Circuit Documentation

Summary

This circuit is designed to monitor environmental conditions such as humidity, temperature, and air quality. It also controls a water pump based on the state of a rocker switch. The main components include an Arduino UNO, a DHT11 humidity and temperature sensor, an MQ-2 gas sensor, a 16x2 I2C LCD, a two-channel relay, a water pump, a rocker switch, and a 18650 Li-Ion battery.

Component List

1. Arduino UNO

   • Description: A microcontroller board based on the ATmega328P.
   • Pins: UNUSED, IOREF, Reset, 3.3V, 5V, GND, Vin, A0, A1, A2, A3, A4, A5, SCL, SDA, AREF, D13, D12, D11, D10, D9, D8, D7, D6, D5, D4, D3, D2, D1, D0

2. DHT11 Humidity and Temperature Sensor

   • Description: A sensor for measuring humidity and temperature.
   • Pins: VDD, DATA, NULL, GND

3. MQ-2 Gas Sensor

   • Description: A sensor for detecting gas levels.
   • Pins: GND, VCC, ANALOG, Digital

4. Two Channel Relay 5V

   • Description: A relay module for controlling high voltage devices.
   • Pins: VCC, IN2, IN1, GND, NC2, C2, NO2, NC1, C1, NO1

5. 18650 Li-Ion Battery

   • Description: A rechargeable lithium-ion battery.
   • Pins: Positive, Negative

6. Water Pump

   • Description: A small water pump.
   • Pins: positive, negative

7. Rocker Switch

   • Description: A switch to control the water pump.
   • Pins: output, input

8. 16x2 I2C LCD

   • Description: A 16x2 character LCD with I2C interface.
   • Pins: GND, VCC, SDA, SCL

Wiring Details

Arduino UNO

• A0 connected to MQ-2 (ANALOG)
• A4 connected to 16x2 I2C LCD (SDA)
• A5 connected to 16x2 I2C LCD (SCL)
• D2 connected to DHT11 Humidity and Temperature Sensor (DATA)
• D3 connected to Two Channel Relay 5V (IN2)
• D4 connected to Rocker Switch (input)

DHT11 Humidity and Temperature Sensor

• VDD connected to 16x2 I2C LCD (VCC)
• DATA connected to Arduino UNO (D2)
• GND connected to 16x2 I2C LCD (GND)

MQ-2 Gas Sensor

• VCC connected to 16x2 I2C LCD (VCC)
• ANALOG connected to Arduino UNO (A0)
• GND connected to 16x2 I2C LCD (GND)

Two Channel Relay 5V

• VCC connected to 16x2 I2C LCD (VCC)
• IN2 connected to Arduino UNO (D3)
• GND connected to 16x2 I2C LCD (GND)
• NC2 connected to Water Pump (positive)
• C2 connected to 18650 Li-Ion Battery (Positive)

18650 Li-Ion Battery

• Positive connected to Two Channel Relay 5V (C2)
• Negative connected to Water Pump (negative)

Water Pump

• positive connected to Two Channel Relay 5V (NC2)
• negative connected to 18650 Li-Ion Battery (Negative)

Rocker Switch

• input connected to Arduino UNO (D4)
• output connected to 16x2 I2C LCD (GND)

16x2 I2C LCD

• VCC connected to DHT11 Humidity and Temperature Sensor (VDD)
• GND connected to DHT11 Humidity and Temperature Sensor (GND)
• SDA connected to Arduino UNO (A4)
• SCL connected to Arduino UNO (A5)

Code Documentation

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

// Pin definitions
#define DHTPIN 2
#define DHTTYPE DHT11
#define MQ2PIN A0
#define RELAYPIN 3
#define SWITCHPIN 4

// Initialize the DHT sensor
DHT dht(DHTPIN, DHTTYPE);

// Initialize the LCD
LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {
  // Start serial communication
  Serial.begin(9600);

  // Initialize the DHT sensor
  dht.begin();

  // Initialize the LCD
  lcd.init();
  lcd.backlight();

  // Set pin modes
  pinMode(MQ2PIN, INPUT);
  pinMode(RELAYPIN, OUTPUT);
  pinMode(SWITCHPIN, INPUT);

  // Initial state of the relay
  digitalWrite(RELAYPIN, LOW);
}

void loop() {
  // Read humidity and temperature from DHT11
  float humidity = dht.readHumidity();
  float temperature = dht.readTemperature();

  // Read air quality from MQ-2
  int airQuality = analogRead(MQ2PIN);

  // Display data on LCD
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Hum: ");
  lcd.print(humidity);
  lcd.print("%");
  lcd.setCursor(0, 1);
  lcd.print("Temp: ");
  lcd.print(temperature);
  lcd.print("C AQ: ");
  lcd.print(airQuality);

  // Check the state of the switch
  if (digitalRead(SWITCHPIN) == HIGH) {
    // Turn on the water pump
    digitalWrite(RELAYPIN, HIGH);
  } else {
    // Turn off the water pump
    digitalWrite(RELAYPIN, LOW);
  }

  // Wait for a second before the next loop
  delay(1000);
}

This code initializes the sensors and LCD, reads data from the DHT11 and MQ-2 sensors, displays the data on the LCD, and controls the water pump based on the state of the rocker switch.