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From: Tong Narak
Subject: Re: Drive white leds from bicycle generator
Date: Thu, 21 Nov 2002 14:08:02 +0700
Organization: C.S. Communications Co. Ltd.
NNTP-Posting-Date: Thu, 21 Nov 2002 07:08:04 +0000 (UTC)
X-Mailer: Mozilla 4.8 [en] (Windows NT 5.0; U)
You need buck and boost IC.
If u can control voltage, u can control the current.
( Your LEDs are normal RED LED ? )
In practical, forward voltage with each LED aren't
identicle. we accept 20% tolerant when seeing with human eyes.
So u can use Buck and boost constant voltage regulator.
Search at maxim-ic.com or TI.com
There are a lot of ICs for 6-12VDC input.
Hope these help.
> How can I drive 20 white leds from a 6V 3W (AC) bicycle generator
> (dynamo)? Output voltage of the dynamo varies with cycling speed. How
> can the light output be at maximum at a low cycling speed, and remain
> constant with increasing speed (= increasing voltage)?
> Putting as much leds in series as possible is a bit of a problem, due
> to the output voltage of the dynamo.
> The circuit has to be simple, since there is not much space in a
> bicycle headlight.
> Any ideas?
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