NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/sci/electron/21587

Internet Message Format | 1992-12-26 | 1.8 KB

Path: sparky!uunet!spool.mu.edu!agate!usenet.ins.cwru.edu!skybridge!wb8foz
From: [e-mail] (David Lesher)
Newsgroups: sci.electronics
Subject: Re: RFI free dimmer switches...
Date: 26 Dec 1992 15:45:07 GMT
Organization: NRK Clinic for habitual NetNews abusers - Beltway Annex
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Reply-To: [e-mail] (David Lesher)
NNTP-Posting-Host: skybridge.scl.cwru.edu

I'm a little confused by the present discussion.

If you only turn ON at the zero-crossing, you will, I suspect, avoid
RFI problems. But, first off, does this not give you problems in
modulating the output? You could only have setting that are multiples
of the number of {half} cycles. [I suppose that is not TOO limiting,
though, is it?]

Secondly, won't such a dimmer make the lamp singing problem far worse?
The filament gets heated, and cools, over a much longer period than
with chopper-type dimmers.

I suppose the solution is to use line power of a frequency far above
the audio range. Back when I was taking a course on electronic power
control, I recall reading of scheme to provide large office buildings
with ~100khz to run the gas discharge lighting. The idea was to reduce
the losses in the ballasts. Not only does that increase the "light/kw$"
but it would also reduce the "waste heat/lumen" that has to be cooled
by the HVAC.  Wonder what ever came of that idea....
--
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