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?
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?
** Yep - it is called a " sine wave dimmer ". ** The latter is just as scarce as what you first asked for - dickwad.
...... Phil
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 ....
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...
^^^^^^^
why be a wanker ?
The guy might be asking an idiotic question, but we were all like that at one stage.
Fred
Your name is very familiar from the early '70s.
....... Phil
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