Hey all, new here. Great site. I have been thinking about this also, but I must admit, I am an electronics ...... I understand the 555 timer deal, and how to get different frequencies, but they only output 200ma. All the piezos I have found are from 5 to 15 watts.
So would you have to run the output from the 555
through a transistor and have that act as a relay feeding the piezo with a higher current?
Also, have you thought of any self tuning circuitry for when the piezo is under load it will increase the current/voltage automatically to keep it at its resonant frequency?
Just wondering.