Measuring Obstacle Distance Using Ultrasonic Sensor

#define echoPin 11 // Echo Pin

#define trigPin 12 // Trigger Pin

#define LEDPin 13 // Onboard LED

int maximumRange = 100; // Maximum range needed

int minimumRange = 0; // Minimum range needed

long duration, distance; // Duration used to calculate distance

void setup() {

 Serial.begin (9600);

 pinMode(trigPin, OUTPUT);

 pinMode(echoPin, INPUT);

 pinMode(LEDPin, OUTPUT); // Use LED indicator (if required)

}

void loop() {

/* The following trigPin/echoPin cycle is used to determine the

 distance of the nearest object by bouncing soundwaves off of it. */

 digitalWrite(trigPin, LOW);

 delayMicroseconds(2);

 digitalWrite(trigPin, HIGH);

 delayMicroseconds(10);

 digitalWrite(trigPin, LOW);

 duration = pulseIn(echoPin, HIGH);

 //Calculate the distance (in cm) based on the speed of sound.

 distance = duration/58.2;

 if (distance >= maximumRange || distance <= minimumRange){

 /* Send a negative number to computer and Turn LED ON

 to indicate “out of range” */

 Serial.println(“-1”);

 digitalWrite(LEDPin, HIGH);

 }

 else {

 /* Send the distance to the computer using Serial protocol, and

 turn LED OFF to indicate successful reading. */

 Serial.println(distance);

 digitalWrite(LEDPin, LOW);

 }

 delay(1000);

}