I am looking to use piezo sensors are force sensors, and am having a hard time understanding how to interface it with my Arduino.
According to the official Arduino docs, only a 1M resistor in parallel w/ the sensor is required (http://www.arduino.cc/en/Tutorial/Knock
But piezo sensors output AC waveforms, and thats not being accounted for in the example. What happens when the negative parts of the waveform enters the ATMega's ADC? Are they ignored, or can it cause problems?
I want to protect my ADC from damage, so I thought of also placing a 1N4007 diode in parallel with the sensor (in addition to the resistor) to only allow positive voltages through - but then theres the 1.0V voltage drop problem. Most of the small signals will not come through.