Ultrasonic HC-SR04 Distance Measuring Transducer Sensor
HC-SR04 consists of ultrasonic transmitter, receiver, and control circuit.
When trigged it sends out a series of 40KHz ultrasonic pulses and receives echo from an object.
The distance between the unit and the object is calculated by measuring the traveling time of sound and output it as the width of a TTL pulse.

power supply :5V DC
quiescent current : <2mA effectual angle: <15° ranging distance : 2cm – 500 cm resolution : 0.3 cm