Is there such thing as a switchmode variac?

Yes: Episode #27 of "Flash Gordon", Dr Zarkov uses one to
kickstart the rocket motors on Flash's spaceship after the
lithium ion cells fail.

Im sure that you could do that (If you know what you are doing) but
why would you bother ?

Most likely not.



Most probably, but why bother? What is wrong with a standard variac?

Dave :)

snipped-for-privacy@hotmail.com wrote in news:1157355573.625800.244310
@m73g2000cwd.googlegroups.com:



There are supplies that can do that designed for EMC mains fluctuations/
flicker etc. They can simulate brownouts and are programmable. They would
probably work like a variac but they probably only go to 20-30 amps. They
will cost $5000 or more. (one brand I've seen is "Best") A 30 amp variac is
probably about 1/0th that price. What exactly do you want to achieve?

I wanted to be able to control a variac by a PC/uC.  I was guessing
that an interface to the switchmode variac would be as simple as a low
voltage control input in the feedback loop somewhere.

The other low-tech option I was thinking of was a motor (with
positional feedback) driving the variac knob.

It's not all that difficult. About 1988, we connected a geared dc motor to the
knob
of a variac. The output voltage and current were displayed using 3.5 digit LCD
modules.

or a 50Hz oscillator - feeding a digital volume control chip - feeding a
power amp (an AM1600 will give 110V RMS or so out )  maybe feeding a
Transformer (better watch the DC offset of the amp then - I dont think an
AM1600 would work here ...) depending on what Voltage range you want ....
Bit complex isnt it ? the Motor feeding a Variac would be cheaper/easier
....

**  A hotmailer and Google Groper  -  double whammy  !





 **  Yep  -  it is called a " sine wave dimmer ".






**  The latter is just as scarce as what you first asked for - dickwad.



......  Phil

Phil Allison wrote:



                        ^^^^^^^

why be a wanker ?

The guy might be asking an idiotic question, but we were all like
that at one stage.

Fred

< snipped-for-privacy@gmail.com



 **  Don't I know you  ?

Your name is very familiar from the early '70s.





.......  Phil

I very much doubt there is such a beast as a switch mode variac.
However, you can get motorised variacs which can be externally
controlled, but they won't be cheap...
http://www.australianrectifiers.com.au/motorised.htm