#define echo 4
#define trigger 5
#define Relay1 6
#define Relay2 7
#define Relay3 8

float time = 0, distance = 0;

void setup()
{
  Serial.begin(9600);

  pinMode(trigger, OUTPUT);
  pinMode(echo, INPUT);
  pinMode(Relay1, OUTPUT);
  pinMode(Relay2, OUTPUT);
  pinMode(Relay3, OUTPUT);

  delay(2000);
}

void loop()
{
  measure_distance();

  digitalWrite(Relay1, HIGH);

  if (distance >= 0 && distance <= 5)
  {
    digitalWrite(Relay2, HIGH);
    digitalWrite(Relay3, LOW);
  }
  else if (distance >= 10 && distance <= 15)
  {
    digitalWrite(Relay2, LOW);
    digitalWrite(Relay3, HIGH);
  }
  else
  {
    digitalWrite(Relay2, LOW);
    digitalWrite(Relay3, LOW);
  }

  delay(500);
}

void measure_distance()
{
  digitalWrite(trigger, LOW);
  delayMicroseconds(2);
  digitalWrite(trigger, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigger, LOW);
  
  time = pulseIn(echo, HIGH);
  
  distance = time * 0.034 / 2;
  
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");
}