Author Topic: Continuity tester with glitch capture  (Read 8789 times)

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Offline hammil

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Continuity tester with glitch capture
« on: March 30, 2013, 01:06:50 am »
Hey all

After my first foray into reverse engineering, I found that a decent continuity tester is completely invaluable. The trouble is, they only tend to come with high-end multimeters.

I reasoned that the circuit wouldn't be too complex or expensive to make... So with that, I thought I would create one.

Here's a simulation of the concept: http://bit.ly/14tB0os

I guess I was trying to come up with the 'ultimate' continuity tester - adjustable sensitivity, adjustable pulse duration, /very/ sensitive glitch capture, and a voltage low enough that it wouldn't turn on even the finest Schottkey diodes.

The schematic is attached to this post

PCB layout: http://uploads.oshpark.com/uploads/project/top_image/VjPcSEKu/i.png
http://uploads.oshpark.com/uploads/project/bottom_image/VjPcSEKu/i.png ( I can't seem to get logos to flip properly in KiCad.. )

The components are all generic and as labelled, with the exception of the buzzer ( http://uk.farnell.com/projects-unlimited/ai-1223-twt-5v-r/audible-signal/dp/1653527 ) the connectors ( http://uk.farnell.com/jsp/search/productdetail.jsp?SKU=1698984&MER=baynote-1698984-pr ), and the comparators ( http://uk.farnell.com/stmicroelectronics/ts393idt/comparator-dual-micropwr-8soic/dp/1750194 , although an LM393 could be used without any problems ).

Power consumption should be in the microamps while not buzzing, so I didn't bother with a switch.

I'm thinking I might make a little line of devices like these... A low-cost JFET probe is in the pipelines, as is a redesign of the differential probe I talked about before.
 

Offline ivan747

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Re: Continuity tester with glitch capture
« Reply #1 on: April 06, 2013, 01:04:25 am »
Neat! But I think the switch is really necessary. I like these sort of little circuit boxes. Now we have the ĀµCurrent, the 4-wire resistance adapter Dave got in the mail and this continuity tester .

What kind of pots are you going to use?

I am planning to make a True RMS to DC converter box with this form factor.
 


Offline Marco

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Re: Continuity tester with glitch capture
« Reply #3 on: June 28, 2015, 04:45:09 am »
None of these seem able to catch discontinuity glitches.

AFAICS a continuity tester should work like this :

- If short in last X seconds and not beeping for last X seconds then toggle beep on
- If open in last X seconds and beeping for last X seconds then toggle beep off

Can't do this with a simple Schmitt, need some logic.
 

Offline timofonic

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Re: Continuity tester with glitch capture
« Reply #4 on: July 02, 2015, 04:31:56 pm »
None of these seem able to catch discontinuity glitches.

AFAICS a continuity tester should work like this :

- If short in last X seconds and not beeping for last X seconds then toggle beep on
- If open in last X seconds and beeping for last X seconds then toggle beep off

Can't do this with a simple Schmitt, need some logic.

I see.

What kind of logic? Secuential?
 

Offline ivan747

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Re: Continuity tester with glitch capture
« Reply #5 on: July 06, 2015, 03:47:34 am »
I bet you you can do it with an op amp, an RC charge circuit and a comparator. Op amp can even be optional.
 

Offline Marco

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Re: Continuity tester with glitch capture
« Reply #6 on: July 06, 2015, 02:40:19 pm »
I bet you you can do it with an op amp, an RC charge circuit and a comparator. Op amp can even be optional.

A simple latching continuity tester sure, but as I said ... ideally it should be able to catch discontinuity glitches as well.

If there is a break while it's latched beeping it should remember that break and latch silence after the reset period, the circuit needs memory.
 

Offline timofonic

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Re: Continuity tester with glitch capture
« Reply #7 on: July 07, 2015, 07:54:37 am »
I found another circuit here...
https://www.eevblog.com/forum/index.php?topic=45769.0

Memory = flipflop or microcontroller?
 

Offline Marco

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Re: Continuity tester with glitch capture
« Reply #8 on: July 07, 2015, 12:48:06 pm »
In this day and age, probably a micro ... even if it will only be a 10 line program.
« Last Edit: July 07, 2015, 12:50:29 pm by Marco »
 


Offline timofonic

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Re: Continuity tester with glitch capture
« Reply #10 on: July 09, 2015, 10:35:50 pm »
a list of some here : http://kripton2035.free.fr/continuity-repos.html

Thanks! Too much options. What's the best? I got confused! :O
 

Online kripton2035

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Re: Continuity tester with glitch capture
« Reply #11 on: July 10, 2015, 06:59:30 am »
I made the cypress lockin milliohmmeter and I like it.
I'm now extending (trying to) the range to 100 ohms or so, trying to change the measuring frequency,
and adding a speaker to hear the continuity... I made it on a veroboard and the last digit is really stable !

I also like the elm-chan one, and the elv kd1 (that could for sure be simplified)

Offline timofonic

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Re: Continuity tester with glitch capture
« Reply #12 on: July 16, 2015, 11:20:21 am »
I made the cypress lockin milliohmmeter and I like it.
I'm now extending (trying to) the range to 100 ohms or so, trying to change the measuring frequency,
and adding a speaker to hear the continuity... I made it on a veroboard and the last digit is really stable !

I also like the elm-chan one, and the elv kd1 (that could for sure be simplified)

Please post your modifications if you want. It could be greatly appreciated ;)
 

Offline flashdrive71

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Re: Continuity tester with glitch capture
« Reply #13 on: March 07, 2019, 01:13:37 pm »
because you listed url's for different websites did you ever see article for  Ultimate continuity tester hides many tricks up it's sleeve 10-2-2008 .by louis vlemincq. I looking for the fig.1 and fig.2 schematics from Electronic Design Magazine they are missing on article on website and Electronic Design does not have them in their data base. If you have them can you email them to me. It was great article but need to see what the schematics looked like.

 

Online Gyro

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Re: Continuity tester with glitch capture
« Reply #14 on: March 07, 2019, 01:21:02 pm »
... and that's why I never get around to throwing anything away!  :)


P.S. Irrc, fig.2 just showed how it worked to identify wrongly phased transformer windings.

https://www.electronicdesign.com/analog/ultimate-continuity-tester-hides-many-tricks-its-sleeve
« Last Edit: March 07, 2019, 01:27:20 pm by Gyro »
Chris

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