This is the HC-SR04 ultrasonic ranging sensor. It works on the principle of the ultrasonic wave. This economical sensor provides 2cm to 400cm of non-contact measurement functionality with a ranging accuracy that can reach up to 3mm. The module itself acts as a transmitter and receiver. It is mostly used in applications like Automatic car parking system, Distance measurement and Object detection in a conveyer belt.
VCC – Power Supply
Trig – Trigger (Transmit ultrasonic)
Echo – Echo (Receives the transmitted ultrasonic waves)
GND – Ground