Luxeon Trunk Lighting

[ResQTech]

What would do a better job of lighting up my trunk (driven at spec):
a) 3 - 1w Bin Q4H
b) 2 - 3w Bin SY0L

Also, what would be the best way to drive each of these configs to spec off 12VDC? Resistors? Parallel? Series?

[evan9162]

I would think that three 1Ws would be better, since you can a) overdrive them (i know, just broke your rules), and b) you'll have more sources of light, thus, fewer shadows.

In any case, the best way do drive either configuration is with all in series, and either a dropping resistor, or even better, an lm317T in current mode.

[RussH]

I agree with Evan, but what do you have on hand? You could flip a coin. I think I would use the 1W with 3 in series & an Lm317. Note that the LM317 works as a current regulator with only 1 resistor and costs less than 50 cents. It's very good for automobile use since its good for 2 -37v input. In a car, the normal variation is from 11v (dead battery) to normally 14.8 -15.5v (possibly 16v or 17v in some apps) max alternator output. Thats a lot of variation for a resistor.

You could use 2 Lux3s in series with an LM317 current regulator & the total of 6W (closer to 8W at 1 amp) should give you more light. But you would get close to as much light driving the 1Ws at 600-700ma (about 2W each depending on Vf). The 1W technically should be more efficient - not that much of a consideration here. My preference would be to save the Lux3s for where they really shine.
(I couldn't help it!) -RussH

[gadget_lover]

The nice thing about adding a lux to a car is that you don't have to be as concerned with size or efficiency. The 12 volt battery will run a luxeon for a long time even if you use 1 resistor per luxeon. The variance as the battery charge goes up and down won't be apparent because you'll use it intermittantly.

I'd go with the 3 'Q's for the more distributed lighting. Low dome if possible. The lumens will be about the same as two 'S', give or take 10%.

Daniel

[Zelandeth]

Hmm, for this application I can see another advantage of the 1W units. If one dies for any reason, it's going to ve a lot cheaper a failure than if a 3W suffers a premature failure.