I have 9 piezos connected to an Arduino Micro with a 60 Kohm resistor setup for impedance on each piezo. When I power the Arduino from USB, the readings I get are very accurate and nice.
The problem is that when I try to power it from a 9V battery, the readings are much higher. My 1st thought is that now that the reference voltage is 9V instead of 5V, it causes issues. Would this be correct?
For a fix, would it make sense to put a 5V voltage regulator between the straight 9V and the AREF pin on the Arduino so that all reference voltage will be from 5V instead of 9V?
As a second / side question, if the Arduino Micro datasheet says that it requires 6V minimum to operate, how does it work when powered from the 5V USB?