Random Resistance Generator

Discussion in 'The Projects Forum' started by StokeBloke, Jan 21, 2009.

  1. StokeBloke

    Thread Starter New Member

    Jan 21, 2009
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    0
    Hi, I'm new here. I am looking to make a small laser crab (link to specs) light more interesting. The unit I have has two small trimmer controls on the back to give manual control over the two spinning mirrors. I would like to be able to switch from full manual control to allow a circuit to feed random resistance to the board at a rate of about one value per quarter or eighth of a second.

    This would give a visual output that looked more like a dancing beam. The 'auto' control is very limited in as much as it has one speed control for changing patterns, but it really doesn't change fast anywhere near quickly enough to fool the eye into seeing a dancing beam. I was wondering if something using a 555 timing signal to trigger a random resistance would be possible. The unit's power supply is 6volts DC.

    I have excellent soldering skill, a good, if somewhat basic grasp of components. However I lack any circuit design ability :eek:

    Cheers
    Stokie
     
    Last edited: Jan 21, 2009
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Where will you place this "random resistance"?

    How is this thing controlled?
     
  3. StokeBloke

    Thread Starter New Member

    Jan 21, 2009
    2
    0
    There are currently two external trimmers for manual setting of the unit (they control the speed of the two slightly off-set mirrors). I would remove/bypass these trimmers and instead feed the motors from the random output circuit. So the input to the trimmer would become the input to the circuit, and the output from the circuit would replace the output from the trimmer.

    It'd be like having someone constantly twiddling with the trimmers every quarter of a second. That would mean the pattern wouldn't 'settle' and give the impression of a dancing laser.

    Does that make sense?

    Stokie
     
  4. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Your description is a bit confusing.
    Which motors?
    We don't know what is after the trimmers so how we can modify it?
    Is there a circuit diagram?
    By trimmers you mean potentiometers, right?
     
  5. HarveyH42

    Active Member

    Jul 22, 2007
    425
    5
    Likely be simpler to just build a motor controller to replace the entire circuit. Pulse-width modulation can be used to control the motor speed (probably what the existing circuit does...). There are chips that do nothing else, some take a digital signal to set the speed. Don't have any part numbers to give you. A microcontroller could do this as well.
     
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