Circuit Documentation

Summary

This circuit is designed to interface an Arduino Leonardo with an LCD screen and an MQ-5 gas sensor, with the addition of a buzzer for alerting purposes. The Arduino Leonardo serves as the central processing unit, reading the analog output from the MQ-5 sensor to detect the presence of gases and displaying the sensor value on the LCD screen. If the gas concentration exceeds a certain threshold, the buzzer is activated as an alarm.

Component List

LCD Screen 16x2 I2C

• Description: A 16x2 character LCD display with an I2C interface for displaying text.
• Pins: SCL, SDA, VCC, GND

MQ-5 Gas Sensor

• Description: A gas sensor for detecting LPG, natural gas, and coal gas. Outputs both digital and analog signals.
• Pins: VCC, GND, Digi Out, Analog out

Buzzer

• Description: An audible signaling device that can be used to alert users to certain conditions.
• Pins: PIN, GND

Arduino Leonardo (Rev3b)

• Description: A microcontroller board based on the ATmega32u4, with digital and analog I/O pins.
• Pins: D0/RX, D1/TX, D2/SDA, D3 PWM/SCL, D4/A6, D5 PWM, D6 PWM/A7, D7, n.c., IOREF, RESET, 3V3, 5V, GND, VIN, A0, A1, A2, A3, A4, A5, D8/A8, D9 PWM/A9, D10 PWM/A10, D11 PWM, D12/A11, D13 PWM, AREF, SDA, SCL

Wiring Details

LCD Screen 16x2 I2C

• SCL: Connected to SCL on Arduino Leonardo
• SDA: Connected to SDA on Arduino Leonardo
• VCC: Connected to 5V on Arduino Leonardo
• GND: Connected to GND on Arduino Leonardo

MQ-5 Gas Sensor

• VCC: Connected to 5V on Arduino Leonardo
• GND: Connected to GND on Arduino Leonardo
• Analog out: Connected to A0 on Arduino Leonardo

Buzzer

• PIN: Connected to D3 PWM/SCL on Arduino Leonardo
• GND: Connected to GND on Arduino Leonardo

Documented Code

#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 16, 2);

#define Buzzer 3
#define Sensor A0

void setup() {
  Serial.begin(9200);
  lcd.init();
  lcd.backlight();
  
  pinMode(Buzzer, OUTPUT);
  Serial.println("MQ5 Heating Up!");
  delay(20000);
}

void loop() {
  int value = analogRead(Sensor);
  lcd.setCursor(0, 0);
  lcd.print("VALUE:");
  lcd.print(value);
  lcd.print("  ");

  if (value > 400) {
    digitalWrite(Buzzer, HIGH);
    lcd.setCursor(0, 1);
    lcd.print("GAS DETECTED!");
  } else {
    digitalWrite(Buzzer, LOW);
    lcd.setCursor(0, 1);
    lcd.print("             ");
  }
}

Code Explanation

• The code begins by including the LiquidCrystal_I2C library, which is used to control the LCD screen via the I2C protocol.
• Two preprocessor directives define the pins for the buzzer and the gas sensor.
• In the setup() function, the serial communication is started, and the LCD screen is initialized with its backlight turned on. The buzzer pin is set as an output, and a delay is included to allow the MQ-5 sensor to heat up.
• The loop() function continuously reads the analog value from the MQ-5 sensor and displays it on the LCD. If the value exceeds 400, the buzzer is turned on, and a warning message is displayed on the LCD. If the value is below the threshold, the buzzer is turned off, and the warning message is cleared.