I didn't really finish it yet. I will try adding two potentiometers, two rheostats, and one potentiometer and one rheostat to see which one works best. Then I'll let you know.
I think the SPST switch is fine. As for the capacitor, as long as it's 1200uf and 50V, it should be fine. But as for the transducer, I'm not sure because I tried using a piezo buzzer. But still, I think you should try using the transducer, then if it doesn't work, use the buzzer. You could also try adding a piezoelectric crystal to see if there will be any difference. As for the box, I didn't put mine in a box yet because I still didn't finish it. But it should be somewhere from 10 to 30cm.
you can try other ways to , read this all of it and go experiment fill me in the results when you get them
I tried reading it but I couldn't really understand his handwriting.
yes it is a bit hard to read but the circuits easy to read at least , ive done some testing of 2 out of all my electromagnets and using the 240vac 50hz to american 120 volts converter and i get better results when i take the 2 magnets off the electromagnet at the end so its a bit strange im documenting it in my book