From: John Woodgate
Subject: Re: Dawn Light schematic?
Date: Mon, 14 Oct 2002 20:24:33 +0100
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Mon, 14 Oct 2002 20:18:57 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that Larry Sabo
wrote (in ) about 'Dawn
Light schematic?', on Mon, 14 Oct 2002:
>My wife (and thousands of other northerners) suffers from Seasonal
>Affective Disorder (S.A.D.), so I'm interested in building a dawn
>light simulator. These can be bought commercially, but the cost is
>prohibitive. I'll buy a full spectrum fluerescent light but though I'd
>augment that a dawn light simulator.
I don't have a schematic, but they are filament lamps controlled by a
triac dimmer. The unusual feature is that the firing angle extends to
around 160-170 degrees, so that the light starts very dim. This requires
a more complicated phase-shift circuit that the ordinary wall dimmer.
I managed to persuade the IEC low-frequency harmonics emissions
committee that they should be effectively exempted from the emission
requirements because they are only used in small numbers and there is no
other technique that can reasonably be used.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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