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Is there such thing as a switchmode variac?

Discussion in 'Hobby Electronics' started by [email protected], Sep 4, 2006.

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  1. Guest

    Is there such thing as a switchmode variac and where can I get one?

    A google search seems to only turn up links to testing switchmode power
    supplies by using a variac on the input.

    Failing that, I suppose you could cannabilise the sinewave output stage
    of a 12-240 inverter and bung it on the end of a variable high voltage
    DC supply?
     
  2. Mark Harriss

    Mark Harriss Guest


    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.
     
  3. Kr

    Kr Guest


    Im sure that you could do that (If you know what you are doing) but
    why would you bother ?
     
  4. Most likely not.
    Most probably, but why bother? What is wrong with a standard variac?

    Dave :)
     
  5. Geoff C

    Geoff C Guest

    wrote in @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?
     
  6. Phil Allison

    Phil Allison Guest

    ** 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
     
  7. Guest

    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.
     
  8. dmm

    dmm Guest

    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.
     
  9. 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
    .....
     
  10. Ross Herbert

    Ross Herbert Guest


    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
     
  11. Guest

    ^^^^^^^

    why be a wanker ?

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

    Fred
     
  12. Phil Allison

    Phil Allison Guest

    <

    ** Don't I know you ?

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





    ........ Phil
     
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