@Professor Chaos posted:You don't need a high voltage to trigger a triac itself. I think most of the designs you're referring to use a microcontroller to monitor the zero crossing of the AC wave, and then trigger the triac with a logic pulse at the desired time point in the AC cycle...
The CW-80 schematic has been posted several times on OGR...for example here. Presumably you aren't planning to use a microcontroller... but rather a potentiometer to choose where/when in the line cycle you turn on the triac to chop down the voltage. I don't recall seeing the schematics published for the MTH Z-1000 (and its cousins) controller schematics...but that would be an example of a potentiometer controlling the chopping time. I'm assuming part of your objective is to learn and experiment as part of the hobby experience.
The MTH Z-4000 patent is decades old, but it's a good reference to learn/study how to synthesize a more "pure" sinewave (vs. a triac chopped sinewave). If done today, I'd look at more modern techniques such as used in home-theater "digital" amplifiers ...where in amazingly compact packages you get hundreds of Watt of audio power. Audio amps are, say, 20-20,000 Hz...which of course includes 60 Hz. So just put in a low-level 60 Hz sinewave signal into a modern audio amplifier and voila!
