(Topic ID: 166055)

DIY Logic Probe... Easy & Cheap

By Zambo

7 years ago



Topic Stats

  • 6 posts
  • 4 Pinsiders participating
  • Latest reply 7 years ago by Zambo
  • Topic is favorited by 9 Pinsiders

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    #1 7 years ago

    I put together this logic probe circuit the other night based on this project...

    http://www.talkingelectronics.com/projects/100%20IC%20Circuits/1-100_IC-Ccts.html (about halfway down the page).

    I built it inside a sharpie like pen from the dollar store, and I already had the parts on hand. It seems to work just fine and the cost is only 3 or 4 bucks. I will be using it to trouble shoot an Mpu i'm having problems with.

    Probes_(resized).jpgProbes_(resized).jpg

    #2 7 years ago

    where'd the yellow LED go?

    #3 7 years ago

    That's awesome.

    #4 7 years ago

    Oh yeah, I found the yellow (pulse) led to be redundant, because the red and green leds flash quickly or stay on steadily when a pulse is detected. I found the buzzer to be annoying too, but you can build it anyway you want.

    #5 7 years ago

    I'd say you want the pulse LED. I just did a Bally MPU with a bad clock buffer. One clock phase lit up all three LEDs. The other clock phase lit up just the red and green. When i checked with a DMM it said 2.5v which is what i would expect.

    The real story when i got the scope out was that the clock phase that only lit up the green and red probe LEDs was a mostly flat line across near 2.5v (bad u15). No yellow pulse LED i may have spun my wheels for longer as to why the MPU was locked up.

    Still really neat. Inside a sharpie... thats great. That kit becomes bad ass if someone can add the audible buzzing circuit to it. I think you need two chirpers, one for LOW led and one for HIGH led.

    #6 7 years ago
    Quoted from barakandl:

    I'd say you want the pulse LED. I just did a Bally MPU with a bad clock buffer. One clock phase lit up all three LEDs. The other clock phase lit up just the red and green. When i checked with a DMM it said 2.5v which is what i would expect.

    Good to know... i'll probably make the next one with all three.

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