LED Logic Probe, for use with quick pulses

Discussion in 'General Electronics Chat' started by Mad Professor, Apr 21, 2009.

  1. Mad Professor

    Thread Starter Active Member

    Apr 15, 2009
    Good Day All.

    I would like some help and advice.

    I have been building my own stepper motor controller.
    The controller works fine by it's self, but now I would like to add some LED's to it, so that I can see the input pulses.

    As my controller gets all its signals from my computers LPT port it's all 0-5v logic.

    I have 3 LED's I want to add to my controller, Enable, Step, & Dir.

    The Enable and Dir pin are not pulsed quickly so I get the full brightness of the LED's

    But the step pin is pulsed very quickly, so the LED works but is so dim you can hardly see it.

    Is there anyway I can get the LED to pulse at its full brightness.

    Here’s how I have got the LED's wired atm.
    Last edited: Apr 21, 2009
  2. bertus


    Apr 5, 2008
  3. tkng211

    AAC Fanatic!

    Jan 4, 2008
    You can use any simple monostable circuit to strech the pulse. The well known IC 555 or CMOS 4011, 4001 can do. You can easily google the circuits, and they are cheap and easy to get.