// Define the pin for the LED
const int ledPin = 13; // Use built-in LED pin on Arduino Uno

// Define the pin for the NTC thermistor
const int thermistorPin = A0; // Analog input pin A0

// Variables for the thermistor and calculated temperature
int thermistorValue; // Raw ADC value from thermistor
float temperature;   // Calculated temperature in degrees Celsius

void setup() {
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600); // Initialize serial communication at 9600 baud
}

void loop() {
  // Read the raw ADC value from the thermistor
  thermistorValue = analogRead(thermistorPin);

  // Convert the ADC value to resistance (using a voltage divider formula)
  float resistance = 10000.0 / (1023.0 / thermistorValue - 1);

  // Steinhart-Hart equation to calculate temperature in Celsius
  float steinhart;
  steinhart = resistance / 10000;     // (R/Ro)
  steinhart = log(steinhart);                  // ln(R/Ro)
  steinhart /= 3950;                   // 1/B * ln(R/Ro)
  steinhart += 1.0 / (25 + 273.15); // + (1/To)
  steinhart = 1.0 / steinhart - 273.15; // Invert Steinhart

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

  // Blink LED based on temperature
  if (temperature < 25.0) {
    digitalWrite(ledPin, HIGH); // Turn LED on
    delay(500); // Wait for 500 milliseconds
    digitalWrite(ledPin, LOW); // Turn LED off
    delay(500); // Wait for 500 milliseconds
  } else {
    digitalWrite(ledPin, LOW); // Keep LED off
    delay(1000); // Wait for 1 second
  }
}