There are a few resources out in the ether to help with LED projects. A
couple I use are:

loads of all kinds of data here:

http://www.uwgb.edu/nevermab/led.htm

And an easy and neat calculation gizmo, for both series and parallel
applications:

http://led.linear1.org/led.wiz

Alistair

'82 westy, diesel converted to gas in '94
http://www.members.shaw.ca/albell/

On 3-Dec-05, at 6:50 AM, Edward Maglott wrote:

Always looking for a good hack, I noticed recently an LED flashlight on
sale for $10 at the Eckerd Drugstore.  This has 21 bright white LEDs in
it
and uses 3 aaa batteries in series.  All the bulbs are in parallel, so
each
one is getting straight 4.5V DC.  It makes a nice little flashlight, and
I'll probably use it as one before hacking it up for the bulbs.  This
works
out to $.21/LED, which is a great price, especially if you consider most
electronics places you would have to order them from, and pay shipping,
meet a minimum order, etc.  I measured .4 amps draw or 1.8W.  .4 amps
might
run down those 3 aaa batteries pretty fast.  I think it said 10 hours on
the package.  If you buy one, be sure to use the "try it" button and
make
sure all 21 LEDs are working, one was bad on the one I bought...

Here's a link to the same item on a
website:              http://snipurl.com/kgds

Now my question.  What size resistor do I need to run one of these LED
bulbs on the 12V system of the vanagon?  I want to put one in the back
light of an aftermarket tach I have, which is very dim at night...

Thanks, and enjoy.

Edward