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1  Using Arduino / Sensors / Any idea??? Multiple Piezos as sensor with Mux Shield on: March 25, 2011, 08:54:46 pm

I am looking for helps here.
Any feedbacks or suggestions would be so helpful and great since I am not really familiar with using Arduino and sensing system.

I am working on a prototype for a sound installation. 
I've got 6 of 4' by 4' wooden platforms that underneath of each platform has 4 piezo transducer sensors and one contact mic.

the contact mic is for MOTU inputs, and other 4 piezo sensors ( that wired to Mux shield  ( as 24 analog inputs. I refer to the Arduino circuit diagram called "Knock "( basically 1M ohm for each inputs. Also, I am using Mux Shield Anlog Input sketch for reading sensors. (

So on my breadboard, there are 24 piezos x 1M ohms and connect to analog inputs(mux 0 and mux 1) and all shared the same ground.

Then,  I have faced two problems.

1) When I only worked with Arduino(only 6  analog inputs) without Mux shield, i get some values when i knock the platform; however, when i use Mux shields (more piezos are hooked up), the values are very small range to use.  For example, Mux0 the first 4 inputs worked, but nothing else, everything else says 0.

2) I have heard that piezo wire voltages could drop out if the wire is 16ft long, so I try to use Operational Amplifier,
but it doesn't seem to work at all with Mux Shield.

So I don't know where to start debugging this.
I am happy to think about Arudino Mega, If this could be the best solutions. But again, not sure whether that will be the best solutions,
and I have to reduce inputs.

Thank you for reading this long concerns. I  looked through the forums on Piezo pre Amplifier circuit, but not sure how I can even start.
Partially, I think i don't understand the mechanism enough.
I really appreciate your inputs. Once again, thank you so much.
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