#define TRIG_PIN 18
#define ECHO_PIN 5
#define LED 2
#define LED2 4
#define LED3 16
float duration_us,distance_cm;
void setup()
{
  Serial.begin(9600);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(LED, OUTPUT);
  pinMode(LED2, OUTPUT);
  pinMode(LED3, OUTPUT);
}
void loop()
{
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  duration_us=pulseIn(ECHO_PIN,HIGH);
  distance_cm=0.017*duration_us;
  if(distance_cm<50)
  {
    digitalWrite(LED, HIGH);
  }
  else
  {
    digitalWrite(LED, LOW);
  }
  if(distance_cm==50)
  {
    digitalWrite(LED2, HIGH);
    Serial.print("distanceA:");
    Serial.print(distance_cm);
    Serial.println("cm");
  }
  else
  {
    digitalWrite(LED2, LOW);
    Serial.print("distanceB:");
    Serial.print(distance_cm);
    Serial.println("cm");
  }
  if(distance_cm>50)
  {
    digitalWrite(LED3, HIGH);
    Serial.print("distanceC:");
    Serial.print(distance_cm);
    Serial.println("cm");
  }
  else
  {
    digitalWrite(LED3, LOW);
  } 
}