IOT based Air Pollution Monitoring System using Arduino

In this project we are going to make an IOT Based Air Pollution Monitoring System in which we will monitor the Air Quality over a webserver using internet and will trigger a alarm when the air quality goes down beyond a certain level, means when there are sufficient amount of harmful gases are present in the air like CO2, smoke, alcohol, benzene and NH3. It will show the air quality in PPM on the LCD and as well as on webpage so that we can monitor it very easily.

Previously we have built the LPG detector using MQ6 sensor and Smoke detector using MQ2 sensor but this time we have used MQ135 sensor which is the best choice for monitoring Air Quality as it can detects most harmful gases and can measure their amount accurately. In this IOT project, you can monitor the pollution level from anywhere using your computer or mobile. We can install this system anywhere and can also trigger some device when pollution goes beyond some level, like we can switch on the Exhaust fan or can send alert SMS/mail to the user.

 

Required Components:

  • MQ135 Gas sensor
  • Arduino Uno
  • Wi-Fi module ESP8266
  • 16X2 LCD
  • Breadboard
  • 10K potentiometer
  • 1K ohm resistors
  • 220 ohm resistor
  • Buzzer

 

Circuit Diagram and Explanation:

First of all we will connect the ESP8266 with the Arduino. ESP8266 runs on 3.3V and if you will give it 5V from the Arduino then it won’t work properly and it may get damage. Connect the VCC and the CH_PD to the 3.3V pin of Arduino. The RX pin of ESP8266 works on 3.3V and it will not communicate with the Arduino when we will connect it directly to the Arduino. So, we will have to make a voltage divider for it which will convert the 5V into 3.3V. This can be done by connecting three resistors in series like we did in the circuit. Connect the TX pin of the ESP8266 to the pin 10 of the Arduino and the RX pin of the esp8266 to the pin 9 of Arduino through the resistors.

ESP8266 Wi-Fi module gives your projects access to Wi-Fi or internet. It is a very cheap device and make your projects very powerful. It can communicate with any microcontroller and it is the most leading devices in the IOT platform. Learn more about using ESP8266 with Arduino here.

Then we will connect the MQ135 sensor with the Arduino. Connect the VCC and the ground pin of the sensor to the 5V and ground of the Arduino and the Analog pin of sensor to the A0 of the Arduino.

Connect a buzzer to the pin 8 of the Arduino which will start to beep when the condition becomes true.

In last, we will connect LCD with the Arduino. The connections of the LCD are as follows

  • Connect pin 1 (VEE) to the ground.
  • Connect pin 2 (VDD or VCC) to the 5V.
  • Connect pin 3 (V0) to the middle pin of the 10K potentiometer and connect the other two ends of the potentiometer to the VCC and the GND. The potentiometer is used to control the screen contrast of the LCD. Potentiometer of values other than 10K will work too.
  • Connect pin 4 (RS) to the pin 12 of the Arduino.
  • Connect pin 5 (Read/Write) to the ground of Arduino. This pin is not often used so we will connect it to the ground.
  • Connect pin 6 (E) to the pin 11 of the Arduino. The RS and E pin are the control pins which are used to send data and characters.
  • The following four pins are data pins which are used to communicate with the Arduino.

Connect pin 11 (D4) to pin 5 of Arduino.

Connect pin 12 (D5) to pin 4 of Arduino.

Connect pin 13 (D6) to pin 3 of Arduino.

Connect pin 14 (D7) to pin 2 of Arduino.

  • Connect pin 15 to the VCC through the 220 ohm resistor. The resistor will be used to set the back light brightness. Larger values will make the back light much more darker.
  • Connect pin 16 to the Ground.

Iot-air-quality-monitoring-system-using-arduino-circuit

 

Working Explanation:

The MQ135 sensor can sense NH3, NOx, alcohol, Benzene, smoke, CO2 and some other gases, so it is perfect gas sensor for our Air Quality Monitoring Project. When we will connect it to Arduino then it will sense the gases, and we will get the Pollution level in PPM (parts per million). MQ135 gas sensor gives the output in form of voltage levels and we need to convert it into PPM. So for converting the output in PPM, here we have used a library for MQ135 sensor, it is explained in detail in “Code Explanation” section below.

Sensor was giving us value of 90 when there was no gas near it and the safe level of air quality is 350 PPM and it should not exceed 1000 PPM. When it exceeds the limit of 1000 PPM, then it starts cause Headaches, sleepiness and stagnant, stale, stuffy air and if exceeds beyond 2000 PPM then it can cause increased heart rate and many other diseases.

When the value will be less than 1000 PPM, then the LCD and webpage will display “Fresh Air”.  Whenever the value will increase 1000 PPM, then the buzzer will start beeping and the LCD and webpage will display “Poor Air, Open Windows”. If it will increase 2000 then the buzzer will keep beeping and the LCD and webpage will display “Danger! Move to fresh Air”.

 

Code Explanation:

Before beginning the coding for this project, we need to first Calibrate the MQ135 Gas sensor. There are lots of calculations involved in converting the output of sensor into PPM value, we have done this calculation before in our previous Smoke Detector project. But here we are using the Library for MQ135, you can download and install this MQ135 library from here: https://github.com/GeorgK/MQ135.

Using this library you can directly get the PPM values, by just using the below two lines:

MQ135 gasSensor = MQ135(A0);
float air_quality = gasSensor.getPPM();

But before that we need to calibrate the MQ135 sensor, for calibrating the sensor upload the below given code and let it run for 12 to 24 hours and then get the RZERO value.

#include "MQ135.h"
void setup (){
Serial.begin (9600);
}
void loop() {
MQ135 gasSensor = MQ135(A0); // Attach sensor to pin A0
float rzero = gasSensor.getRZero();
Serial.println (rzero);
delay(1000);
}

After getting the RZERO value. Put the RZERO value in the library file you downloaded "MQ135.h": #define RZERO 494.63

 

Now we can begin the actual code for our Air quality monitoring project.

In the code, first of all we have defined the libraries and the variables for the Gas sensor and the LCD. By using the Software Serial Library, we can make any digital pin as TX and RX pin. In this code, we have made Pin 9 as the RX pin and the pin 10 as the TX pin for the ESP8266. Then we have included the library for the LCD and have defined the pins for the same. We have also defined two more variables: one for the sensor analog pin and other for storing air_quality value.

#include <SoftwareSerial.h>
#define DEBUG true
SoftwareSerial esp8266(9,10); 
#include <LiquidCrystal.h> 
LiquidCrystal lcd(12,11, 5, 4, 3, 2);
const int sensorPin= 0;
int air_quality;

Then we will declare the pin 8 as the output pin where we have connected the buzzer. lcd.begin(16,2) command will start the LCD to receive data and then we will set the cursor to first line and will print the ‘circuitdigest’. Then we will set the cursor on the second line and will print ‘Sensor Warming’.

pinMode(8, OUTPUT);
lcd.begin(16,2);
lcd.setCursor (0,0);
lcd.print ("circuitdigest ");
lcd.setCursor (0,1);
lcd.print ("Sensor Warming ");
delay(1000);

 

Then we will set the baud rate for the serial communication. Different ESP’s have different baud rates so write it according to your ESP’s baud rate. Then we will send the commands to set the ESP to communicate with the Arduino and show the IP address on the serial monitor.

Serial.begin(115200);
esp8266.begin(115200);
  sendData("AT+RST\r\n",2000,DEBUG);
  sendData("AT+CWMODE=2\r\n",1000,DEBUG);
  sendData("AT+CIFSR\r\n",1000,DEBUG);
  sendData("AT+CIPMUair_quality=1\r\n",1000,DEBUG);
  sendData("AT+CIPSERVER=1,80\r\n",1000,DEBUG);
pinMode(sensorPin, INPUT);
lcd.clear();

 

For printing the output on the webpage in web browser, we will have to use HTML programming. So, we have created a string named webpage and stored the output in it. We are subtracting 48 from the output because the read() function returns the ASCII decimal value and the first decimal number which is 0 starts at 48.

if(esp8266.available())
  {
    if(esp8266.find("+IPD,"))
    {
     delay(1000);
     int connectionId = esp8266.read()-48;  
     String webpage = "<h1>IOT Air Pollution Monitoring System</h1>";
       webpage += "<p><h2>";   
       webpage+= " Air Quality is ";
       webpage+= air_quality;
       webpage+=" PPM";
       webpage += "<p>";

 

The following code will call a function named sendData and will send the data & message strings to the webpage to show.

     sendData(cipSend,1000,DEBUG);
     sendData(webpage,1000,DEBUG);
     
     cipSend = "AT+CIPSEND=";
     cipSend += connectionId;
     cipSend += ",";
     cipSend +=webpage.length();
     cipSend +="\r\n";

 

The following code will print the data on the LCD. We have applied various conditions for checking air quality, and LCD will print the messages according to conditions and buzzer will also beep if the pollution goes beyond 1000 PPM.

lcd.setCursor (0, 0);
lcd.print ("Air Quality is ");
lcd.print (air_quality);
lcd.print (" PPM ");
lcd.setCursor (0,1);
if (air_quality<=1000)
{
lcd.print("Fresh Air");
digitalWrite(8, LOW);

 

Finally the below function will send and show the data on the webpage. The data we stored in string named ‘webpage’ will be saved in string named ‘command’. The ESP will then read the character one by one from the ‘command’ and will print it on the webpage.

String sendData(String command, const int timeout, boolean debug)
{
    String response = ""; 
    esp8266.print(command); // send the read character to the esp8266
    long int time = millis();
    while( (time+timeout) > millis())
    {
      while(esp8266.available())
      {
        // The esp has data so display its output to the serial window 
        char c = esp8266.read(); // read the next character.
        response+=c;
      }  
    }
    if(debug)
    {
      Serial.print(response);
    }
    return response;
}

 

Testing and Output of the Project:

Before uploading the code, make sure that you are connected to the Wi-Fi of your ESP8266 device. After uploading, open the serial monitor and it will show the IP address like shown below.

IOT-getting-localserver-IP

 

Type this IP address in your browser, it will show you the output as shown below. You will have to refresh the page again if you want to see the current Air Quality Value in PPM.

Iot-air-quality-monitoring-system-output

We have setup a local server to demonstrate its working, you can check the Video below. But to monitor the air quality from anywhere in the world, you need to forward the port 80 (used for HTTP or internet) to your local or private IP address (192.168*) of you device. After port forwarding all the incoming connections will be forwarded to this local address and you can open above shown webpage by just entering the public IP address of your internet from anywhere. You can forward the port by logging into your router (192.168.1.1) and find the option to setup the port forwarding.

Code: 

#include "MQ135.h"
#include <SoftwareSerial.h>
#define DEBUG true
SoftwareSerial esp8266(9,10); // This makes pin 9 of Arduino as RX pin and pin 10 of Arduino as the TX pin
const int sensorPin= 0;
int air_quality;
#include <LiquidCrystal.h> 
LiquidCrystal lcd(12,11, 5, 4, 3, 2);

void setup() {
pinMode(8, OUTPUT);
lcd.begin(16,2);
lcd.setCursor (0,0);
lcd.print ("circuitdigest ");
lcd.setCursor (0,1);
lcd.print ("Sensor Warming ");
delay(1000);
Serial.begin(115200);
esp8266.begin(115200); // your esp's baud rate might be different
  sendData("AT+RST\r\n",2000,DEBUG); // reset module
  sendData("AT+CWMODE=2\r\n",1000,DEBUG); // configure as access point
  sendData("AT+CIFSR\r\n",1000,DEBUG); // get ip address
  sendData("AT+CIPMUair_quality=1\r\n",1000,DEBUG); // configure for multiple connections
  sendData("AT+CIPSERVER=1,80\r\n",1000,DEBUG); // turn on server on port 80
pinMode(sensorPin, INPUT);        //Gas sensor will be an input to the arduino
lcd.clear();
}

void loop() {

MQ135 gasSensor = MQ135(A0);
float air_quality = gasSensor.getPPM();

if(esp8266.available()) // check if the esp is sending a message 
  {
    if(esp8266.find("+IPD,"))
    {
     delay(1000);
     int connectionId = esp8266.read()-48; /* We are subtracting 48 from the output because the read() function returns the ASCII decimal value and the first decimal number which is 0 starts at 48*/ 
     String webpage = "<h1>IOT Air Pollution Monitoring System</h1>";
       webpage += "<p><h2>";   
       webpage+= " Air Quality is ";
       webpage+= air_quality;
       webpage+=" PPM";
       webpage += "<p>";
     if (air_quality<=1000)
{
  webpage+= "Fresh Air";
}
else if(air_quality<=2000 && air_quality>=1000)
{
  webpage+= "Poor Air";
}

else if (air_quality>=2000 )
{
webpage+= "Danger! Move to Fresh Air";
}

webpage += "</h2></p></body>"; 
     String cipSend = "AT+CIPSEND=";
     cipSend += connectionId;
     cipSend += ",";
     cipSend +=webpage.length();
     cipSend +="\r\n";
     
     sendData(cipSend,1000,DEBUG);
     sendData(webpage,1000,DEBUG);
     
     cipSend = "AT+CIPSEND=";
     cipSend += connectionId;
     cipSend += ",";
     cipSend +=webpage.length();
     cipSend +="\r\n";
     
     String closeCommand = "AT+CIPCLOSE="; 
     closeCommand+=connectionId; // append connection id
     closeCommand+="\r\n";
     
     sendData(closeCommand,3000,DEBUG);
    }
  }

lcd.setCursor (0, 0);
lcd.print ("Air Quality is ");
lcd.print (air_quality);
lcd.print (" PPM ");
lcd.setCursor (0,1);
if (air_quality<=1000)
{
lcd.print("Fresh Air");
digitalWrite(8, LOW);
}
else if( air_quality>=1000 && air_quality<=2000 )
{
lcd.print("Poor Air, Open Windows");
digitalWrite(8, HIGH );
}
else if (air_quality>=2000 )
{
lcd.print("Danger! Move to Fresh Air");
digitalWrite(8, HIGH);   // turn the LED on
}
lcd.scrollDisplayLeft();
delay(1000);
}
String sendData(String command, const int timeout, boolean debug)
{
    String response = ""; 
    esp8266.print(command); // send the read character to the esp8266
    long int time = millis();
    while( (time+timeout) > millis())
    {
      while(esp8266.available())
      {
        // The esp has data so display its output to the serial window 
        char c = esp8266.read(); // read the next character.
        response+=c;
      }  
    }
    if(debug)
    {
      Serial.print(response);
    }
    return response;
}

Video: 

Comments (26)

  • Jyoti Ramdas Mate's picture
    Jyoti Ramdas Mate

    I am in 3rd year e&tc engineering and I want to do mini project on IOT but which is different and we can use it day to day life

    Dec 28, 2016
  • jay patel's picture
    jay patel

    plz tell me in detail how to calibrate mq135 gas sensor

    Jan 25, 2017
  • yash 's picture
    yash

    why in this code mq 135 gas sensor is show error?
    it is showing comipling error.

    Jan 31, 2017
  • navakarthiga ramakrishnan's picture
    navakarthiga ra...

    Haii sir/mam ,i am doing 3rd year engg .i need a clear explanation and video for connecting the equipments of this air pollution monitoring system for my mini project contest.plz tell me in detail as soon as possible.

    Mar 02, 2017
  • pranjal choudhury's picture
    pranjal choudhury

    I can give you the whole project which I made it for my project.

    May 14, 2017
  • vinothini's picture
    vinothini

    hi sir/mam...i am doing electronics and communication 3rd year...i need a clear arduino code in this project......because u given code is incorrect...so it is had error for arduino software....pls give a correct code...thanking you sir/mam...

    Mar 10, 2017
  • Manthan's picture
    Manthan

    I will run all code but, show the error for particular term of 'gasSensor'

    Mar 25, 2017
  • mitali's picture
    mitali

    i need a flowchart of iot based air quality monitoring project. please help me.

    Apr 03, 2017
  • Abhijeet Singh's picture
    Abhijeet Singh

    Respected sir,
    I am a graduated student. I went through your project and assemble the parts as you have shown. But it is not working. I wanted to contact you but didn't found any way to contact. Please reply ASAP.
    Thank You.

    Apr 28, 2017
  • Manthan's picture
    Manthan

    please, give correct code for esp8266 module particular in this project. i have successfully run full code,but show the error for wifi module is given to the below. give reply fastly.
    deprecated conversion from string constant to 'char*' [-Wwrite-strings]

    if(esp8266.find("+IPD,"))

    Apr 29, 2017
  • Roop's picture
    Roop

    While calibrating the sensor(MQ-135) the serial output is " inf " (after 6 hours of leaving it as it is) can someone please tell me what could be the problem.
    regards
    Roop

    May 08, 2017
  • albert sancho's picture
    albert sancho

    In this project, what is esp8266 for?

    May 10, 2017
  • Rounak Priyam Chowdhury's picture
    Rounak Priyam C...

    Sir can u please upload detailed pictures of the project.and the programme is also not working correctly so can you help me out with this...
    it would be great if you respond..
    thank you sir

    Jun 09, 2017
  • anand's picture
    anand

    while uploading the esp8266 code getting error

    Aug 19, 2017
  • B.Aswinth Raj's picture
    B.Aswinth Raj

    What error is it?

    Are you able to upload other programs successfully? If no, then the problem is most likely with your Connections 

    Check your connections again and let us know what kind of error you get

    Aug 20, 2017
  • Hari's picture
    Hari

    Hi,
    How you made your ESP 8266 to connect to WIFI and what is the AT command used in the code to make a connection to wifi network.

    Aug 21, 2017
  • Jaskunwar Singh's picture
    Jaskunwar Singh

    how to forward the port 80 (used for HTTP or the internet) to your local or private IP address and what is it?

    Sep 01, 2017
  • irfanzainur's picture
    irfanzainur

    Hi,
    How you made your ESP 8266 to connect to WIFI and what is the AT command used in the code to make a connection to wifi network.

    Sep 10, 2017
  • hepshiba beula's picture
    hepshiba beula

    my code has been uploaded successfully but i didn't get anything on the serial monitor.could you help me??

    Oct 15, 2017
  • hepshiba beula's picture
    hepshiba beula

    i didn't use the lcd part sir

    Oct 17, 2017
  • maginhawa's picture
    maginhawa

    Hello there. We would like to use this as our project for this coming finals. We would like to ask for your help regarding this. Do you have any videos on how you connected everything (wires and configurations)? If none, maybe at least the step by step procedures?

    Thank you so much. Your help would be so much appreciated

    Nov 08, 2017
  • AISHA's picture
    AISHA

    You can use the circuit diagram to make the connections. If you have any problem in getting it to work use the comments or forums. This is how all the website works

    Nov 14, 2017

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