Help for MQ2 Sensors

[NahianMugdho]

Hello, I'm using the following library for MQ-2 sensors - https://github.com/kartun83/micropython-MQ
I'm using ESP-8266 in this case. Here is my code-

from machine import Pin,ADC,Timer

from MQ2 import MQ2
                       

met=MQ2(0)
val = met.readLPG()
print(val)

I'm getting the following errors-

Traceback (most recent call last):
File "", line 8, in
File "MQ2.py", line 18, in readLPG
File "BaseMQ.py", line 150, in readScaled
ValueError: math domain error

I couldn't find out any specific example about this library. Please help me out.

[jimmo]

@NahianMugdho You can follow this through the code: math domain error in readScaled means that it tried to do math.log(0). If you trace readLPG to readScaled, this means that readRatio() must be returning zero. This means that __readRs__ is returning zero, which means self.__calculateResistance__(self.pinData.read()) is returning zero.

If you read the __calculateResistance__ function, the only way that returns zero is when the ADC value is 1023.

Suspect there's something wrong with your wiring and the ADC isn't reading the right pin from the sensor.

Note: you might also need to configure baseVoltage to 3.3 if you're powering the MQ2 from the ESP8266. e.g.

met=MQ2(0, baseVoltage=3.3)