int tr=13;
int ec=7;
int l=10;
int t;
int d;
void setup(){
  pinMode(tr,OUTPUT);
  pinMode(ec,INPUT);
  pinMode(l,OUTPUT);
  Serial.begin(9600);
}
void loop(){
  digitalWrite(tr,LOW);
  delayMicroseconds(2);
  digitalWrite(tr,HIGH);
  delayMicroseconds(10);
  digitalWrite(tr,LOW);
  t=pulseIn(ec,HIGH);
  d=t*0.0344/2;
  Serial.print("DISTANCE:");
  Serial.print(d);
  Serial.println("cm");
  if(d<100){
    digitalWrite(l,HIGH);}
    else{
      digitalWrite(l,LOW);
    }
  
  delay(100);
}