Friday July 19, 2024

Using a Logic Probe

Author: Wayne Eggert
Date: 09/23/2011

In this tutorial we will help demystify the logic probe, an important tool in your evil genius workshop that you probably never knew you needed.. until now that is!  You'll learn WHEN to use a logic probe, WHEN NOT to use a logic probe and why a logic probe probably won't get you any more dates with women than you already have.  And no, it's not because women aren't logical!  We already knew that.  Just kidding members of the female audience!

What is a logic probe?
A logic probe is a tool to help analyze the behavior of an active electronic circuit.  This means you use the logic probe while the circuit board has power running through it and things are happening.  Things you can't see.  Well not yet anyway.  It's relatively cheap, a typical logic probe costs between $15-25 and can be found at most electronic stores, eBay, etc.  The brand really doesn't matter.. some have audible beeps along with the typical HIGH/LOW led indicators on them.

Here's a picture of a typical logic probe:
Logic Probe

Now if that's not a sexy looking logic probe, I don't know what is!  Look, there's nothing wrong with calling electronic test equipment sexy.  Don't judge me!

Notice the two alligator clips attached to the end of the logic probe, one red and one black.  The red alligator clip hooks to the power supply of the circuit and the black alligator clip hooks to the ground of the circuit.  This gives the two voltage reference points that the logic probe needs to analyze the circuit.  So the entire time you're using a logic probe the red and black alligator clips are connected to power and ground respectively.  You then hold the logic probe in your hand and touch various parts of the circuit with the needle-like "probe" on the other end to analyze signals on various IC pins, transistor pins, etc.

Did I lose you already?  Don't worry, it will make more sense as we go along.  If not, it will definitely start sinking in when you actually put the thing to use or my name isn't Larry!

Continue onward..

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Re: Great article.
Posted 09/30/12 10:55AM by AceBHound
Thanks for pointing out the spelling mistake! Always happy to fix any of those cause they drive me nuts too =)
Great article.
Posted 09/27/12 5:01PM by Anonymous Techdoser
Great article. Just one small nit-picking point. On page two, you use the word "here" when you mean "hear". Sorry about that. I saw this mistake made twice today.