#include <LiquidCrystal_I2C.h>

#define I2C_ADDR    0x27
#define LCD_COLUMNS 16
#define LCD_LINES   2

LiquidCrystal_I2C lcd(I2C_ADDR, LCD_COLUMNS, LCD_LINES);

const int lry = 3;
const int bzz = 4;
const int btn = 2;

bool vbt = false;
bool et = false;

void setup() {
  lcd.init();
  pinMode(lry, OUTPUT);
  pinMode(bzz, OUTPUT);
  pinMode(btn, INPUT_PULLUP);
  digitalWrite(lry, LOW);
  digitalWrite(LED_BUILTIN, HIGH);
}

void loop() {
  const float BETA = 3950; // should match the Beta Coefficient of the thermistor
  int analogValue = analogRead(A0);
  float celsius = 1 / (log(1 / (1023. / analogValue - 1)) / BETA + 1.0 / 298.15) - 273.15;
  vbt = digitalRead(btn);

  if (celsius > 40 || celsius < 10 || vbt == LOW) {
    lcd.backlight();
    lcd.setCursor(0, 0);
    lcd.print(celsius);
    lcd.println(" Degree C");
    digitalWrite(lry, HIGH);
    digitalWrite(LED_BUILTIN, LOW);
    tone(bzz, 1500);
    delay(500);
    tone(bzz, 1200);
    delay(500);
  } else {
    noTone(bzz);
    digitalWrite(lry, LOW);
    digitalWrite(LED_BUILTIN, HIGH);
    lcd.noBacklight();
    lcd.clear();
  } if (celsius < 0 || celsius > 50) {
    lcd.setCursor(0, 1);
    lcd.println("Extreme Temp!");
    et = true;
  } else if (et == true) {
    lcd.clear();
    et = false;
  }

  delay(100);
}