Resistors Heating up

Discussion in 'Electronics & Electrics' started by DraGoN-BoY, Sep 20, 2006.

  1. DraGoN-BoY

    DraGoN-BoY Member

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    Hi, I'm trying to wire up some LEDs and the problem I'm encountering is that the resistors seem to be producing a fair amount of heat.

    I've wired a series of 3 SMD LEDs with a resistor.
    The SMD LEDs are rated 3.2-3.6 Vf, 20mA and 100mW.
    The resistor I have is 0.25W 180ohm.
    Source voltage is 13v.
    Code:
          -- LED  -- LED -- LED -- Resistor -- |
          |                                    |
    (+) --| LED  -- LED -- LED -- Resistor ----| -- (-) 
          |                                    |
          -- LED  -- LED -- LED -- Resistor -- |
    
    Would upgrading the resistors to the 5W ceramic ones help?
    Thanks
     
  2. dakiller

    dakiller (Oscillating & Impeding)

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    Quick calculations put the power in the resistor to be perfectly fine
    Resistors are meant to get hot, and as long as you keep under 100C or so you're well within the limits
     
  3. OP
    OP
    DraGoN-BoY

    DraGoN-BoY Member

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    Thanks, was just a bit concerned.
    :)
     
  4. mAJORD

    mAJORD Member

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    the resistor is disipating around 80-100mw along with each LED.

    being a 250mw resistor that means it wil be frigging hot @ 250mw, but not in danger of shitting itself in time (like daik said, below 100 or whatever the rating is for those resistors) so I'd expect it to be quite hot to touch still @ 100.
     
  5. nux

    nux Member

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    I get about 0.0642 watts which is well within spec.
     

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