79 lines
2.5 KiB
C++
Executable File
79 lines
2.5 KiB
C++
Executable File
/**************************************************************************/
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/*!
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@file MQ135.h
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@author G.Krocker (Mad Frog Labs)
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@license GNU GPLv3
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First version of an Arduino Library for the MQ135 gas sensor
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TODO: Review the correction factor calculation. This currently relies on
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the datasheet but the information there seems to be wrong.
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@section HISTORY
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v1.0 - First release
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*/
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/**************************************************************************/
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#ifndef MQ135_H
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#define MQ135_H
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#if ARDUINO >= 100
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#include "Arduino.h"
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#else
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#include "WProgram.h"
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#endif
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/// The load resistance on the board, in KOhms
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#define MQ135_RLOAD 10.0
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/// Calibration sensor resistance at atmospheric CO2 level, in KOhms
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#define MQ135_RZERO 76.63
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/// Parameters for calculating ppm of CO2 from sensor resistance
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//#define PARA 116.6020682
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//#define PARB (-2.769034857)
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/// Correlation parameters from Davide Gironi <http://davidegironi.blogspot.ru/2014/01/cheap-co2-meter-using-mq135-sensor-with.html>
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#define PARA 56.0820
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#define PARB (-5.9603)
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/*
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/// Parameters to model temperature and humidity dependence
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#define CORA 0.00035
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#define CORB 0.02718
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#define CORC 1.39538
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#define CORD 0.0018
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*/
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/// Atmospheric CO2 level for calibration purposes, in PPM.
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/// See http://co2now.org/
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#define MQ135_ATMOCO2 397.16
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/// Test voltage applied to the A pins of MQ-135, in volts. Usually, it's equal to power supply voltage.
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#define MQ135_VC 5.0
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/// analogRead reference voltage, in volts. By default it's a power supply voltage on Arduino. Can be changed with analogReference().
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#define MQ135_VREF 5.0
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class MQ135 {
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private:
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uint8_t _pin;
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// Calibration sensor resistance at atmospheric CO2 level, in KOhms
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float _rzero;
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// Atmospheric CO2 level for calibration purposes, in PPM, see http://co2now.org/
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float _atmoco2;
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// analogRead reference voltage, in volts
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float _vref;
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// Load resistance on board, in KOhms
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float _rload;
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// Test voltage applied to the A pins of MQ-135, in volts
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float _vc;
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public:
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MQ135(uint8_t pin, float rload = MQ135_RLOAD, float rzero = MQ135_RZERO,
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float atmoco2 = MQ135_ATMOCO2, float vref = MQ135_VREF,
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float vc = MQ135_VC);
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float getCorrectionFactor(float t, float h);
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float getResistance();
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float getCorrectedResistance(float t, float h);
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float getPPM();
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float getCorrectedPPM(float t, float h);
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float getRZero();
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float getCorrectedRZero(float t, float h);
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};
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#endif
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