Description: In this Arduino Tutorial we will learn how the HC-SR04 Ultrasonic Sensor works and how to use it with Buzzer and LED. Hardware Required: - Arduino Board - Ultrasonic Sensor HC-SR04 - Buzzer - LED - Breadboard and Jump Wires Connections: HC-SR04 Sensor - The HC-SR04 Ultrasonic Module has 4 pins, Ground, VCC, Trig and Echo. 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. - The HC-SR04 sensor attach to the Breadboard - The Sensor VCC connect to the Arduino Board +5V - The Sensor GND connect to the Arduino Board GND - The Sensor Trig connect to the Arduino Board ANALOG 1 - The Sensor Echo connect to the Arduino Board ANALOG 0 LED - The LED attach to the Arduino UNO - The LED (from LED's long leg) connect to the Arduino Board Digital 13 - The LED short leg (-) connect to the Arduino Board G