# ADC for many piezos at once

I'm building an electronic musical instrument, using piezoelectric contact microphones as inputs. I want ~80 buttons, each with a piezo connected to an ADC. The idea is that you hit the piezo, then depending on how hard you hit it I trigger a louder or quieter sound.

I'm trying to figure out what to use for the ADC. I could run ~14 arduinos, but that seems kind of silly? Is there a better way to get ~80 ADCs?

I'm also trying to figure out about how to set up the circuits. For each one I could just put a piezo and 1M resistor in parallel across the ADC:

ADC in0 ---+------+
|      |
1MOhm  piezo
|      |


This is fine, but requires a relatively high sample rate from the ADC to accurately capture the peak of the input signal. It seems like I should be able to put something in series with the piezo to cut off the negative side of the signal, and then something else to smooth out the signal, which would let me run a much lower sampling rate?

(This question is basically "what should the electronics for a an electronic drum kit's input look like", though that's not what I'm building.)

• How big a voltage might the piezo produce and have you checked how much overload any fairly standard ADC can handle? – Andy aka Nov 24 '16 at 17:33
• Jeff, have you tried capturing sampled data from one transducer? to see if it yields voltage appropriate for your application? I've dismissed piezo's as inappropriate for a somewhat similar application. Kilovolt pulses are possible for sharp tapping, making for poor sensitivity for finger-tapping. – glen_geek Nov 24 '16 at 19:29