Path: utzoo!utgpu!water!watmath!clyde!att!pacbell!lll-tis!helios.ee.lbl.gov!pasteur!agate!eos!jbm
From: jbm@eos.UUCP (Jeffrey Mulligan)
Newsgroups: sci.electronics
Subject: Re: speaking of LEDs
Message-ID: <1652@eos.UUCP>
Date: 3 Oct 88 19:25:29 GMT
References: <1988Oct2.053515.18004@utzoo.uucp>
Organization: NASA Ames Research Center, California
Lines: 21

From article <1988Oct2.053515.18004@utzoo.uucp>, by henry@utzoo.uucp (Henry Spencer):
<>>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...
 
< In any power-critical application, one would probably want to use red,
< not green.  In all the LED families I'm familiar with, red is streets
< ahead of green on luminous efficiency.  However, this doesn't affect
< the issue much, since the forward drop in red LEDs is only a little
< lower than green.

For the caving application, you would probably want to compute the
luminous efficiency using the scotopic luminosity function (rods
instead of cones).  This would shift the balance towards green
by 1-2 orders of magnitude.

-- 

	Jeff Mulligan (jbm@aurora.arc.nasa.gov)
	NASA/Ames Research Ctr., Mail Stop 239-3, Moffet Field CA, 94035
	(415) 694-6290