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MQ135 GAS SENSOR

Arduino library for the MQ135 gas sensor

Datasheet

Can be found here

Application

They are used in air quality control equipments for buildings/offices, are suitable for detecting of NH3, NOx, alcohol, Benzene, smoke, CO2, etc

advanced Features compared to base

Not every device is the same. Changing the Header files is not a good way to program for a variety of devices

  • Set RZero and ATMCO2 directly in Constructor -> MQ135 gasSensor = MQ135(AIR_PIN, 52.7, 404.48);
  • Added a RefPin which is supposed to measure the Vcc of the MQ135. Constructor -> MQ135 gasSensor = MQ135(AIR_PIN,AIR_PIN_REF, 52.7, 404.48);
  • RZERO, ATOMCO2, RefPin, RLoad can be set by functions

Features

This library has:

  • Corrections for temperature and humidity
  • Measurements:
    • getResistance
    • getCorrectedResistance
    • getPPM
    • getCorrectedPPM
    • getRZero
    • getCorrectedRZero
    • setRZero(float newVal);
    • setATMCO2(float newVal);
    • setRLOAD(float newVal);
    • setRefPin(uint8_t pin);

Example

The example provided shows how to implement the Sensor with MySensors. For temperature I use a barometric pressure sensor. Humidity is received from my MySensor network (don't have a spare DHT sensor) RL[kOhm] I measure with a Voltmeter between GND and Vcc on the MQ135.

More Info

https://hackaday.io/project/3475-sniffing-trinket/log/12363-mq135-arduino-library