I made the circuit here to automatically switch on my workshop dust extractor when I use a power tool. It works fine when used with a drill press or router. However with a Dremel 4000 it only switches on when the Dremel is at its highest speed. I imagine this is because the Dremel has an electronic speed adjustment.
Is it possible to modify the circuit to work with the Dremel or should I look at using a different approach - perhaps using a current sensing transformer?