SR04 Ultrasonic sensor Range Finder

Ultrasonic is a good way to use for detection and range measurement. It is commonly use in nowadays car park in Singapore, especially in modern shopping mall to detect the presence of a vehicle. If you drive, you will definity know when you are reversing your car and its near an object you will hear a "beep beep" sound which car uses ultrasonic sensors.

In robotics. Example, ClusterBot.

Video Tutorial with Arduino - from Youtube

Some video example of using this sensor.

Working concept

A short ultrasonic pulse is transmitted at the time 0, reflected by an object. The senor receives this signal and converts it to an electric signal. The next pulse can be transmitted when the echo is faded away. This time period is called cycle period. The recommend cycle period should be no less than 50ms. If a 10μs width trigger pulse is sent to the signal pin, the Ultrasonic module will output eight 40kHz ultrasonic signal and detect the echo back. The measured distance is proportional to the echo pulse width and can be calculated by the formula above. If no obstacle is detected, the output pin will give a 38ms high level signal.