led

right now i'm in the thinking stages of a LED project I might cosider down the road.  What I need to know is the following. 

In a vehicles rear brake lights, normally these occupy the standard bulb and connector.  Is it possible (and safe) to directly wire in say an LED into this wiring, to create LED style brake lights?  I do realize I'd have to use a voltage divider to knock down the voltage so the LED won't blow out.  I am thinking of using say 10 Leds hooked up together, what other electronic compenents should I concider using ot make the circuit more reliable?  Will i need diodes?  If so do they go between ground and the positive side of the LED?  What type of diodes? etc etc.................

Any help is GREATLY appreciated.

Rye2

The Disadvantage of LED's

  I am an engineer and do-it-yourselfer and have contemplated making my own LED signals and/or replacement lamps also. Not to discourge you (have fun experimenting!) but I'll share what is not so obvious. LED's light output is VERY DIRECTIONAL and the viewing angle at which they are reasonably bright is much less than that of an incandescent bulb. Also, virtually all auto lamp/lems assemblies using incandescenat bulbs are designed so that the majority of the light output comes from a concave or parabolic reflector. The reflector uses light emitted primarily from the sides and back of the incandescant bulb. Virtually all affordable LED replacement lamps only emit light straight out the back. This renders the light assemby's original reflector useless and results in a light having one small "hot spot". I have see some LED replacement bulbs which emitted light out the sides also, which somewhat improved its ability to work with the original reflector to increase the "bright area" and reduce the "hot spot" effect. However, it was quite pricey ($50+) and I still didn't think it lit up the taillight lens/assembly with as large and safe of light area as an original incandescent bulb. However, the results you can obtain with cheap and/or premium LED replacement lamps will vary a lot with the size and shape of the light/lens. Even the cheap LED replacement can work pretty good with smaller lights which are basicly round in shape. Also keep in mind how the bulb is positioned/oriented in the original assembly. My truck uses conventional 194's  for the front side markers. The LED replacement 194's didn't work well at all because the my side marker lamps position the bulb SIDEWAYS . The LED replacement was design so that the light output is at the tip end of the repleacement bulb with hardly any light output at the sides. Lamp assemblies specifically designed for LED's generally don't use any reflector. The spread a fairy larger number of LED's (20-40) over the surface of the lens to create a large light area. I've seen Ebay auctions where you could purchase individual LED's specifically engineered for wide viewing angles and automotive applications. Commerical LED signals usually wire enough LED's in series to consume the 12 volts. This eliminates the nees for volage regulators/dropping resistors. The downside is that if one goes out, all in the circuit go. But as long as you have enough LED's in series, the current flow should be low and their life long. If I was going to try something, I would probably get an old taillight assembly,  some polyester casting resin, and red die. I would "cast in" two dozen or so bright LED's with the LED's touching the back surface of the lens. This would be a good attempt to resolve the reflector/directional issue. OEM LED taillights on the high-line cars have just that: the LED's are right at the surface of the lens.