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Need help for xmas project!

Discussion in 'General Electronics Discussion' started by McCallister1, Dec 13, 2011.

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  1. McCallister1

    McCallister1

    2
    0
    Dec 13, 2011
    Hi all,

    New to the forum & need some guidance for a Christmas project I started not knowing it would end up getting this in-depth...

    Anyway, I am making a "manly" garage wall frame type thing for my Dad. I want to have the backside of this frame back lit with LED strips. I want to run one strip of green colored LED lights on the top edge and then one strip of yellow LED lights on the bottom edge. I was looking at getting some 5050SMD lights(one of each color). They are 12v DC products.

    I want to be able to run these off batteries so there are no cords to mess around with plugging into an AC outlet. The site I was looking at buying them from says a 19.5 inch length of each(30 LEDS per strip) has the following:

    Green: draws 500mA(6 watts)
    Yellow: draws 600mA(7.2 watts)

    What would you recommend I use for a power supply? I was thinking two 9 volt batteries together(18 volts)& then using resistor(s) in a series as someone with more knowledge than I recommended. Of course I'd want a simple switch in there too. Can I run both strips on the same power source?

    I really don't think this is a complicated task for most who know what they are doing & hoping to get a bit of guidance to get this completed. I am pretty good at hands on, but just want to be sure I don't fry out $35 of LEDS.

    Thank you in advance!
     
  2. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    You have to use resistors to control the current. Those LED's will drop 12 [email protected] range of current. If you do not use a series resistor the LED's will draw too much current and toast themselves.

    I think your series resistors are gonna need to be rather big as well, if they need to drop 6V at .5A that is equal to 3 watts of power. Seems like a waste when using batteries.

    I also don't think you are gonna get much run time out of (2)9V battery (if even possible, I can see the battery getting extremely hot.) They have good voltage but very low current available. About 1/4 of a AA http://www.techlib.com/reference/batteries.html
     
    Last edited: Dec 13, 2011
  3. McCallister1

    McCallister1

    2
    0
    Dec 13, 2011
    Thanks for the input. As you can see I have very little knowledge of the proper set up for this. I really want to not use AC for aesthetic reasons. If 9v batteries are not a wise choice, what would you recommend for a DC source that will not drain super fast and not get very hot as you stated? Thanks!
     
  4. alfa88

    alfa88

    332
    4
    Dec 1, 2010
    One of the things I pondered as a child when watching Star Trek was their phaser pistols and what kind of marvelous power source was contained in them. Fast reverse to 2011. I think the smallest and best you'll be able to find are lithium( not to be confused with di-lithium; sorry, Star Trek humor) AA cells but they come at a cost and also die out eventually.
     
  5. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
  6. alfa88

    alfa88

    332
    4
    Dec 1, 2010
    That looks like a more elegant solution to me.
     
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