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From: tom@syssoft.com (Rodentia)
Newsgroups: sci.electronics
Subject: Re: light bulbs buzz when dimmed
Message-ID: <1991Apr10.034706.15607@syssoft.com>
Date: 10 Apr 91 03:47:06 GMT
References: <1991Apr2.162037@maximo.enet.dec.com> <13181@ur-cc.UUCP> <4613@alliant.Alliant.COM>
Reply-To: tom@ssi.UUCP (Rodentia)
Distribution: na
Organization: Systems & Software, Inc., Irvine, CA
Lines: 14

So you can get lightbulbs to buzz at >60Hz by chopping the waveform.
This seems to be a case of what might be called base frequency pulse
width modulation (if there's a better term for it, let me know).

Now it seems that you could do a higher frequency pulse width 
modulation, and the buzz/whine would be inaudible.  This would seem
to be cheaper than a variable transformer (then again, maybe not).

Comments?
-- 
Thomas Roden                                      | tom@syssoft.com
Systems and Software, Inc.                        | Voice: (714) 833-1700 x454 
"If the Beagle had sailed here, Darwin would have | FAX:   (714) 833-1900
come up with a different theory altogether." - me |