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3 LED light question Answered

I am just curious as to what I might need, if any for a resistor. I plan to run 3 white LED's, using a single 9v. I jumped ahead and hooked up one set to see how it works, and it seems to work great, each LED is packaged as running at 3.2v, so I figured 3 would be alright on a 9v battery. Is a resistor required or necessary if I multiply in this manner?

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Soloratov

10 years ago

Thanks guys. I think I figured it out after reading some other guides here. I now have the LEDs running in parallel....all negatives together, all positives together.....think thats parallel.......anyway, they are all being supplied from 2 AA batteries. Work beautifully, nice and bright, and so far so good after about 30min. It's intermittent use so we'll see, but according to some other guides here, this should do the job nicely.

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UziMonkey

10 years ago

You should be running these LEDs in parallel with resistors for each. Unless there's a really good reason not to do this, connect them in parallel.

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11010010110UziMonkey

Reply 10 years ago

there is really good reason - when in parallel they kill the battery 3 X faster

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UziMonkey11010010110

Reply 10 years ago

If each LED has a forward voltage drop of 3.2v, you're already running them at the minimum voltage (if they'll light at all at 9v, a fully charged 9v provides closer to 10v). As soon as the battery loses any life, the LEDs will probably stop lighting. Running them in parallel will probably let you run them for longer on the same battery, even though it's drawing more current.

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11010010110UziMonkey

Reply 10 years ago

the forward voltage thing is not really that strict. leds often work ok on a bit lower voltage since batteries lose their voltage fast at end of life (not like capacitors) i think the fact that leds work on lower voltage won't make up for the faster discharge there is also an option of 2 series + 1 on its own which is like a compromise and maybe itll give max life the best way is try and see

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11010010110

10 years ago

if the leds dont heat at all and are not unusually bright that should be ok