Arduino Project

#include <dht.h>

#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

int sensorPin = 7;
int buttonPin = 8;
int relayPin = 9;

int relayState = LOW;
int previous = LOW;
char* modes[] = {"Auto", "On", "Off"};
int mode = 2;

dht DHT;
#define DHT11_PIN 7

float celsius = 0;
char celsiusString[30];

void setup() {
  lcd.begin(16, 2);
  Serial.begin(9600);
  pinMode(sensorPin, OUTPUT);
  pinMode(relayPin, OUTPUT);
  digitalWrite(relayPin, LOW);
  pinMode(buttonPin, INPUT);
}

void readTemp() {

}

void checkMode() {
  int buttonState = digitalRead(buttonPin);
  if (buttonState == HIGH && previous == LOW){
    mode++;
    if (mode % 3 == 1) { // On
      relayState = HIGH;
      digitalWrite(relayPin, relayState);

    } else if (mode % 3 == 2) { // Off
      relayState = LOW;
      digitalWrite(relayPin, relayState);
    }
  }
  previous = buttonState;
}

void autoMode() {
  if (mode % 3 == 0) { // Auto
      if (celsius >= 20.0 && relayState == LOW) {
          relayState = HIGH;
          digitalWrite(relayPin, relayState);
      } else if (celsius <= 17.0 && relayState == HIGH) {
          relayState = LOW;
          digitalWrite(relayPin, relayState);
      }
   }
}

void printLcd() {
  int chk = DHT.read11(DHT11_PIN);
  lcd.clear();
  lcd.print("Temp: ");
  lcd.print(DHT.temperature);
  lcd.print((char)223);
  lcd.print("C");
  lcd.setCursor(0,1);
  lcd.print("Mode: ");
  lcd.print(modes[(mode%3)]);
   Serial.print(celsius);
}

void loop() {
  readTemp();

  checkMode();
  autoMode();

  printLcd();

  delay(250);
}