This project involves the development of an Internet of Things (IoT) based service that monitors air pollution over the Internet through a web server, and it will sound a warning if sufficient amounts of hazardous gasses like

carbon dioxide, smoke, alcohol, benzene and NH3 enter the air at a certain level. On the LCD and on the webpage, we will be able to read the air quality in PPM, so we can easily monitor it. This time the air quality sensor was the MQ135 sensor instead of the MQ6 sensor, which we used previously for making LPG detectors. The MQ135 sensor can detect most harmful gases without affecting their amount. You can monitor pollution levels in this IOT project using your computer or mobile device no matter where you are. In addition to installing this system anywhere, we can also set up some device that will turn on the exhaust fan or send SMS/email notifications to the user when pollution reaches some level.

MQ135 Gas sensor Arduino Uno Wi-Fi module ESP8266

Breadboard 10K potentiometer 1K ohm resistors 220-ohm resistor Buzzer In order to use ESP8266, we need to first connect it to the Arduino. You can't use Arduino to power an ESP8266 as it runs on 3.3V, but if you give it 5V, then it won't function properly and might even be damaged. 3.3V should be connected to VCC and CH_PD on Arduino. When connected directly to the Arduino, the RX pin of the ESP8266 works with 3.3V voltage and thus cannot communicate with the Arduino. Thus, we will need to create a

voltage divider so that the 5V can be converted into 3.3V. You can do this by increasing the resistance of three resistors as we did in the circuit. By connecting the ESP8266's TX pin to Arduino pin 10, and its RX pin to Arduino pin 9, you can make the ESP8266 transmit data. Your projects can connect to the internet and Wi-Fi using an ESP8266 Wi-Fi module. You can create very powerful projects with this inexpensive device. ESP8266 is a leading IOT device, capable of communicating with any microcontroller. Discover more about using ESP8266 with Arduino here. Our next step will be to connect the MQ135 sensor to the Arduino. The sensor's VCC and ground pins should be connected to the Arduino's 5V and ground, while the sensor's Analog pin should be connected to the Arduino's A0. In addition, we'd like to connect the LCD to the Arduino through pin 8, which is responsible for beeping when the condition occurs.

A gas sensor can detect NH3, NOx, alcohol, benzene, smoke, CO2, and a few other gases, so the MQ135 sensor is ideal for our Air Quality Monitoring Project. With Arduino we can detect the pollutants, and we will get their concentration in parts per million. Gas sensors such as MQ135 provide output based on voltage levels that must be converted into PPM. Therefore, I have used a library for MQ135 to convert the output in PPM, and you can find the details below in the "Code Explanation" section. Despite being within a safe limit of air quality (350 PPM), the sensor gave us a value of 90 when no gas was close by. It causes headaches, sleepiness, stagnant, stale air, and increased heart rate when it exceeds 1000 PPM and changes can be seen in other conditions when it exceeds 2000 PPM.

The LCD and webpage will display "Fresh Air" when the value is less than 1000 PPM. A buzzer will start beeping every time the value reaches 1000 PPM, displaying "Poor Air, Open Windows" on the LCD and webpage. In the event that it reaches 2000, the buzzer will continue to beep and the LCD and webpage will indicate "Stay away from fresh air".