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From: email@example.com (carltons)
Subject: Re: powering a bulb or led(s) with audio amplifier?
References: <3DB1323B.1F9EA4F0@stanford.edu> <firstname.lastname@example.org> <3DB929D1.F8551A8C@stanford.edu> <email@example.com>
User-Agent: NewsWatcher-X 2.2.3b2
NNTP-Posting-Date: Mon, 28 Oct 2002 01:55:53 GMT
Date: Mon, 28 Oct 2002 01:55:53 GMT
In article ,
firstname.lastname@example.org (N. Thornton) wrote:
> email@example.com (carltons) wrote in message
> > In article ,
> > firstname.lastname@example.org (N. Thornton) wrote:
> > > "Bevan Weiss" wrote in message
> > news:<email@example.com>...
> > > > > brightness. so a simpler question: how do i hook up a bulb so as to
> > > > > ensure the brightest peak light without damaging my amp? put the
> > > > > a resistor - relative to the impedance of the speaker - in
> > > > > the speaker?
> > > We'd need to know power output and impedance of your amp.
> > Incandescent bulbs vary in resistance depending on how much voltage is
> > applied and how long it is applied. They have a positive temperature
> > coefficient, which means that when cold they draw lots of amps and when
> > they heat up at their rated voltage, they draw the correct amps to match
> > their rating at a lower current than start up. Designing with a lamp is a
> > royal pain.
> I'm thinking that the lamp still wont exceed the amps current rating -
> I hope. As long as its switched on at low vol and the knob turned up
> all should be well. The lamp can be a tenth the R at low V and the amp
> would normally acept that.
> The only time you'd hit the trouble zone is if the amp was switched on
> at full vol, then youd have a surge current in the bulb that could be
> way past the amps abilities. Nearly all domestic stereos will handle
> that, but an old 1970s one would probably roll over and die. So switch
> on then volume up, and accept risk.
You could also limit the current.
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