int L0 = 4;
 int L1 = 21;
 int L2 = 22;
 int L3 = 25;

 void setup() { 
  Serial.begin(9600);  // inicializa puerto serie 
 pinMode(L1, OUTPUT);
 pinMode(L2, OUTPUT);
 pinMode(L3, OUTPUT);
 pinMode(L0, OUTPUT);
 }
 void loop() { 
 
int sensorValue = analogRead(A0); //Lectura del ADC valores de 0 a 1023 
float voltage = sensorValue * (3.3 / 1023.0); //escalamos a voltaje  
//Enviamos por el puerto serie 
Serial.print("ADC= "); 
Serial.print(sensorValue); 
Serial.print("  Voltaje= "); 
Serial.println(voltage);  
delay(100);   
 delay(500); 
 if (voltage > 2){
    digitalWrite(L1, HIGH);
  }
    else{
    digitalWrite(L1, LOW);
  }
  if (voltage > 4){
    digitalWrite(L2, HIGH);
  }
  else {
    digitalWrite(L2, LOW);
  }
  if (voltage > 6){
    digitalWrite(L3, HIGH);
  }
  else{
    digitalWrite(L3, LOW);
  }
  if (voltage > 8 ){
    digitalWrite(L0, HIGH);
  }
  else{
    digitalWrite(L0, LOW);
  }
}