int trig =2;
int eco =3;

float duration;
float distance;

void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(trig, OUTPUT);
pinMode(eco, INPUT);
pinMode(7, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:

digitalWrite(trig, LOW);
digitalWrite(trig, HIGH);
delay(2000);

digitalWrite(trig, LOW);
duration=pulseIn(eco,HIGH);
distance=(duration*0.0343)/2;
if(distance<50){
  digitalWrite(7, HIGH);
}
else{
  digitalWrite(7, LOW);
}

Serial.print("DISTANCE IS cm ");
Serial.println(distance);

}