calc calls for 270ohm 1/8 watt??

Discussion in 'The Projects Forum' started by mvp, Jan 22, 2014.

  1. mvp

    Thread Starter New Member

    Jan 21, 2014
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    Wiring 4 led parallel. calculator calls for 270 1/8 watt resistor. Is it ok to go 1/4? Cant find 1/8 locally.
    4 led, 12v, 3.6, 20ma
     
  2. tshuck

    Well-Known Member

    Oct 18, 2012
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    Using a higher wattage resistor will be fine...but how exactly are you planning on wiring these?
     
  3. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Yes, it is fine, it gives you more "safety room".

    1/8 W is 0.125 W.
    1/4 W is 0.25 W. So, if for some reason you made a mistake somewhere and have more than 0.125 W power at the 0.125 W resistor, the resistor will break because it is not build to dissipate more than 0.125 W, but if you use 0.25 W resistor, then resistor will survive. Unless you exceed the 0.25 W also.
     
  4. mvp

    Thread Starter New Member

    Jan 21, 2014
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    Parallel
    1 resistor per 2 led
     
  5. tshuck

    Well-Known Member

    Oct 18, 2012
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    And those 2 LEDs are in series, right?

    Like part c here:
    [​IMG]
     
  6. mvp

    Thread Starter New Member

    Jan 21, 2014
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    Yes, (c)..sorry, I'm new to this
     
  7. tshuck

    Well-Known Member

    Oct 18, 2012
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    No worries, but there are some nuances with LEDs. Actually putting them in parallel will cause them to share current differently, making some light and some dim. Then some melt and the others light, then they all become dim forever.
     
  8. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Always double (or triple) the calculated wattage for safety and to keep it from running so hot.
    But yes always ok to go higher on the wattage.. never lower.
     
  9. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Like the above said, in parallel there might or might not be some variation in brightness between the parallel branches. To even out the brightness, you may have to "play around" with resistors. Put a slightly larger resistor at the brighter branch or put slightly smaller resistor on the dimmer branch, or do that to both branches.
     
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