adcoperational-amplifierpiezo
I've been trying to develop an electric guitar tuner using a piezo disk to detect vibration.
I have this design but at the moment the design fluctuates randomly from 0 to 5.09V when it should remain at zero until the piezo is pressed.
The voltage source is a regulated 9V battery which is connected to the rails on my breadboard.
simulate this circuit – Schematic created using CircuitLab
Can anyone explain why this is happening?
Cheers
Slight improvement (less power consumption and fewer parts):
simulate this circuit – Schematic created using CircuitLab
U1 has to be very low input bias current, of course. You might want to add some series resistors to the non-inverting inputs in case the piezo voltage exceeds 2.5V.
Voltage will be low in the mv range, you should have a high impedance say 1Meg resistor in parallel with the piezo, and then feed that to a little opamp preamp.
As far as sampling, nyquist is the bare minimum, I'd probably sample much higher but give it a try and look at the waveform you get. If low sample rate is enough for you then go for it.
Best Answer
If you have wired it up the way it is pictured, you are missing a ground connection