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4v 800ma to 3v 60ma

Discussion in 'General Electronics Discussion' started by vrh35, Jun 10, 2012.

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  1. vrh35


    Jun 10, 2012
    I have a extra mobile charger with output rating of 4 v 800ma.I want it to drive 3 leds (3v 20ma ). What resistor should i use to get the desired output. Can any one please help me?
  2. weird_dave


    May 9, 2012
    You'll need to have a resistor for each LED and have them in parallel.
    The answer is R = V / I
    Where V is 4v-3v = 1V
    I is 20ma = 0.02
    So R = 50ohms. (51 will do nicely:) )
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    That's one resistor per LED, with all of them wired in parallel.

    Check out this thread for more details.
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