const int tr = 33,ec = 25;
void setup() {
  Serial.begin(115200);
  pinMode(tr, OUTPUT);
  pinMode(ec, INPUT);
  pinMode(32, OUTPUT);//green
  pinMode(26, OUTPUT);//yellow
  pinMode(27, OUTPUT);//red
}
void loop() {
  digitalWrite(tr, HIGH);
  delayMicroseconds(10);
  digitalWrite(tr, LOW);
  int du = pulseIn(ec,HIGH);
  float cm = (int)(du / 58.7);
  Serial.print("Distance : ");
  Serial.println(cm);

  if (cm >= 100) {
    digitalWrite(32, HIGH);
  }else{
    digitalWrite(32, LOW);
  }
  if (cm <= 100 && cm >= 30) {
    digitalWrite(26, HIGH);
  }else{
    digitalWrite(26, LOW);
  }
  if (cm <= 30) {
    digitalWrite(27, HIGH);
  }else{
    digitalWrite(27, LOW);
  }
}