> An interesting caution. When using these directly connected to a processor
> pin NEVER tap them sharply.
> They act as voltage generators when mechanically excited ..

Yes, they can be used as input sensor (push switch), although you must apply
a "shock" pressure, with some mechanical help ( fingertips are to soft ).
A light hit with a peace of wood or a pencil can generate more than 5 volts
with ease, but of coarse for a very short moment. If mounted under glass or
pvc it works too, make sure that the pressure is applied around or besides
the
solder blob, to prevent cracking of the coated area.
So, an input actuator with audio feedback is what this can be.
If manual actuation is wanted, then add an opamp with 1000x gain (or more).

At van Wijk.

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