I found some youtube vids on Ultrasonic Cleaning, and thought it would be a cool DIY project. On eBay I found this. Some other transducers in the same range requires 400-800V supply. Anyone have any idea how to drive this thing? What kind of signal does it need? My guess is a 40kHz sine wave in the voltage supply range.
I was thinking a sine wave generator, and stepping it up to 400V++, mabye change the Watt/voltage with a potmeter.
The same seller on eBay also sells the driver board, but I want to make it myself. The images seems to include trafos, something three-legged that needs coolig and some passive components.
Best Answer
Recently, I fixed an ultrasonic cleaning device (f = 40 kHz). The circuit consists of two high voltage bipolar transistor feeding a resonant converter. The piezo actuator is connected to the secondary of the converter's transformer. I have strong reason to believe that the circuit is of the Royer resonant converter type because it has two bipolar transistors, see this answer for more info.
There's another self-oscillating schematic with just one transistor in Sam Goldwasser's Sci.Electronics.Repair FAQ
Some clever techniques allow you to build the ciruit in a way that it catches onto the resonant frequency of the piezo acutuator, maximizing the output amplitude just right.
For your circuit, it would be a good starting point to check whether the triac has the job to turn the rest of the circuit on or off or if it is used to modify the power using a phase angle control technique. The rest of the circuit around the two bipolar transistors will very likely be some sort of resonant oscillator or converter stage.
Use caution. The entire thing is likely connected to the mains supply, featuring high and dangerous voltages with reference to earth ground (= your body).
Related, with a schematic: Replacement Transistor for Ultrasound Cleaner