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LED dimmer problem

Discussion in 'General Electronics Discussion' started by harshilsharma63, Dec 4, 2012.

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  1. harshilsharma63

    harshilsharma63

    2
    0
    Dec 4, 2012
    Hi, I'm making an LED dimmer based on the 555 timer IC as shown here. The problem I'm having is that whenever I try to simulate it in Multisim, it shows a crack around the OUT of the IC on taking the potentiometer below 2% or above 98% ( Of which I've uploaded the pics). I want to know why this happens and also want a solution to this.

    Other circuits are welcomed. Keep in mind that I'll be attaching the circuit inside my pc cabinet and will be powering it from 12 V molex supply, so the circuit should be sturdy and should last long, really long. Also, I'm no electronics guy, a Computer Science student.
     

    Attached Files:

  2. Miguel Lopez

    Miguel Lopez

    252
    63
    Jan 25, 2012
    Multisim sometimes give such problems when making hard transients and in the ends of potentiometer.
    Add small resistors in both ends of the potentiometer.
    Add a resistor in the emitter of 2N2222 to ground (1K is suitable).
     
  3. harshilsharma63

    harshilsharma63

    2
    0
    Dec 4, 2012
    Is this just Multisim's issue? Will the original circuit work properly from 0 to 100 % ?
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    11,513
    2,651
    Nov 17, 2011
    Almost.
    Build it and see.
     
  5. Miguel Lopez

    Miguel Lopez

    252
    63
    Jan 25, 2012
    Years ago I build one of such dimmer circuit by varying duty cycle in the 555. It worked fine.

    +1 :D
     
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