>Chris Harper wrote in a message to Ivy Iverson:
 >
 > CH>  On Tuesday August 20 1996, Ivy Iverson of (1:154/170) wrote
 > CH> to Arlo Hagler:
 >
 >
 > CH> I used to have several LEDs mounted to things like the
 > CH> bottoms of the legs on the bed, desk, etc..., in my bedroom,
 > CH> and ran them off a 9V battery so I wouldn't have to turn on
 > CH> the light for trips to the bathroom, etc..., at night.
 > CH> Worked real well unless someone left something laying around
 > CH> on the floor.
 >
 > CH> One question though. Do LEDs ever "burn out"? I've yet to
 > CH> hear of it. Anyone know the average life span?
 >
 >I would also be interested in knowing if they burn out.  I would also like
 >to know how many you can hook up to a 12-volt battery or even a 9 volt
 >battery for starters.
LED = Light Emiting Diode. Diodes do "burn out" so to speak. Too much reverse 
bias (hooked up backwards) will do it. So will too much forward bias current. 
Diodes are PN junctions. One half positive material, the other negative 
material. Hooked up with a forward bias (P side more positive than the N side 
by the RATED voltage) will cause conduction. LED's come in all sorts of 
voltage ratings, with different current ratings too. You pick how many LED's 
you need, then select the voltage and current ratings to match your setup. If 
wired in series (N of one hooked to P of the next, and so on) 3 volt LED's 
can have four across a 12 volt circuit. If wired in parallel, use the same 3 
volt/4 LED series bundle, and use as many bundles as you want, up to the 
limit of your power source current.
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