How to use HC-SR04 ultrasonic ranging module
Samuel Alexander, a 10th grader from Surabaya, Indonesia, has posted an Instructable on how to use the HC-SR04 ultrasonic module with Arduino for simple distance ranging applications. HC-SR04 is a common choice among hobbyists for obstacle detecting in robotic applications, and his Instructable would be helpful for beginners to learn how to hook this ultrasonic ranging module in your Arduino project.
Ultrasonic ranging