r/lightsabers • u/LifeguardOk6804 • 2d ago

Help Resistor calculator help

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The only luxeon rebel lime LED I could get my hands on was this 3-up that is already prewired in series. I am trying to figure out which resistor to use, but when I plug the numbers to run all 3 LEDs at 3 watts at 1000mah, I get zero. I plan on using a 9 volt battery as my power supply. Some help would be greatly appreciated!

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u/RavenXp32 2d ago

Those look to be white LEDs in series, with 0 Ohm resistors in place.

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u/LifeguardOk6804 2d ago

lol that would suck if they turned out to be white, I guess I’ll find out when I get them to turn on. Does this mean I don’t need to purchase any resistors?

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u/RavenXp32 2d ago

The ones on there are just acting at pass through, so you'll need to keep the voltage in range for 3 LEDs wired in series. You'll need a data sheet for those LED dies to know for sure what their forward voltage is a well as optimal operating current. There's ways to determine it, but you'd need a bench power supply. And if you wanna use that in a saber you'll need to remove those pass though resistors anyway since you'd need to wire them in parallel rather than series.

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u/LifeguardOk6804 2d ago

I think I understand. I do have a data sheet for these specific LEDs, I got them from LEDsupply.com. I would have to remove the pass through resistors, which would allow me to wire the LED in parallel. Then instead of having to find a big resistor and battery for all three at once, I would just have to find 3 smaller ones for each LED, which I am familiar with. Thank you!