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Old 6th Jan 2011, 7:18 pm   #41
brosskgm
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Default Re: My Homebrew ESR Meter for testing el caps

Do you by chance have a another option for the 680 Ohm array? I have 560 Ohm, 560K, 1K, 10K, arrays. But no 680 Ohm. I have plenty of single ones, just no arrays. Is there a way to use 8 regular 1/4w resistors?

Thanks so much for your help.
Bob
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Old 11th Jan 2011, 1:55 pm   #42
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Default Re: My Homebrew ESR Meter for testing el caps

Quote:
Originally Posted by David G4EBT View Post
............I hope these notes, togehter with those in another post outlining the setting up and troubleshooting, are of help and encouragement to anyone contemplating building this handy and cheaply made little project.
Do you by chance have an updated schematics?
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Old 11th Jan 2011, 9:15 pm   #43
David G4EBT
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Default Re: My Homebrew ESR Meter for testing el caps

Quote:
Originally Posted by brosskgm View Post
Do you by chance have a another option for the 680 Ohm array? I have 560 Ohm, 560K, 1K, 10K, arrays. But no 680 Ohm. I have plenty of single ones, just no arrays. Is there a way to use 8 regular 1/4w resistors?
I take it that you are referring to the excellent veroboard layout by 'Topcap' at post #29 as the PCB layout does in fact use discrete 680R resistors for R2 - R6. (You don't need eight - only five). I hope I'm not poking my nose in, when really, I'm referring to Topcap's layout, but these comments might help:

There's no reason at all that you can't do as was the case in the PCCB layout and use separate resistors, rather than use an array in a common package, assuming that the resistors are physically small enough to sit side by side in 0.1" pitch veroboard. (I've just tried five .25 Watt resistors side by side on veroboard and they sit quite happily).

All that you'd need to do is to ensure that the oututs of the five gates of IC1 - that's pins 4,6,8,10 &12 - each have a 680R resistor connected to them, with the outputs of those five resistors commoned and connected to the track hole that feeds C4, R17, R18 and TP1.

This will of course only make sense if you have the circuit in front of you!

Hope that helps.

Best of luck with the project.

David
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Old 11th Jan 2011, 10:08 pm   #44
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Default Re: My Homebrew ESR Meter for testing el caps

Quote:
Originally Posted by brosskgm View Post
Do you by chance have an updated schematics?
No - the changes I made are very minor and to summarise, were:

1) The fitting of a three-terminal 100mA 5V+ regulator to enable a 9V PP3 to be used in place of four rechargeable batteries. This can clearly be seen on the PCB layout of the modifications at post #36 above. Basically, the switched 9V+ from the battery goes to the input of the regulator, the centre pin is ground, and the output is 5V + regulated.

2) The original circuit by the designer had a front panel 25k pot to adjust the meter to zero (that is full scale deflection) with the test leads shorted, to compensate for the recharageable batteries losing their voltage. By fitting a 5V regulator, once FSD has been adjusted, it shouldn't need adjusting again. Apart from that, several contructors couldn't understand from the original schematic how to connect the wire up the panel pot and meter. For these reaosns I added a pre-set pot to the PCB layout, so all that's now needed is to connect two pins as shown on the updated layout directly to the meter +/-

In that regard, apart from a prest pot rather than a front panel pot being used, the schematic is no different from the original, though the construction is simplfied.

I also explained to to get the meter to read FSD, I had to reduce the value of R17 from 10k to 3k3.

3) I'd fitted an LED to my meter as a warning to show when it was switched on, and several would-be contructors asked how to wire up such an an LED. To make life simple I added an on-board series resistor and two pins to the PCB to enable an LED to be connected to the PCB with two wires and no need for an off-board series resistor.
(If an LED is considered unnecessary, the LED resistor neededn't be fitted to the board, and the LED pins on the board need not be fitted).

4) The 0.47uF 400V cap C7 comes in different styles and sizes - some with axial leads, some radial, so I added an extra pad to enable various sizes to be used. The redundant hole can just be ignored.

5) I moved C1 to a new position on the layout, but the schematic remains as the original.

None of the above will make much sense without being read in conjunction with the layout highlighting these modifications at Post #36 above, and referring to the original schematic. I hope that if that's done, it all makes perfect sense!

Admittedly, though the elements of the circuit aren't complex, it helps in troubleshooting if a scope is to hand, but it's worth stressing that when testing and setting up the device, unless the test leads are shorted out, there will be no deflection on the meter and 0.0mvpp at C2 into the AC amplifier (Q1 etc).

With the test leads shorted, if all is well, it should only be necessary to adjust the 22k pre-set pot on the PCB to zero the meter - zero being the needle right over to the right hand side of the scale. In use, the higher the ESR of a capacitor under test, the further to the left will be the needle, just as with an analogue Ohm-mter.

If the meter doesn't work, it's unlikely to be the transistor or IC that are at fault as they're not especialy delicate. But as the ICs are just a few pence each, it's easy enough to swap one to see if the original is indeed duff.

From my post-bag over the lest few months, it's clear that lots of these little gizmos have been built and are in use, and though it's not a complex project to build or set up, quite a few constructors have had difficulties. Invariably it's been due to either shorted tracks, dry joints, polarity of diodes wrong, wrong value components (by a factor of 10 or 100), or IC not inserted correctly. If poss, test all components such as resistors and caps before insertion to check that their values are correct.

There are now only 8 off-board connections:

meter +/-;
cap test leads;
9V/0V battery (via a switch);
LED.


I hope that these notes, together with earlier troube-shooting notes, are more of a help than a hindrance!

Best of luck,

David
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Old 17th Jan 2011, 11:53 pm   #45
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Default Re: My Homebrew ESR Meter for testing el caps

Thanks for your reply David.

I'm still hoping for a schematics or something to import to eagle that will help.
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Old 20th Mar 2011, 10:10 pm   #46
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Default Re: My Homebrew ESR Meter for testing el caps

I recently came across this design for a very low esr meter:-

http://koti.mbnet.fi/hsahko/elek/kv/esr/index.en.shtml

It seems similar to the Lawrence Glaister design but it's aimed at measuring the esr of psu caps. It uses a 555 timer as the oscillator but this could be replaced by the 74HC14 if desired. Haven't built it myself as I'm moving on to other projects for now.
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Old 3rd Jun 2011, 10:51 am   #47
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Default Re: My Homebrew ESR Meter for testing el caps

Hi all

I've just successfully built one of these using Robs veroboard layout and the specified meter from ESR.
Just to finish it off I would like to print a meter scale, has any body who has constructed one of these managed to design a suitable scale?

I did download some software called Meter Basic but that didn't like my printer and made my head hurt.
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Old 3rd Jun 2011, 9:28 pm   #48
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Default Re: My Homebrew ESR Meter for testing el caps

What sort of scale does it need?

This was made by scanning and editing a protractor.
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I have a variety of scanned ones and also much software.

I can make you one if it's not complicated.
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Old 5th Jun 2011, 5:13 pm   #49
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Default Re: My Homebrew ESR Meter for testing el caps

Thanks for the kind offer Neon, I was rather hoping that another constructer had built one using the same meter as I and they had produced a suitable scale that I could print off and attatch to mine. I will have another play with the software tonight.
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Old 5th Jun 2011, 8:13 pm   #50
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Default Re: My Homebrew ESR Meter for testing el caps

Mike, is this of any use? It was used on a 3'' meter. I have a better resolution file you can have if you PM me with an email address.

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Old 6th Jun 2011, 6:53 am   #51
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Default Re: My Homebrew ESR Meter for testing el caps

Thanks Colin, PM sent
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Old 23rd Jun 2011, 6:38 pm   #52
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Default Re: My Homebrew ESR Meter for testing el caps

Hi Everyone,

I am finally getting around to making one of these for myself, and I am going to use Robs Veroboard layout. While I was at it, I redrew the diagram to include the 5 Volt regulator to make it complete.

I also found a array with 5 of 680 ohm resistors in a 6 pin pack, and so I will need to modify the layout slightly.

I must have had a senior moment, or more like it, a senior couple of days, because the more I looked at the Veroboard layout the more it did not make sense. Some of the pins on the IC did not connect to the right components.

Then it dawned on me, I saw that that Rob had switched a couple of the Op-amps to make the layout simpler. In the original diagram the oscillator used pins 1 and 2, while in Robs layout he used pins 5 and 6.

So I will carry on, also like some of you I could not find a suitable 50uA meter, so I got a 100uA one instead. I have three 50uA meters but they are are big round ones, quite heavy and bulky and would dwarf the project, but I intend to try them in order to compare the difference.
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Old 8th Jul 2011, 2:29 pm   #53
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Default Re: My Homebrew ESR Meter for testing el caps

Hi Everyone,

Attached are a couple of pictures of my attempt to build the ESR meter. I still have to make the meter face plate, but my dexterity with Paint is impeding me somewhat.

I thought I was being very careful concerning the 2N2222 transistor, but it still caught me out. I have a PN2222 type in a TO-92 case, and when I first switched on, I got...Nothing!. After checking all the usual suspects, I looked at the transistor and it appeared to be OK. So rather than messing with the veroboard, I recreated the amp and meter circuit on a breadboard, and again nothing, so I swapped the transistor 180 degrees, and was greeted with the 50uA meter banging up against the FSD stop. Success!

I replaced R17 (10K) with a 5K pot on the veroboard, and it gave FSD on the meter at about half rotation.

For C5 (0.47uF 400V) I used a 250 volt one for the time being, and will change it when I order some more parts.

In checking some of my older caps they all look to be in the good range so far
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Old 8th Jul 2011, 4:00 pm   #54
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Default Re: My Homebrew ESR Meter for testing el caps

That looks neat.
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Old 8th Jul 2011, 5:04 pm   #55
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Default Re: My Homebrew ESR Meter for testing el caps

Wow, nice job. Very neat. Makes mine look like a bird's nest in comparison. Andy.
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Old 3rd Oct 2011, 8:41 am   #56
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Default Re: My Homebrew ESR Meter for testing el caps

Hello All,

The Pontefract & district radio society have also run this ESR meter as a club project
http://www.pdars.com/about/homebrew the link for the project is here:
http://www.g0nqe.co.uk/projects/

There is also free meter scale software available, link here: http://tonnesoftware.com/ although a bit of a learning curve there is also other useful free software there.

I managed to make a nice looking scale for my own and I built the Ludens ESR meter, in an ABS box as I had managed to buy a job lot at a radio rally.

But I think Daves ESR meter looks the business. I wish my carpentry skills were up to it.


Regards to all Peter(GW4ZUA)
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Old 7th Nov 2011, 1:56 pm   #57
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Default Re: My Homebrew ESR Meter for testing el caps

Finally finished mine, same version as David G4EBT, the one designed by VE7IT, but made on Veroboard and with David's addition of a 5V regulator, a few very minor differences to suit components I had, 1N914's instead of 1N4148's as I couldn't find the ones I had, a 2N4401 as Meat Pye in post #10, as the supplier of the 74HC14 and 78L05 didn't have any 2N2222's, as ESR Electronics Ltd were out of stock of the 50μA meter, I tried using a 500μA one I had to hand, the most it would read connected directly to the bridge rectifier was 20% FSD, so I reduced the emitter resistor from 100Ω to 47Ω and put a 0.22μF capacitor across it to get sufficient deflection, whether or not this is the reason for it, but a 10Ω resistor now reads about 80% FSD instead of 50%, but otherwise it all seems to work fine, with 0Ω at FSD and 150Ω just moves the needle a fraction, but I'll probably get hold of the correct meter eventually, the only other addition was a 1N4004 before the 78L05, having very nearly connected the PP3 the wrong way, I checked on the web and found that reversed polarity is about the only way to destroy a 78L05, and mainly caused by doing what I nearly did.
Other than just trying it out on loose caps' I had in the drawer, the only item I had to test was the controller board from my central heating boiler, this was changed last year as the boiler was giving trouble and the service man had left me the old one, from the seven electrolytics on the board the readings were.

2 @ 0Ω
1 @ 5Ω
2 @ 10Ω
1 @ 50Ω
1 @ 100Ω

so it looks like a bit of test equipment than could prove useful, I couldn't say for certain whether the caps' are the cause of the boiler problems, but most of them are suspect, especially the last two which read really bad, its certainly easier than having to unsolder them all for testing.

John
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Old 28th Nov 2011, 10:22 am   #58
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Default Re: My Homebrew ESR Meter for testing el caps

Would a 74HC04 work instead of a 74HC14? Asking as I have one but not the other... might just try and see.

Both are inverters and pin for pin compatible.

The HCU04 part is unbuffered -- it's essentially a pair of MOSFETs. It's an inverter, but it's more like a unity-gain analog inverter -- if the inputs are not square waves, the outputs won't be square waves. I have seen it (and why I have a couple) as it is sometimes used with a crystal in oscillator circuits.

The 74HC14, on the other hand, is a Schmitt trigger inverter. This device WILL square up unsquare inputs but that is it as far as I can see.

72

Dom
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Old 30th Nov 2011, 1:03 am   #59
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Default Re: My Homebrew ESR Meter for testing el caps

Hi Dom, I think you will need the Schmitt trigger version to make it oscillate reliably. Les
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Old 1st Dec 2011, 2:47 pm   #60
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Quote:
Originally Posted by Top Cap View Post
Hi Dom, I think you will need the Schmitt trigger version to make it oscillate reliably. Les
Les, I ended up trying both as was sent a pair of IC in the post... thanks anon... , the other version does work too (sort of). Problem right now is the FSD I replaced R17 with 1K8 and pot is at zero and still get no more than 44uA. I used a 2N2222A. The signals all seem fine. 0.1uF 400V not 0.47uF 400V capacitor but not sure if that would explain it. Doesn't matter is PP3 or SLA powered....

I added a set of terminals for a DVM, will add a DPDT switch too as the DVM has proven useful for low value high voltage caps as the high resistance end is a tad cramped and the DVM on 10uA scale makes it easier to read.

I am thinking a PIC with LCD read out might be an option....

72

Dom
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