Re: Best way to power array of LEDs?

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#297

From: daestrom
Date: Sat, 05 Oct 2002 00:27

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"Lizard Blizzard" <NOSPAM@rsccd.org> wrote in message
news:ankkbu$lv9i$1@hades.csu.net...
> Keith Wootten wrote:
> > In message <3d9d452f.4128065@news.xs4all.nl>, "Wouter van Ooijen
> > (www.voti.nl)" <wouter@voti.nl> writes
>
> > You can mitigate this to a useful extent by using a small filament bulb
> > instead of a resistor.  The positive temperature coefficient of the bulb
> > will help to keep the current variation reasonable as the supply voltage
> > changes.  The bulb should be selected to run at more or less normal
> > brightness at maximum supply voltage while passing maximum LED current.
>
>
>
> Using a lamp to serve as a more or less constant current 'ballast' is a
> good idea, but if it is run at anywhere near normal brightness, the
> lamp's lifetime will be short in relation to the LEDs.  And of course
> when the lamp goes open, the LEDs no longer get current.  So it would be
> much wiser to use it at much lower than normal brightness so that the
> lifetime is extended considerably, comparable to the LEDs.
>
> --
ROTFL,  Sorry, it just struck me as funny.  We normally use LED's because of
their superiority over incandescent lamps.  So now we're going to use an
incandescent lamp as  a critical part of an LED circuit.  Isn't there some
irony there???

daestrom

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From: "daestrom" <daestrom@twcny.rr.com>
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