Merge pull request #1 from swablab/feature/GrafZ

add own library

lib/MQ135/MQ135.cpp

@@ -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);
 }
 
-
+double MQ135::getVoltage() {
-/**************************************************************************/
+    return (double)analogRead(pin) * VStep;
-/*!
-@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::getResistance() {
-/*!
+    double voltage = getVoltage();
-@brief  Get the resistance of the sensor, ie. the measurement value
+    double rs = ((VIn * RL) / voltage) - RL;
-
+    if (rs < 0) {
-@return The sensor resistance in kOhm
+        rs = 0;
-*/
+    }
-/**************************************************************************/
+    return rs;
-float MQ135::getResistance() {
-  int val = analogRead(_pin);
-  return ((1023./(float)val) * 5. - 1.)*RLOAD;
 }
 
-/**************************************************************************/
+double MQ135::getPPM(float a, float b) {
-/*!
+    double ratio = getResistance() / R0;
-@brief  Get the resistance of the sensor, ie. the measurement value corrected
+    double ppm = a * pow(ratio, b);
-        for temp/hum
+    if (ppm < 0) {
-
+        ppm = 0;
-@param[in] t  The ambient air temperature
+    }
-@param[in] h  The relative humidity
+    return ppm;
-
-@return The corrected sensor resistance kOhm
-*/
-/**************************************************************************/
-float MQ135::getCorrectedResistance(float t, float h) {
-  return getResistance()/getCorrectionFactor(t, h);
 }
 
-/**************************************************************************/
+double MQ135::getPPMLinear(float a, float b) {
-/*!
+    double ratio = getResistance() / R0;
-@brief  Get the ppm of CO2 sensed (assuming only CO2 in the air)
+    double ppm_log = (log10(ratio) - b) / a;
-
+    double ppm = pow(10, ppm_log);
-@return The ppm of CO2 in the air
+    if (ppm < 0) {
-*/
+        ppm = 0;
-/**************************************************************************/
+    }
-float MQ135::getPPM() {
+    return ppm;
-  return PARA * pow((getResistance()/RZERO), -PARB);
 }
 
-/**************************************************************************/
+double MQ135::getAcetona() {
-/*!
+    return getPPM(34.668, -3.369);
-@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::getAlcohol() {
-/*!
+    return getPPM(77.255, -3.18);
-@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::getCO2() {
-/*!
+    // return getPPMLinear(-0.3525, 0.7142) + ATMOCO2;
-@brief  Get the corrected resistance RZero of the sensor for calibration
+    return getPPM(110.47, -2.862) + ATMOCO2;
-        purposes
+}
-
+
-@param[in] t  The ambient air temperature
+double MQ135::getCO() {
-@param[in] h  The relative humidity
+    return getPPM(605.18, -3.937);
-
+}
-@return The corrected sensor resistance RZero in kOhm
+
-*/
+double MQ135::getNH4() {
-/**************************************************************************/
+    return getPPM(102.2, -2.473);
-float MQ135::getCorrectedRZero(float t, float h) {
+}
-  return getCorrectedResistance(t, h) * pow((ATMOCO2/PARA), (1./PARB));
+
+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;
 }

lib/MQ135/MQ135.h

@@ -1,56 +1,66 @@
-/**************************************************************************/
+#ifndef MQ135New_H
-/*!
+#define MQ135New_H
-@file     MQ135.h
-@author   G.Krocker (Mad Frog Labs)
-@license  GNU GPLv3
 
-First version of an Arduino Library for the MQ135 gas sensor
+#include "Arduino.h"
-TODO: Review the correction factor calculation. This currently relies on
-the datasheet but the information there seems to be wrong.
 
-@section  HISTORY
+/// Resistor on Sensor in kΩ
+#define RL 10
 
-v1.0 - First release
+/// Voltage on Sensor in V
-*/
+#define VIn 5
-/**************************************************************************/
-#ifndef MQ135_H
-#define MQ135_H
-#if ARDUINO >= 100
- #include "Arduino.h"
-#else
- #include "WProgram.h"
-#endif
 
-/// The load resistance on the board
+/// Board analog Input Resolution
-#define RLOAD 10.0
+/// Default: 2^10
-/// Calibration resistance at atmospheric CO2 level
+#define Resolution 1024
-// #define RZERO 76.63
-#define RZERO 480
-/// Parameters for calculating ppm of CO2 from sensor resistance
-#define PARA 116.6020682
-#define PARB 2.769034857
 
-/// Parameters to model temperature and humidity dependence
+/// CO2 Level in Atmosphere
-#define CORA 0.00035
-#define CORB 0.02718
-#define CORC 1.39538
-#define CORD 0.0018
-
-/// Atmospheric CO2 level for calibration purposes
 #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);
+  /// Get R0 in default conditions for calibration purposes.
-  float getResistance();
+  /// Assume CO2 Level is the default Atmospheric Level (~400ppm)
-  float getCorrectedResistance(float t, float h);
+  float getR0();
-  float getPPM();
+  /// Get R0 in custom conditions for calibration purposes.
-  float getCorrectedPPM(float t, float h);
+  /// Can be used, if you know the current CO2 Level.
-  float getRZero();
+  double getR0ByCO2Level(float ppm);
-  float getCorrectedRZero(float t, float h);
+  /// 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

platformio.ini

@@ -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

src/main.cpp

@@ -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);
+const int maxCount = 10;
-dht dht_sensor;
-const int maxCount = MEASURE_DELAY / NOISE_DELAY;
 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);
+  co2_sensor.setR0(100);
-  pinMode(PIN_DHT11, INPUT);
-  pinMode(PIN_LED_GREEN, OUTPUT);
-  pinMode(PIN_LED_YELLOW, OUTPUT);
-  pinMode(PIN_LED_RED, OUTPUT);
-  pinMode(PIN_NOISE, OUTPUT);
 }
 
-float measure() {
+void printValues(float ppm, float temp, float humidity);
-  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 loop() {
-  if (count >= maxCount || ppm < 0) {
+  if (count >= maxCount || count < 0) {
-    ppm = measure();
+    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);
   }