MQ135_V2.ino

#include "Nokia_5110.h"
#include "DHT.h"
#include "MQ135.h"

#define LCD_RST 7
#define LCD_CE 6
#define LCD_DC 5
#define LCD_DIN 4
#define LCD_CLK 3

#define DHT_PIN 2
#define DHT_TYPE DHT11

#define MQ135_ANALOG_PIN 4

Nokia_5110 lcd = Nokia_5110(LCD_RST, LCD_CE, LCD_DC, LCD_DIN, LCD_CLK);
DHT dht(DHT_PIN, DHT_TYPE);
MQ135 gasSensor = MQ135(MQ135_ANALOG_PIN);

void setup() {
  lcd.println("DHTxx test!");
  dht.begin();

  lcd.clear();
  lcd.setContrast(55);
}

void loop() {
  lcd.setCursor(0, 2);
  lcd.print("MQ135: ");
  int mq135 = analogRead(MQ135_ANALOG_PIN);
  lcd.print(mq135);

  lcd.println("");
  lcd.print("PPM: ");
  lcd.print(gasSensor.getPPM());

  lcd.println("");
  lcd.println("");
  lcd.print("Zero: ");
  lcd.print(gasSensor.getRZero());

  lcd.setCursor(0, 0);
  lcd.print("DHT11: ");
  int humidity = dht.readHumidity();
  int temperature = dht.readTemperature();
  if (isnan(humidity) || isnan(temperature)) {
    lcd.setCursor(0, 4);
    lcd.print("Failed sensor!");
  } else {

    lcd.print(humidity);
    lcd.print("% ");
    lcd.print(temperature);
    lcd.print("*C");
  }

  delay(1000);
}