[sdiy] Very cheap SPI pressure sensors.. anybody ??

[Ingo Debus]

> Am 19.03.2021 um 20:46 schrieb cheater cheater <cheater00social at gmail.com>:
> 
> Forgot to describe what the PCB would look like. You have a square
> area split into two rectangles. Those rectangles are two plates of a
> capacitor. Above it is a solid square of metal (foil, plate, ...).
> This one has no split. It's not connected anywhere. The closer it is
> to the two plates below it, the more the capacitance changes.

You mean, you can detect punched holes in paper this way? I doubt it. The relative permittivity of paper isn’t that big.
It could work if the piano roll is not made of paper but of some conductive foil.

Ingo