Power 4.5vdc LEDs with 12vdc

Discussion in 'General Electronics Chat' started by frogman_94, Dec 5, 2011.

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  1. frogman_94

    Thread Starter New Member

    Dec 5, 2011
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    I have a string of battery powered LED Christmas lights that use 4.5v (3xC-size batteries). I want to power them from my scooter's 12v battery. I have two different colors, one is red and one is green. I see a 20 ohm resistor in one and a 10 ohm resistor in the other. I'm not sure which one has which. There are 30 LEDs in each string. I know I have to add another resistor to the circuit to make up for the increase in voltage. But how much do I add?
     
  2. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    I don't think this topic will comply with the terms of service if you are planning on lighting your scooter with colored LED's, but maybe a moderator will allow it.
     
  3. frogman_94

    Thread Starter New Member

    Dec 5, 2011
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    This is for a Christmas light parade and I didn't want to buy a ton of batteries.
     
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Use a 7805 regulator and heatsink if needed.
     
  5. frogman_94

    Thread Starter New Member

    Dec 5, 2011
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    Thanks, I will pick some up tonight and give it a try. I also might look for a 12v to 4.5v car adapter.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    How right you are.

    The All About Circuits forum Administrative Team has elected not to host discussions of automotive electrical system modifications/enhancements due to safety concerns, the potential of legal ramifications and the possible circumvention of vehicle regulations at the state and federal level.

    This thread is against the AAC forum rules, Chapter 6, as seen here:

    http://www.allaboutcircuits.com/l_tos.html


    Automotive modifications of any kind are strictly forbidden. Therefore, this thread will be closed.

    Please try to understand the reasons behind this action, and feel free to browse and use the forums.

    You might find answers to your questions in one of these forums:

    http://forum.allaboutcircuits.com/sh...ad.php?t=54400
     
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