Adafruit HC-SR04 Ultrasonic Sonar Distance Sensor

Adafruit HC-SR04 Ultrasonic Sonar Distance Sensor is used for automation, interactive art, and motion sensing. The sensor, which is common in robotics projects, is fast, fairly easy to use, and low cost. The Trig signal can be 3V or 5V, while the "return" Echo signal is 5V logic. For that reason, two 10K resistors are included for use as a divider to convert the 5V logic level to a safe 2.5V for 3V devices. The sensor works at about 2cm to 400cm away, but 10cm to 250cm can provide ideal results.