Proper resistor selection

[imgumby001dammit]

With a 3.7v batt, and a 12w led (rgbw), using red and blue to make purple, and leaving green for FOC, no white, what would be the proper resistors. I know there’s math involved, but I suffer from discalcula, and math is an issue for me. So please, only make fun of me a little bit.

[firehand10k]

It depends on the correct forward voltage of the individual diodes. They vary by manufacturer and model so there is no accurate way to answer this without more information.

[Infinit01]

With a 3.7v batt, and a 12w led (rgbw), using red and blue to make purple, and leaving green for FOC, no white, what would be the proper resistors. I know there’s math involved, but I suffer from discalcula, and math is an issue for me. So please, only make fun of me a little bit.

Give me the forward voltage for each color and I’ll calculate them for you. They normally give specs when you buy them

[imgumby001dammit]

High Power 12Watt RGBW LED Chip 3W 4 CHIPS,Viewing Angle: 120-140°
Brightness: red: 90LM green:160LM blue:50LM white :220LM
Wavelength: red: 620-625nm; green:520-525nm; blue:460-465nm; White 6000K
Forward Voltage:red: 2.0-2.2v green:3.2-3.4v blue:3.2-3.4v white :3.2-3.4v
Forward Current: 700mA

This is all I have. Is this the correct info?

[firehand10k]

Yup that's the correct info. Wait a bit.

[scifidude79]

No math skills needed:

http://led.linear1.org/1led.wiz/

2.2 ohm 2w for the red
1 ohm 1w for the other colors

[Infinit01]

SFD got it

[imgumby001dammit]

Ok, so, all my resistors are 3w. How will that affect me?

[scifidude79]

Not a whole lot. It may dissipate more heat. Wattage really doesn't affect brightness. I've used 3w resistors in a number of builds and it's not an issue.

[Infinit01]

Wattage is used for head dissipation so having a little higher wattage isn't a bad thing

[imgumby001dammit]

Thanks fellas. I got sent to the bottom of Wyoming for a couple of day, so I won’t be able to drop that led into the Sentinel till I get back. Should be pretty straightforward once I get on it. You guys ever wire up illuminated switches?

[Infinit01]

Thanks fellas. I got sent to the bottom of Wyoming for a couple of day, so I won’t be able to drop that led into the Sentinel till I get back. Should be pretty straightforward once I get on it. You guys ever wire up illuminated switches?

You're welcome, I have.  Give me a few, shutting down work network for an office move. Give me the specs on your LED AV and I'll see if it matches up to mine

[imgumby001dammit]

So, epic fail on the FOC. But, the resistors independently wired worked. I blew the red at some point between testing before soldering , and testing after soldering. I wired the white instead, but the silver flash dosent flash. I’m not sure if I dammaged the board or what. However, I did create a cool blue out of the blue and green led combo. It’s more green than arctic. Here’s a look.




It goes from left to right; GB, AB, NB(Nick Blue;)). At least I did something cool out of all this work. The first RGBW is still salvageable, plus, I have the original luxeon Star in CG.

[Infinit01]

Great work, Gumby.  Keep it up!!!!

[scifidude79]

Arctic blue is always nice. Sorry to hear you may have damaged something. I'm truly amazed that I've never done that. There have been a couple times where I swear I've overheated a sound board or two, but they're pretty robust.