Ultrasonic Sensor Module - HC-SR04

The Ultrasonic Sensor uses Ultrasonic waves to determine the distance of an object like Bats, hence it can be used as a distance measuring sensor. There are two Ultrasonic Transducers present in which one acts as a Transmitter which transmits a high frequency Ultrasonic signal and other acts as a receiver which will wait for the receiving of echo signal which gets reflected by any object in its path. The time between the two signals when divider by speed of sound gives us the distance of the object. Theoretically the sensor claims to have a measuring distance of 2cm to 400cm. However, a range up to 75-80cm can be easily achieved practically. They are cheap, easy to interface and require low power to operate. They can be used to measure the depth of water as waves can travel in water, detect and avoid obstacles in the path of a robot and also as a parking assist sensor.

Product Description

This module is powered by 5V supply. To start the measurement the trigger pin has to be made high for 10usec and then turned off. This will make the transmitter to send an Ultrasonic wave of frequency 40HZ. Echo pin goes high for a period of time which will be equal to the time taken for the Ultrasonic wave to return back to the sensor.

The amount of time the Echo pin remains high is measured by the controller and the distance traveled by the wave is calculated by multiplying with the speed of sound and hence the distance of the object from the sensor is measured by halving the distance traveled by the wave.