Code of the Arduino alarm system project. Learn how to use the ultrasonic sensor (HC-SR04) with Arduino. This tutorial will teach you what it is, how to assemble the sensor on Arduino, and, at the end, you'll implement it into an alarm system project.

The HC-SR04 is an affordable and easy to use distance measuring sensor which has a range from 2cm to 400cm (about an inch to 13 feet). The sensor is composed of two ultrasonic transducers. One is transmitter which outputs ultrasonic sound pulses and the other is receiver which listens for reflected waves.

Here’s how we need to connect the HC-SR04 sensor to an Arduino board. The Ground and the VCC pins of the module needs to be connected to the Ground and the 5 volts pins on the Arduino Board respectively and the trig and echo pins to any Digital I/O pin on the Arduino Board.

Ultrasonic sensor HC-SR04 is used to measure the distance to an object by using ultrasonic waves. The ultrasonic sensor HC-SR04 includes four pins: TRIG pin: this pin receives the control signal (pulse) from Arduino. ECHO pin: this pin sends a signal (pulse) to Arduino. Arduino measures the duration of pulse to calculate distance.