Piezo sensor sensitivity

Discussion in 'General Electronics Chat' started by stefan.54, Feb 23, 2016.

  1. stefan.54

    Thread Starter New Member

    Dec 26, 2015
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    Quick question: I want to make some drum triggers(using and arduino board for processing) and I was wondering if the diameter of a piezo sensor has any direct relation to sensitivity?
     
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Yes. The output voltage is a function of both the piezo element area and the mechanical stress applied. Compared to the energy available in a drum hit, my guess is that a small sensor will pick up anything except brushes. You're not the first to ask about this, so there probably are DIY projects on the innergoogle.

    ak
     
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  3. ScottWang

    Moderator

    Aug 23, 2012
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    Please see the discussion -- Piezo Trigger Switch.

    I attached two circuits as amplifier for the piezo in #11 and #28, you just treat the circuits as switches when you hit the piezo.
     
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  4. stefan.54

    Thread Starter New Member

    Dec 26, 2015
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    Thanks a lot!
     
  5. ScottWang

    Moderator

    Aug 23, 2012
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    Using the piezo to be a input component, it just like using the speaker as microphone and the effect of speaker is good, it is depends on the designing of amplifier.

    You can using the adruino I/O port to input from the circuits that I attached in the old thread.
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
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    If you pinch the special JFET out of an electret MIC capsule and hook it up to my TL431 booster circuit - a piezo disc could well be *TOO* sensitive.

    Hook up the TL431 with a Vcc supply and bias it so it drops half the Vcc across the load resistor - that will put exactly 2.5V on the control/input pin, which is just about right for the JFET. That alone may be sensitive enough, but you can get *MASSIVE* gain by splitting the feedback resistor in 2 and AC grounding the tap between the 2, that gives you loads of DC nfb to stabilise the operating point, but no AC nfb to reduce the gain.
     
  7. ScottWang

    Moderator

    Aug 23, 2012
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    One question can be many methods to solve it, show your circuit, I will test it ... :)
     
  8. ian field

    Distinguished Member

    Oct 27, 2012
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    It was published in Elektor magazine a couple of years ago.

    Start with a TL431 and a load resistor about 200R - 2k2 or so.

    Load the input pin with the electret capsule.

    Put a 47k pot in series with about 1k2 from cathode to input. Adjust the pot for 1/2 Vcc on the cathode.

    With the pot connected to input and the 1k2 to cathode, measure the pot and replace it with a fixed resistor.

    If you need maximum gain, the 1k2 from cathode allows you to add a capacitor to shunt AC nfb without shunting the output at cathode.

    My first prototype had a very scruffy 100uF cap and it worked perfectly, subsequent builds with good condition capacitors were prone to local radio breakthrough - you may have to put 56R - 100R in series with the cap to stunt HF response.
     
  9. ScottWang

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    Aug 23, 2012
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  10. ian field

    Distinguished Member

    Oct 27, 2012
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  11. ScottWang

    Moderator

    Aug 23, 2012
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    So, you want to use the microphone to replace the piezo?
    I had been designed the microphone to control relay as on/off toggle switch.
     
  12. ian field

    Distinguished Member

    Oct 27, 2012
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    You could have tried bothering to read what I said:

    "If you pinch the special JFET out of an electret MIC capsule and hook it up to my TL431 booster circuit".
     
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