Resistor calculation math?

[Noyl Wendor]

It doesn't seem from the manual that I should need two resistors for the main led. I went off the idea that the single resistor would be sufficient. I didnt account for running at 2 amps. So the resistor I am using is a bit too much.

[Jay-gon Jinn]

We have said this elsewhere: if one die pops, the other one is GUARANTEED to pop too if you combine into one resistor. A die popping is more likely too, as a manufacturing defect/imperfection could cause it to draw more current than designed, and you would be happily giving it twice the current it's designed to take.

Resistors are cheap. Wiring one for each isn't that bad. The question is whether the risk is worth the reward. The reward is that you'll save yourself five minutes, a couple of cents, and a little room. The risk is that you'll have to remake your entire LED module later.

I've used the single resistor method ever since we started using mutli-die leds, and have never had one of the led's "pop," but if you feel safer doing it that way, that's your perogative.

It's your saber Noyl, wire it up whichever way you prefer.

[Noyl Wendor]

Im going with a single resistor. But I'm sure lowering the resistor value. So that should fix the issue

[Bark]

I've used the single resistor method ever since we started using mutli-die leds, and have never had one of the led's "pop," but if you feel safer doing it that way, that's your prerogative.

It's your saber Noyl, wire it up whichever way you prefer.

It's not a "feeling." Link: Why exactly can't a single resistor be used for many parallel LEDs?

[Silver Serpent]

Does it work? Yes, if the LEDs are perfectly (or very closely) matched. Is it something I'd recommend to a beginner as normal practice? No.

The risk of thermal runaway goes up as the number of LEDs in parallel increases. If you've just got two LEDs in parallel, the risk is minimal. It goes up from there. For a budding sabersmith, I'd always advise to err on the side of caution. There's enough ways to burn out an expensive LED without adding more risk to the mix. Especially when resistors are just inexpensive insurance.

Once you've got a handful of sabers under your belt, you're confident in your abilities, and don't mind the possibility of replacing the LEDs, then by all means try it out.

[Noyl Wendor]

Well I'm pretty confident on the single resistor. Mainly I was looking for confirmation on the math LM not at home ATM. But what info I do have tells me this resistor I listed at the beginning of the thread is the one to use. As far as wiring resistors to each die I would like to save the room if I can. Both LEDs are the same (ggw tried cree) so in my mind one resistor makes sense. From everything I've read there's not really a down to using one resistor.