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8 channel logic probe

8 channel logic probe
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This is a logic probe based on a circuit I found on this link:
http://www.swansontec.com/sprobe.html

It is made using 4x LM324 quad opamps, giving it a total of 8 channels. Using 4 sets of DIP switches, each channel has an individually configurable pullup or pulldown, as well as a tactile switch that is individually configurable to either the positive or ground rail. The 10 wire harness plugs into the top port: 1 lead for each channel and the other two wires for power and ground. The bottom port gives access to the same connections, less the positive rail - for easy connection to my 8 channel logic analyzer.

The logic probe circuit works very well, but it does have one limitation. The LM324 does not run very close to the rails. It need about 4V before the LEDs become clearly visible. But it works well at 5V.

6 comments
May 30, 2009. 1:45 AMmicroman171 says:
Wow! Your protoboard skills are Great!
May 30, 2009. 4:46 PMmicroman171 says:
Must hav been hard to get your head around? Did you have to do any debugging? IE did it work first time? It sucks on large circuits when the DONT work first time, as it is damned hard to find the fault.
May 31, 2009. 2:43 PMmicroman171 says:
What does a logic probe do...? Does it just tell you wether the pin in input or output?

I imagine that could be pretty useful =)

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Author:klee27x