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What resistor to use on LED light?

1446 Views 11 Replies 7 Participants Last post by  DaveintheGrave
Needing a LED light for an owl that I will be lighting his eyes up with. The only LED bulbs that I can find at my Radio Shack are just the bulbs without the resistor already attached. What is the rule of thumb on this? I plan on running it with a little 9 volt battery. Is there a formula for what resistor to use for a certain sized LED light? Any advise would help greatly!
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If anyone is interested, I have a spreadsheet I put together that does all the work for you, for 1 - 5 LEDs. Just drop me a message with your email and I'll send it to you!
Dave, 330 ohms sounds about right for 2 LEDs on a 9 volt battery. Only about 15 mA draw, so it should last quite a while!
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