IoT based Air Pollution Monitoring System using Arduino

Please follow the circuit diagram, the ESP8266 communicates using software serial to Arduino. In the Arduino program as you can see in the below line

SoftwareSerial esp8266(9,10); // This makes pin 9 of Arduino as RX pin and pin 10 of Arduino as the TX pin

Pin 9 and 10 of Arduino is defined as Rx and Tx respectively, so we just have to connect Tx of ESP to pin 9 and Rx of ESP to pin 10. You can always change these values in the program if required  

Hello Ashwinth Raj,

I have done all the required wiring and uploaded the code. Done calibration of MQ135 for 5 hours (I know it has to be done for at least 12 hours, I aborted it to further check all the functionality). 

LCD screen is also functioning as expected. But after connecting to WiFi (ESP8266) I'm not getting a web page showing sensor data as mentioned in the article. 

Kindly suggest what is missing from my side? I have done a voltage divider using three 1K resistors as per the diagram.

Hello Ashwinth Raj,

I used URL http://192.168.4.1/test and the page has started opening on a mobile phone browser. However, I need to calibrate the sensor for perfect reading. I have calibrated it for 5 hours to get RZERO value. The same has been added in the MQ135.h file also. But the display is showing only 2.95 PPM which must be incorrect. How to get rid of this issue? Please guide. 

Regards,

Mithilesh Pandey

Using MQ sensor with Arduino is a bit tricky, I have never found them to be accurate. Also make sure you do 24 hrs pre-heating. If you want a detailed understanding I would suggest you to read this 

https://circuitdigest.com/microcontroller-projects/arduino-mq137-ammoni…

This is a different MQ sensor that measures ammonia, but the procedure for all MQ sensor remains the same.