Day 3

// Analog sensors: pot, LDR, thermistor
#include <math.h>

const int POT_PIN  = A0;
const int LDR_PIN  = A1;
const int THERM_PIN = A2;

// Thermistor constants (NTC 10k, B=3950)
const float R_NOMINAL  = 10000.0;  // 10kΩ at 25°C
const float T_NOMINAL  = 25.0;     // °C
const float B_COEFF    = 3950.0;
const float R_SERIES   = 10000.0;  // series resistor

float readThermistor() {
  // Average 10 samples for stability
  float sum = 0;
  for (int i = 0; i < 10; i++) {
    sum += analogRead(THERM_PIN);
    delay(1);
  }
  float adc = sum / 10.0;

  // Convert ADC to resistance
  float R = R_SERIES * (1023.0 / adc - 1.0);

  // Steinhart-Hart simplified: B parameter equation
  float steinhart = R / R_NOMINAL;
  steinhart = log(steinhart);
  steinhart /= B_COEFF;
  steinhart += 1.0 / (T_NOMINAL + 273.15);
  steinhart = 1.0 / steinhart;
  return steinhart - 273.15;  // Kelvin to Celsius
}

void setup() {
  Serial.begin(9600);
  Serial.println("Sensor readings:");
}

void loop() {
  int pot  = analogRead(POT_PIN);
  int ldr  = analogRead(LDR_PIN);
  float temp = readThermistor();

  int pot_pct   = map(pot, 0, 1023, 0, 100);
  int light_pct = map(ldr, 0, 1023, 100, 0); // invert: low ADC = bright

  Serial.print("Pot:");   Serial.print(pot_pct);   Serial.print("%  ");
  Serial.print("Light:"); Serial.print(light_pct); Serial.print("%  ");
  Serial.print("Temp:");  Serial.print(temp, 1);   Serial.println("°C");

  delay(500);
}