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How to use Piezo Electric Tape?

Discussion in 'General Electronics Discussion' started by hosseinz8050, Dec 22, 2011.

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  1. hosseinz8050

    hosseinz8050

    3
    0
    Dec 22, 2011
    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:
    [​IMG]
    Thanks...
     
  2. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    Hi hosseinz8050,

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

    Olivier
     
  3. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    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.
     
  4. hosseinz8050

    hosseinz8050

    3
    0
    Dec 22, 2011
    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.
     
  5. duke37

    duke37

    5,364
    769
    Jan 9, 2011
    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.
     
  6. hosseinz8050

    hosseinz8050

    3
    0
    Dec 22, 2011
    Hi
    I am using rectifier but the same problem was occurred again!!!
    Where exactly rectifier must be put?
    thanks.
     
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