Arduino Ultrasonic Distance Arduino (HC-SR04) Ultrasonic Sensor displays the distance on the (1602) LCD Module in cm.

Arduino PIN-Protected Alarm System with Motion Detection An Arduino project implementing a security alarm system featuring PIN code access via a 4x4 keypad, status updates on a 16x2 LCD, motion ...

[Clint] was working with the Arduino library, based on the Parallax PING, which uses a single pin for trigger and echo. The HC-SR04 uses separate pins.