Resistor Opinions NBv3 + B/B/W

[rumpska]

Hey all,

I was wondering if anyone could share some opinions regarding resistors. I'll be working with:

- Battery: 18650 3.7V 3400mAh
- LED: Blue/Blue/White Cree Tri XP-E2 (Blue Vf@1000mA = 3.47V)
- Sound: NBv3
- I'll be using FoC with the White LED as well - I'll probably just use a 0.5Ohm 3W resistor for that fella.

From what I understand, it's recommended to run B/G/W LEDs at 1A, and red at 700mA. I've got 2 Blues, so I'd aim for 1A. Looking around, it seems like most people with similar setups are opting for the 0.5Ohm, 3W Resistor.

If I planned on using 1A for the blues, however, Ohm's Law would dictate that I should use a 0.23Ohm resistor [(3.7-3.47)/1]. I would think that using a 0.5Ohm would decrease the brightness quite a bit, while preserving some battery life, but I could be wrong.

Any insight on using the 0.5Ohm vs. going for a smaller resistor? Has anyone compared the resulting brightness of the two?

Thanks

[Forgetful Jedi Knight]

Welcome to the Forums.

The difference in resistance isn't that big of a deal since you're talking a fraction of an Ohm. Besides, not every value is produced, so it is common to round up to the next commonly made resistor size. Also that "extra" also helps take into account that a common 3.7V batter has a charge closer to 4.2V when completely charged. Yes, it doesn't last long, but that extra little bit of resistance helps protect your electronics setup.

[rumpska]

Sounds good. Thank you for the quick response! I appreciate the help

[Noyl Wendor]

You may want to wire those blues separate. One each with its own resistor.

[rumpska]

Sorry, should have clarified. I am planning on wiring each LED (including white) with its own resistor - and it seems the 0.5Ohm, 3W one is a good option to use for all 3 LEDs.