YAEM - Yet Another ESR Meter

[prenato]

It's another of those projects you just *have* to build; at least once:) Check it out:

http://paulorenato.com/joomla/index.php?option=com_content&view=article&id=94:building-an-esr-meter&catid=4:projects&Itemid=4

Paulo

[Radio Tech]

I threw one of these together this afternoon. But was a failed attempt.  So have to troubleshoot and see where I goofed at. I am pretty sure I layed the circuit out right. But maybe my choice of caps did not work out. I noticd on his schematic he shows 2 electrolytic caps. But in his picture there are 3.  So maybe I used a ceramic when it should had been an electrolytic.

[Radio Tech]

Found the problem. Stupid me in a hurry.
Jumped pin 3 and 7 instead of 2 and 6. Dang perfboard. lol

[psycho0815]

There is one cap in the schematic between +5V and GND left to the 555. It's drawn as a normal cap but it says 100µ, so i'm guessing that's the third electrolytic. Event though that wasn't the problem. i still thougt i'd point that out.

[Radio Tech]

There is one cap in the schematic between +5V and GND left to the 555. It's drawn as a normal cap but it says 100µ, so i'm guessing that's the third electrolytic. Event though that wasn't the problem. i still thougt i'd point that out.

Yep, got ya.
Anyway I found my problem.  Pin 2 and 6 should be jumped together. When I flipped the board I jumped 3 and 7 by mistake.
Will change those tonight and see if I smoked the chip, I have plenty though.

[psycho0815]

Yep, got ya.
Anyway I found my problem.  Pin 2 and 6 should be jumped together. When I flipped the board I jumped 3 and 7 by mistake.
Will change those tonight and see if I smoked the chip, I have plenty though.

Happens to me all the time. really annoying.

[Radio Tech]

yep, was rushing through it lol.

Anyway, got home and changed the jumper. Connected the scope and got the got the measurements at test point 1 and 2. Test point 3 is another story. I tried 3 different meters and nadda.
I used a "used 100uf cap between the 3904 collector and the 1N4148 diodes. That is where I lose the signal.

[prenato]

Glad you got it working Radio Tech. Regarding my hand-drawn schematic, I wasn't too consistent with the electrolytic symbol as noted. The 100 uF is supposed to be electrolytic (hard to find other types that large:)

Paulo

[Radio Tech]

Glad you got it working Radio Tech. Regarding my hand-drawn schematic, I wasn't too consistent with the electrolytic symbol as noted. The 100 uF is supposed to be electrolytic (hard to find other types that large:)

Paulo

Hey Paulo, Thank you. I enjoyed the build. I will post pics of mine later.  Was just in the shop long enough to correct the problems I created lol. I do happen to have a few odd components around.
Here is a re-draw for you. Open in paint and have fun.


EDIT for capacitor correction

[prenato]

Glad you got it working Radio Tech. Regarding my hand-drawn schematic, I wasn't too consistent with the electrolytic symbol as noted. The 100 uF is supposed to be electrolytic (hard to find other types that large:)

Paulo

Hey Paulo, Thank you. I enjoyed the build. I will post pics of mine later.  Was just in the shop long enough to correct the problems I created lol. I do happen to have a few odd components around.
Here is a re-draw for you. Open in paint and have fun.

Hi radio tech. Great job re-drawing my ugly schematic! Would you allow me to replace my original in the article with your drawing?(with proper attribution to you of course)?

[Radio Tech]

Hi radio tech. Great job re-drawing my ugly schematic!   :-+Would you allow me to replace my original in the article with your drawing?(with proper attribution to you of course)?

First, there is nothing wrong with your hand drawn schematic. It is a thing of beauty!
Second, I would be honored if you used my re-draw.  Maybe add it to your site and not replace yours.
But feel free to use it however you see fit.   

[prenato]

Hi radio tech. Great job re-drawing my ugly schematic!   :-+Would you allow me to replace my original in the article with your drawing?(with proper attribution to you of course)?

First, there is nothing wrong with your hand drawn schematic. It is a thing of beauty!
Second, I would be honored if you used my re-draw.  Maybe add it to your site and not replace yours.
But feel free to use it however you see fit.   

Thanks a lot "Radio tech". I updated the article by adding your excellent drawing. Should be there now:)

[Radio Tech]

Glad to be of service Paulo. I am very honored you used that mate. I really like the design of your tester.

[6502nop]

@paulo

I was doing exactly what RadioTech did (using gEDA), however, my eyes saw the values of the capacitors (C5 and C6 on RT's schematic) as 100 nano, and not 100 micro, as RT has listed. Would you be so kind as to re-check the actual values and let me know for sure? All other components match with what I read.

Also, is there any way you could determine the actual full-scale current of that meter? That'd be helpful to those who may want to use a digital meter. I'm guessing it's probably a 500uA or 1mA movement.

@RadioTech

Shouldn't the cap C5 have the positive terminal toward the collector of Q1 (being that it's always biased through R8 to +5V)?

nop

[Radio Tech]

@RadioTech

Shouldn't the cap C5 have the positive terminal toward the collector of Q1 (being that it's always biased through R8 to +5V)?

nop

Good catch. I will confirm and change the original tonight and re-upload it.

[prenato]

 6502nop,

Good catch! The original (hand-drawn) has the correct values 100nF for C5 and C6. I already corrected the re-draw in the website with a note. Thanks for catching this.

Paulo

[Radio Tech]

Paulo,
Thanks for correcting that. 

[6502nop]

@RT
No worries. I did the same thing in these very forums. One of our Spanish readers pointed out my error.

@prenato
So, both 100nanos, then? Any info on the meter (and transformer part#)?

While I'm here, how 'bout some other things?

--> The values for the 555, according to the online 555 calculator, gives us about a 145KHz output. Looking at my National (TI) datasheet, page 8, figure 6, "Free Running Frequency", the standard (analog) version of the 555 shouldn't be running over 100KHz. The CMOS (TLC or 7555) version can easily do 145KHz, so if you're having problems with this circuit, increase the value of the 470pF to about 680pF. This should give you 100KHz.

--> I think it may be prudent to those following this thread/project for us to "bullseye" that transformer. Just quantifying it as a 2:1 will have folks hooking up some 120V-60V power transformer and not getting anywhere. I don't have, nor can I seem to scrounge, any of the type I'm guessing to use, but I'd like some input from those who have this working:

 - Needs to operate at ~100KHz.
 - Only needs to run at ~10V or so.
 - Doesn't need huge isolation value (50V is plenty).
 - Small ferrite core style is preferred.

With that in mind, a couple of candidates popped up in my searches:

Murata 78604/3C RF/Pulse mode transformer.
Coilcraft WB1015-PCL Wideband RF transformer (the -SML is surface mount).

The Coilcraft site allows for free sample requests, but my browser/settings wouldn't allow me to fill out the form. Maybe some adventurous forum member could do so, try it out, and report back as to how well they work? Note that the Coilcraft is only a 1.5:1 ratio, so you'd have to adjust the output resistor on the 555 accordingly (maybe 220/270R?).

nop

[Radio Tech]

6502nop,
Just so you and everyone knows, the transformer I used was from Radio Shack. I will update this post later with the part number. But I think it is the only audio transformer they sell for under 3 bucks.

Also when I was testing last night the circuit was running at 108 khz.

[prenato]

@6502nop

1) You are right that 100KHz is on the limit of the 555 capabilities. This is why I chose it (it is still specified in the astable operation plots in the datasheet so should be supported). It should not be exceeded though as you pointed out.

2) The meter is just an old one I had on my spare parts bin so I don't have any specs on it unfortunately. A 50 uA or so should be adequate but please experiment/prototype before using. The 10K Ohm Pot in series compensates for the meter sensitivity so it should be possible to use very different values without an issue. If it deflects too much, increase the POT value.

3) I mentioned in the article the transformer I used was exotic so I don't expect anyone to use it (it's used in T1/E1 transmission where most of the spectrum lies from 10KHz to 2MHz so was adequate for 100 KHz) More generically, I agree with your list of recommendations. Some Audio transformers might work but the bandwidth is typically around 20KHz so wouldn't be my first choice. Something out of a switching power supply that usually operate at frequencies closer to 100KHz would seem a better choice.

Paulo

[prenato]

By the way, in case you want/can buy the transformer it's Pulse Engineering PE-65351:

http://ww2.pulseeng.com/products/datasheets/T608.pdf

There are a bunch of other transformers in there that are also T1/E1 transformers so should be adequate as well (with 2:1 turns ratio).

Paulo

[Radio Tech]

By the way, in case you want/can buy the transformer it's Pulse Engineering PE-65351:

http://ww2.pulseeng.com/products/datasheets/T608.pdf

There are a bunch of other transformers in there that are also T1/E1 transformers so should be adequate as well (with 2:1 turns ratio).

Paulo

Thanks, found them on ebay. 10 bucks for 2 and free shipping.  But takes a month to get here:(
Guess we can roll our own

[6502nop]

@RT
Just so you and everyone knows, the transformer I used was from Radio Shack. I will update this post later with the part number. But I think it is the only audio transformer they sell for under 3 bucks.
Also when I was testing last night the circuit was running at 108 khz.

If that's the 1000ohm:8ohm xfrmr, then I've got a couple of those lying around. What amazes me is that it's working. It's specified as a 20:1 ratio, and one helluva dropout above 3KHz. I'll give one a try and see what happens.

@PR
By the way, in case you want/can buy the transformer it's Pulse Engineering PE-65351:

@RT
Thanks, found them on ebay. 10 bucks for 2 and free shipping.  But takes a month to get here:(
Guess we can roll our own

I've already zoomed in on the picture and D/Ld the datasheet. The Murata 76804/3Cs are only $1.57 at Mouser (in stock - and they're perfect for breadboards!). Apparently, Coilcraft only ship samples to high-end developers working for companies that tend to order in giant quantities. Meh.

I also realized that the Murata 1:1CT xformers could be used, just use the full input for the primary, and use the CT on the secondary - it'll work out to 2:1. So, this puts the 76815/3C on the list, too.

So, with all that in mind, allow me to present my schematic:

nop

@paulo, feel free to cut and paste to your site. You were awesome enough to post your idea here, the least we can do is return the favor.

[Radio Tech]

So, with all that in mind, allow me to present my schematic:

nop

@paulo, feel free to cut and paste to your site. You were awesome enough to post your idea here, the least we can do is return the favor.

Thanks for the contribution. Nice.

[6502nop]

Ummm...

How 'bout Rev. B?

Whilst trying to get this darn thing working, I ran into some snags. My hand-wound transformer wasn't doing the job, so I swapped it with my RS model that RT suggested, and it did the same. Or didn't do the same. However that phrasing works.

So, I swapped and tweaked and played. The one thing in all this was back when I first drew up the schematic, I thought that those 12R resistors at R4/5 were too damn small. I swapped them out with some 100Rs, and Zing! I was sweeping my meter. I threw my original transformer back in, and the performance was about the same (yeah, I know - whodathunk?). More swapping showed that it liked to be loaded with 150R for R4/5.

For those still toying with this, if yours isn't working, try swapping those resistors out.

Now, for your entertainment, here's the revised schematic (with more notes)...

nop

[Radio Tech]

Ummm...

How 'bout Rev. B?

Whilst trying to get this darn thing working, I ran into some snags. My hand-wound transformer wasn't doing the job, so I swapped it with my RS model that RT suggested, and it did the same. Or didn't do the same. However that phrasing works.

So, I swapped and tweaked and played. The one thing in all this was back when I first drew up the schematic, I thought that those 12R resistors at R4/5 were too damn small. I swapped them out with some 100Rs, and Zing! I was sweeping my meter. I threw my original transformer back in, and the performance was about the same (yeah, I know - whodathunk?). More swapping showed that it liked to be loaded with 150R for R4/5.

For those still toying with this, if yours isn't working, try swapping those resistors out.

Now, for your entertainment, here's the revised schematic (with more notes)...

nop

Cool.
I have not had time to get back on mine. But the last time I played with it I could not get any deflection on the meter. So I changed out the 12 ohm resistors. I then had full deflection but what evercap you tested it was always reading zero. I tried 1 ohm to 25 ohm resistors and still it read zero.  Then I saw I have installed 12K resistors instead of 12 ohm.  When replaced I get no deflection on meter. So I am going to play around with those.