Yet another resistor question. Haven't seen this one asked yet, though.
Hey all. I've built sabers before, but they've all been current driven via a PC or a CF with a Color Extender. I haven't had to use resistors for high power LEDs yet.
I'm planning an NVv4 RGB saber with a PEx using the R/G/rB Tri Cree in the store and an 18650 cell. My main question is: should I use 4.2v or 3.7v to calculate what resistors to use? I don't know why I wouldn't use 4.2 (max), but I get weird values that aren't available in the store. That strikes me as weird, because I feel like they should be in the store.
with 4.2v:
R - (4.2 - 2.65)/1 = 1.55 ohm (I'd probably use the 1.5 ohm 5W resistor in the store, even though it's unnecessarily large. I only need 1.5 - 2W resistor)
G - (4.2 - 3.7)/1 = 0.5 ohm (Easy: 0.5 ohm 3W would be fine)
B - (4.2 - 3.4)/1 = 0.8 ohm (I'd probably use a 1 ohm 2W for this, but I'm worried that would be to much.)
with 3.7v:
R - (3.7 - 2.65)/1 = 1.05 (Probably safest to go with the 1.2 ohm 3W, but you could also probably get away with 1 ohm 2W)
G - (3.7 - 3.7)/1 = 0 (I know i can just use the drive parameter to limit the green a bit, but I'd be much more comfortable throwing in a small resistor)
B - (3.7 - 3.4)/1 = 0.3 (0.47 ohm 0.5W is probably the most appropriate thing for this)
What do you NB veterans use to limit the current in your Tri Cree R/G/rB? I'd be worried only using 3.7 v to calculate the resistors, as that would lead to them being overdriven when the battery is fully charged. My gut is to use 0.5 ohm 3W on the G and the rB and use the 1.5 ohm 5W for the red.
