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  1. #1
    RC Enthusiast
    Join Date
    Aug 2012
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    35

    need help makin LED underbody lights ....

    hey guys. i need some help figuring out what resistor i need to make my DIY LED underbody light work. heres the deal .... they will run off of a 9volt battery .... the led's i picked up at radio shack are ...

    5 mm high brightnes
    intensity: 2850 mcd ( typical )
    chromaticity coordinates: x=.334,y=0.197 ( typical )
    viewing angle: 30 degrees
    fw current: 30mA
    fw supply:3.5v ( typical ),4.0v (max)

    thats all the info on the bag the leds came in. i know if we touch them right to the 9v batt they burn up ... ( tried it .. lol ) so what size resistor would i need to run these off a 9v batt ?? thanks guys,scott

  2. #2
    RC Champion
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    Hope this might help led calculator
    Guide books aren't part of the packaging.

  3. #3
    RC Enthusiast
    Join Date
    Aug 2012
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    thanks trx de max .... ill give t a shot ... :-)

  4. #4
    RC Qualifier
    Join Date
    Mar 2011
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    661
    V=IR.

    You have a set voltage limit and want such milliamperes. Solve for R.

    Why not just go simple with some EL, electroluminescent, wire? Cheap and awesome!

  5. #5
    RC Enthusiast
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    Aug 2012
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    electroluminescent wire? where do you pick this stuff up ??

  6. #6
    RC Qualifier
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    Jun 2011
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    North-West Ohio
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    I bought 2 of these bad boys at Walmart.. took out the lights, wired both up in parallel to a 9V and it makes a really bright pair of head-lights.. Just taped on with electrical tape..
    Makes cars flash their brights at me.. hehee











    Can be done under 5$.. assuming you already have a 9V and solder/gun..
    Last edited by ithrowstones; 02-14-2013 at 05:45 PM.
    Never trust a fart.

  7. #7
    RC Qualifier
    Join Date
    Mar 2011
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    661
    Quote Originally Posted by coolbikeguy View Post
    electroluminescent wire? where do you pick this stuff up ??
    I think my roommate got a bunch off amazon. Ours ended up on a ford themed beer pong table and seems waterproof enough so far.

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