const float BETA = 3950; // Beta Coefficient of the thermistor

void setup() {
  Serial.begin(9600);
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  int analogValue = analogRead(A0);
  
  // Avoid division by zero
  if (analogValue > 0) {
    float celsius = 1 / (log(1 / (1023.0 / analogValue - 1)) / BETA + 1.0 / 298.15) - 273.15;

    // Print temperature to Serial Monitor
    Serial.print("Temperature (°C): ");
    Serial.println(celsius);

    // Check if temperature is in the range 20 to 25
    if (celsius > 20 && celsius < 25) {
      digitalWrite(LED_BUILTIN, HIGH); // Turn on LED
    } else {
      digitalWrite(LED_BUILTIN, LOW); // Turn off LED
    }
  } else {
    Serial.println("Invalid analog value.");
  }

  delay(1000); // Wait 1 second before repeating
}