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Merge pull request #1 from swablab/feature/GrafZ

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add own library
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Johannes Gaiser 2021-04-11 17:48:25 +02:00 • committed by GitHub
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4 changed files with 137 additions and 212 deletions
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170
lib/MQ135/MQ135.cpp
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@ -1,123 +1,83 @@
/**************************************************************************/
/*!
@file MQ135.cpp
@author G.Krocker (Mad Frog Labs)
@license GNU GPLv3
First version of an Arduino Library for the MQ135 gas sensor
TODO: Review the correction factor calculation. This currently relies on
the datasheet but the information there seems to be wrong.
@section HISTORY
v1.0 - First release
*/
/**************************************************************************/
#include "MQ135.h"
/**************************************************************************/
/*!
@brief Default constructor
@param[in] pin The analog input pin for the readout of the sensor
*/
/**************************************************************************/
MQ135::MQ135(uint8_t pin) {
_pin = pin;
this->pin = pin;
pinMode(pin, INPUT);
}
/**************************************************************************/
/*!
@brief Get the correction factor to correct for temperature and humidity
@param[in] t The ambient air temperature
@param[in] h The relative humidity
@return The calculated correction factor
*/
/**************************************************************************/
float MQ135::getCorrectionFactor(float t, float h) {
return CORA * t * t - CORB * t + CORC - (h-33.)*CORD;
double MQ135::getVoltage() {
return (double)analogRead(pin) * VStep;
}
/**************************************************************************/
/*!
@brief Get the resistance of the sensor, ie. the measurement value
@return The sensor resistance in kOhm
*/
/**************************************************************************/
float MQ135::getResistance() {
int val = analogRead(_pin);
return ((1023./(float)val) * 5. - 1.)*RLOAD;
double MQ135::getResistance() {
double voltage = getVoltage();
double rs = ((VIn * RL) / voltage) - RL;
if (rs < 0) {
rs = 0;
}
return rs;
}
/**************************************************************************/
/*!
@brief Get the resistance of the sensor, ie. the measurement value corrected
for temp/hum
@param[in] t The ambient air temperature
@param[in] h The relative humidity
@return The corrected sensor resistance kOhm
*/
/**************************************************************************/
float MQ135::getCorrectedResistance(float t, float h) {
return getResistance()/getCorrectionFactor(t, h);
double MQ135::getPPM(float a, float b) {
double ratio = getResistance() / R0;
double ppm = a * pow(ratio, b);
if (ppm < 0) {
ppm = 0;
}
return ppm;
}
/**************************************************************************/
/*!
@brief Get the ppm of CO2 sensed (assuming only CO2 in the air)
@return The ppm of CO2 in the air
*/
/**************************************************************************/
float MQ135::getPPM() {
return PARA * pow((getResistance()/RZERO), -PARB);
double MQ135::getPPMLinear(float a, float b) {
double ratio = getResistance() / R0;
double ppm_log = (log10(ratio) - b) / a;
double ppm = pow(10, ppm_log);
if (ppm < 0) {
ppm = 0;
}
return ppm;
}
/**************************************************************************/
/*!
@brief Get the ppm of CO2 sensed (assuming only CO2 in the air), corrected
for temp/hum
@param[in] t The ambient air temperature
@param[in] h The relative humidity
@return The ppm of CO2 in the air
*/
/**************************************************************************/
float MQ135::getCorrectedPPM(float t, float h) {
return PARA * pow((getCorrectedResistance(t, h)/RZERO), -PARB);
double MQ135::getAcetona() {
return getPPM(34.668, -3.369);
}
/**************************************************************************/
/*!
@brief Get the resistance RZero of the sensor for calibration purposes
@return The sensor resistance RZero in kOhm
*/
/**************************************************************************/
float MQ135::getRZero() {
return getResistance() * pow((ATMOCO2/PARA), (1./PARB));
double MQ135::getAlcohol() {
return getPPM(77.255, -3.18);
}
/**************************************************************************/
/*!
@brief Get the corrected resistance RZero of the sensor for calibration
purposes
@param[in] t The ambient air temperature
@param[in] h The relative humidity
@return The corrected sensor resistance RZero in kOhm
*/
/**************************************************************************/
float MQ135::getCorrectedRZero(float t, float h) {
return getCorrectedResistance(t, h) * pow((ATMOCO2/PARA), (1./PARB));
double MQ135::getCO2() {
// return getPPMLinear(-0.3525, 0.7142) + ATMOCO2;
return getPPM(110.47, -2.862) + ATMOCO2;
}
double MQ135::getCO() {
return getPPM(605.18, -3.937);
}
double MQ135::getNH4() {
return getPPM(102.2, -2.473);
}
double MQ135::getTolueno() {
return getPPM(44.947, -3.445);
}
float MQ135::getR0() {
double r0 = getResistance() / 3.6;
return r0;
}
double MQ135::getR0ByCO2Level(float ppm) {
if (ppm > ATMOCO2) {
ppm -= ATMOCO2;
}
else {
return NAN;
}
double tmp = -(log10(ppm / 110.47) / -2.862) + log10(getResistance());
return pow(10, tmp);
}
void MQ135::setR0(float r0) {
R0 = r0;
}

94
lib/MQ135/MQ135.h
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@ -1,56 +1,66 @@
/**************************************************************************/
/*!
@file MQ135.h
@author G.Krocker (Mad Frog Labs)
@license GNU GPLv3
#ifndef MQ135New_H
#define MQ135New_H
First version of an Arduino Library for the MQ135 gas sensor
TODO: Review the correction factor calculation. This currently relies on
the datasheet but the information there seems to be wrong.
#include "Arduino.h"
@section HISTORY
/// Resistor on Sensor in kΩ
#define RL 10
v1.0 - First release
*/
/**************************************************************************/
#ifndef MQ135_H
#define MQ135_H
#if ARDUINO >= 100
#include "Arduino.h"
#else
#include "WProgram.h"
#endif
/// Voltage on Sensor in V
#define VIn 5
/// The load resistance on the board
#define RLOAD 10.0
/// Calibration resistance at atmospheric CO2 level
// #define RZERO 76.63
#define RZERO 480
/// Parameters for calculating ppm of CO2 from sensor resistance
#define PARA 116.6020682
#define PARB 2.769034857
/// Board analog Input Resolution
/// Default: 2^10
#define Resolution 1024
/// Parameters to model temperature and humidity dependence
#define CORA 0.00035
#define CORB 0.02718
#define CORC 1.39538
#define CORD 0.0018
/// Atmospheric CO2 level for calibration purposes
/// CO2 Level in Atmosphere
#define ATMOCO2 397.13
/// Helper to calculate Voltage from Input
/// Voltage = input * Vin / (Resolution - 1)
const double VStep = (double)VIn / (Resolution - 1);
class MQ135 {
private:
uint8_t _pin;
/// input pin
uint8_t pin;
/// calibration Resistance
float R0;
public:
/// Constructor with analog input Pin
MQ135(uint8_t pin);
float getCorrectionFactor(float t, float h);
float getResistance();
float getCorrectedResistance(float t, float h);
float getPPM();
float getCorrectedPPM(float t, float h);
float getRZero();
float getCorrectedRZero(float t, float h);
/// Get R0 in default conditions for calibration purposes.
/// Assume CO2 Level is the default Atmospheric Level (~400ppm)
float getR0();
/// Get R0 in custom conditions for calibration purposes.
/// Can be used, if you know the current CO2 Level.
double getR0ByCO2Level(float ppm);
/// Set R0 Value for calibration.
void setR0(float r0);
/// Gets the resolved sensor voltage
double getVoltage();
/// Calculates the Resistance of the Sensor
double getResistance();
/// Calculates ppm on a exponential curve
/// (Different Gases have different curves)
double getPPM(float a, float b);
/// Calculates ppm on a linear curve
/// (Different Gases have different curves)
double getPPMLinear(float a, float b);
/// Gets ppm of Acetona in Air (C3H6O)
double getAcetona();
/// Gets ppm of Alcohol in Air
double getAlcohol();
/// Gets ppm of CO in Air
double getCO();
/// Gets ppm of CO2 in Air
double getCO2();
/// Gets ppm of NH4 in Air
double getNH4();
/// Gets ppm of Tolueno in Air (CH3)
double getTolueno();
};
#endif

7
platformio.ini
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@ -8,7 +8,10 @@
; Please visit documentation for the other options and examples
; https://docs.platformio.org/page/projectconf.html
[env:uno]
[env:mega]
platform = atmelavr
board = uno
board = megaatmega2560
framework = arduino
; lib_deps =
; adafruit/Adafruit BME280 Library @ ^2.1.2
; miguel5612/MQUnifiedsensor @ ^2.0.1

78
src/main.cpp
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@ -1,10 +1,7 @@
#include <Arduino.h>
#include <MQ135.h>
#include <dht.h>
#define PIN_MQ135 A0
#define PIN_DHT11 A1
#define PIN_LED_GREEN DD2
#define PIN_LED_YELLOW DD3
#define PIN_LED_RED DD4
@ -13,93 +10,48 @@
#define MEASURE_DELAY 1000
#define NOISE_DELAY 100
MQ135 co2_sensor = MQ135(PIN_MQ135);
dht dht_sensor;
const int maxCount = MEASURE_DELAY / NOISE_DELAY;
const int maxCount = 10;
int count = 0;
float ppm = -1;
bool noise = false;
bool noiseActive = false;
float ppm;
MQ135 co2_sensor(PIN_MQ135);
void setup() {
Serial.begin(9600);
pinMode(PIN_MQ135, INPUT);
pinMode(PIN_DHT11, INPUT);
pinMode(PIN_LED_GREEN, OUTPUT);
pinMode(PIN_LED_YELLOW, OUTPUT);
pinMode(PIN_LED_RED, OUTPUT);
pinMode(PIN_NOISE, OUTPUT);
co2_sensor.setR0(100);
}
float measure() {
Serial.print(RZERO);
Serial.println("---------------------------");
Serial.print("DHT:\t");
int chk = dht_sensor.read11(PIN_DHT11);
switch (chk)
{
case DHTLIB_OK:
Serial.print("OK,\t");
break;
case DHTLIB_ERROR_CHECKSUM:
Serial.print("Checksum error,\t");
break;
case DHTLIB_ERROR_TIMEOUT:
Serial.print("Time out error,\t");
break;
case DHTLIB_ERROR_CONNECT:
Serial.print("Connect error,\t");
break;
case DHTLIB_ERROR_ACK_L:
Serial.print("Ack Low error,\t");
break;
case DHTLIB_ERROR_ACK_H:
Serial.print("Ack High error,\t");
break;
default:
Serial.print("Unknown error,\t");
break;
}
Serial.println();
Serial.print ("temperature: ");
Serial.println (dht_sensor.temperature);
Serial.print ("humidity: ");
Serial.println (dht_sensor.humidity);
float val = analogRead(A0);
Serial.print ("raw = ");
Serial.println (val);
float zero = co2_sensor.getCorrectedRZero(dht_sensor.temperature, dht_sensor.humidity);
Serial.print ("rzero: ");
Serial.println (zero);
float ppm = co2_sensor.getCorrectedPPM(dht_sensor.temperature, dht_sensor.humidity);
Serial.print ("ppm: ");
Serial.println (ppm);
return ppm;
}
void printValues(float ppm, float temp, float humidity);
void loop() {
if (count >= maxCount || ppm < 0) {
ppm = measure();
if (count >= maxCount || count < 0) {
ppm = co2_sensor.getCO2();
count = 0;
if (ppm < 1000) {
noiseActive = false;
digitalWrite(PIN_LED_GREEN, 1);
digitalWrite(PIN_LED_YELLOW, 0);
digitalWrite(PIN_LED_RED, 0);
}
else if (ppm <= 2000) {
noiseActive = false;
digitalWrite(PIN_LED_GREEN, 0);
digitalWrite(PIN_LED_YELLOW, 1);
digitalWrite(PIN_LED_RED, 0);
}
else {
noiseActive = true;
digitalWrite(PIN_LED_GREEN, 0);
digitalWrite(PIN_LED_YELLOW, 0);
digitalWrite(PIN_LED_RED, 1);
}
}
if (ppm > 2000) {
if (noiseActive) {
noise = !noise;
digitalWrite(PIN_NOISE, noise);
}