Pages: [1]   Go Down
Author Topic: Any idea??? Multiple Piezos as sensor with Mux Shield  (Read 680 times)
0 Members and 1 Guest are viewing this topic.
Offline Offline
Karma: 0
Posts: 1
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset


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.

Georgina Ontario
Offline Offline
Sr. Member
Karma: 5
Posts: 437
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

You should post your code.

The people can look at it.

Just another Hacker

Offline Offline
Faraday Member
Karma: 30
Posts: 2602
Per aspera ad astra.
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

 IMHO, multiplexers chips have a big pass-trough capacitance, that with high impedance source
 could significantly drop amplitude of signal.

I download a Mux Shield schematic and find out that there is no option to bias  
output/input pin  with DC offset VCC/2, as recommended by chip maker, at least all their performance testing was done so. Not going deeply in CMOS operation specific,
there are two solution:
- bias input/output with VCC/2;
- OP amplifier before mux, you says it doesn't works, please show schematic and type OP
you try with. OP has to be high input resistance (FET input stage) 1Mohm and above.

Pages: [1]   Go Up
Jump to: