MQ2 Sensor w/AirQuality Sketch

[robosensor]

@gigaguy
example response of sensors for natural gas (left) and alcohol (right):

[epierre]

@robosensor this graph shows well the limit ofg the MQ gas sensors, they somehow all react to the same gases, and thus are not one gas specific.

[robosensor]

@epierre in general, you are right, but there are exceptions.

This measurements, but one sensor per graph:

And 6-day graph of all sensors:

[epierre]

@robosensor sure, but people need to know not to rely for their life on these classes of sensors.

[Viper_Scull]

is it normal that the reads of my MQ-2 sensor are 0ppm in fresh air?
If I use a lighter to throw some gas, the reads skyrocket and then without gas they go back to zero.
Should I adjust the sensitivity?

[epierre]

@Viper_Scull If you follow my method, it considers clean air has no toxic gas so it should be 0.

If you are able to do a calibration, you could change that, but I would recommend to keep the straight lean air way if you cannot do that.

[Viper_Scull]

@epierre said:

@Viper_Scull If you follow my method, it considers clean air has no toxic gas so it should be 0.

If you are able to do a calibration, you could change that, but I would recommend to keep the straight lean air way if you cannot do that.

@epierre I use the AirQualitySensor example in the MySensors library that I believe is your work indeed. Happy now to know that it's ok 0ppm for clean air.

One thing I noticed on the sketch is that last_mq inital value is 0. If we are in clean air, no value is send to the gateway when connected because val_mq = last_mq, so the controller would have no data to display unless it sets it to zero by default or gas is present.

By the way, I can't get domoticz to recognize this sensor. It receives the name of the sketch and the version, but although I can see that the sensor sends the value, there's no sign of it in the log of domotic and no device is recognized.

[epierre]

@Viper_Scull I have someone else reporting this, you should ask @GizMoCuz for him to support it

[Viper_Scull]

@epierre, already asked. Turns out, domoticz doesn't support V_VARs. Changing V_VAR1 in the sketch for V_DUST_LEVEL works.

[Moshe Livne]

@Viper_Scull Domoticz supports V_VARs, just not as a viewable or modifiable value on the controller. It will store and return the V_VARs values for the sketch, nothing more.