I am trying to make a pressure sensor to use with my raspberry pi zero. I would like to avoid making another purchase, so while an ADC or FSR would be easier I would like to figure this method out.
Basically, I am trying to read a change in pressure using a piezo transducer on my raspberry pi. This is problematic because Pi is digital, and I cant measure voltage change accurately.
However, I found this method of measuring capacitance (using timer): this article
I was wondering if I would be able to use the piezo transducer as a capacitor whose capacitance is dependent on pressure change.
Here is a diagram of the ciruit I have in mind:
simulate this circuit – Schematic created using CircuitLab
Would this possibly work?
Best Answer
I was able to measure a rate of change in pressure using a similar circuit to this. I replaced r2 in the circuit with a 40k pot, and after much calibration was able to detect the scale of pressure depending on the time values between high voltages (above1.3v) on the gpio pin. However, I achieved hardly any resolution due to horrendous noise problems, as well as the fact that the piezo is not a capacitor (as people commented) and I was essentially just scaling the piezo's voltage response. Basically, it works as a knock sensor, not as intended.