//blink
int led_yellow = 9;
int led_green = 11;
int led_red =10 ;
int echo =12 ;
int trig =13 ;
float distance , duration ;
void setup() {
  Serial.begin(9600);
  pinMode(led_yellow , OUTPUT);
  pinMode(led_green , OUTPUT);
  pinMode(led_red , OUTPUT);
  pinMode(echo, INPUT);
  pinMode(trig, OUTPUT);


}

void loop() {
  digitalWrite(trig, LOW);
  delayMicroseconds(2);
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);

  duration = pulseIn(echo, HIGH);
  distance = (duration*.0343)/2;
  Serial.print("Distance: ");
  Serial.println(distance);
  delay(100);
if (distance < 100) {
digitalWrite(led_red , HIGH);
digitalWrite(led_yellow, LOW);
digitalWrite(led_green, LOW);
}
else if (distance >100 && distance < 300){
digitalWrite(led_red, LOW);
digitalWrite(led_yellow, HIGH);
digitalWrite(led_green, LOW);
}
else  {
  digitalWrite(led_red, LOW);
  digitalWrite(led_green, HIGH);
  digitalWrite(led_yellow, LOW);
}
}