float V2;
int readVal;
int analogPin=A0;
int dt=500;
int ledPin= 10;
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(analogPin, INPUT);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  readVal=analogRead(analogPin);
  V2= (5.*readVal)/1023.;
  if (V2>3.0){
    digitalWrite(ledPin, HIGH);
  }
  if (V2<=3.0){
    digitalWrite(ledPin, LOW);
  }
  Serial.println(V2);
  delay(dt);
}