How to Use HC-SR04 Ultrasonic Sensor with Arduino for Distance Measurement

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The HC-SR04 is a popular ultrasonic sensor in the Arduino ecosystem that measures distances ranging from 3 cm to 300 cm using 40 kHz sound waves. It works by emitting ultrasonic pulses from a trigger pin, waiting for the echo to bounce back from an object, and calculating distance based on the sound's travel time. The sensor connects to an Arduino UNO via just four pins — VCC, GND, Trig, and Echo — making it accessible for beginners. With an accuracy of approximately ±3 mm and reliable performance across lighting conditions, it is widely used in robotics, smart parking, obstacle avoidance, and home automation projects. The distance is calculated using the formula: Distance (cm) = Echo Time (µs) ÷ 58.3, derived from the speed of sound.

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