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Piezoelectric disks and sensors are very useful in a wide variety or projects. They can be used as contact mics, vibration sensors, or as buzzers in devices such as cell phones or sirens. Piezoelectric sensors can be used in a variety of projects as switch inputs, in conjunction with a Transistor switch, or as analog sensors from vibration or striking.

A piezo disk with two leads can be mounted to a vibrating surface from a musical instrument or speaker to create a contact mic or acoustic pickup. The voltage produced from a guitar, for instance, is within the voltages easily amplified by a standard guitar amplifier.

Peculiarities of working with Piezoelectric disks:

  • Voltages swing between positive and negative.
  • Piezoelectric disks send out many spikes from a single strike - this can make it difficult to get accurate readings and

  sometimes results in a 'bounce' effect similar to a switch.

Solutions to these problems:

  • A Zener diode placed in the signal chain prevents the voltage swing by keeping the signal positive.

  Alternatively, a single sided Opamp such as the LM324 may be used to keep the voltage from swinging below GND.

  Both of these solutions result in a loss of accuracy if using the piezo in conjunction with analog to digital converters   to measure force. However, without some sort of threshold or gating in your design the piezo's bounce will prove   to be very annoying.

The following is some simple PIC code for those of you using the PIC's internal ADC to read a piezo disk. The threshold is arbitrary and may be adjusted for your own application. In this instance the application was a contact microphone used to read a guitar's pitch and convert it to MIDI.

This page is an Article on bildr. Articles are pages that define or explain a concept, method, or generic item.

NOTE: All information contained within this article is pure opinion. Although this article is intended to help people, it may contain faulty or misleading information. This article is not to be considered professional opinion or advice, and is in no way a replacement for reading all safety/instructional documentation. Always remember to protect yourself when handling/using hazardous materials, as well as test new techniques before using them on projects/work intended to be handed in or used.

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