jbarchuk:
Check out 'butteryfly in a jar' at youtube. I'm 99% convinced it's a piezo. One guy writes 'spoiler alert - see how it works.' He plays with the butterfly, opens the lid, and shows where the batteies and switch are. And that's it. He shows how it OPERATES but not how it WORKS. So that's yet another 2:43 of my life waste that I'll never get back.Another forum there's a buncha discussion the butterfly, capacitance, piezo, and the thread ends where someone writes 'I'll take one apart and let you know.' That was in 2011. [checking sundial [sigh]]
Given $ vs ease of design, piezo is cheap, easy and reliable.
Trouble is... my jar spends a lot of time with the CPU in sleep mode. You have to put your hand on it for a second or so to wake it up via capsense. It would miss a quick tap on a piezo.