This is an Arduino-based Proximity Sensor circuit wired using the popular HC-SR04 Ultrasonic ranging module,used here for non-contact object detection purpose. The HC-SR04 module includes ultrasonic transmitters, receiver and control circuit. You only need to supply a short pulse to the trigger input to start the ranging, and then the module will send out burst of ultrasound at 40 kHz and raise its echo.


1) Arduino UNO, Breadboard, Jumper Wires

2) Ultrasonic Sensor HC-SR04

3) LED

4) 1 kOhm Resistor [x2]

5) Buzzer Sound 5V

6) Transistor BC547