#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// Define LCD address and dimensions
#define LCD_ADDR 0x27
#define LCD_COLS 20
#define LCD_ROWS 4

LiquidCrystal_I2C lcd(LCD_ADDR, LCD_COLS, LCD_ROWS);

// Define potentiometer pin
const int tempSetpointPotPin = A0;

// Define temperature sensor pin
const int tempSensorPin = A1;

// Define fan output pin
const int fanPin = 9;

// Define temperature thresholds
const int temp20CResistance = 2000; // 2K ohm
const int temp4CResistance = 4000; // 4K ohm

// Define potentiometer resistance
const int potResistance = 1200; // 1.2K ohm

// Variables for temperature control
int setpointTemp = 25; // Initial setpoint temperature
int hysteresis = 2; // Hysteresis temperature
int currentTemp = 0;

void setup() {
  // Initialize LCD
  lcd.init();
  lcd.backlight();

  // Set fan pin as output
  pinMode(fanPin, OUTPUT);
}

void loop() {
  // Read potentiometer value
  int tempSetpointReading = analogRead(tempSetpointPotPin);

  // Calculate setpoint temperature based on potentiometer reading
  setpointTemp = map(tempSetpointReading, 0, 1023, 4, 25);

  // Read temperature sensor
  int sensorValue = analogRead(tempSensorPin);

  // Convert sensor value to resistance
  int sensorResistance = map(sensorValue, 0, 1023, 0, 5000);

  // Convert resistance to temperature
  currentTemp = map(sensorResistance, temp20CResistance, temp4CResistance, 20, 4);

  // Display current temperature, setpoint temperature, hysteresis, and fan status on LCD
  lcd.setCursor(0, 0);
  lcd.print("Temp: ");
  lcd.print(currentTemp);
  lcd.print("C");

  lcd.setCursor(0, 1);
  lcd.print("Setpoint: ");
  lcd.print(setpointTemp);
  lcd.print("C");

  lcd.setCursor(0, 2);
  lcd.print("Hysteresis: ");
  lcd.print(hysteresis);
  lcd.print("C");

  // Check if temperature is above setpoint + hysteresis
  if (currentTemp > setpointTemp + hysteresis) {
    digitalWrite(fanPin, HIGH); // Turn on fan
    lcd.setCursor(0, 3);
    lcd.print("Fan: ON ");
  } else if (currentTemp < setpointTemp) {
    digitalWrite(fanPin, LOW); // Turn off fan
    lcd.setCursor(0, 3);
    lcd.print("Fan: OFF");
  }

  delay(1000); // Update every second
}