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What resistor to use on LED light?

1448 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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I've built probably a hundred LED circuits consisting of two LEDs and a 9-volt battery. I always used a 330 ohm resistor with no problems.
Well, I've never run a set continuously to see. But the battery would probably last all season, if its only run a few hours each night. The 9-volts do last a long time.
Thanks, Creepy! I don't remember where I got the info. to use that resistor, but it always worked so I stuck with it all these years.
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