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Percussion

Workshopshed

If someone is looking for a good way to do a drum type input to their project I can also recommend this circuit I found earlier in the year. It works nicely with some LM393 comparators.

 

image

 

Enchanted Objects Design Challenge - Knock Knock

http://www.scienceprog.com/thoughts-on-interfacing-piezo-vibration-sensor/

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  • The low forward drop of the Schottky diodes is a nice feature in this role.  Their low capacitance is another good reason to use them here.  Zeners can have low deltaC. 

  • in reply to D_Hersey

    If you really care about performance you would do much better to use a dual diode designed for the purpose like this one:

     

    2069352 NXPNUP1301UNUP1301U

     

    This one is optimised for high speed - if you need to optimise for low leakage you'll need something else.

     

    It's important to protect an input that will be directly connected to a piezo device quite carefully - they can produce quite high voltages when struck hard but also if the temperature changes. We had issues making piezo electric accelerometers for (automotive knock sensors) in large numbers, part of the production process involved heating the device to about 150C for several hours, once they had cooled down many of the parts retained enough charge in the peizo to produce a visible spark when shorted (open circuit voltage > 1kV as well) - it took a while for us to work out just how tough the protection on the test amplifier needed to be because it took at least 1000 such hits per day.

     

    The buzzer type piezo elements people seem to use in percussion sensors can be quite a high capacity (20nF or more) so can easily wreck small semiconductor devices.

     

    MK

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  • in reply to D_Hersey

    If you really care about performance you would do much better to use a dual diode designed for the purpose like this one:

     

    2069352 NXPNUP1301UNUP1301U

     

    This one is optimised for high speed - if you need to optimise for low leakage you'll need something else.

     

    It's important to protect an input that will be directly connected to a piezo device quite carefully - they can produce quite high voltages when struck hard but also if the temperature changes. We had issues making piezo electric accelerometers for (automotive knock sensors) in large numbers, part of the production process involved heating the device to about 150C for several hours, once they had cooled down many of the parts retained enough charge in the peizo to produce a visible spark when shorted (open circuit voltage > 1kV as well) - it took a while for us to work out just how tough the protection on the test amplifier needed to be because it took at least 1000 such hits per day.

     

    The buzzer type piezo elements people seem to use in percussion sensors can be quite a high capacity (20nF or more) so can easily wreck small semiconductor devices.

     

    MK

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