The SR04 ultrasonic range finder provides precise non-contact distance measurements from about 3 centimeters to 3 meters. It is very easy to connect to basic stamp or the javelin, requiring only two I/O pins.the SR04 library makes this device very simple to use and is an ideal component for robotics applications.
Ultrasonic Sensor HC-SR04
3 cm to 3 m
Trigger - TTl Pulse 10uS Echo Pulse - Positive TTL level signal
Length x Width x Height
43mm x 20mm x 17mm