Ultrasonic sensors
Ultrasonic sensors(also known as transceivers when they both send and receive, but more generally called transducers) work on a principle similar to radar or sonar, which evaluate attributes of a target by interpreting the
echoes from radio or sound waves respectively. Active ultrasonic sensors generate high frequency sound waves and evaluate the echo which is received back by the sensor,measuring the time interval between sending the signal and receiving the echo to determine the distance to an object. Passive ultrasonic sensors are basically microphones that detect ultrasonic noise that is present under certain conditions.
HC-SR04 Ultrasonic Module Working
Ultrasonic Module Operation:-
1. Provide TRIGGER signal, at-least 10μS High Level (5V) pulse.
2. The module will automatically transmit eight 40KHz ultrasonic burst.
3. If there is an obstacle in-front of the module, it will reflect the ultrasonic
burst.
4. If the signal is back, ECHO output of the sensor will be in HIGH state (5V)
for duration of time taken for sending and receiving ultrasonic burst. Pulse
width ranges from about 150μS to 25mS and if no obstacle is detected, the echo pulse width will be about 38m
m about 150μS to 25mS and if no obstacle is detected, the
echo pulse width will be about 38ms.