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Re: Variac vs. Fan speed control

Subject:  Re: Variac vs. Fan speed control
  Date:   Tue, 06 May 1997 06:45:00 -0500 (EST)
  From:   Benson_Barry%PAX5-at-mr.nawcad.navy.mil
    To:   tesla-at-pupman-dot-com


Hi Alfred, All,
What about the Sidac, page 170 of Digi-Key catalog # 964?
Barry

 ----------
From: "tesla"-at-pupman-dot-com-at-PMDF-at-PAXMB1
To: Benson Barry; "tesla"-at-poodle.pupman-dot-com-at-PMDF-at-PAXMB1
Subject: Re: Variac vs. Fan speed control
Date: Wednesday, April 30, 1997 11:47PM

<<File Attachment: 00000000.TXT>>
Subject:  Re: Variac vs. Fan speed control
  Date:   Wed, 30 Apr 1997 15:57:28 +0500
  From:   "Alfred A. Skrocki" <alfred.skrocki-at-cybernetworking-dot-com>
    To:    Tesla List <tesla-at-pupman-dot-com>


On Fri, 25 Apr 1997 12:25:29 -0600 (MDT) Chip Atkinson
<chip-at-XiG-dot-com> wrote;

> > Hay Chip, ever hear of a Faraday shield? Seriously, Chip I currently
> > use phase shift light dimmers to control my rotory spark gaps {I use
> > universal motors} and I have no problems BUT I totaly enclose the
> > dimmers in a grounded metal box. Apparently what happened in your
> > case is the triac was picking up some of the radiated R.F and being
> > driven into continuous conduction, try it again but this time enclose
> > the control in a grounded metal enclosure.
>
> Hmm... That may be.   I believe that the case was non-metal, so that I
> guess I could shield it.  However I now have three variacs available,
> and they go from 0 to full, whereas the fan control only went to about 20
> volts or so (just guessing).  I didn't measure it.  It was from my olde
> coiling days, before I knew about shielding, etc.

Variacs are always nice if you've got em! There is some lag inherent
to triac phase shift controls. Like a Tesla coil they need a voltage
avalanche device to run this used to be a diac which would conduct
at a few volts, some companies substituted a neon -2 lamp which
would conduct at something between 75 to 85 volts (really bad - you
get half on to full on) now a lot of units use two silicon diodes in
parallel each conducting in the opposite direction, these will start
conducting at a few volts! So they've improved over the years and
they are a lot cheaper now too! It used to cost over $5.00 just for a
200 V 10 amp triac let alone the potentiometer , resistors, mylar
capacitor and diac (you can't even bye a diac any more!)to build the
whole unit! Now you can get a whole working unit for close to $5.00
at your nearest K-Mart's.

                               Sincerely

                                \\\|///
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                           Alfred A. Skrocki
                   alfred.skrocki-at-cybernetworking-dot-com
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