Piezo elements are actually one of the coolest crystals you’ll play with. Flex them, they generate a voltage (pretty high, actually). Pass power through them, and they’ll flex. Do it fast enough, and they’ll start to make a sound! So besides making annoying little beepy noises, you could use it as a sensor to detect a knock or other similar vibration.

Specifications

• Operating Voltage: 1.0 ~ 20.0V
• Rated Voltage: 3.0V
• Diameter: Ø12.5mm
• Total Height: 6.3mm
• Capacitance: 15,000pF
• Current Consumption: ≤2mA
• Resonance Freq: 4,000Hz
• Sound Pressure Level at 10cm: ≥75db
• Connection Method: Pin Type
• Self Drive: No