How to use Piezo Electric Tape?

[hosseinz8050]

Hi.
I want to use piezo electric tape to convert pressure to electric voltage and then to 8 bit digital data. I designed a 741 amplification circuit, but it's not work properly. I am searching very much for an example of piezo electric tape circuit but I could not find any thing on the internet.
please give me an example of amplification circuit to 5 volt output and also piezo electric tape as an input to the circuit. The following figure shows the piezo electeric tape:

Thanks...

 

[OLIVE2222]

Hi hosseinz8050,

You can do more searches with piezo scavenging and piezo harvesting keywords.

Olivier

 

[Resqueline]

You'll need a lot better op-amp than the 741 to make the high input impedance amplifier needed for this purpose.
You'll also need to define the lower frequency limit, since a piezo sensor is unsuitable for static measurements.
The piezo sensor has an inherent capacitance that together with the amplifier input impedance defines this limit.

 

[hosseinz8050]

Hi dear Resqueline
thanks for your recommendation. I am forced to using piezoelectric tape with op amp.
The stage in my circuit is as follows:
piezoelectric sensor--->op-amp---> ADC0804(analog to digital converter)---> Multiplexor---> PIC18F4550.
My problem in this circuit is:
When I connect piezoelectric to the circuit, the digital output is not zero(00000000), when no pressure is applied to the piezoelectric!!!
I can not understand the source of this problem.
please help me!!!!
Thanks.

 

[duke37]

Have a look at "charge amplifiers" in Wikipedia.
You should use a fet input op-amp.
The sensor only gives an output when the input changes, you will probably need a rectifier after the op-amp in order to get a reasonably steady signal for the computer to read.

 

[hosseinz8050]

Hi
I am using rectifier but the same problem was occurred again!!!
Where exactly rectifier must be put?
thanks.