Newsgroups: sci.electronics
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: speaking of LEDs
Message-ID: <1988Oct2.053515.18004@utzoo.uucp>
Organization: U of Toronto Zoology
References: <491@ole.UUCP> <7200014@silver> <779@mplvax.nosc.MIL>
Date: Sun, 2 Oct 88 05:35:15 GMT

In article <779@mplvax.nosc.MIL> cdl@mplvax.ucsd.edu.UUCP (Carl Lowenstein) 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...
>
>Why not connect the two LEDs in series and use a smaller resistor. ...
>Answer of sorts ... the forward drop across the LED
>is too great.  About 2 volts for green...

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.
-- 
The meek can have the Earth;    |    Henry Spencer at U of Toronto Zoology
the rest of us have other plans.|uunet!attcan!utzoo!henry henry@zoo.toronto.edu