float temp;

void setup() {
  pinMode(28, INPUT);
  pinMode(27, OUTPUT);
}

void loop() {
  temp = analogRead(28);
  temp = (temp * 5.0 * 33.333) / 1024.0;

  // Check if temperature is less than 20
  if (temp < 20) {
    digitalWrite(27, LOW);
  }
  // Check if temperature is between 20 and 40
  else if (temp >= 20 && temp < 100) {
    digitalWrite(27, HIGH);
  }
}