Piezo Tranducer Sensor

Discussion in 'General Electronics Chat' started by Teena123, Dec 8, 2012.

  1. Teena123

    Thread Starter Member

    Nov 22, 2012
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    Hello I am working on a piezo transducer sensor to measure vibration, I would like to know how many volts does a piezo transducer produces with a 5 volts input volts, i am trying to connect it to a transistor and display my output on a red led display Help any one please ?
     
    Last edited by a moderator: Dec 8, 2012
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Which specific transducer are you using?

    The transducers I know of need no supply voltage and produce an output in the millivolt (or less) range.
     
  3. KJ6EAD

    Senior Member

    Apr 30, 2011
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  4. Teena123

    Thread Starter Member

    Nov 22, 2012
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    I'm using a ceramic piezoelectric transducers?
     
  5. Audioguru

    New Member

    Dec 20, 2007
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    A piezo transducer has a recommended load resistance spec'd on its datasheet. It might need a very high resistance like the input of a Jfet or an opamp, not the low resistance of the input of a transistor.

    If they vibrate a little then their output voltage is a little. If you hit them then guess how much is the output level? "x" Volts?
    On an e-drum circuit they limit the output voltage from the piezo transducer to a few volts with zener diodes.
     
  6. Teena123

    Thread Starter Member

    Nov 22, 2012
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    ok so i can use an op amp and a fet transistor then the output would be to display the led but what kind od op amp and fet transistor should i use?
     
  7. tubeguy

    Well-Known Member

    Nov 3, 2012
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    I've run drum-pad type piezo transducers/pickups directly into a normal mic-level input at normal settings for testing purposes after repair. They give a nice tom-tom type drum sound when tapped.

    This implies a mic level type signal voltage and a normal op-amp input might be fine. Using these as a pickup for bass guitar amazed me. (ex. bass player)

    I would guess the voltage is lower when used as a string pick-up. From watching the video it appears that it does reproduce the frequency of the individual notes.

    The piezo in the video looks just like the type used in the old motorola piezo tweeters
     
    Last edited: Dec 8, 2012
  8. Audioguru

    New Member

    Dec 20, 2007
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    What kind of "vibration" will your piezo transducers pickup?
    Please post the dfatasheet for the piezo transducer so we can see what is recommended for its load resistance.
     
  9. Teena123

    Thread Starter Member

    Nov 22, 2012
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    its to pick up engine vibration, the piezo transducer specifications are Piezo Transducer 27mm/4.2kHz
    Resonant frequency: 4.2kHz ±0.5kHz
    Impedance at resonance: 500Ω
    Capacitance: 14nF ±30%
    Maximum input voltage: 30V p-p
    Operating temperature: -20°C to +70°C.
     
  10. #12

    Expert

    Nov 30, 2010
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    That is not at all what we expected. 500 ohms is very low for that kind of transducer. It is in the range that a common transistor can be used, but an opamp such as the TL071 would still be a good choice and easier to design with (only my opinion because I'm good with opamps).

    (AG: is the TL071 the low noise version? I get it mixed up with the TL081.)
     
  11. Audioguru

    New Member

    Dec 20, 2007
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    I think the piezo with a very low impedance of only 500 ohms is not a transducer, it is wrongly a beeper with a built-in oscillator.
    A Piezo transducer has a fairly flat frequency response below its 4.2kHz resonance and it needs a preamp with a very high input impedance like an opamp with Jfet inputs.

    A TL07x is the same as a TL08x except it is selected for low noise.
     
  12. Teena123

    Thread Starter Member

    Nov 22, 2012
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    okay thanks you. so i should use a TL071 op amp do i need a fet transistor?
     
  13. Teena123

    Thread Starter Member

    Nov 22, 2012
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    One last thing the engine would be producing about 166hz i want to use this frequency into the op amp to produce a light on led when the frequency is about 166 and the light goes off when the frequency is less than 166hz. what resistance and voltage values should i use???
     
  14. Audioguru

    New Member

    Dec 20, 2007
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    No because the TL071 opamp already has Jfet inputs so its input resistance can be extremely high.
     
  15. Audioguru

    New Member

    Dec 20, 2007
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    You need a bandpass filter IC or circuit. Look in Google at Multiple Feedback Bandpass Filter. The bandpass filter feeds a transistor, comparator or opamp that turns on the LED.
     
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