Interfacing HC-SR04 Ultrasonic Module with Arduino Pro Mini

SR04 is a module that can detect distance between 2cm to 400cm by sending out ultrasonic waves and calculating the time between the sent signal and echo received.

Steps:

1. Send the trigger signal - a TTL 10us signal
2. Wait for the echo pin to get high.
3. Calculate the time for which the echo pin is high using a timer.
4. Calculate the distance using 

Distance = high level time * velocity (340M/S) / 2

Here is the code for Arduino Pro Mini -

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const int echo = 11; const int trig = 10; long duration; long dist; void setup() { pinMode(echo,INPUT); pinMode(trig,OUTPUT); Serial.begin(9600); } void loop() { digitalWrite(trig,HIGH); delayMicroseconds(10); digitalWrite(trig,LOW); duration=pulseIn(echo,HIGH); dist = duration / 58; Serial.println(dist); Serial.println(duration); delay(1000); }

The above code is very basic and does not have the out of range or too close feature. Hopefully I will update it in the next post.