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(4) The principle of ultrasonic sensor
As the above picture shown, it is like two eyes. One is transmitting
end, the other is receiving end.
The ultrasonic module will emit the ultrasonic waves after trigger
signal. When the ultrasonic waves encounter the object and are
reflected back, the module outputs an echo signal, so it can
determine the distance of object from the time difference between
trigger signal and echo signal.
The t is the time that emitting signal meets obstacle and returns.
and the propagation speed of sound in the air is about 343m/s,
therefore,
distance = speed * time, because the ultrasonic wave
emits and comes back, which is 2 times of distance, so it needs to
be divided by 2, the distance measured by ultrasonic wave = (speed
* time)/2
1. Use method and timing chart of ultrasonic module:
Setting the delay time of Trig pin of SR04 to 10μs at least, which can
trigger it to detect distance.
2. After triggering, the module will automatically send eight 40KHz
ultrasonic pulses and detect whether there is a signal return. This
step will be completed automatically by the module.
3. If the signal returns, the Echo pin will output a high level, and the
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