SHOKITECH Piezoelectric Sensor Transducer 27mm Dia with wire ( Pack of 3) Electronic Components Electronic Hobby Kit

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. Piezoelectric Sound Disc is a transducer that works on the phenomenon of piezoelectricity i.e. electric charge accumulates in ceramic in response to applied mechanical stress or vice versa. Due to accumulated charge, these plates generate an electric signal which leads to vibration of plates and produces different humming sounds. The frequency of vibration governs the audio that gets produced.