// finds the distance of an object & based on the distance the relay is on or off
void setup() {
  
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
  pinMode(5, OUTPUT);  
  pinMode(26, OUTPUT);  //trigger
  pinMode(27, INPUT);   //echo
}
long wdistance()
{
  digitalWrite(26, LOW);  // trigger signal off
  delay(10);  //10 milliseconds
  digitalWrite(26, HIGH);  //  trigger signal on
  delay(100);
  digitalWrite(26, LOW);  // trigger signal off
  float d=pulseIn(27,HIGH);//It returns the length of the pulse in microseconds. 
  return(d*0.03/2);  //divided to find one way distance
  delay(1000);
}
void loop() {       
  // put your main code here, to run repeatedly:
  
  int c=wdistance();
  Serial.println(String(c));
  if(c>=300){         //300 is the distance
    digitalWrite(5, HIGH);  //relay on
    Serial.println("Detected");
  }
  else{
    digitalWrite(5, LOW);  //relay off
    Serial.println("Not Detected");
  }
  delay(1000);
}