This is my version of the Big Lev ultrasonic acoustic levitator:
Thanks to Twitter: @AsierMarzo for making this possible.
The hole spacing on various brands of transducers varies - mine have 10mm between pins (c/c). The diameter is 16mm and the height is 12mm. Pins are about 9mm long.
A section of a sphere will have a focal points for each row of transducers resulting in 3 distinct focal points. I changed the angles of the transducers to get one focal point (not sure if this makes things better or worse:).
The legs are designed to allow the space between the spheres to be changed. A wide range of spacings appear to work.
I put a receiver in the center of each sphere so the waveforms can be viewed on a scope. (I use the DSO 2250 USB by Hantek).
I had an old Dell laptop power brick to power this. So I used a DROK DC buck converter to lower the voltage to abount 19 volts. All other components are per the instructable.
There are some lines of code to be commented / uncommented to make the transducers visible so you can see the focal points.
I use $fn=180 to get smooth prints but be aware that rendering time for me was over 4 hours at this number of facets (on a fast desktop). Side note: computers with more cores do not speed up rendering in Openscad as the cgal engine is a sequential beast - and cannot be parsed out to multiple processors.
The spheres should be rotated in the slicer so that the legs are flat on the print table and the sphere is verticle - no support required.
The caps can be printed open end up.
The electronic components were mounted on Adafruit breadboards and will fit into the included tray. I added a 5v 40mm fan to cool the driver chip: at 20V and 1.2A the heat sink remains cool enough to touch.
Filament temp: 215
Plate temp: 60
Small Brim 6mm