IC test clip with LEDs

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

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

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James Harris
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James Harris
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This is my take on such a device:

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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:

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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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Reply to
Computer Nerd Kev

That brings back memories!

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
Reply to
James Harris

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.

Reply to
Ralph Mowery

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.

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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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Reply to
Computer Nerd Kev

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:

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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
Reply to
James Harris

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:-

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if that wraps then:-

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Reply to
Geo

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).

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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Reply to
Computer Nerd Kev

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.

Is there a better way to monitor

A logic analyzer. You can get slow USB ones for under $100, and pretty fast ones for $300.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Phil Hobbs

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