//Define the pins for the ultrasonic sensor
const int trigPin = 7; // Trigger pin
const int echoPin = 8; //Echopin
int buzzer = 12;

void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(trigPin, OUTPUT); // set Trigger pin
pinMode(echoPin, INPUT); // set echopin

pinMode(3, OUTPUT); // green
pinMode(4, OUTPUT); // amber
pinMode(5, OUTPUT); // red 
pinMode(buzzer, OUTPUT);

}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);

//MEasure the time taken for the pulse to
long duration = pulseIn(echoPin, HIGH);

//calculate
//speed oif sound
// distance
int distance = duration * 0.0343 / 2;

//Print the distance
Serial.print("Distance: ");
Serial.print(distance);
Serial.println(" cm");
delay(100);

if(distance>100)
{
digitalWrite(3, HIGH);
digitalWrite(4, LOW);
digitalWrite(5, LOW);
digitalWrite(buzzer, 0);
}
else if(distance>25)
{
digitalWrite(3, LOW);
digitalWrite(4, HIGH);
digitalWrite(5, LOW);
digitalWrite(buzzer, 1);
 tone(buzzer, 500, 400);
 delay(400);
 digitalWrite(buzzer, 0);
 tone(buzzer, 500, 400);
 delay(400);
}
else
{
  digitalWrite(3, LOW);
  digitalWrite(4, LOW);
  digitalWrite(5, HIGH);
  digitalWrite(buzzer, 1);
   tone(buzzer, 1000, 100);
   delay(100);
   digitalWrite(buzzer, 0);
   tone(buzzer, 1000, 100);
   delay(100);
}
}