Building an ESR meter, some help and someone to check my PCB layout

[garry7263]

I decided to build an ESR meter. I wanted a hybrid that didn't use 4 AA batteries and uses a 9 volt so there would not be a voltage drop and need constant adjusting. This is the original schematic and board layout.

[garry7263]

Re: Building an ESR meter, some help and someone to check my PCB layout

Schematic

[garry7263]

Re: Building an ESR meter, some help and someone to check my PCB layout

Using the power supply off of this schematic

[garry7263]

Re: Building an ESR meter, some help and someone to check my PCB layout

This is the circuit, and the PCB minus a dpdt switch and LED to show power on and to turn it on.

[garry7263]

Re: Building an ESR meter, some help and someone to check my PCB layout

Question about the meter to be used. The original schematic calls for a 50uA meter but all I can find is a 200uA. In line with the potentiometer is a 10k resistor. Should I reduce that to maybe 1k, or remove it all together to get full deflection from the meter?

If anyone can double check my PCB layout and make sure I have it layed out right I would appreciate the help.

Thanks

[barry wilkins]

Re: Building an ESR meter, some help and someone to check my PCB layout

I built this circuit over a year ago ,if you dont use a 50uA meter it will not work because of sensitivity , I had to make a few mods the circuit can drift with temperature.
It does show caps with poor ESR from 100uF upwards ,below this value the reactance of the cap overrides the readings.

Barry Wilkins

[Mad_Professor]

Re: Building an ESR meter, some help and someone to check my PCB layout

I want to build something like this, but my knowledge of designing electronics is very limited.

[redwire]

Re: Building an ESR meter, some help and someone to check my PCB layout

Just a note, I feel this ESR tester is for older radio gear and hard to discern many failing caps in SMPS applications. It's rated 90% meter deflection for 1 ohm... I think this is the original design, the PCB files are here too.

I built a few simple ESR meters and did not have great results. I took my bucket of dead electrolytics and retested them and for most ESR meter circuits, their problem is resolution, i.e. the meter needle moves a hair between 0.01 and 0.2ohm and I find that is essential to diagnose a weak or dud cap. There's other threads here about building a more sensitive unit.

If you would like feedback on the PCB layout, I would fatten the traces to 35-100 thou as space permits, for anything leading in/out around the 10 ohm resistors and the ground traces. Copper is free on a PCB. But if you look at the original breadboarded ESR meter, it's not that critical. You have the wrong value for R10, it should be 25K not 24R. A 78L05 is enough to power this and a reverse-battery protection diode is good to include. I don't see a need for the massive 0.47uF/400V series cap- if you are testing with live DC present, and reverse the leads by accident there will be smoke, so I wouldn't do it.

This is an interesting source: ESR Meter Repository
Another popular ESR meter (Ludens) but it didn't perform unless modified, and I never quite finished the mods...

[garry7263]

Re: Building an ESR meter, some help and someone to check my PCB layout

Thank you for your input. I redrew the board layout and thickened the traces to .032. I rerouted a few things and tightened them up. I did leave the one trace that cuts through pins 6-7 at .024 for a tad more clearance, but still thicker than the original .016. The value for the one resistor should have been 24k, the original calls for 25k but that shouldn't be that critical. If it really makes a difference then I will have to run a 1k in series to make up the difference as the 24k was all I could find.

[garry7263]

Re: Building an ESR meter, some help and someone to check my PCB layout

I believe the large cap is there to soak up the power just in case you accidentally test a charged capacitor, though that cap would be discharged through the resistor. I dont really plan on testing a charged cap to begin with.

I need this mostly to test electrolytic caps on a power supply, and maybe to help troubleshoot some other boards. If something is questionable, I would just replace it. Just not wanting to unsolder every component to test it. I don't have a scope. Go figure, the one thing my father never owned was a scope and he had worked as a electrical technician all his life for GE, and Eastman Kodak.

[Kiriakos GR]

Re: Building an ESR meter, some help and someone to check my PCB layout

Go figure, the one thing my father never owned was a scope and he had worked as a electrical technician all his life for GE, and Eastman Kodak.

In this case it is time for the son to do the big step ahead.

[garry7263]

Re: Building an ESR meter, some help and someone to check my PCB layout

Don't know if I can afford to spend for a scope being out of work at the moment but I have been contemplating it when I get some cash flow. I have some PA amplifiers and other audio gear that needs some attention.

[redwire]

Re: Building an ESR meter, some help and someone to check my PCB layout

That pcb looks much better. If you are home etching the pcb, a jumper instead of the trace between pins 6-7 might be easier.
I find the zero-potentiometer is usually adjusted each time you use the meter, to null out test lead resistance, so it might be panel-mounted.

If you use Schottky meter-rectifier diodes, that helps the low-end sensitivity quite a bit (1.4V drop vs 0.6V). Use say 1N5817,18,19 instead of 1N4148's. They have fatter leads.

[budm]

Re: Building an ESR meter, some help and someone to check my PCB layout

You can add an Emitter bypass cap in parallel with R12 (for the Amplifier Transistor T1) to get more gain, cap can be 0.47uf 25~50V Polyester type.
This is whatI built using 555:
http://s807.photobucket.com/user/bud...83297498167691

https://www.badcaps.net/forum/showth...highlight=acer

[garry7263]

Re: Building an ESR meter, some help and someone to check my PCB layout

Could I solder the cap to the back? I can leave the leads a little bit longer on R12to solder to. Then possibly change values to adjust?

I could order a 50uA meter later if I really needed to.

[ben7]

Re: Building an ESR meter, some help and someone to check my PCB layout

I might make something like this, but instead have an arduino monitor the rectified voltage, and display it on a screen. This way I will easily be able to see the slight differences in the ESR.

[Mad_Professor]

Re: Building an ESR meter, some help and someone to check my PCB layout

I might make something like this, but instead have an arduino monitor the rectified voltage, and display it on a screen. This way I will easily be able to see the slight differences in the ESR.

Hey, I have a spare atmega168 chip laying here, if you do proceed to build something like that, may I have a copy of that schematic and code, please?

[magistertc]

Re: Building an ESR meter, some help and someone to check my PCB layout

@Garry:
I built this a while back, used with a Simpson model 313 meter which has 100uA input. I increased R11 on the transistor to 3R3 and added 0.1uF cap parallel to R12. Substituted a 5K pot (instead of 25K) in series with the meter. Bought the IC, rest of the parts came from my spares bin. Resolution is good above 100uF and good enough down to 2uF to spot a high-ESR cap.

[ben7]

Re: Building an ESR meter, some help and someone to check my PCB layout

Hey, I have a spare atmega168 chip laying here, if you do proceed to build something like that, may I have a copy of that schematic and code, please?

Oh yeah, I'm not planning on making it proprietary

[garry7263]

Re: Building an ESR meter, some help and someone to check my PCB layout

Here is the board layout I will go with. I added a few pads to place a cap parallel to R12 and enlarged all the pads. All the traces are .032 and in place of just one jumper I ran 2 short jumpers to keep it neat and away from the IC (instead of running the trace between 6 & 7).

I will look to see if I have any 1N581x diodes, but this might be something I will have to substitute later, as well as finding a 50uA meter. I may try to find a smaller value variable resistor if I need to. I can play with the 10k resistor as well if needed. I am planning to use the transparency/iron on method to make the PCB, but may end up drawing it by hand if I need to. If I do draw it by hand I will mate a template for the tabs first by putting two layers of plastic tape on a printout of the PCB, then using sharpened brass tubing, make holes for the tabs and peel off the top as a template for the pads and then just draw the traces with sharpie and a ruler. Hope the transparency trick works because it will save a lot of time.

I will get the transparencies this afternoon. I think I can fit 12 on one sheet so I will be able to play with heat a little and practice before making the final.

I guess take plenty of pics and do a build on this thread as well for anyone interested in seeing the progress. Should go really quick once the PCB is etched.