// Single LED brightness control with NTC
// LED on D3 (PWM), Thermistor on A0 with 10k resistor

const int thermistorPin = A0;
const int ledPin = 3;

int rawValue;
float temperature;

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

void loop() {
  rawValue = analogRead(thermistorPin);

  // Convert to voltage (3.3V reference)
  float V = rawValue * (3.3 / 1023.0);

  // Voltage divider with 10k resistor
  float R = (3.3 * 10000.0 / V) - 10000.0;

  // Beta equation (B=3950, R0=10k at 25C)
  const float BETA = 3950.0;
  float tempK = 1.0 / ((1.0 / 298.15) + (1.0 / BETA) * log(R / 10000.0));
  temperature = tempK - 273.15;

  Serial.print("Temp: ");
  Serial.print(temperature);
  Serial.println(" °C");

  if (temperature < 25.0) {
    analogWrite(ledPin, 25);   // ~10% brightness
  } 
  else if (temperature < 30.0) {
    analogWrite(ledPin, 128);  // ~50% brightness
  } 
  else {
    analogWrite(ledPin, 255);  // 100% brightness
  }

  delay(500);
}