Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!evax!utacfd!merch!rwsys!kf5iw!k5qwb!lrk
From: lrk@k5qwb.UUCP (Lyn R. Kennedy)
Newsgroups: sci.electronics
Subject: Re: light bulbs buzz when dimmed
Message-ID: <989VZ1w163w@k5qwb.UUCP>
Date: 4 Apr 91 19:27:19 GMT
References: <7893@jhunix.HCF.JHU.EDU>
Organization: Radio Amateur k5qwb
Lines: 32

ins_atge@jhunix.HCF.JHU.EDU (Thomas G Edwards) writes:

> In article <1991Apr3.223655.18202@cbnewse.att.com> random@cbnewse.att.com (Da
> >> an annoying buzz when dimed.  Is there a better circuit for dimming
> >> the bulbs that will prevent that !@#$%^&*&^%$# buzz?
> 
> >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).
> 
> O.K...but exactly why do the bulbs buzz when dimmed, but not when at
> full power?  My guess on this always was there was some kind of
> clamping of the waveform going on, making it look more and more like
> a square-wave with associated audible harmonics?  In that case perhaps
> a variable-transformer would make life better.
> 
> -Tom

Most electronic dimmers turn off at the zero crossing and then switch
on for the last part of each half-cycle. This might well cause more
buzz than a variable tranformer. Surely you will try it and let
us know.


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                 lrk@k5qwb.UUCP    lrk%k5qwb@kf5iw.UUCP
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Lyn Kennedy      K5QWB @ N5LDD.#NTX.TX.US.NA
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