Published July 9, 2021 © CC BY-NC

Air Analyzer, Using Almost All Kinds of MQ Sensors

An air monitor that can measure CO, CO2, H2, CH4, NH3, Alcohol, Bangene, Acetone, Hexane, Toluene, Smoke and Flammable gas concentration.

IntermediateFull instructions providedOver 1 day20,668

Air Analyzer, Using Almost All Kinds of MQ Sensors

Things used in this project

Hardware components

Arduino Nano R3

DFRobot I2C 16x2 Arduino LCD Display Module

MQ3 Gas sensor

MQ4 Gas sensor

MQ135 Gas sensor

MQ7 Gas sensor

MQ8 Gas sensor

MQ9 Gas sensor

Software apps and online services

Arduino IDE

Hand tools and fabrication machines

Breadboard, 830 Tie Points

Story

For a long time, I wanted to monitor every component in the air only using low-cost MQ sensors. So I ordered a set of 9 MQ sensors and made this project, in which I can measure the concentration of many kinds of gas in the air only using some MQ sensors. This kind of sensor is not so accurate and needs lots of calibration, but they are the best cheap gas sensors out there. You can find a set of nine gas sensors for only $6 to $7. in my project, I use 6 of them and measure the gas concentration of 12 gases.

So lats start!

Wait!!! Before starting any work, you should power your sensor and let it burn for at least 24 hours. This step is very important because MQ sensors come polluted, and burning helps them to clean themselves. You have to power the sensors with 5V and put them In a clean place.

MQ sensors output an analog voltage that varies with the concentration of some selected gases. So, we can read the analog value via Arduino ADC and find the gas concentration in the air.

I use 6 MQ sensor (MQ3, MQ4, MQ7, MQ8, MQ9 and MQ135).

Uses of the sensors

MQ3 for measuring Alcohol, Benzene, and Hexane

MQ4 for measuring Methane and smoke

MQ135 for measuring CO2, NH4, Toluene, and Acetone

MQ7 for measuring CO

MQ8 for measuring H2

MQ9 for measuring flammable gas

Connections

I connect them to Arduino nano because it has 8 ADC, which I need. Six ADC for the sensors and two for the I2C communication with the LCD.

Connect the Arduino with sensors as follow-

MQ3 Ao - Arduino A0

MQ4 Ao - Arduino A1

MQ135 Ao - Arduino A2

MQ7 Ao - Arduino A3

MQ8 Ao - Arduino A6

MQ9 Ao - Arduino A7

Connect the Arduino and the LCD as follow-

Arduino A4 - LCD SDA

Arduino A5 - LCD SCL

Now the big challenge!!!

Connecting the hardware and Reading the analog value is easy, but the most difficult thing is to calibrate the sensors and calculating the ppm(parts per million) value for a specific gas. After searching for a long time on the internet, I find a library for those sensors. And comparing the calculation with the datasheet of the sensors, it seems promising.

Here I found an article that explains the working and the calculation for an MQ sensor- UNDERSTANDING A GAS SENSOR.

I use the library and write a code to use six of those sensors with an Arduino nano and show different gas concentrations on air.

You can find the library here - MQUnifiedsensor library

For coding, first of all, I include the LiquidCrystal_I2C and MQUnifiedsensor library and then define the display parameter and the Input PIN for the sensors. Then in the setup section, I initialize the display and the sensors and set the R0 value for every sensor. You have to calibrate your sensors to find this R0 value. For that, uncomment a section in the setup function and upload the code to your Arduino with the pre-burned sensor connected. Then you will find the R0 value for every sensor in the serial monitor. Note the values and change them in the setup function. It is recommended that calibrate the sensors once in a clean environment and set the R0 value. The part to uncomment is indicated in the code.

And in the loop function, I set the A and B values for the exponential equation for different gases. Here A and B value is for PPM = A*ratio^B. Those values are different for different gas in different sensors.

After that, I display the gas concentration on the LCD by two values on a page. There is a 3-second delay between every page.

The Video Clip For The Project

Code

air_analyser code

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


#define LCD_I2C_ADDRESS 0x3f 
#define LCD_DISP_COLS   16
#define LCD_DISP_ROWS   2

#include <MQUnifiedsensor.h>

#define         Board                   ("Arduino NANO")
#define         Pin3                     (A0)  //Analog input 0 of your arduino
#define         Pin4                     (A1)  //Analog input 1 of your arduino
#define         Pin135                   (A2)  //Analog input 2 of your arduino
#define         Pin7                     (A3)  //Analog input 3 of your arduino
#define         Pin8                     (A6)  //Analog input 6 of your arduino
#define         Pin9                     (A7)  //Analog input 7 of your arduino

LiquidCrystal_I2C lcd( LCD_I2C_ADDRESS, LCD_DISP_COLS, LCD_DISP_ROWS );


#define         RatioMQ3CleanAir          (60) //RS / R0 = 60 ppm 
#define         RatioMQ4CleanAir          (4.4) //RS / R0 = 4.4 ppm 
#define         RatioMQ135CleanAir        (3.6) //RS / R0 = 10 ppm 
#define         RatioMQ7CleanAir          (27.5) //RS / R0 = 27.5 ppm  
#define         RatioMQ8CleanAir          (70) //RS / R0 = 70 ppm   
#define         RatioMQ9CleanAir          (9.6) //RS / R0 = 9.6 ppm 
#define         ADC_Bit_Resolution        (10) // 10 bit ADC 
#define         Voltage_Resolution        (5) // Volt resolution to calc the voltage
#define         Type                      ("Arduino NANO") //Board used
//Declare Sensor
MQUnifiedsensor MQ3(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin3, Type);
MQUnifiedsensor MQ4(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin4, Type);
MQUnifiedsensor MQ135(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin135, Type);
MQUnifiedsensor MQ7(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin7, Type);
MQUnifiedsensor MQ8(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin8, Type);
MQUnifiedsensor MQ9(Board, Voltage_Resolution, ADC_Bit_Resolution, Pin9, Type);


void setup() {
  Serial.begin(9600);
  lcd.begin();

  lcd.backlight();
                 
  lcd.setCursor (0,0);                  
  lcd.print("                ");
  lcd.setCursor (0,1);
  lcd.print("                ");
  lcd.setCursor (0,0);
  lcd.print("   Air");
  lcd.setCursor (0,1);
  lcd.print("    Analyzer");
  delay(1000);
  lcd.setCursor (12,1);
  lcd.print(".");
  delay(1000);
  lcd.setCursor (13,1);
  lcd.print(".");
  delay(1000);
  lcd.setCursor (14,1);
  lcd.print(".");
  delay(1000);
  lcd.setCursor (15,1);
  lcd.print(".");
  delay(1000);                         

  MQ3.init();
  MQ3.setRegressionMethod(1); //_PPM =  a*ratio^b
  MQ3.setR0(0.45);
  MQ4.init();
  MQ4.setRegressionMethod(1); //_PPM =  a*ratio^b
  MQ4.setR0(14.23);
  MQ135.init();
  MQ135.setRegressionMethod(1); //_PPM =  a*ratio^b
  MQ135.setR0(9.03);
  MQ7.init();
  MQ7.setRegressionMethod(1); //_PPM =  a*ratio^b
  MQ7.setR0(5.90);
  MQ8.init();
  MQ8.setRegressionMethod(1); //_PPM =  a*ratio^b
  MQ8.setR0(0.91);
  MQ9.init();
  MQ9.setRegressionMethod(1); //_PPM =  a*ratio^b
  MQ9.setR0(13.93);



//While calibrating Your sensor Uncomment this calibration portion and calibrate for R0.
  /*****************************  MQ CAlibration ********************************************
  Serial.print("Calibrating please wait.");
  float  MQ3calcR0 = 0,
         MQ4calcR0 = 0,
         MQ135calcR0 = 0,
         MQ7calcR0 = 0,
         MQ8calcR0 = 0,
         MQ9calcR0 = 0;
  for (int i = 1; i <= 10; i ++)
  {
    //Update the voltage lectures
    MQ3.update();
    MQ4.update();
    MQ135.update();
    MQ7.update();
    MQ8.update();
    MQ9.update();

    MQ3calcR0 += MQ3.calibrate(RatioMQ3CleanAir);
    MQ4calcR0 += MQ4.calibrate(RatioMQ4CleanAir);
    MQ135calcR0 += MQ135.calibrate(RatioMQ135CleanAir);
    MQ7calcR0 += MQ7.calibrate(RatioMQ7CleanAir);
    MQ8calcR0 += MQ8.calibrate(RatioMQ8CleanAir);
    MQ9calcR0 += MQ9.calibrate(RatioMQ9CleanAir);

    Serial.print(".");
  }
  MQ3.setR0(MQ3calcR0 / 10);
  MQ4.setR0(MQ4calcR0 / 10);
  MQ135.setR0(MQ135calcR0 / 10);
  MQ7.setR0(MQ7calcR0 / 10);
  MQ8.setR0(MQ8calcR0 / 10);
  MQ9.setR0(MQ9calcR0 / 10);
  Serial.println("  done!.");

  Serial.print("(MQ3 - MQ9):");
  Serial.print(MQ3calcR0 / 10); Serial.print(" | ");
  Serial.print(MQ4calcR0 / 10); Serial.print(" | ");
  Serial.print(MQ135calcR0 / 10); Serial.print(" | ");
  Serial.print(MQ7calcR0 / 10); Serial.print(" | ");
  Serial.print(MQ8calcR0 / 10); Serial.print(" | ");
  Serial.print(MQ9calcR0 / 10); Serial.println(" |");

  /*****************************  MQ CAlibration ********************************************/ 
}

void loop() {
  //Update the voltage lectures
  MQ3.update();
  MQ4.update();
  MQ135.update();  
  MQ7.update();
  MQ8.update();
  MQ9.update();


  MQ3.setA(0.3934); MQ3.setB(-1.504); //Alcohol
float Alcohol = MQ3.readSensor(); 

  MQ3.setA(4.8387); MQ3.setB(-2.68); //Benzene
float Benzene = MQ3.readSensor(); 
  
  MQ3.setA(7585.3); MQ3.setB(-2.849); //Hexane
float Hexane = MQ3.readSensor(); 

  MQ4.setA(1012.7); MQ4.setB(-2.786); //CH4
float CH4 = MQ4.readSensor(); 

  MQ4.setA(30000000); MQ4.setB(-8.308); //smoke 
float smoke = MQ4.readSensor(); 
 
  MQ135.setA(110.47); MQ135.setB(-2.862); //CO2 
float CO2 = MQ135.readSensor(); 
  
  MQ135.setA(44.947); MQ135.setB(-3.445); // Toluene
float Toluene = MQ135.readSensor(); 
  
  MQ135.setA(102.2 ); MQ135.setB(-2.473); //NH4 
float NH4 = MQ135.readSensor(); 
  
  MQ135.setA(34.668); MQ135.setB(-3.369); //Acetone
float Acetone = MQ135.readSensor(); 
 
  MQ7.setA(99.042); MQ7.setB(-1.518); //CO
float CO = MQ7.readSensor(); 

  MQ8.setA(976.97); MQ8.setB(-0.688); // H2
float H2 = MQ8.readSensor();

  MQ9.setA(1000.5); MQ9.setB(-2.186); //flamable gas
float FG = MQ9.readSensor();



  Serial.print("Alcohol:  "); Serial.println(Alcohol);
  Serial.print("Benzene:  "); Serial.println(Benzene);
  Serial.print("Hexane:   "); Serial.println(Hexane);
  Serial.print("Methane:  "); Serial.println(CH4);
  Serial.print("Smoke:    "); Serial.println(smoke);
  Serial.print("CO2:      "); Serial.println(CO2);
  Serial.print("Toluene:  "); Serial.println(Toluene);
  Serial.print("NH4:      "); Serial.println(NH4);
  Serial.print("Acetone:  "); Serial.println(Acetone);  
  Serial.print("CO:       "); Serial.println(CO);
  Serial.print("H2:       "); Serial.println(H2);
  Serial.print("FG:       "); Serial.println(FG);
  Serial.println("--------------------------------------------------------");

lcd.clear();
delay(70);
lcd.setCursor (0,0);
lcd.print("Alcohol ");
lcd.print(Alcohol);
lcd.setCursor (13,0);
lcd.print("ppm");
lcd.setCursor (0,1);
lcd.print("Benzene ");
lcd.print(Benzene);
lcd.setCursor (13,1);
lcd.print("ppm");
delay(3000);

lcd.clear();
delay(70);
lcd.setCursor (0,0);
lcd.print("Hexane  ");
lcd.print(Hexane);
lcd.setCursor (13,0);
lcd.print("ppm");
lcd.setCursor (0,1);
lcd.print("CH4     ");
lcd.print(CH4);
lcd.setCursor (13,1);
lcd.print("ppm");
delay(3000);


lcd.clear();
delay(70);
lcd.setCursor (0,0);
lcd.print("Smoke   ");
lcd.print(smoke);
lcd.setCursor (13,0);
lcd.print("ppm");
lcd.setCursor (0,1);
lcd.print("CO2     ");
lcd.print(CO2);
lcd.setCursor (13,1);
lcd.print("ppm");
delay(3000);


lcd.clear();
delay(70);
lcd.setCursor (0,0);
lcd.print("Toluene ");
lcd.print(Toluene);
lcd.setCursor (13,0);
lcd.print("ppm");
lcd.setCursor (0,1);
lcd.print("NH4     ");
lcd.print(NH4);
lcd.setCursor (13,1);
lcd.print("ppm");
delay(3000);


lcd.clear();
delay(70);
lcd.setCursor (0,0);
lcd.print("Acetone ");
lcd.print(Acetone);
lcd.setCursor (13,0);
lcd.print("ppm");
lcd.setCursor (0,1);
lcd.print("CO      ");
lcd.print(CO);
lcd.setCursor (13,1);
lcd.print("ppm");
delay(3000);


lcd.clear();
delay(70);
lcd.setCursor (0,0);
lcd.print("H2      ");
lcd.print(H2);
lcd.setCursor (13,0);
lcd.print("ppm");
lcd.setCursor (0,1);
lcd.print("FG      ");
lcd.print(FG);
lcd.setCursor (13,1);
lcd.print("ppm");
delay(3000);

}

Credits

Abid hossain

4 projects • 47 followers

Student of BSEEE in United International University, Bangladesh. Loves to learn and make new stuff.

Air Analyzer, Using Almost All Kinds of MQ Sensors

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

So lats start!

Uses of the sensors

Connections

Now the big challenge!!!

The Video Clip For The Project

Schematics

air analyser_scm

Code

air_analyser code

Credits

Abid hossain

Comments

Embed the widget on your own site

Air Analyzer, Using Almost All Kinds of MQ Sensors

Air Analyzer, Using Almost All Kinds of MQ Sensors

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

So lats start!

Uses of the sensors

Connections

Now the big challenge!!!

The Video Clip For The Project

Schematics

air analyser_scm

Code

air_analyser code

Credits

Abid hossain

Comments

Related channels and tags