HC-SR04, Ultrasonic, Distance Sensor+SainSmart LCD Keypad Shield Ultrasonic Module HC-SR04 Distance Sensor automatically sends eight 40 kHz and detect whether there is a pulse signal back The SainSmart LCD Keypad shield module for Arduino Diecimila Duemilanove, UNO, MEGA1280, MEGA2560 board. Buy them TOGETHER and get at the REDUCE price. It is a big bargain!!!