The HC-SR04 ultrasonic sensor uses sonar to determine distance to an object. It offers excellent non-contact range detection with high accuracy and stable readings in an easy-to-use package, from about 3cm to 300cm. Its operation is not affected by sunlight or black material like other kind of sensor, although acoustically soft materials like cloth can be difficult to detect – at least in the far range. It comes complete with ultrasonic transmitter and receiver module.
