[vox-tech] Re: Re: Problem - PS/2 port still live after shutdown (Jay Strauss)

[Mark K. Kim]

On Wed, 26 Feb 2003, Harry S wrote:

==8<--
> Your question had me wonder... (Any E.E. Students out there???)
> -What is the typical life of LEDs, years?

Depends on how you're using it.  If you run it continuously (as opposed to
pulsing the signal) at 2/3 of the maximum continuous current, it'll run
virtually forever.  If you run it continuously at 100% of the maximum
continuous current, it'll run for as long as the spec sheet says it will.
I've seen LEDs rated at 20 years at maximum continuous current.

> -What is the typical power usage of LEDs, milliwatts?

I've seen LEDs with 1.5V voltage drop across them.  I think I've seen LEDs
with 0.7V voltage drop across also.  I imagine there are many others, but
those two should be the most common in consumer electronics.

As far as the current goes, it depends on the circuit, and each LED's
maximum rating is different.  It's generally in the tens of milliamps
range for the typical LEDs I've seen.

Power ("wattage") is voltage times the current (P = vi).  If I had to
guess, the LEDs on those Microsoft mice are using about 20mA * 1.5V = 30mW
per LED, give or take.  It's just a guess.  Whatever the case, it's in the
correct order of magnitude, though.

BTW, we have USB mice at work that won't turn off their LEDs after power
off.  They're all running Windows 98SE.  The mice are Microsoft optical
mice (corded.)  Several of us use the same mice on computers with Windows
98SE, but only some of the mice won't turn off after power off.  It's a
little annoying.  It might be a motherboard thing, rather than an OS
thing.

-Mark
 (been tearing his hair out for the past 6 months working with LEDs...)

-- 
Mark K. Kim
http://www.cbreak.org/
PGP key available upon request.