Photo: Suyash Dwivedi · CC BY-SA 4.0
HC-SR04 ultrasonic sensor
Measures distance with an echo, from about 2 cm to 4 m. The eyes of the obstacle-avoiding and keep-distance robots.
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A 10 µs pulse on TRIG makes it send a short burst of ultrasound. ECHO then stays HIGH for as long as the sound takes to reach the object and come back. Distance in cm = pulse length in µs / 58.
- Wait about 60 ms between measurements, so old echoes die away.
- Soft or slanted surfaces can send no echo back.
Learn it in Measuring distance with the HC-SR04 and read How ultrasonic sensors see.
