Ultrasonic Ranging Module HC - SR04

This sensor is used to determine the non-contract distance between 2cm-400cm function.
We can use it tell the distance and to do something in that distance as well. 

Specifications:
This sensor has four legs such as 
- VCC = input voltage range from 2v to 5.5v
- TRIG = Trigger it used to send the sound out 
- ECHO = it used to calculate the waiting time when the sound from trigger is returning back
- GND = is ground