Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!cornell!uw-beaver!tikal!ole!ray
From: ray@ole.UUCP (Ray Berry)
Newsgroups: sci.electronics
Subject: Re: speaking of LEDs
Message-ID: <497@ole.UUCP>
Date: 4 Oct 88 17:31:20 GMT
References: <491@ole.UUCP> <7200014@silver> <779@mplvax.nosc.MIL> <1988Oct2.053515.18004@utzoo.uucp>
Reply-To: ray@ole.UUCP (Ray Berry)
Organization: Seattle Silicon Corporation, Bellevue, WA.
Lines: 18

>>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...

   I suspect a single-chip switching converter could be configured as an
efficient method of powering a couple LEDs - for instance, two lamps in
serial driven through a convertor designed to convert 5-9 vdc to a 20 mA.
output current.  A 9 volt alkaline could then power the lamps efficiently
over a wide range of its service life.  

-- 
Ray Berry						KB7HT
Seattle Silicon Corp., 3075 112th Ave NE.,  Bellevue WA 98004
(206) 828 4422               UUCP:...!uw-beaver!tikal!ole!ray
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