# Dollar Store Candle Conversion Help



## Doc Doom (Aug 28, 2008)

I bought a couple of Dollar Store LED candles that run on two AA batteries and want to convert them to run off a 12V DC wall wart. I've worked with LEDs before but problem is I don't know anything about these LEDs. Any idea what size resistor to use? I don't want to let the magic smoke out.


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## Palmdale Haunter (Mar 3, 2012)

Try Google... LED Calculator Resistor...
I am no electronics expert just enough knowledge to be dangerous actually. 
Making a small assumtion about the AA batteries I assume 3 Volts is your terminal voltage and assuming 20 mA so it looks like a 1/2 watt 470 ohm resistor may be what is needed... 
led.linear1org/led.wiz


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## corey872 (Jan 10, 2010)

Certainly good assumptions if the candle has one LED...if it has more than one, this would be a conservatively safe estimate and you might be able to bump the resistor down/current up a bit.

The 'ideal' way to test would be to measure current draw with a fully charged set of batteries, then install a resistor to match that with the 12V source. This would require having a small volt/amp meter, though they can often be found for well under $10 and are invaluable for testing and troubleshooting a number of circuits.

As an example...$4.99 + 20% off coupon:

http://www.harborfreight.com/7-function-multimeter-98025.html


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## Palmdale Haunter (Mar 3, 2012)

Remember I said I was no expert.....
Just for the record I'm a nurse by training an electronics engieering is not part of the core curriculum...


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## corey872 (Jan 10, 2010)

No prob - wasn't trying to imply anything bad, (apologies if it came out that way) as I said "good assumptions" and they will be conservatively safe which is the best practice. I threw out the 'ideal' way just as info, but not everyone has the hardware to do 'ideal' so we all get by with what we can do!


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## hpropman (Jul 27, 2008)

The 470 OHM sounds about right for 12 volts


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## Doc Doom (Aug 28, 2008)

I hooked up both 400 and 500 ohms and saw no visible difference between either set up or the original double AA power source. Kept all the magic smoke intact too.

Thanks for the help.


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