const int trigpin = 5;
const int echopin = 7;
const int led = 13;
const int sensor = 4;
int state = LOW;
int val = 0;

//define sound speed in cm/us
#define SOUND_SPEED 0.034
#define CM_TO_INCH 0.393701

#define BUZZER_PIN 2
long duration;
float distanceCm;
float distanceInch;

void setup() {
  Serial.begin(115200);//starts the serial communication
  pinMode(trigpin, OUTPUT);// Sets the trigPin as an Output
  pinMode(echopin, INPUT);//Sets the echoPin as an Input
  pinMode(BUZZER_PIN, OUTPUT);
  
  pinMode(led,OUTPUT);
  pinMode(sensor,INPUT);
  Serial.begin(9600);
  }

void loop() {
  // Clears the trigPin
  digitalWrite(trigpin, LOW);
  delayMicroseconds(2);
  // Sets the trigPin on HIGH state for 10 micro seconds
  digitalWrite(trigpin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigpin, LOW);
  // Reads the echopin, returns the sound wave travel time in microseconds
  duration= pulseIn(echopin, HIGH);

  // Calculate the distance
  distanceCm = duration*SOUND_SPEED/2;

  // Convert to inches 
  distanceInch=distanceCm*CM_TO_INCH;

  // Prints the distance in the Serial Monitor
  
  if(distanceCm>0)
  { 
  digitalWrite(BUZZER_PIN, HIGH);
  delay(3000);
  Serial.print("Object detected\n");
  Serial.println(distanceInch);
  }
  else
  {
  digitalWrite(BUZZER_PIN, LOW);
  Serial.print("No Object detected");
  }
  delay(1000);

 val=digitalRead(sensor);
 if(val==HIGH){
   digitalWrite(led,HIGH);
   delay(2000);
 } 
 else{
   digitalWrite(led,LOW);
   delay(2000);
 }
}