From: John Woodgate
Subject: Re: Extending battery life
Date: Mon, 20 Jan 2003 17:20:19 +0000
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Mon, 20 Jan 2003 20:03:07 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that joe wrote (in
) about 'Extending battery life',
on Thu, 16 Jan 2003:
>I'm powering a couple of led's (2mA lower one's) using 2 AAA (3 Volts)
>batteries only, is there anyway I can extend the battery life, at the moment
>the batteries last about 2 weeks, but I preferably like them to last about 6
>months. Due to the size of the device, the maximum size battery I can use is
>'C'. Any suggestions ?
You could make them flash, **without** increasing the current, 0.5
seconds on, 5 seconds off. That would give you something over 20 weeks
life, based on the 2 week figure. Obviously, AA or C cells would give
much longer life.
I wonder if a 'ring-of-two' constant-current circuit, using the two LEDs
as the base bias devices, would work with three cells down to a very low
voltage per cell, i.e. about 0.75 V. I've absolutely no stock of round
tuits, so I can't do the calculations, I'm afraid.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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