This is an Arduino-based Proximity Sensor circuit wired using the popular HC-SR04 Ultrasonic ranging module ... and best understood by referring the wiring diagram. If everything goes right,you should ...

The HC-SR04 ultrasonic range sensor is a pretty cool pre-wired module that ... If it’s in a way that we all understand (see the timing diagram below), when the trigger pin (Trig) of the module is set ...