LED Taillights, Custom Made for the 914 Options

[Spoke]

I've wanted to convert my 914 taillights to LED for a while but never got around to it.

Finally I started working on the design of the taillights. This will be a single custom PCB for each side and will have all the LEDs and control circuits on it. One PCB will be used for both sides.

The plan is to remove the existing plastic reflector and bulb assembly and mount a custom board in its place. With proper standoffs, I should be able to mount the board using the same 2 screw holes that secure the reflector.

I'm trying to decide now how many LEDs to use for each purpose. Right now, I have 8 LEDs for the backup lights, 20 LEDs for the running/Brake lights, 24 LEDs for the turnsignals, and 4 LEDs for the side marker.

I've been observing modern cars with LED taillights and some use a few LEDs (like 8) and some a lot (+20).

I would like your opinions on how many LEDs you think would be good to use. On the board below, the LEDs are spaced about 0.7 inches apart. These will be medium brightness white LEDs. (I'll let the lenses provide the color).

The first cut at the board is shown below for the driver's side. The side marker LEDs will be right angle LEDs pointing out the side of the board. They can be seen on the extreme left side of the board.

If these work out, I could manufacture them for World members. One thing though, they won't be cheap. The LEDs are about $0.50 through Digikey and there are more than 55 LEDs on each right now. Plus there's 2 dc-dc converters for providing constant current for the tail/brake and turnsignal LEDs.

Cheers
(IMG:style_emoticons/default/beerchug.gif)

[Madswede]

7TPorsh:

Always wondered about this. Does this mean the same when using regular bulbs? If I use red incandescent bulbs; are they better than clear?

I would think that most standard incandescent bulbs produce a wide range of wavelenghts and the red envelope does the filtering to remove unwanted colors producing the red light. While the red lens will pass most of the red light, there will still be some additional filtering losses so you would probably be better using a clear bulb and do all of the filtering with the lens. I don't believe most LED's are truly monochromatic (like a laser), but rather they produce a variety of wavelengths within a fairly narrow band. {red(ish) or blue(ish) or.....} Anybody know about this???

Oddly enough I was just researching LEDs a bit ago. Wiki has a decent summary on the technology behind how LEDs work, and to summarize it all up, it would seem you're exactly correct in saying that LEDs emit light in a relatively narrow range of wavelengths (colors). It seems they may or may not be totally monochromatic depending on the semiconductor material and doping materials used (there is such a thing as a diode laser, apparently). I'm certain you're also correct about incandescent bulbs emitting a wide range (more or less white light) of wavelengths.

In contrast, LEDs typically emit light in a certain color (i.e. not white) due to how the light comes about from the electrons' behavior in the diode's doped semiconducting material. Hence, LEDs do not typically use filters at all unless for some special application or circumstance. It's tricky to get white light from an LED and while it is of course possible, there are several ways of doing it (including using more than one actual LED in each "light" assembly).