PWM for LEDs - non-LED resistor wattage?

Discussion in 'The Projects Forum' started by jaesun, Mar 25, 2009.

  1. jaesun

    Thread Starter New Member

    Mar 24, 2009
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    0
    I just want to apologize in advance because this might be an incredibly dumb question.

    I've gone through the PWM circuit designs which I want to use for 2 blue LEDs (3v voltage drop and 100 mA current rating) in series using a 12 volt wall wart. I figured out that I'll need a 62 ohm 1 watt resistor.

    I can't figure out the wattage of the other resistors. Is it 1/8 watts? Should I use 1/4 or 1/2? I want to use the PWM circuit for a few other LED projects, so I'd like to know if changing the source voltage and LED parameters will change the wattage required for the other resistors.
     
  2. jaesun

    Thread Starter New Member

    Mar 24, 2009
    3
    0
    my bad, I neglected to mention that this is for the PWM circuit using the 555.
     
  3. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Where is the circuit or a link to the circuit?
     
  4. jaesun

    Thread Starter New Member

    Mar 24, 2009
    3
    0
  5. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    I suggest 1/4W resistors. 12V * 12V / 1KΩ = more than 1/8 Watt.
     
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