Description
A Piezo element comes in handy when you need to detect vibration or a knock. This sensor measures 20mm in diameter and just 0.42mm thick. You can use these for tap or knock sensors pretty easily by reading the voltage on the output. An Arduino or compatible microcontroller with an analog input should be able to detect the voltage change with relative ease. They can also be used for a very small audio transducer such as a buzzer.