car trunk lighting

[blackdragonx1186]

i recently bought a car, and it does not have a trunk light. well, being the flashaholic that i am, i want to put something better than a stock setup back in. i was thinking of http://www.dealextreme.com/details.dx/sku.26110 with 3 or 4 of http://www.dealextreme.com/details.dx/sku.13286. i was thinking i could just thermally glue to various points to give me a decent spread of light. no reflectors or optics, as i dont want them to get knocked off easily. i would be putting the leds in parallel, so they are not overdriven. what i want to know is will that driver put out a typical ~3.7v, even with more than 12v in? i could go with p4's that would handle the full 1A and put them in series to handle the voltage, i just want to keep it as cheap as possible.

 

[Lyndon]

I think that's overkill. Use a series string of 3 LEDs with a small resistor to the 12V car power. Charging voltage is about 13.6V, so work with that. You have thousands of watts available to turn on a few watts of LED for a few seconds on average, efficiency is not a concern.

 

[blackdragonx1186]

my other plan lol. what wattage resistor and ohm value?

 

[Lyndon]

At 3.7V nominal @ 1A per LED the resistor will drop (Vbatt- Vled) =
(13.8 - 3 * 3.7)= 2.7V across the resistor, so to provide 1A
R= 2.7ohm. I'd pick the next higher value since the LED may drop down to 3.2V or so as it heats up. Factor in that you may leave the trunk open for half hour on a hot day in Albuquerque and perhaps drop current down to 0.75A or so for safety and recalculate resistor value.

Resistor power rating required is (I^2 * R) = 1*1*2.7= 2.7W. Select a 5W resistor since you can often find those with mounting holes to bolt to a heatsink and they aren't very large.

 

[blackdragonx1186]

thank you sir. once i get everything in i'll get some install pics.