Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!amdcad!ames!ucsd!sdcc6!mplvax!cdl
From: cdl@mplvax.nosc.MIL (Carl Lowenstein)
Newsgroups: sci.electronics
Subject: Re: speaking of LEDs
Message-ID: <779@mplvax.nosc.MIL>
Date: 30 Sep 88 16:58:55 GMT
References: <491@ole.UUCP> <7200014@silver>
Reply-To: cdl@mplvax.ucsd.edu.UUCP (Carl Lowenstein)
Organization: U.C. San Diego, Marine Physical Laboratory
Lines: 21

In article <7200014@silver> commgrp@silver.bacs.indiana.edu writes:

>Some cave-explorer friends are experimenting with the new LEDs for 
>emergency light sources:  Two LEDs, each in series with a 33-ohm 
>resistor, connected to two alkaline AA-cells, will make enough light 
>to get out of the cave, for 24 hours.  
>--
>Frank
>reid@gold.bacs.indiana.edu

Why not connect the two LEDs in series and use a smaller resistor.
Don't use the battery energy heating a resistor when you could be using
it to make LED light.

Answer of sorts to the question above:  the forward drop across the LED
is too great.  About 2 volts for green.  Revise the question:  How
about 3 alkaline cells and 2 LEDs.  Should be a better match to the
problem, at a 50% weight penalty.
-- 
	carl lowenstein		marine physical lab	u.c. san diego
	{ihnp4|decvax|ucbvax}	!ucsd!mplvax!cdl