The HC-SR04 is a popular, ultrasonic sensor for non-contact distance measurement, using sound waves to detect objects from 2cm to 80cm away, ideal for robotics and obstacle avoidance with microcontrollers like Arduino.
It works by sending a 40kHz ultrasonic pulse (via its Trigger pin) and measuring the time (via its Echo pin) for the sound to bounce back, calculating distance using the speed of sound.
Operating voltage: 5V
Practical Measuring Distance: 2cm to 80cm