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From: Kevin McMurtrie
Subject: Re: LED Flasher Circuit Needed
User-Agent: MT-NewsWatcher/3.2 (PPC Mac OS X)
Date: Mon, 11 Nov 2002 10:25:16 GMT
NNTP-Posting-Date: Mon, 11 Nov 2002 02:25:16 PST
In article ,
>I've got a .750 volt D.C. source capable of about 130 ma. available. Is
>there a circuit available capable of flashing an LED or multiple LED's in a
>sequential pattern? I realize it's not much to work with but any ideas are
>appreciated. I did get my hands on a National LM2623 boost converter but it
>needs about 1.1 volt to start and a minimum of .9 after that.
>Thanks in advance.
At that voltage you can only use one transistor to get things going. A
simple transistor oscillator driving a center tapped transformer may do
it. (Power on center tap, drive one side, get feedback from other side.)
If that's not enough current, you can use it to jump start a step-up
regulator. I've been able to drive 12V worth of LEDs from as little as
0.1V before loosing current regulation. The circuit continued at
reduced output down below 0.05V. Below that it stalled and needed a
4.5V jump start.
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