int t=33;
int e=27;
void setup()
{
  Serial.begin(9600);
  pinMode(t, OUTPUT);
  pinMode(e, INPUT);
  pinMode(4, OUTPUT);
}

void loop()
{
  digitalWrite(t,LOW);
  digitalWrite(t,HIGH);
  delayMicroseconds(10);
  digitalWrite(t,LOW);
  float dur = pulseIn(e,HIGH);
  float dist = (dur*0.0343)/2;
  Serial.print("Distance in cm: ");
  Serial.println(dist);
  if(dist<100)
  {
    digitalWrite(4,HIGH);
    
  }
  else
  {
    digitalWrite(4,LOW);
  }
}