FC-22 MQ135 Gas sensor reading and calibration problems

Hello,

I am working on a project that includes the FC22 MQ135 gas sensor.
I have went through pages and pages and yet did not find the real answer.

Anyways, my problem is the reading and calibrating. I get the results as i
use the analogRead() and also the MQ135.h library, but don’t know which one is the
correct reading… It’s confusing for me as a novice in Arduino programming.

Also the calibrating, on this type of sensor there is a little screw that can be
tinkered around, but i did not found the proper documentation for it (only shopping sites).
Of course, there is the MQ135 datasheet, but the FC22 is not explained.

here is the MQ135.h code

#include “MQ135.h”

MQ135 gasSensor = MQ135(A1);

int ppm = gasSensor.getPPM();

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

void loop() {
float rzero = gasSensor.getRZero();
float ppm = gasSensor.getPPM();
Serial.println(ppm);

delay(5000);

}

And the readings are like


11.54
11.42
11.54
11.54

The reading with the analogRead() code:


176
175
172
175

Thanks in forward!

Did you ever find any answers on the FC-22-I? I just bought one and they are very confusing. I read that they need to be burned in for 12-24 hours, then you need to work out what their "zero" reading is, because all sensors might be different.

When I'm reading values from getRZero() and getPPM(), the values returned fluctuate a lot. I'm trying to work out how sensitive to change they are. I'm also trying to figure out how to use the adjustment potentiometer screw at the back. Like you I got no documentation.

sikinchara: Also the calibrating, on this type of sensor there is a little screw that can be tinkered around, but i did not found the proper documentation for it (only shopping sites). Of course, there is the MQ135 datasheet, but the FC22 is not explained.

This is a question I have seen several times in google. The little screw is just a alarm link to a second LED, if the gas goes up the led turns ON. You can change sensibility of this alarm by moving the screw.

If anyone needs more help with the MQ135... I did this repository> https://github.com/Ravenneo/CO2-sensor

Is made by a noob (me) so I am also open to change whatever is necessary.