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From: wb8foz@mthvax.cs.miami.edu (David Lesher,,255RTFM,255rtfm)
Newsgroups: sci.electronics
Subject: Re: How to reduce noise from light dimmers?
Keywords: dimmer, RF
Message-ID: <1990Nov08.222904.9443@mthvax.cs.miami.edu>
Date: 8 Nov 90 22:29:04 GMT
References: <1458@eastman.UUCP> <35639@cup.portal.com> <1990Nov6.133221.7556@athena.mit.edu> <3987@osc.COM>
Reply-To: wb8foz@mthvax.cs.miami.edu (David Lesher)
Distribution: na
Organization: NRK Clinic for habitual NetNews Abusers
Lines: 17

Others said:

>The problem is that they use a triac to cut off the current in the middle of a
>cycle.  As it is the current shuts off very quickly, generating all sorts of
>RF noise.


Ahemmm.......
Unless they are using GTO [Gate Turn Off] devices, dimmer triacs can
only turn off at the zero-crossing. They work by delaying turn on until
later in the cycle half. That's where the noise comes from.

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