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LED tail lights for motorcycle

Discussion in 'Electronic Basics' started by Rust, Apr 6, 2004.

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  1. Rust

    Rust Guest

    I am currently working on adding LED turn signals and tail lights to my
    motorcycle.

    I have already built the turn signals using 5 20v, 30mA, orange LEDs and a
    50 ohm resistor on each side. Pretty simple actually.

    My problem is now that I want to do the same for my tail lights. I'd like
    to use 10mm red LEDs. I was thinking about using 24 (4 rows of 6 each) - 12
    for my rear lights, and 12 for my brake lights. The problem i'm running
    into is that the amount of voltage seams too low. I have seen LED clusters
    with 30+ LEDs and they work fine on a standard 12v system. Is there some
    device that boosts the voltage? Am I missing something?

    I'd appreciate anything y'all could offer. Thank you.

    Trey
     
  2. soundman

    soundman Guest

    Instead of trying to drive all 12 in one circuit, separate them into three
    sets of 4 and use a separate current limiting resistor with each set of 4.

    With a forward voltage of 2V for each, the 4 will drop 8V leaving 5V - 6V to
    drop across the resistor. You should end up with a resistor in the range of
    220R.

    Take care to avoid over driving the LEDs. They will lose performance
    quickly if the current is allowed to remain higher than the stated maximum.
    Personally I would reduce the current level by 10 - 20% below the maximum.
    Also, unlike the turn indicators, these LEDs are likely to be on for a long
    time and there can be a significant heat build up. Generally LEDs don't
    like getting warm. I know that there is only a 2W power rating with all 24
    LEDs on, but there does need to be some means for the heat to be dissipated.
    For differentiation, you will probably need to drive the tail light at a
    lower current than the brake light, so this will probably solve the problem
    of heat build up.

    Good luck
     
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