Arduino and Ultrasonic sensor

Ultrasonic sensor is a ranging sensor used to measure the distance of an object. It has a ping emitter and a receiver. Emitter radiates the sound waves. Receiver receives the same. Distance is calculated by measuring the time interval. The formula to find distance is
Distance = time interval * speed of sound waves/2.

Components Required:

Arduino board
Ultrasonic sensor
Connecting wires

Pin connection.

Vcc- 5v
Grnd - 0v
Dout - any digital pin

Step 1. Make the connection  as specified above.
Step 2: upload the below sketch

Arduino code

1. #define trigPin 13
2. #define echoPin 12
3. #define led 11
4. #define led2 10
5. 
   
6. void setup() {
7.   Serial.begin (9600);
8.   pinMode(trigPin, OUTPUT);
9.   pinMode(echoPin, INPUT);
10.   pinMode(led, OUTPUT);
11.   pinMode(led2, OUTPUT);
12. }
13. 
    
14. void loop() {
15.   long duration, distance;
16.   digitalWrite(trigPin, LOW);  // Added this line
17.   delayMicroseconds(2); // Added this line
18.   digitalWrite(trigPin, HIGH);
19. //  delayMicroseconds(1000); - Removed this line
20.   delayMicroseconds(10); // Added this line
21.   digitalWrite(trigPin, LOW);
22.   duration = pulseIn(echoPin, HIGH);
23.   distance = (duration/2) / 29.1;
24.   if (distance < 4) {  // This is where the LED On/Off happens
25.     digitalWrite(led,HIGH); // When the Red condition is met, the Green LED should turn off
26.   digitalWrite(led2,LOW);
27. }
28.   else {
29.     digitalWrite(led,LOW);
30.     digitalWrite(led2,HIGH);
31.   }
32.   if (distance >= 200 || distance <= 0){
33.     Serial.println("Out of range");
34.   }
35.   else {
36.     Serial.print(distance);
37.     Serial.println(" cm");
38.   }
39.   delay(500);
40. }

Step 3. Open the serial monitor to see the output.