HC-SR04 Ultrasonic Distance Sensor Module 4-Pin for Arduino & Raspberry Pi

HC-SR04 Ultrasonic Distance Sensor is a compact 4-pin module that gives robots and projects the ability to "see" with sound. It uses echolocation, emitting high-frequency pulses and timing echoes to calculate distance, making it a reliable, low-cost option for Arduino and Raspberry Pi builds. It measures from 2cm to 400cm (about 13 feet) and performs well in darkness or bright sunlight where IR sensors often fail, including on glass, mirrors, and dark surfaces. With separate Trigger (input) and Echo (output) pins for clear signal management and good repeatability—accuracy can be as fine as 3mm—it’s straightforward to integrate and is compatible with common libraries like NewPing for advanced control and filtering.