const int trig = 9, echo = 10;
const int verde = 3, amarillo = 4, rojo = 8;


void setup() {
  Serial.begin(9600);
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);

  pinMode(verde, OUTPUT);
  pinMode(amarillo, OUTPUT);
  pinMode(rojo, OUTPUT);
}

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

  long t = pulseIn(echo, HIGH);

  int d = t * 0.034 / 2;

  Serial.println(d);

  if (d>=100) {
    digitalWrite(verde, HIGH);
    digitalWrite(amarillo, LOW);
    digitalWrite(rojo, LOW);
  }

  else if (d>50 && d<100) {
    digitalWrite(verde, LOW);
    digitalWrite(amarillo, HIGH);
    digitalWrite(rojo, LOW);
  }

  else if (d<=50) {
    digitalWrite(verde, LOW);
    digitalWrite(amarillo, LOW);
    digitalWrite(rojo, HIGH);
  }
  
  delay(200);
}