> > Here's a link to the same item on a > website: http://snipurl.com/kgds
Heh. I got one of these on ebay once. Man, what junk. Good source of parts, I reckon, but a god-awful flashlight. 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... > Well, assuming .4A and 4.5V, it's a fairly simple application of Ohm's Law. First, you figure out how much excess voltage you need to "get rid of" (we're actually limiting current flow, but it helps to think in reverse): 12V - 4.5V = 7.5V then you plug the numbers into the formula R=E/I (where E is volts and I is amps). 7.5v / .4a = 18.75ohms So a 20ohm resistor ought to do the trick. One of the problems, of course, is that we only have measured and obvserved numbers to work with rather than the actual specs for the LEDs. Close enough estimate though, I think. Someone correct me if I've made a gross error. It's early and I'm not awake! -- John Bange '90 Vanagon - "Geldsauger" |
Please note - During the past 17 years of operation, several gigabytes of
Vanagon mail messages have been archived. Searching the entire collection
will take up to five minutes to complete. Please be patient!
Return to the archives @ gerry.vanagon.com
The vanagon mailing list archives are copyright (c) 1994-2011, and may not be reproduced without the express written permission of the list administrators. Posting messages to this mailing list grants a license to the mailing list administrators to reproduce the message in a compilation, either printed or electronic. All compilations will be not-for-profit, with any excess proceeds going to the Vanagon mailing list.
Any profits from list compilations go exclusively towards the management and operation of the Vanagon mailing list and vanagon mailing list web site.