void setup() {

  pinMode(20,OUTPUT);
  pinMode(26, INPUT);
  Serial1.begin(9600);

}

void loop() {
  int temperatura = analogRead(26);
  Serial1.println(String(temperatura));
  delay(100);
  if (temperatura<=511){
digitalWrite(20, HIGH);
digitalWrite(21, LOW);
  }
  else {
    digitalWrite(20, LOW);
    digitalWrite(21, HIGH);
  }
}