Ultrasonic Distance Sensor (HC-SR04)

Overview

An ultrasonic distance sensor is a device that measures distance to an object using sound waves beyond human hearing range (typically 40kHz). The HC-SR04 is a common module used in robotics projects like the Alphabot V2.

Key Features

• Operating Voltage: 5V DC
• Measuring Range: 2cm - 400cm (practical limit often 200cm)
• Accuracy: ~3mm
• Measuring Angle: 15° cone
• Response Time: 100ms between measurements

Key Components

• Transmitter: Emits ultrasonic pulses
• Receiver: Detects reflected pulses (echoes)
• Control circuit: Manages timing and signal processing

Working

• The sensor emits an ultrasonic burst (8 pulses at 40kHz)
• The sound travels through air at ~343 m/s (varies with temperature)
• The wave reflects off objects in its path
• The sensor measures the time between transmission and echo reception
• Distance is calculated using: Distance = (Speed of Sound × Time)/2