References: <0001HW.B9C26E7400A7161B165FEAC0@news.covad.net> <firstname.lastname@example.org>
Subject: Re: Best way to power array of LEDs?
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Date: Sat, 05 Oct 2002 00:27:59 GMT
NNTP-Posting-Date: Fri, 04 Oct 2002 20:27:59 EDT
Organization: Road Runner
"Lizard Blizzard" wrote in message
> Keith Wootten wrote:
> > In message <email@example.com>, "Wouter van Ooijen
> > (www.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