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Project Documentation

Arduino Mega 2560 Environmental Monitoring System with Relay Control and Data Logging

Image of Arduino Mega 2560 Environmental Monitoring System with Relay Control and Data Logging

Circuit Documentation

Summary

This circuit is designed to monitor environmental parameters such as temperature, humidity, CO2 levels, and soil moisture. It utilizes an Arduino Mega 2560 as the central microcontroller to read data from DHT22 sensors, MQ135 sensors, a capacitive soil moisture sensor, and to control a 4-channel relay module and an RGB LED matrix. The data is displayed on both an LCD and an OLED display. A rotary encoder allows the user to navigate through different data pages on the OLED display. The circuit also includes an RTC module for timekeeping and an SD card module for data logging.

Component List

Arduino Mega 2560

Microcontroller board based on the ATmega2560
Provides numerous digital and analog I/O pins
Features I2C, SPI, and UART communication interfaces

4 Channel Relay Module

Module with 4 electromechanical relays
Each relay has normally open (N.O.), common (COM), and normally closed (N.C.) terminals
Controlled by digital outputs from the Arduino

OLED 128x64 I2C Monochrome Display

Small display for showing text and graphics
Uses I2C communication protocol
Typically used for displaying sensor data or menus

LCD I2C Display

Alphanumeric liquid crystal display with I2C interface
Displays time, date, and other status information

Rotary Encoder (x2)

Input device that provides rotational position feedback
Includes push-button functionality
Used for navigating the OLED display interface

MQ135 Gas Sensor (x2)

Air quality sensor for detecting a wide range of gases, including NH3, NOx, alcohol, benzene, smoke, and CO2
Provides both analog and digital outputs

DFRobot Capacitive Soil Moisture Sensor (V1.0)

Sensor for measuring the moisture content in soil
Outputs an analog signal that varies with the moisture level

RTC DS1307

Real-time clock module for timekeeping
Uses I2C communication protocol
Maintains time with a coin cell battery when power is lost

DHT22 Temperature and Humidity Sensor (x2)

Digital sensor for measuring ambient temperature and humidity
Provides calibrated digital output

WS2812 RGB LED Matrix 1x8

Strip of 8 individually addressable RGB LEDs
Controlled via a single digital pin

2cm x 8cm PCB

Small prototyping printed circuit board
Used for mounting and interconnecting components

SD Card Module

Module for reading and writing to SD cards
Uses SPI communication protocol
Utilized for data logging purposes

Wiring Details

Arduino Mega 2560

3V3 connected to SD card module +3.3V
5V connected to various components' VCC pins
GND connected to various components' GND pins
A0 to A2 connected to analog pins of sensors
D21/SCL and D20/SDA connected to I2C devices (LCD, OLED, RTC)
D17 PWM/RX2 to D14/TX3 connected to relay module inputs IN 1 to IN 4
D5 PWM to D11 PWM connected to rotary encoder pins CLK, DT, SW
D12 PWM connected to WS2812 RGB LED matrix DIN
D52, D50, D51, D46 connected to SD card module SCK, MISO, MOSI, CS
D24, D22 connected to DHT22 sensors OUT pins

4 Channel Relay Module

VCC+ and VCC- (GND) connected to 5V and GND respectively
IN 1 to IN 4 controlled by Arduino pins D14/TX3 to D17 PWM/RX2

OLED 128x64 I2C Monochrome Display

VDD and GND connected to 5V and GND respectively
SCK and SDA connected to Arduino D21/SCL and D20/SDA

LCD I2C Display

VCC and GND connected to 5V and GND respectively
SDA and SCL connected to Arduino D20/SDA and D21/SCL

Rotary Encoder (x2)

+ and GND connected to 5V and GND respectively
SW, DT, CLK connected to Arduino pins D7 PWM, D6 PWM, D5 PWM for one encoder and D11 PWM, D10 PWM, D9 PWM for the other

MQ135 Gas Sensor (x2)

VCC and GND connected to 5V and GND respectively
A0 connected to Arduino A1 and A2

DFRobot Capacitive Soil Moisture Sensor (V1.0)

VCC and GND connected to 5V and GND respectively
A connected to Arduino A0

RTC DS1307

VCC and GND connected to 5V and GND respectively
SCL and SDA connected to Arduino D21/SCL and D20/SDA

DHT22 Temperature and Humidity Sensor (x2)

VCC and GND connected to 5V and GND respectively
OUT connected to Arduino D22 and D24

WS2812 RGB LED Matrix 1x8

VCC and GND connected to 5V and GND respectively
DIN connected to Arduino D12 PWM

SD Card Module

+3.3V, GND, +5V connected to Arduino 3V3, GND, 5V respectively
CS, MOSI, SCK, MISO connected to Arduino D46, D51, D52, D50

Documented Code

/*
 * This Arduino Sketch reads data from DHT22 sensors for temperature and
 * humidity, MQ135 sensors for CO2 levels, and a soil moisture sensor. It
 * displays the data on an LCD and OLED screen. The LCD shows the date and
 * time, while the OLED cycles through pages displaying temperature, humidity,
 * CO2 levels, and soil moisture. A rotary encoder is used to switch between
 * the pages on the OLED display. The code also controls a relay module and an
 * RGB LED matrix based on specific conditions.
 */

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Adafruit_SSD1306.h>
#include <Adafruit_GFX.h>
#include <DHT.h>
#include <RTClib.h>
#include <Adafruit_NeoPixel.h>
#include <SD.h>

#define DHTPIN0 22
#define DHTPIN1 24
#define DHTTYPE DHT22
#define MQ135PIN0 A2
#define MQ135PIN1 A1
#define SOILMOISTUREPIN A0
#define OLED_RESET -1
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define RELAY1 14
#define RELAY2 15
#define RGB_PIN 12
#define NUMPIXELS 8
#define SD_CS 46

DHT dht0(DHTPIN0, DHTTYPE);
DHT dht1(DHTPIN1, DHTTYPE);
LiquidCrystal_I2C lcd(0x27, 16, 2);
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
RTC_DS1307 rtc;
Adafruit_NeoPixel pixels(NUMPIXELS, RGB_PIN, NEO_GRB + NEO_KHZ800);
File dataFile;

int page = 0;
const int totalPages = 4;
unsigned long previousMillis = 0;
const long interval = 20000;
bool relay2State = false;

void setup() {
  Wire.begin();
  lcd.begin();
  lcd.backlight();
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.display();
  delay(2000);
  display.clearDisplay();
  dht0.begin();
  dht1.begin();
  rtc.begin();
  pinMode(9, INPUT);
  pinMode(10, INPUT);
  pinMode(11, INPUT);
  pinMode(RELAY1, OUTPUT);
  pinMode(RELAY2, OUTPUT);
  pixels.begin();
  if (!SD.begin(SD_CS)) {
    lcd.print("SD init failed!");
    return;
  }
  dataFile = SD.open("datalog.txt", FILE_WRITE);
}

void loop() {
  DateTime now = rtc.now();
  lcd.setCursor(0, 0);
  lcd.print(now.year(), DEC);
  lcd.print('/');
  lcd.print(now.month(), DEC);
  lcd.print('/');