Automotive courtesy lights

[Blackbeagle]

My car isn't equipped with very much in the way of courtesy lights. I plan to add trunk lights and under the dash to illuminate the footwell. After thinking about it, I want to use LEDs - low heat, vibration resistant, small so I can hide them wherever...

The question I have is that since voltage varies from 11-14VDC, I've been thinking about using a voltage regulator like the 7805 so I can start at a stable voltage to calculate my resistors. One of my friends insists I'm thinking it to far and should just recalc for about 13.5V, go direct from the 12V. Anyone have any thoughts?

 

[Saaby]

I have a neighbor that got some pre-made LED lights for his van at Checker. They come pre-wired to a 12V plug. Might be handy for part of the project. Blue LEDs only though, about $20.

 

[e=mc²]

I have done just that, that is, directly powering Nichia NSPW500B White LEDs with each LED having it's own dropping resistor of 33Ω 1/2Watt. I have had them in use for just about two years now, with no problems. Even if the voltage spikes up to 15V, that would mean each led would rec approx 35ma of current. This is assuming a Vf of 4 volts. I know this seems like a high Vf, but with the batch of leds I received 2 yrs ago, at 30 ma I measured Vf to be 4 volts exactly on all 100 leds. They were from the same batch number, which made things easire. The only thing not consistant throughout the batch, and this is being real nit picky, is the ever-so-slight color variation of the white light. But for my instrument cluster, floorwell, and behind dash accent lighting, it is NOT even noticable.

Ed

 

[Entropy]

Check out http://www.geocities.com/george_tlc/led.html

He's a CPFer (georges80) who has done some cool mods, including turnkey Luxeon replacements for Toyota Land Cruisers. The board should be easy to reconfigure for lighting elsewhere. The nice thing is that these boards are current regulated step-down DC/DC converters. (i.e. very efficient, cool-running, and independent of input voltage)

 

[highlandsun]

Don't forget to throw in a capacitor for a nice soft fadeout...

 

[Zelandeth]

Hmm, capacitor, nice touch. *goes to implement idea*

My car's had LEDs fitted for a few months now (Green for heater controls, red-orange for rear screen heater/fog light switches, and red for the hazard flasher switch) was simply to give some illumination as there was none before and I was getting fed up of nearly killing myself fumbling for the heater controls which are halfway across the dash. I just assumed the circuit voltage to be 13.6V which is what it averages out at with the engine at slow tickover, with the lights on. Haven't had any trouble with them being driven directly, each with their own dropping resistor, running directly from the dash illumination circuit. No dimming's apparent when the system's under load (unlike the incandescent lamps in the instrument cluster), and no overloading problems.