Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!pencil.cs.missouri.edu!pencil!rich
From: rich@pencil.cs.missouri.edu (Rich Winkel)
Newsgroups: sci.electronics
Subject: Re: light bulbs buzz when dimmed
Message-ID: <rich.670896283@pencil>
Date: 6 Apr 91 00:04:43 GMT
References: <1991Apr2.162037@maximo.enet.dec.com> <1991Apr3.223655.18202@cbnewse.att.com>
Organization: UMC Math Dept.
Lines: 17

random@cbnewse.att.com (David L. Pope) writes:
]> an annoying buzz when dimed.  Is there a better circuit for dimming
]> the bulbs that will prevent that !@#$%^&*&^%$# buzz?
]Yes, but since the buzz is being caused by the fillament vibrating
]at line-current frequency, it would involve a d.c. supply which
]would require a little engineering (to determine d.c. power max
]and min for the bulbs you are using). The actual cause of the buzz
]is the length of the fillament in the bulbs, so maybe you could
]find large diameter bulbs designed for dimming (that is, with short
]fillaments).

I always thought it was due to the harmonics generated by the abrupt
cutoff in the wave.  Dimmer circuits work by chopping off the voltage
at various phases of the 60 Hz wave, right?  This should add a lot
of high frequency harmonics to the wave.  Surely the buzzing I hear
in a dimmed lightbulb isn't at 60Hz.  So a lowpass filter might do
the trick (?? coming from an electronics novice).