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How to use Piezo Electric Tape?

hosseinz8050

Dec 22, 2011
3
Joined
Dec 22, 2011
Messages
3
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:
piezo_shield.jpg

Thanks...
 

OLIVE2222

Oct 2, 2011
690
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Oct 2, 2011
Messages
690
Hi hosseinz8050,

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

Olivier
 

Resqueline

Jul 31, 2009
2,848
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Jul 31, 2009
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2,848
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

Dec 22, 2011
3
Joined
Dec 22, 2011
Messages
3
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

Jan 9, 2011
5,364
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Jan 9, 2011
Messages
5,364
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

Dec 22, 2011
3
Joined
Dec 22, 2011
Messages
3
Hi
I am using rectifier but the same problem was occurred again!!!
Where exactly rectifier must be put?
thanks.
 
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