Better PWM?

Discussion in 'General Electronics Chat' started by JohnnyGlock, Aug 6, 2009.

  1. JohnnyGlock

    Thread Starter New Member

    May 23, 2009
    3
    0
    Hi, I'm somewhat of a newb, so any help would be appreciated.

    I'm trying to use PWM to control the brightness of some Blue LED's (about 8 of them) in my car.

    I've set up a 555 timer circuit on a breadboard using this schematic: [​IMG]
    http://picasaweb.google.com/lh/photo/HVYSSHYf-H8yNNP5jVTiPA?feat=directlink

    I've replaced the 10k resistor with a 50k log potentiometer to control the brightness.
    It works, but I'm not really happy with the control with the pot. The lights dim quickly during the last ~10-20% of the pot's rotation, and from ~20%--100%, the LEDs stay at full brightness. Is there any way I can modify this circuit to get better control?

    What I'd like is for the potentiometer's turn to control the brightness more precisely.

    Thanks!
     
  2. bertus

    Administrator

    Apr 5, 2008
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  3. Wendy

    Moderator

    Mar 24, 2008
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  4. fanie

    Active Member

    Jan 20, 2007
    63
    0
    Try this circuit.

    It's basically the same circuit that Bertus posted a link to, but I like using the extra 3 nand gates in parallel to drive the FET with, it switches better.
     
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