Dimming white leds

Discussion in 'The Projects Forum' started by boatsman, Aug 25, 2013.

  1. boatsman

    Thread Starter Senior Member

    Jan 17, 2008
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    I have an array of 12 white leds powered by three AAA batteries. The light they emit is bright. I want to be able to adjust the intensity of the array from off to full brightness. If I just use a potentiometer the leds are either on or off. How can I make a simple dimmer?
     
  2. bertus

    Administrator

    Apr 5, 2008
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  3. wayneh

    Expert

    Sep 9, 2010
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    There are several simpler circuits that folks use, but PWM as recommended by Bertus is the best, especially if you want a nice full range of control.

    The second best approach is probably the LM317 based circuits.

    Last choice is what you already tried. It could be made to work, but a potentiometer that can handle the power will be more expensive.
     
  4. LDC3

    Active Member

    Apr 27, 2013
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    Did you notice that the power is coming from 3 AAA cells? The voltage is about 4.5 V and probably has a current less than 100 mA. A 1/2 watt potentiometer is probably cheaper than building any circuit.
     
  5. DickCappels

    Moderator

    Aug 21, 2008
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    It sounds like your basic problem is that your pot (actually used as a rheostat in this case) has too high of a resistance. Try a lower resistance part, such as 10k, 5k, or 1k and you will not see the on/off effect.
     
  6. boatsman

    Thread Starter Senior Member

    Jan 17, 2008
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    Thank you all for your replies. It's given me options I can try out.
     
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    The PWM solution will be a lot more energy efficient (ie give longer battery life) than just using a resistor (or large pot).

    It will also give a better light quality when dimmed.

    That makes it a better option, even though it takes more effort to build.
     
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