powering leds from car power supply

Discussion in 'The Projects Forum' started by makavelly001, Mar 18, 2011.

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  1. makavelly001

    Thread Starter New Member

    Mar 12, 2011
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    Hi all and thanks in advance for any input and response. My project is to drive between 35-40 SMD RGB leds in a series, but I want to power the leds using the power source from my car. I would like to have 5 rgb leds in each series and about 7-8 strings.. I understand that leds work more efficiently with constant voltage and current and therefore using the power from the automobile will be inefficient as the voltage and current fluctuate. To overcome this problem I have decided to look into some step up dc/dc converters that will output 30 -35 volts from 12-15 volts input (car battery) and output a constant current of 10 amps. My questions for this project are the following:

    1. Is this the best way to increase the needed voltage and current to drive the leds from an automobile power supply?

    2. If this is the best way to increase the needed power, should I connect the dc/dc converter directly to the battery or fuse box.?

    3. Do I need an inline fuse ?


    4. Do I need to worry about CCA blowing the dc/dc converter and the leds as the current can exceed 600 amps during start-up of the car ?

    What is CCA ?: http://www.autobatteries.com/basics/selecting.asp
    CCA is critical for good cranking ability. It's the number of amps a battery can support for 30 seconds at a temperature of 0 degrees F until the battery voltage drops to unusablelevels. A 12V battery with a rating of 600 CCA means the battery will provide 600 amps for 30 seconds at 0 degrees before the voltage falls to 7.20 V (six cells).

    5.Should the dc/dc converter have Short-circuit Protection and what should be the Maximum Input Current:

    Below I have pasted the links to several Step Up DC/DC Converters which I believe might be suitable but I am unsure. PLEASE, PLEASE HAVE A LOOK AND SEE IF THEY ARE SUITABLE FOR THE TASK.
    The following are from the company site: http://www.xscyz.com/


    http://www.xscyz.com/index.php?main_page=product_info&cPath=67&products_id=190
    http://www.xscyz.com/index.php?main_page=product_info&products_id=274
    http://www.xscyz.com/index.php?main_page=product_info&cPath=69&products_id=197&zenid=9106c8ca4c116f7ee6a047c88bb43162
    http://www.xscyz.com/index.php?main_page=index&cPath=69
    http://www.xscyz.com/index.php?main_page=product_info&products_id=189
    http://www.xscyz.com/index.php?main_page=product_info&cPath=69&products_id=284
    http://www.musclecars.net/parts/Pow...up-DC-DC-Converter-For-Sale_200527576514.html

    I have also listed the specs on the leds: in case voltage and current draw becomes a factor.
    FOrward voltage min typical max for. current
    RED LED 2.0 2.3 2.8 120 ma
    GREEN LED 3.0 3.5 4.0 150 ma
    BLUE LED 3.0 3.5 4.0 150ma
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    You can't use RGB LEDs in series. It won't work.
     
  3. makavelly001

    Thread Starter New Member

    Mar 12, 2011
    5
    0
    Thanks for replying. Forgive me because I am naive in terms of electronics. Should they be in parallel then or how should I desigh the circuit?
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I don't think we can support discussion on your topic, as it is the use of LEDs in an automotive application.

    It would likely be illegal to use RGB LEDs on the exterior, and for the interior, it would seem to fall under the "distracting" category in the "Automotive Guidelines" thread.

    Link: http://forum.allaboutcircuits.com/showthread.php?t=40361
     
    Last edited by a moderator: Mar 18, 2011
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