27mm Brass Piezo Discs with 3 contacts
These are perfect for constructing contact mics, CBG pickups, touch-sensors, drum triggers, speakers, buzzers, etc
Picture Illustration: (comparision)
Note: The 3rd lead is Feedback Electrode (Hartley Oscillator..
BMP280 Barometric Pressure and Altitude Sensor I2C/SPI Module is a cheapest and tiny Atmospheric Sensor Breakout to measure barometric pressure, and temperature readings all without taking up too much space. Basically, anything you need to know about atmospheric conditions you can find out from this..