Bela Piezo Hardware Example

cwru

In this example: https://github.com/BelaPlatform/Bela/wiki/Example-projects-and-tutorials#sample-piezo

You use a matched pair of 1.8MOhm resistors. Any rhyme or reason for that rating of resistor or is the matched pair to give half the voltage (V * R2/R1 + R2) in this configuration all that matters so long as the current the load requires doesn't exceed the rating of the chosen resistors? I suspect the latter but curiosity got the better of me so I thought I'd ask. In any case, it looks lovely on the Bela IDE oscilloscope. Nice and reactive and the scaling is perfect. Thanks for these hardware examples!

giuliomoro

mostly any value > 100k will do ... the purpose is to bias the signal so that it doesn't oscillate around ground. You will want to add a 1k or so in series with the piezo in order to protect the analog input from very large input signals.

Yes, we need to amend the diagram with the correct value resistors and the series resistor.