Date: Thu, 07 Mar 2002 15:31:00 -0500

Author: John Cockman

Subject: Re: Variac


In my experience, the dimmers don't offer nearly the control of a variac.
Also, they come on at about half the input voltage, and then turn off at
about a quarter of the input voltage. The non-zero operation requires a
choke because of the RF. I have built several dimmers using the same idea
(a triac controlled by a diac). However, I built them to vary from zero to
the input voltage, and they make great lighting, heat and universal motor
controls. However, these controllers do slice up the sine wave.


----- Original Message -----
From: "Gerald Zani"
Sent: Thursday, March 07, 2002 9:27 AM
Subject: Re: Variac

> Tapper,
> Does anyone use a new solid state dimmer control to replace a traditional
> variac?
> Jerry
> At 08:16 AM 3/5/2002 -0600, you wrote:
> >I don't know which "previous poster" Paul is referring to, but to be on
> >safe side I want to remind everyone that our "What's It Take To Shock
> >exhibit at The Science Place has a 20 kilohm current limiting resistor in
> >the output circuit of the variac. I described this in my message. One
> >never play with variacs without such a safety device in place.
> >
> >poj
> >
> >----- Original Message -----
> >From: "Paul Nord"
> >To:
> >Sent: Monday, 04 March, 2002 17:00
> >Subject: Re: Variac
> >
> >
> > > I think that the previous poster intended to warn you about dangerous
> > > CURRENTS, not voltages. The variac is regulating the voltage. But
> > > only regulation on the output power is the 20 Amp breaker in your
> > > That limits you to 110V X 20A = 2200W. So, if you dial your variac
> > > to 1 volt you might be able to draw 2200W / 1V = 2200A of current.
> > > However, that's an upper limit. You'd probably loose a lot in the
> > > transformer itself. But even 10% of that is a big current.