On Tue, 28 Jan 2003, Bill Marshall wrote:

> I've been thinking of getting a big ol' chunk of Lexan, taillight sized, and
> drilling 50-80 holes in it, stuffing colored LEDs into the holes, and wiring
> up the thing as a taillight.  I'm curious as to what I will have to change on
> the van to support that electrically.

For the brake lights, probably nothing.  You'll need to use a dropping
resistor to limit the LED current to a safe value.  The red LEDs I'm using
for my CHMSL have a voltage drop of 1.8 volts each, so I wired them into
series strings of 5 and then wired the strings in parallel.  That gives 9
volts, and 20 mA per string.  Figuring out the resistance to be used to
drop the remaining 4.8 volts (for a 13.8 volt system) then becomes a
simple Ohm's law problem.  The wattage dropped across the resistor can
become fairly hefty if you use enough LEDs; make sure you don't use
something under-rated.

If you decide to replace your turn signals, you'll need to change the
flasher or provide something to simulate the current drain of a bulb.

There are some pretty bright white LEDs now, but I'm not sure if they're
really bright enough to be practical as reverse lights.  They're also kind
of expensive.

             _ _
  __ _ _   _| | |  | David M. Brodbeck (N8SRE)              Ypsilanti, MI
 / _` | | | | | |  +-----------------------------------------------------
| (_| | |_| | | | @ cyberspace.org
 \__, |\__,_|_|_| "To the optimist, the glass is half full.  To the
 |___/             pessimist, the glass is half empty.  To the engineer,
                   the glass is twice as big as it needs to be."