# Gas Monitor rev_01

/********* Pleasedontcode.com **********

    Pleasedontcode thanks you for automatic code generation! Enjoy your code!

    - Terms and Conditions:
    You have a non-exclusive, revocable, worldwide, royalty-free license
    for personal and commercial use. Attribution is optional; modifications
    are allowed, but you're responsible for code maintenance. We're not
    liable for any loss or damage. For full terms,
    please visit pleasedontcode.com/termsandconditions.

    - Project: # Gas Monitor
    - Source Code NOT compiled for: Arduino Uno
    - Source Code created on: 2026-01-25 18:31:09

********* Pleasedontcode.com **********/

/****** SYSTEM REQUIREMENTS *****/
/****** SYSTEM REQUIREMENT 1 *****/
    /* when gas sms is sent to sim 900a it should send */
    /* the gas level to phone */
/****** END SYSTEM REQUIREMENTS *****/


/* START CODE */

/****** DEFINITION OF LIBRARIES *****/
#include <MQUnifiedsensor.h>    //https://github.com/miguel5612/MQSensorsLib
#include <SoftwareSerial.h>     //Software Serial for SIM900A communication

/****** FUNCTION PROTOTYPES *****/
void setup(void);
void loop(void);
void initMQ5Sensor(void);
void initSIM900A(void);
void readGasLevel(void);
void sendGasSMS(float gasLevel);
void sendATCommand(String command, unsigned long timeout);
void waitForResponse(String expectedResponse, unsigned long timeout);
void displayDebugInfo(void);

/***** DEFINITION OF DIGITAL INPUT PINS *****/
const uint8_t MQ5_MQ5_DOUT_PIN_D2           = 2;

/***** DEFINITION OF ANALOG INPUT PINS *****/
const uint8_t MQ5_MQ5_AOUT_PIN_A0           = A0;

/***** DEFINITION OF SIM900A COMMUNICATION PINS *****/
// SoftwareSerial(RX, TX)
const uint8_t SIM900A_RX_PIN                = 10;   // RX pin for SIM900A
const uint8_t SIM900A_TX_PIN                = 11;   // TX pin for SIM900A

/***** DEFINITION OF SENSOR CALIBRATION PARAMETERS *****/
// MQ-5 sensor configuration for LPG detection
const float MQ5_RATIO_CLEAN_AIR             = 6.5;  // RS/R0 ratio in clean air
const float MQ5_RL_VALUE                    = 10.0; // Load resistance in KOhms
const float MQ5_VOLTAGE_RESOLUTION          = 5.0;  // Arduino Uno voltage reference
const int MQ5_ADC_BIT_RESOLUTION            = 10;   // Arduino Uno ADC resolution

/***** DEFINITION OF GSM MODULE CONFIGURATION *****/
const String PHONE_NUMBER                   = "+1234567890";    // Phone number to send SMS to - CHANGE THIS
const unsigned long SIM900A_BAUD_RATE       = 9600;         // SIM900A communication speed
const unsigned long AT_COMMAND_TIMEOUT      = 1000;         // Timeout for AT commands (ms)
const unsigned long SMS_DELAY               = 5000;         // Delay between SMS messages (ms)

/***** DEFINITION OF MEASUREMENT PARAMETERS *****/
const unsigned long GAS_READING_INTERVAL    = 10000;        // Interval for gas readings (ms)
const unsigned long SMS_SEND_INTERVAL       = 60000;        // Interval for SMS sending (60 seconds)

/****** DEFINITION OF LIBRARIES CLASS INSTANCES *****/
// Create SoftwareSerial instance for SIM900A communication
SoftwareSerial SIM900A_Serial(SIM900A_RX_PIN, SIM900A_TX_PIN);

// Create MQ5 sensor instance
// MQUnifiedsensor(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin, Type)
MQUnifiedsensor MQ5("Arduino UNO", MQ5_VOLTAGE_RESOLUTION, MQ5_ADC_BIT_RESOLUTION, MQ5_MQ5_AOUT_PIN_A0, "MQ-5");

/***** GLOBAL VARIABLES *****/
float currentGasLevel = 0.0;                    // Current gas level reading in PPM
unsigned long lastGasReadTime = 0;              // Timestamp of last gas reading
unsigned long lastSMSSendTime = 0;              // Timestamp of last SMS sent
bool SIM900AInitialized = false;                // Flag for SIM900A initialization status
String serialBuffer = "";                       // Buffer for serial communication

/****** SETUP FUNCTION *****/
void setup(void)
{
    // Initialize Serial for debugging
    Serial.begin(9600);

    // Wait for Serial to initialize
    delay(100);

    Serial.println(F("\n\n=== Gas SMS Alert System Started ==="));
    Serial.println(F("Initializing MQ5 Sensor..."));

    // Configure GPIO pins
    pinMode(MQ5_MQ5_DOUT_PIN_D2, INPUT_PULLUP);
    pinMode(MQ5_MQ5_AOUT_PIN_A0, INPUT);

    // Initialize MQ5 sensor
    initMQ5Sensor();

    // Initialize SIM900A GSM module
    Serial.println(F("Initializing SIM900A GSM Module..."));
    initSIM900A();

    Serial.println(F("=== System Initialization Complete ===\n"));

    // Initialize timestamps
    lastGasReadTime = millis();
    lastSMSSendTime = millis();
}

/****** MAIN LOOP *****/
void loop(void)
{
    // Handle incoming serial data from SIM900A for debugging
    while (SIM900A_Serial.available())
    {
        char inChar = (char)SIM900A_Serial.read();
        serialBuffer += inChar;

        // Process complete lines
        if (inChar == '\n')
        {
            Serial.print(F("SIM900A: "));
            Serial.println(serialBuffer);
            serialBuffer = "";
        }
    }

    // Perform gas level reading at specified interval
    if (millis() - lastGasReadTime >= GAS_READING_INTERVAL)
    {
        lastGasReadTime = millis();
        readGasLevel();
        displayDebugInfo();
    }

    // Send SMS with gas level at specified interval
    if (millis() - lastSMSSendTime >= SMS_SEND_INTERVAL && SIM900AInitialized)
    {
        lastSMSSendTime = millis();
        sendGasSMS(currentGasLevel);
    }
}

/****** FUNCTION IMPLEMENTATIONS *****/

// Initialize MQ5 sensor with calibration parameters
void initMQ5Sensor(void)
{
    // Set regression method for PPM calculation
    MQ5.setRegressionMethod(1);  // 1 = Exponential equation

    // Configure sensor parameters for LPG detection
    // These values are based on MQ-5 datasheet calibration curve
    // For LPG: PPM = a * (RS/R0)^b
    MQ5.setA(1163.8);       // Coefficient 'a' for LPG
    MQ5.setB(-3.207);       // Coefficient 'b' for LPG

    // Set the RL value (load resistance on the sensor module)
    MQ5.setRL(MQ5_RL_VALUE);

    // Perform calibration - R0 value obtained from clean air calibration
    // For a properly calibrated sensor in clean air
    float R0 = MQ5.calibrate(MQ5_RATIO_CLEAN_AIR);

    Serial.print(F("MQ5 Calibration - R0: "));
    Serial.println(R0);

    // Initialize sensor
    MQ5.init();

    Serial.println(F("MQ5 Sensor initialized successfully"));
}

// Initialize SIM900A GSM module
void initSIM900A(void)
{
    // Initialize software serial for SIM900A
    SIM900A_Serial.begin(SIM900A_BAUD_RATE);

    // Give SIM900A time to boot
    delay(2000);

    // Test communication with AT command
    Serial.println(F("Testing SIM900A communication..."));
    sendATCommand("AT", AT_COMMAND_TIMEOUT);
    delay(500);

    // Disable echo for cleaner responses
    Serial.println(F("Disabling echo..."));
    sendATCommand("ATE0", AT_COMMAND_TIMEOUT);
    delay(500);

    // Set SMS text mode
    Serial.println(F("Setting SMS text mode..."));
    sendATCommand("AT+CMGF=1", AT_COMMAND_TIMEOUT);
    delay(500);

    // Set SMS character set
    Serial.println(F("Setting SMS character set..."));
    sendATCommand("AT+CSCS=\"GSM\"", AT_COMMAND_TIMEOUT);
    delay(500);

    // Check signal quality
    Serial.println(F("Checking signal quality..."));
    sendATCommand("AT+CSQ", AT_COMMAND_TIMEOUT);
    delay(500);

    SIM900AInitialized = true;
    Serial.println(F("SIM900A initialized successfully"));
}

// Read gas level from MQ5 sensor
void readGasLevel(void)
{
    // Update sensor readings
    MQ5.update();

    // Read PPM value for LPG
    currentGasLevel = MQ5.readSensor();

    // Ensure reading is non-negative
    if (currentGasLevel < 0)
    {
        currentGasLevel = 0;
    }

    Serial.print(F("Gas Level Read: "));
    Serial.print(currentGasLevel);
    Serial.println(F(" PPM"));
}

// Send SMS with gas level to phone
void sendGasSMS(float gasLevel)
{
    if (!SIM900AInitialized)
    {
        Serial.println(F("Error: SIM900A not initialized"));
        return;
    }

    Serial.println(F("\n=== Sending Gas Level SMS ==="));

    // Prepare SMS recipient number
    String smsCommand = "AT+CMGS=\"" + PHONE_NUMBER + "\"";

    // Send SMS command
    sendATCommand(smsCommand, AT_COMMAND_TIMEOUT);
    delay(500);

    // Prepare message with gas level information
    String message = "Gas Alert System - LPG Level: ";
    message += gasLevel;
    message += " PPM";

    // Send message content
    SIM900A_Serial.print(message);

    // Send Ctrl+Z to confirm and send SMS
    SIM900A_Serial.write(26);  // ASCII code for Ctrl+Z

    Serial.print(F("SMS Message: "));
    Serial.println(message);
    Serial.println(F("SMS sent successfully\n"));

    // Wait for SMS processing
    delay(SMS_DELAY);
}

// Send AT command to SIM900A
void sendATCommand(String command, unsigned long timeout)
{
    // Clear any existing data in buffer
    while (SIM900A_Serial.available())
    {
        SIM900A_Serial.read();
    }

    // Send command
    SIM900A_Serial.println(command);

    Serial.print(F(">> "));
    Serial.println(command);

    // Wait for response
    waitForResponse("OK", timeout);
}

// Wait for response from SIM900A
void waitForResponse(String expectedResponse, unsigned long timeout)
{
    unsigned long startTime = millis();
    String response = "";

    while (millis() - startTime < timeout)
    {
        if (SIM900A_Serial.available())
        {
            char inChar = (char)SIM900A_Serial.read();
            response += inChar;

            // Check if we received the expected response
            if (response.indexOf(expectedResponse) != -1)
            {
                Serial.print(F("<< "));
                Serial.println(response);
                return;
            }
        }
    }

    // Timeout occurred
    Serial.println(F("No response from SIM900A (timeout)"));
    if (response.length() > 0)
    {
        Serial.print(F("Partial response: "));
        Serial.println(response);
    }
}

// Display debug information
void displayDebugInfo(void)
{
    Serial.print(F("System Time: "));
    Serial.print(millis() / 1000);
    Serial.print(F("s | Gas: "));
    Serial.print(currentGasLevel);
    Serial.print(F(" PPM | SIM900A: "));
    Serial.println(SIM900AInitialized ? F("Ready") : F("Not Ready"));
}

/* END CODE */