Re: [Amc-list] Blue LED tamed

["Widiker, John D" <john.widiker@xxxxxxx>]

This Blue LED is not a tiny cute one, it's a freaking laser, it's burn
your retinas bright, 200 did absolutely nothing at all. The same one he
has we used 15K on and it was tolerable and hasn't had an issue in 3
weeks of use. 

~J

-----Original Message-----
From: amc-list-bounces@xxxxxxxxxxxx
[mailto:amc-list-bounces@xxxxxxxxxxxx] On Behalf Of Tom Jennings
Sent: Sunday, March 04, 2007 4:37 PM
To: AMC/Rambler owners, drivers and fans.
Subject: Re: [Amc-list] Blue LED tamed

On Sat, 3 Mar 2007, Widiker, John D wrote:

> Subject: [Amc-list] Blue LED tamed

> Tell the person at radio shack you want a 15K (1/4 watt) power 
> limiting resister,

15K is too big!

The resistor is to limit the current through the LED. You need to know
the rated "forward current" for the LED, but nearly all small-ish LEDs
want 20 to 40 milliamps max. More than that they may get brighter, but
their life will drop DRAMATICALLY!! Use more LEDs if you want more
light.

When on, blue LEDs drop about 3 volts across them (this is a constant).
For a typical small blue LED, 20 mils of current, you would use a 470
ohm resistor; for a 40 milliamp LED, half that; 220 ohms. (Resistors
come only in standard values, you won't normally find a 500 ohm
resistor.)

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