Semi OT: [elec]LED gauge lighting

[amalventano@sc.rr.com (Allyn)]

Carl,
    You simply need the correct value resistor in series with the LED and it
will be safe.
here is an example:
<http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=C
TLG%5F010%5F012%5F002%5F009&product%5Fid=276%2D320>
follow along with me:
* this LED is rated at 20mA @ 3.6V. you intend to supply it with 13V
(cluster light power).
* 13V-3.6V=9.4V , meaning you need something else to drop 9.4V, in order to
protect the LED.
* therefore our resistor needs to carry 20mA at 9.4V.
* 9.4V/20mA=470ohms
    Place a resistor of that size (or slightly higher) in series with the
LED and you can then wire it directly to your instrument cluster lighting
supply. Furthermore, your dimmer will still work correctly as the resistor
will help the LED respond linearly to changes in input voltage.
hth
Al (resident electronics geek)

----- Original Message -----
From: <Cmr446@cs.com>
To: <scirocco-l@scirocco.org>
Sent: Monday, January 13, 2003 6:00 PM
Subject: Semi OT: [elec]LED gauge lighting


>   I want to convert my gauge/instrument lighting over to white LED's, but
I'm
> trying to figure out just how to do this. A quick trip to Radio Shack
> provided a 1000mcd white LED at 3v, and the sales people had no idea what
I
> was talking about when I asked if higher voltage and wide angle versions
were
> available. Other than that I did find out that I'll need to run a 470 Ohm
> resistor on the LED, but would I need this with a higher voltage LED?
>
>   Any help before I turn my dash into a fireworks and smoke show would be
> appriciated! :)
>
> Carl
> 77rocco
> 89fox  - donor to be
> 03saturn - 16v, 140hp, no soul...
>
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