Need help for xmas project!

[McCallister1]

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!

 

[jackorocko]

You have to use resistors to control the current. Those LED's will drop 12 volts@wide 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

 

[McCallister1]

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!

 

[alfa88]

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.

 

[jackorocko]

Well that depends on how long you expect your led lights to work? Alfa is correct in that lithium batteries are by far the best battery, but they are expensive and are picky about heat. I also think they would cost more then this http://www.amazon.com/Logisys-PSAD24-24-Watt-Power-Adapter/dp/B003MYLLCC/ref=pd_cp_p_4

 

[alfa88]

That looks like a more elegant solution to me.