• Measures the distance within a wide range of 2cm to 400cm
• Stable performance
• Accurate distance measurement
• High-density
• Small blind distance

The Ultrasonic Sensor HCSR04 module is a transmitter, a receiver and a control circuit in one single module. It offers an excellent range of accuracy and stable readings in an easy-to-use package. Also, its operation is not affected by sunlight or black material like Sharp rangefinders are (although acoustically soft materials like cloth can be difficult to detect).
The Trigger and the Echo pins are the I/O pins that can be connected to the I/O pins of the microcontroller/Arduino. It needs 10 us high-level signal at least Module will send eight 40kHz square waves automatically and will test if there is any signal returned. If there is a signal returned, the output will be high-level signals via IO port ECHO. The duration of the high-level signal is the time from the transmitter to receiving the ultrasonic. Testing distance = duration of high-level sound velocity (340m/s) / 2 You can use the above calculation to find the distance between the obstacle and the ultrasonic module.