int randNumber;
const int EchoPin = 4;
const int TriggerPin = 5;
int estado=0;
int cont=0;
int estAnt=0;

void setup() {
 
   pinMode(TriggerPin, OUTPUT);
   pinMode(EchoPin, INPUT);
pinMode(9, OUTPUT);
    pinMode(8, OUTPUT);
    pinMode(7, OUTPUT);
 pinMode(6, OUTPUT);
 randomSeed(analogRead(0));
 digitalWrite(6, HIGH);
 delay(200);
 digitalWrite(6, LOW);
 digitalWrite(7, HIGH);
 delay(200);
 digitalWrite(7, LOW);
 digitalWrite(8, HIGH);
 delay(200);
 digitalWrite(8, LOW);
 digitalWrite(9, HIGH);
 delay(200);
 digitalWrite(9, LOW);
}

void loop() {
 
  int cm = ping(TriggerPin, EchoPin);

if(cm<=100){
  if(estado == estAnt){
  randNumber = random(6, 10);
  digitalWrite(randNumber, HIGH);
  delay(1000);
  digitalWrite(randNumber, LOW);
estado = estAnt + 1;
}
  }
  else {
    estAnt = estado;
  }

  
}
int ping(int TriggerPin, int EchoPin) {
   long duration, distanceCm;
   
   digitalWrite(TriggerPin, LOW);  //para generar un pulso limpio ponemos a LOW 4us
   delayMicroseconds(4);
   digitalWrite(TriggerPin, HIGH);  //generamos Trigger (disparo) de 10us
   delayMicroseconds(10);
   digitalWrite(TriggerPin, LOW);
   
   duration = pulseIn(EchoPin, HIGH);  //medimos el tiempo entre pulsos, en microsegundos
   
   distanceCm = duration * 10 / 292/ 2;   //convertimos a distancia, en cm
   return distanceCm;
   }