IC test clip with LEDs

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I remember years ago seeing a clip that would fit over an IC and show  
the logic state of each pin on an LED (or an LED pair). Something like this

https://uk.farnell.com/3m/923690-08/test-clip-dil-8way/dp/178270

Do such clips still exist but with LEDs on top and what are they called?


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James Harris



Re: IC test clip with LEDs
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This is my take on such a device:
http://computernerdkev.heliohost.org/logicvis/index.htm

Another DIY design was published in the Aug. 1987 issue of the
Australian version of "Electronics Today International", with the
largely inaccurate name of "In-Circuit Digital IC Tester".
Therefore I made it available on my webpage about DIY IC tester
designs:
http://computernerdkev.heliohost.org/ictesters/index.htm

As noted in my description there, it powers the LEDs from the outputs
of the chip that it's clipped to, which might cause issues in
circuits that can't supply enough extra current.

Similar pre-built devices were sold at the same time, but I don't
know of any still available.

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Re: IC test clip with LEDs
On 17/10/2018 23:34, Computer Nerd Kev wrote:
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That brings back memories!

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I wonder why they fell out of favour. Is there a better way to monitor  
digital ICs in-circuit these days?


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James Harris

Re: IC test clip with LEDs
says...
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I just gave away something like that to a young boy that was bread  
boarding some 7400 series logic circuits.  Had it for years but hardly  
ever used it.  I don't recall who made it,but it was in a box that had  
that clip on thing and 2 other logic probes.  I think one gave out  
pulses and one would light up a led on a pulse.  Seems they could be  
switched for either 5 volts and the one for cmos.


Re: IC test clip with LEDs
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Of course there are Logic Analysers, but they were around back then
too. These days there are some cheap options for connecting to
a PC though, eg.
http://dangerousprototypes.com/docs/Logic_Pirate

The clip-on indicators were easier to use, but I think the key
limitation is that the only signals that can be reliably
analysed are those slow enough for the eye to observe changing
state. That's why I wanted to build one that allowed various
methods to be used in order to sample and effectively slow
down the display.

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Re: IC test clip with LEDs
On 18/10/2018 22:51, Computer Nerd Kev wrote:
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That's true. As just one example, I have a computer board with a  
4-to-16-line decoder which I suspect of possibly asserting more than one  
output at a time or of not asserting some outputs at all. But without  
single stepping the CPU or running a small test program, which is not  
currently possible, I'm not going to see much from pin states which vary  
so quickly.

I wasn't aware of logic analysers. They sound far better if they have  
enough channels. I see many with 8 or 16 channels but a more expensive  
Hantek LA5034 which apparently has 34 channels:  
https://www.circuitspecialists.com/34-ch-usb-logic-analyzer-la-5034.html .  
Does it look good as a PC-based analyser which could be used in many  
situations, or would you recommend a different one?

Whether such a piece of kit would be generally useful or not, such an  
analyser wouldn't help in this specific case as it could not be used to  
check the above decoder without also using a test program to cycle  
through the inputs. The decoder is not socketed so I guess all I can do  
is unsolder the chip and test the 16 permutations of its inputs on a  
breadboard. If I'm wrong and there is a better approach please say!


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James Harris


Re: IC test clip with LEDs
On Sat, 20 Oct 2018 11:50:51 +0100, James Harris


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I have a piece of old kit (Fluke Trendar 200 IC Testclip) that we were
issued with when TTL was mainstream.  It has a 16 pin clip to attach
to the suspect DUT and a 16 pin socket.  A number of special socket
can be plugged in to the one on the unit.  Each special can have long
or short pins - long pins connect to the input of the DUT short pins
only connect to the exclusive OR gates which drive the LEDs.  A good
IC is placed in the socket and the leds indicate a difference between
the good and DUT outputs. There is also a pulse stretcher which can be
switched to any pin.

Some info on google and at least one on ebay:-
https://www.ebay.co.uk/itm/VINTAGE-FLUKE-TRENDAR-200-IC-TEST-CLIP-WITH-CASE-MANUAL-CABLE-PINS-REFERENCE-/232452265430

if that wraps then:-
https://tinyurl.com/y7oawq4k

Re: IC test clip with LEDs
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I don't have any recommendations, but the specs for that model look like
they should suit your application. Make sure that whichever device you
buy supports all the logic signals (TTL/CMOS etc.) that you might want
to use, at all the voltages that you might be running circuits at (the
linked one should).

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Well I just gave you a link to my page on IC testers, hint hint. Some
support various approaches to in-circuit tests, but new testers are a
bit thin on the ground.

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Re: IC test clip with LEDs
On 10/18/2018 12:39 PM, James Harris wrote:
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They aren't much use for anything faster than a burglar alarm.   Usually
they just told you high, low or 'pulsing'.  Nobody builds burglar alarms
out of TTL anymore.

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Is there a better way to monitor
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A logic analyzer.  You can get slow USB ones for under $100, and pretty
fast ones for $300.

Cheers

Phil Hobbs


--  
Dr Philip C D Hobbs
Principal Consultant
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