Fixed mq-3 example

examples/MQ-3/MQ-3.ino

@@ -35,7 +35,7 @@ void setup() {
   Output:  
   Remarks: This function create the sensor object.
   ************************************************************************************/ 
-  MQ3.inicializar(); 
+  MQ3.init(); 
   //pinMode(calibration_button, INPUT);
 }
 
@@ -62,12 +62,23 @@ void loop() {
   //Lecture will be saved in lecture variable
   //float lecture =  MQ3.readSensor("", true); // Return Alcohol concentration
   // Options, uncomment where you need
-  CH4 =  MQ3.readSensor("CH4"); // Return CH4 concentration
-  LPG =  MQ3.readSensor("LPG"); // Return LPG concentration
-  CO =  MQ3.readSensor("CO"); // Return CO concentration
-  Alcohol =  MQ3.readSensor("Alcohol"); // Return Alcohol concentration
-  Hexane =  MQ3.readSensor("Hexane"); // Return Hexane concentration
-  Benzine =  MQ3.readSensor("Benzene"); // Return Benzene concentration
+  MQ3.setA(2*10^31); MQ3.setB(19.01); // Configurate the ecuation values
+  CH4 =  MQ3.readSensor("Exponential"); // Return CH4 concentration
+
+  MQ3.setA(44771); MQ3.setB(-3.245); // Configurate the ecuation values
+  LPG =  MQ3.readSensor("Exponential"); // Return LPG concentration
+
+  MQ3.setA(521853); MQ3.setB(-3.821); // Configurate the ecuation values
+  CO =  MQ3.readSensor("Exponential"); // Return CO concentration
+  
+  MQ3.setA(0.3934); MQ3.setB(-1.504); // Configurate the ecuation values
+  Alcohol =  MQ3.readSensor("Exponential"); // Return Alcohol concentration
+  
+  MQ3.setA(7585.3); MQ3.setB(-2.849); // Configurate the ecuation values
+  Hexane =  MQ3.readSensor("Exponential"); // Return Hexane concentration
+
+  MQ3.setA(4.8387); MQ3.setB(-2.68); // Configurate the ecuation values
+  Benzine =  MQ3.readSensor("Exponential"); // Return Benzene concentration
 
   Serial.println("***************************");
   Serial.println("Lectures for MQ-3");

src/MQUnifiedsensor.cpp

@@ -6,7 +6,13 @@ MQUnifiedsensor::MQUnifiedsensor(String Placa, int Voltage_Resolution, int pin,
   this->_placa = Placa;
   this-> _VOLT_RESOLUTION = Voltage_Resolution;
 }
-MQUnifiedsensor::serialDebug(boolean onSetup)
+MQUnifiedsensor::setA(double a) {
+  this->_a = a;
+}
+MQUnifiedsensor::setB(double b) {
+  this->_b = b;
+}
+MQUnifiedsensor::serialDebug(boolean onSetup, String regressionMethod)
 {
   if(onSetup)
   {
@@ -40,6 +46,7 @@ MQUnifiedsensor::serialDebug(boolean onSetup)
     else
     {
       String eq = "";
+      if(regression == "Linear") eq = "ratio*a + b"
       if(regression == "Exponential") eq = "a*ratio^b"
       Serial.println("|" + _adc + "|" + "v = ADC*" + _VOLT_RESOLUTION + "/1024" + "|" + _sensor_volt + "|" + "RS = ((" + _VOLT_RESOLUTION + "*RL)/Voltage) - RL" + "|" + _RS_Calc + "|" + "Ratio = RS/R0" + "|" + _ratio + "|" + eq + "|" + _PPM);
     }
@@ -57,15 +64,15 @@ void MQUnifiedsensor::init()
 {
   pinMode(_pin, INPUT);
 }
-float MQUnifiedsensor::readSensor(String nameLectureRequeired)
+float MQUnifiedsensor::readSensor(String regressionMethod)
 {
-  setSensorCharacteristics(nameLectureRequeired, print); //In this function update _a and _b
   //More explained in: https://jayconsystems.com/blog/understanding-a-gas-sensor
   _RS_Calc = ((_VOLT_RESOLUTION*_RLValue)/_sensor_volt)-_RLValue; //Get value of RS in a gas
   if(_RS_Calc < 0)  _RS_Calc = 0; //No negative values accepted.
   _ratio = _RS_Calc / this->_R0;   // Get ratio RS_gas/RS_air
   if(_ratio <= 0 || _ratio>100)  _ratio = 0.01; //No negative values accepted or upper datasheet recomendation.
-  _PPM= _a*pow(_ratio, _b);
+  if(regressionMethod == "Exponential") _PPM= _a*pow(_ratio, _b);
+  if(regressionMethod == "Linear") _PPM= _a*_ratio + _b);
   if(_PPM < 0)  _PPM = 0; //No negative values accepted or upper datasheet recomendation.
   if(_PPM > 10000) _PPM = 9999; //No negative values accepted or upper datasheet recomendation.
   return _PPM;

src/MQUnifiedsensor.h

@@ -20,12 +20,14 @@ class MQUnifiedsensor
     void update();
     void setR0(double R0 = 10);
     void setRL(double RL = 10);
+    void setA(double a);
+    void setB(double b);
     void setVoltResolution(double voltage_resolution =  5);
     void serialDebug(boolean onSetup = false); //Show on serial port information about sensor
     
     //user functions
-    float calibrate(boolean print = false);
-    float readSensor(<String regressionMethod = "Exponential", float _a, float _b);
+    float calibrate(boolean print = false, String regressionMethod = "Exponential");
+    float readSensor(String regressionMethod = "Exponential", float _a, float _b);
     
     //get function for info
     double getR0();
@@ -43,7 +45,7 @@ class MQUnifiedsensor
     byte _VOLT_RESOLUTION  = 5.0; // if 3.3v use 3.3
     byte _ratioInCleanAir, _sensor_volt;
     byte _RLValue = 10; //Value in KiloOhms
-    double _adc;
+    double _adc, _a, _b;
     float  _R0, RS_air, _ratio, _PPM, _RS_Calc;  
 };