meter should go to the right.

author: pete g
author_rank: Regular Contributor
timestamp: May 02, 2016, 09:45:47 pm
content: hi dannyf, thanks for the info. is it possible for you to trace the osc sig with the probes open and shorted? then I might have a shot at fixing this project. since its smd, knowing exactly whats wrong will spare the pcb. thanks.

author: dannyf
author_rank: Super Contributor
timestamp: May 02, 2016, 10:37:20 pm
content: QuoteI don't know what that means.If I were to debug it, I would make sure that a) the oscillator is working, and b) the dc working points make sense. and go from there.

author: pete g
author_rank: Regular Contributor
timestamp: May 02, 2016, 11:22:09 pm
content: hi danny, in my first post I stated that the osc is indeed working. i'am getting a 94khz square wave at vpp of 90mv, this at the probes. the dc is a rock solid 5v. whats not working is the metering half of the ciecuit. i'am not asking you to debug, only to provide some assistance.

author: pete g
author_rank: Regular Contributor
timestamp: May 02, 2016, 11:27:13 pm
content: as far as the tracing of the signal, I meant a verbal explanation of the sig flo.

author: dannyf
author_rank: Super Contributor
timestamp: May 03, 2016, 12:31:48 am
content: QuoteIt is fairly simple: an oscillator, through a driver stage, drives a resistor in serial with ESR. The signal over the ESR is amplified by a differential amplifier and the rectified portion goes through the meter.It is fairly complicated for what it does.

author: dannyf
author_rank: Super Contributor
timestamp: May 03, 2016, 12:51:53 am
content: QuoteSo the oscillator + the driver are working.QuoteYou should establish that the DC working points are correct first. Otherwise, you get nothing to work with.

author: pete g
author_rank: Regular Contributor
timestamp: May 03, 2016, 01:20:58 am
content: hi dannyf, I think I found an error on the picture that shows the parts on the board. there is a resistor marked RB that should be R8 the value on the schematic shows this resistor value as 150 ohms. it should be 1500 ohms. is this correct?

author: dannyf
author_rank: Super Contributor
timestamp: May 03, 2016, 11:59:19 am
content: I don't know what/which schematic you are referring to.If you suspect its value is incorrect, parallel a 150ohm resistor to it and see if it works.

author: pete g
author_rank: Regular Contributor
timestamp: May 03, 2016, 04:51:45 pm
content: false alarm, although the value of that resistor has an effect, its not the problem. I misread the resistor (smd) 1500 is 150 ohm. rats!

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: May 03, 2016, 10:35:39 pm
content: pete g and the group,I know a thing or two about this circuit. I have been away from my a laptop for a few days, but I am back now. I will post some waveforms, which should help with the troubleshooting.Several people have built this circuit successfully.Regards,Jay_Diddy_B

author: dannyf
author_rank: Super Contributor
timestamp: May 04, 2016, 12:22:42 am
content: QuoteI obviously don't know what the problem(s) here are. But the issue with the design is that the rectifier is open loop. As such, if there is too much attenuation of the oscillator signal, the meter reading is quite non responsive - a sharp drop off.the way it is attacked here is to use more gain. A better solution is to get the rectifier into the feedback loop.

author: pete g
author_rank: Regular Contributor
timestamp: May 04, 2016, 01:03:34 am
content: checked some voltages. with the leads open q4 & q5 are conducting. .6 forward bias, collectors at 1/2 b plus (2.5v) if I turn off q4 the meter goes all the way to the left.

author: dannyf
author_rank: Super Contributor
timestamp: May 04, 2016, 02:01:49 am
content: 'checked some voltages. with the leads open q4 & q5 are conducting. .6 forward bias, collectors at 1/2 b plus (2.5v) if I turn off q4 the meter goes all the way to the left.'I think you can benefit greatly by being concise. Without a schematic, no one knows what q4 or q5 is. Telling tour readers what vbe is tells them far less than if you told them what VB is and what ve is....Right now,you are saying a lot without being informative. It helps if it is the other way around. Posting a schematic with the DC working points in it will tell your readers far more than all you have said so far.Hope it helps.

author: pete g
author_rank: Regular Contributor
timestamp: May 04, 2016, 02:28:07 am
content: well the problem is. is that there are no voltages on the schematic. i'am really surprised you don"t remember this project as you were a fairly prolific contributor to the thread. I think the schematic can be had the same way I got it and that is search on this website for the 5 transistor jay diddy b esr meter. I thought that would be fairly obvious.

author: Bryan
author_rank: Frequent Contributor
timestamp: May 04, 2016, 05:58:59 am
content: Quote from: pete g on May 04, 2016, 02:28:07 amYes, but there was a number of revisions and different schematics, PCB designs posted, some tested some not. Which one did YOU use.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: May 04, 2016, 07:53:40 am
content: Hi group,I have had some time to take some measurements in the lab.These measurements were taken from the unit described in this thread:https://www.eevblog.com/forum/projects/5-transistor-esr-meter-design/msg171364/#msg171364The schematic is reproduced here:I have added the dc voltages. These voltages were measured with a Fluke 187.The input terminals were open circuit for all measurements and scope waveforms.WaveformsQ3 collector voltage:This waveform should swing from rail to rail. The average voltage should be approximately half of the supply, 2.5V. The frequency is nominally 100kHz.TP1 WaveformThis waveform should be the voltage on Q3 collector time 3 / (150 +3) = 98mV p-pQ4 Base VoltageThe average voltage should be 5v(10K/(10K +27K) = 1.35VQ4 Collector VoltageQ5 Base VoltageQ5 Base voltage is the same as Q4 Base voltageQ5 CollectorThe voltage on Q5 Collector is the same as the voltage on Q4 collector when the input is open.Q4 Base (AC Coupled)Q4 Collector AC coupledThese waveforms and voltages should help you troubleshoot the circuit.Regards,Jay_Diddy_B

author: dannyf
author_rank: Super Contributor
timestamp: May 04, 2016, 10:24:38 am
content: The driver should output a near 5vpp square wave. So the probe, when open, should show about 90mvpp.The bases of the two amplifiers sit at 1.4v, and their emitters at 0.7v, and their collectors at 2.2v. All vs. Ground.Anything materially different from that suggests troubles.

author: pete g
author_rank: Regular Contributor
timestamp: May 04, 2016, 04:15:23 pm
content: wow!! this is great. my question is, if the signal is getting to the meter with the probes open circuited, what keeps the meter from deflecting?

author: dannyf
author_rank: Super Contributor
timestamp: May 04, 2016, 06:40:17 pm
content: It is a bridge configuration. One arm of the bridge has fixed attenuation and another has its attenuation varying based on the duts ESR.If the proves are open, the same unattenuated signal will show up on the meter - it is not going to move at all.The biggest meter movements come when the difference between attenuation is the biggest - when the probe is shorted.

author: pete g
author_rank: Regular Contributor
timestamp: May 04, 2016, 07:13:23 pm
content: I checked all the voltages on the amps. the voltages are correct. not to sound redundant, but signal at the probes is correct, so it appears everything is correct but I still get full scale deflection at tutn on with the probes open?che pasa?

author: pete g
author_rank: Regular Contributor
timestamp: May 04, 2016, 10:43:34 pm
content: thanks dannyf, I think it makes more sense to me. what should the voltages be when the probes are shorted?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: May 04, 2016, 11:35:37 pm
content: Hi,If the probes are shorted you will have the following conditions:All the DC voltages marked in this schematic will remain the same.TP1 will be ground.There will be no ac voltage on Q4 base and no ac voltage on Q4 collector.Can you tell me what kind of diodes you used for D3 and D4?What kind of meter are you using? Do you have the model number or a link?What do you have in series with the meter?Can you post some photographs of your construction?Regards,Jay_Diddy_B

author: pete g
author_rank: Regular Contributor
timestamp: May 05, 2016, 12:28:39 am
content: hi jay, well, thanks to dannyf, the problem is solved. it seems my 78 year all eyes (good excuse as any) let me down. it cleary shows r11 in the bridge circuit should be 1.5k, not 15k. the esr meter works perfectly. so, thanks are in order. jay, thanks so much for taking the time to help. to all who contributed, thanks again. I'am so happy!!!!!

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: May 05, 2016, 12:43:13 am
content: Hi Pete,That is great news !!It would be great if you can post a picture of your finished meter.Regards,Jay_Diddy_B

author: pete g
author_rank: Regular Contributor
timestamp: May 05, 2016, 12:49:53 am
content: I will post a picture of the finished meter.

author: pete g
author_rank: Regular Contributor
timestamp: May 05, 2016, 08:53:33 pm
content: Here is a picture of my finished esr meter by jay diddy b. Nothing fancy but it works.

author: Bryan
author_rank: Frequent Contributor
timestamp: May 06, 2016, 05:54:18 am
content: Very good job on the artwork for the meter faceplate

author: pete g
author_rank: Regular Contributor
timestamp: May 06, 2016, 11:46:42 am
content: thanks, bryan. actually my wife is responsible for it.

author: Bryan
author_rank: Frequent Contributor
timestamp: May 08, 2016, 09:52:46 am
content: She did a great job. Found this software that can do panel meters.http://www.tonnesoftware.com/meter2.html

author: pgr2002
author_rank: Newbie
timestamp: July 13, 2022, 12:16:06 pm
content: Does anyone know if the circuit can handle 1ma meter instead of 50ua. If so what changes should be done in the circuit to handle 1ma panel meter. What can be the value of R24 which is marked x in the circuit diagram.

author: pgr2002
author_rank: Newbie
timestamp: July 13, 2022, 03:55:07 pm
content: Quote from: Jay_Diddy_B on May 04, 2016, 11:35:37 pmI would like to construct this circuit. But I have 1ma meter panel and 2 analog multimeters. What changes can be done to use this 1ma panel meter in the circuit. Also in the circuit diagram I saw R24 marked x. What is the value of this R24 (range). Will this change with different meters viz. with 50ua what can be the value and with 1ma meter what value to be used.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: July 15, 2022, 11:56:58 am
content: Hi,Sorry for the delay in responding.The use of a 1mA meter has been discussed in the main thread for this project.link:https://www.eevblog.com/forum/projects/5-transistor-esr-meter-design/msg3328450/#msg3328450Regards,Jay_Diddy_B

author: pgr2002
author_rank: Newbie
timestamp: August 09, 2022, 01:03:44 pm
content: Quote from: Jay_Diddy_B on May 05, 2016, 12:43:13 amI am having the same problem just like Mr. pete had. When the circuit is switched on the meter (50ua) needle goes far right and even overshoots. And when the leads are shorted it comes down to 90% of the scale to the left. What can be the problem here. The diodes used by me is 1n4148 and 1n5711

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 09, 2022, 11:47:52 pm
content: Quote from: pgr2002 on August 09, 2022, 01:03:44 pmHave you checked the dc voltages that are given in the schematic?Do you have an oscilloscope? Can you share some waveforms?You can watch this video by W2AEW, that shows the circuit working.Link:Regards,Jay_Diddy_B

author: pgr2002
author_rank: Newbie
timestamp: August 10, 2022, 06:04:07 am
content: I saw the video of the workings. I don't have oscilloscope. I am using the 5v adapter to the circuit. I am getting almost the similar voltages except that it is little more. I don't understand why the meter goes to the far right when switched on and when the probes are shorted it comes back to the left to 10 on a 50 meter scale (50ua meter).

author: pgr2002
author_rank: Newbie
timestamp: August 10, 2022, 02:46:57 pm
content: Well this works fine. The capacitor marked c8 valued at 22n is bad in my circuit. After rechecking all the points I found that this capacitor is open. I didn't have 22n but replaced with 0.01uf and the circuit started to work perfectly. Thank you Sir, This justworks splendid. I just worked in breadboard, shortly I will make a pcb. The only thing is the meter will be kept outside the box, since I have 2 panel meters (50 & 100 ua), the rest will be enclosed including power supply. The original values of caps and resistors will be replaced once I get these from the market. The resistor of 3E (R10) is not available right now, but tested with 2.2E. The rest of parts are as mentioned in the circuit. I checked few capacitors and is giving good results. Thank you once again.

author: thejazzcat
author_rank: Newbie
timestamp: November 24, 2022, 04:19:13 pm
content: Hi,I'm building the tester using my Simpson 260 50uA Meter. But I can get full deflection when shorting the test leads.Attached photos of the oscilloscope readings shared bay Jay_Diddy_B for troubleshooting. I'm not getting a Square Wave on the Collectors of Q4 and Q5. The oscillator freq. is lower in my unit (around 90KHz).Any pointers on how to proceed would be much appreciated.All the best.CE

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 24, 2022, 11:25:26 pm
content: Quote from: thejazzcat on November 24, 2022, 04:19:13 pmthejazzcat and the group,Generally speaking, if the dc voltages are correct, the problem is with one or more of the capacitors.Check the 2.2uF capacitors in the emitters of Q4 and Q5. If you have to use an electrolytic capacitor, you can use a much larger value 47 to 100uF 6.3V or greater.Also check the 10nF and 22nF capacitors.Jay_Diddy_B

author: thejazzcat
author_rank: Newbie
timestamp: November 25, 2022, 04:38:45 pm
content: Thanks Jay_Diddy_B.I was using the wrong caps in place of the 2.2uf. Ended up using a couple of 100uf 25V I had at hand (following your recommendation on electrolytics) and now I'm getting the correct deflection on the meter. R24 value is going to be around 15K ohm.I still need to buy the pot to finish the project.You are so kind to share your knowledge on this forum.Thanks mate.

author: p.larner
author_rank: Frequent Contributor
timestamp: December 25, 2023, 04:30:05 am
content: i used a 1ma meter in one i built,if i remember i changed a few resistors as mentioned in the thread linked but had to power it with about 11v not 5v.