#define pitch 300
int red=2;
int green=3;
int trig=12;
int echo=13;
int alarm=10;
double duration, distance;
void setup() {
  // put your setup code here, to run once:
pinMode(red, OUTPUT);
pinMode(green, OUTPUT);
pinMode(trig, OUTPUT);
pinMode(echo, INPUT);
pinMode(alarm, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(trig, LOW);
delayMicroseconds(2);
digitalWrite(trig, HIGH);
delayMicroseconds(10);
digitalWrite(trig, LOW);
delayMicroseconds(2);
duration =pulseIn(echo,HIGH);
distance=(duration/2)*0.0343;//time will be divided by 2 since it's travelling twice, from sender to reciever and vice versa. The speed of sound in cm/microsecond is 0.03435.
//distance=duration*speed
    if (distance < 200) {
      digitalWrite(red, HIGH);
      digitalWrite(green, LOW);
      tone(alarm,pitch);
      delay(600);//delays the frequency at which the alarm is heard
      digitalWrite(red, LOW);
       digitalWrite(green, LOW);
  noTone(alarm);
  delay(600);
    }
    else {
      digitalWrite(red, LOW);
      digitalWrite(green, HIGH);
  noTone(alarm);

}
}