MQ135 sensor

Using Arduino Sensors
1

Hello everybody,

I am working with an Arduino Uno and a MQ135 module arduino : http://www.sainsmart.com/sainsmart-mq135-sensor-air-quality-sensor-hazardous-gas-detection-module-arduino.html

I can get back data from this sensor, I got between 100-900 ppm when I launched serial terminal after compiling and uploading this code below.

int sensorValue;

void setup()
{
  Serial.begin(9600);      // sets the serial port to 9600
}

void loop()
{
  sensorValue = analogRead(0);       // read analog input pin 0
  Serial.println(sensorValue, DEC);  // prints the value read
  delay(100);                        // wait 100ms for next reading
}

But, I would like to get back data from gases like NH3, NOx, alcohol, benzene, smoke and CO2 . I read a lot of topics and the datasheets of the sensor but I don't see how to do.

Some interesting links : https://hackaday.io/project/3475-sniffing-trinket/log/12363-mq135-arduino-library
Davide Gironi: Cheap CO2 meter using the MQ135 sensor with AVR ATmega
If someone could help me, it will be great.

Thanks.

2

You mean you want it to show how much of each of detectable gases, in a mixture is present? won't happen. It just is sensitive to several gases and any of them affects it.

Think of it as a scale. You can weigh flour, you can weigh water, but it won't tell you how much flour and how much water is on the plate.

3

You right, in fact it's not possible to get back data from each of the gases.
Now, I have to do the calibration of this sensor.
I think, I will take an example of this video :Getting right PPM from MQ sensors - YouTube
Iit's seems easier than with this method : Davide Gironi: Cheap CO2 meter using the MQ135 sensor with AVR ATmega
Or, I think I can adapt this method to the MQ135 module sensor : MQ-2 Smoke/LPG/CO Gas Sensor Module | Sandbox Electronics

What do you think ?

4

Hey guys ..
I got reading from mq 135 as..300,325,326,321,324,332,333,.....etc
so how can i convert them into ppm?? or anything else in unit??