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From: wtm@uhura.neoucom.EDU (Bill Mayhew)
Newsgroups: sci.electronics
Subject: Re: LED history ?
Message-ID: <1991Jan23.052308.12366@uhura.neoucom.EDU>
Date: 23 Jan 91 05:23:08 GMT
References: <1991Jan16.034246.12843@zoo.toronto.edu> <1962@atlas.tegra.COM>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 24

LEDs can have interesting circuit properties aside from their light
emitting abilities.  An interesting experiment is to do an i-v plot
on an oscilloscpe for an LED.  LEDs at low current levels can also
be modulated by ambient light, but isn't a terribly great detector.

In a pinch, I've used an LED as a crude voltage regulator.  The
knee of the curve is about 1.8 volts, which beats hooking up three
silicon dioes to get a handy 2 volt drop.  Those low voltage Zeners
can be rather inconvenient to find, if you're just fooling around
just prototyping something.

Most likely the glass LED in the CD player was just a pilot light.
This especially handy if the CD player was a battery op model; it's
easy to forget to shut down before poking around.  Another use
could be a disk presnet sensor light source if there were a photo
transistor on an adjoining board...


==Bill==
-- 
Bill Mayhew      NEOUCOM Computer Services Department
Rootstown, OH  44272-9995  USA    phone: 216-325-2511
wtm@uhura.neoucom.edu   ....!uunet!aablue!neoucom!wtm
via internet: (140.220.001.001)