int readVal;
float V2;
int wait=500;
int myvoltpin=A2;
int redpin=9;


void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(myvoltpin, INPUT);
  pinMode(redpin, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
readVal=analogRead(myvoltpin);
V2=(5./1023.)*readVal;
Serial.println(V2);
if(V2>4.0){
  digitalWrite(redpin, HIGH);
}
if(V2<4.0){
  digitalWrite(redpin, LOW);
}
delay(wait);
}