int LED = 3;
int TRIG =10;
int ECO = 9;
int DURACION;
int DISTANCIA;
int BUZZ = 11;
void setup() {
  // put your setup code here, to run once:
  pinMode(LED,OUTPUT);
  pinMode(ECO, INPUT);
  pinMode(TRIG, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(TRIG, HIGH);
  delay(1);
  digitalWrite(TRIG, LOW);
  DURACION=pulseIn(ECO,HIGH);
  DISTANCIA =DURACION /58.2;
  Serial.println(DISTANCIA);
  delay(200);
  if(DISTANCIA<=20 && DISTANCIA>=0){
    analogWrite(BUZZ, 10);
    digitalWrite(LED, HIGH);
    delay(DISTANCIA*10);
    digitalWrite(LED, LOW); 
    digitalWrite(BUZZ, LOW);   
  }
}