Description: Piezo elements come in handy when you need to detect vibration or a knock. You can use these for tap or knock sensors pretty easily by reading the voltage on the output. They can also be used for a very small audio transducer such as a buzzer.
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This piezo element needs some mass to make a loud noise or detect vibrations.
After I did that, it has a nice high pitched frequency range. It can also detect footsteps throughout my entire house with the standard Arduino ADC and no amplification. How awesome is that?