Fixed example

examples/MQ-3/MQ-3.ino

@@ -9,6 +9,10 @@
   modified 23 May 2019
   by Miguel Califa 
 
+  Updated library usage
+  modified 26 March 2020
+  by Miguel Califa 
+
  This example code is in the public domain.
 
 */
@@ -31,79 +35,38 @@ MQUnifiedsensor MQ3(placa, Voltage_Resolution, ADC_Bit_Resolution, pin, type);
 float CH4, LPG, CO, Alcohol, Hexane, Benzine;
 
 void setup() {
+  //Init the serial port communication - to debug the library
   Serial.begin(9600); //Init serial port
-  //init the sensor
-  /*****************************  MQInicializar****************************************
-  Input:  pin, type 
-  Output:  
-  Remarks: This function create the sensor object.
-  ************************************************************************************/ 
-  MQ3.setRegressionMethod("Exponential");
+
+  //Set math model to calculate the PPM concentration and the value of constants
+  MQ3.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
   MQ3.setA(4.8387); MQ3.setB(-2.68); // Configurate the ecuation values to get Benzene concentration
   
+  // Calibration setup
+  MQ3.setR0(3.86018237);
+
   /* 
-    //Si el valor de RL es diferente a 10K por favor asigna tu valor de RL con el siguiente metodo:
+    //If the RL value is different from 10K please assign your RL value with the following method:
     MQ3.setRL(10);
   */
 
+  /*****************************  MQ Init ********************************************/ 
+  //Remarks: Configure the pin of arduino as input.
+  /************************************************************************************/ 
   MQ3.init(); 
+  /*****************************  MQ Init ********************************************/ 
+  //Input: setup flag, if this function are on setup will print the headers (Optional - Default value: False)
+  //Output: print on serial port the information about sensor and sensor readings
+  //Remarks: Configure the pin of arduino as input.
+  /************************************************************************************/ 
   MQ3.serialDebug(true);
+
   //pinMode(calibration_button, INPUT);
 }
 
 void loop() {
   MQ3.update(); // Update data, the arduino will be read the voltage on the analog pin
-  MQ3.readSensor(); // Sensor will read PPM concentration using the a and b values setted before or on setup
+  MQ3.readSensor(); // Sensor will read PPM concentration using the model and a and b values setted before or in the setup
   MQ3.serialDebug(); // Will print the table on the serial port
-  /*
-  //Rutina de calibracion - Uncomment if you need (setup too and header)
-  if(calibration_button)
-  {
-    float R0 = MQ3.calibrate();
-    MQ3.setR0(R0);
-  }
-  */
-  
-  /*****************************  MQReadSensor  ****************************************
-  Input:   Gas - Serial print flag
-  Output:  Value in PPM
-  Remarks: This function use readPPM to read the value in PPM the gas in the air.
-  ************************************************************************************/ 
-  //Read the sensor and print in serial port
-  //Lecture will be saved in lecture variable
-  //float lecture =  MQ3.readSensor("", true); // Return Alcohol concentration
-  // Options, uncomment where you need
-  /*
-  MQ3.setA(2*10^31); MQ3.setB(19.01); // Configurate the ecuation values
-  CH4 =  MQ3.readSensor(); // Return CH4 concentration
-
-  MQ3.setA(44771); MQ3.setB(-3.245); // Configurate the ecuation values
-  LPG =  MQ3.readSensor(); // Return LPG concentration
-
-  MQ3.setA(521853); MQ3.setB(-3.821); // Configurate the ecuation values
-  CO =  MQ3.readSensor(); // Return CO concentration
-  
-  MQ3.setA(0.3934); MQ3.setB(-1.504); // Configurate the ecuation values
-  Alcohol =  MQ3.readSensor(); // Return Alcohol concentration
-  
-  MQ3.setA(7585.3); MQ3.setB(-2.849); // Configurate the ecuation values
-  Hexane =  MQ3.readSensor(); // Return Hexane concentration
-
-  MQ3.setA(4.8387); MQ3.setB(-2.68); // Configurate the ecuation values
-  Benzine =  MQ3.readSensor(); // Return Benzene concentration
-  */
-
-  /*
-  Serial.println("***************************");
-  Serial.println("Lectures for MQ-3");
-  Serial.print("Volt: ");Serial.print(MQ3.getVoltage(false));Serial.println(" V"); 
-  Serial.print("R0: ");Serial.print(MQ3.getR0());Serial.println(" Ohm"); 
-  Serial.print("CH4: ");Serial.print(CH4,2);Serial.println(" mg/L");
-  Serial.print("LPG: ");Serial.print(LPG,2);Serial.println(" mg/L");
-  Serial.print("CO: ");Serial.print(CO,2);Serial.println(" mg/L");
-  Serial.print("Alcohol: ");Serial.print(Alcohol,2);Serial.println(" mg/L");
-  Serial.print("Hexane: ");Serial.print(Hexane,2);Serial.println(" mg/L");
-  Serial.print("Benzine: ");Serial.print(Benzine,2);Serial.println(" mg/L");
-  Serial.println("***************************");
-  */
+  delay(500); //Sampling frequency
 }

src/MQUnifiedsensor.cpp

@@ -99,7 +99,7 @@ float MQUnifiedsensor::readSensor()
   //if(_PPM > 10000) _PPM = 99999999; //No negative values accepted or upper datasheet recomendation.
   return _PPM;
 }
-float MQUnifiedsensor::calibrate() {
+float MQUnifiedsensor::calibrate(float ratioInCleanAir) {
   //More explained in: https://jayconsystems.com/blog/understanding-a-gas-sensor
   /*
   V = I x R 
@@ -116,7 +116,7 @@ float MQUnifiedsensor::calibrate() {
   float R0; //Define variable for R0
   RS_air = ((_VOLT_RESOLUTION*_RL)/_sensor_volt)-_RL; //Calculate RS in fresh air
   if(RS_air < 0)  RS_air = 0; //No negative values accepted.
-  R0 = RS_air/_ratioInCleanAir; //Calculate R0 
+  R0 = RS_air/ratioInCleanAir; //Calculate R0 
   if(R0 < 0)  R0 = 0; //No negative values accepted.
   return R0;
 }

src/MQUnifiedsensor.h

@@ -27,7 +27,7 @@ class MQUnifiedsensor
     void serialDebug(bool onSetup = false); //Show on serial port information about sensor
     
     //user functions
-    float calibrate();
+    float calibrate(float ratioInCleanAir);
     float readSensor();
     
     //get function for info
@@ -42,7 +42,6 @@ class MQUnifiedsensor
     byte _pin;
     byte _firstFlag = false;
     byte _VOLT_RESOLUTION  = 5.0; // if 3.3v use 3.3
-    byte _ratioInCleanAir;
     byte _RL = 10; //Value in KiloOhms
     byte _ADC_Bit_Resolution = 10;