Looks like a very nice design! I was going to make my own using a hall effect sensor, a PICAXE micro, and a relay. The use of a MPU gives a bit more flexibility in programming the current sensing sensitivity and delayable on-off period.
No, I created the original version of this gadget back in 1973 entirely on my own. The updated version is also entirely my work. Up until I saw a Sears unit for power tools in 2003, I had never seen or heard of such a thing before. I have already emailed the editor about the SCR mistake. I don't know where he got that from. I took for granted that everyone who would be interested in building the gadget would know what an SCR was.
It would indeed be very unique if it actually used a "Selective Catalytic Reduction" voltage regulator. With better editing, I think the article would have stated more correctly that it uses a Silicon Controlled Rectifier voltage regulator.
I use a similar circuit to turn on a shopvac whenever any woodworking tools are turned on for dust collection. It was built from an 30 year old Radio or Popular or Elementary Electronics magazine article (was that yours?.) Is that a Klipsch in the background?
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