int trig = 7;
int echo = 2;
float distance;
long duration;
int led=5;
void setup() {
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
  pinMode(led, OUTPUT);

  Serial.begin(115200);
  Serial.println("Ultrasonic sensor ON");
}

void loop() {
  digitalWrite(trig,LOW);
  delayMicroseconds(10);
  digitalWrite(trig,HIGH);
  delayMicroseconds(10);
  digitalWrite(trig,LOW);

  duration=pulseIn(echo,HIGH);
  distance=(duration*0.0343)/2;
  if(distance<=20){
    digitalWrite(led, HIGH);
  }
  else{
    digitalWrite(led,LOW);
  }
  Serial.println(distance);
  delay(50);


}