Added pendent to validate example

examples/ESP8266/ESP8266.ino

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+// This is an example of implementation using ESP8266
+// Never connect the sensor direct to the ESP8266, sensor high level is 5V
+// ADC of ESP8266 high level is 3.3
+// To connect use a voltage divisor, where 5V will 3v3 on the middle point like
+// this {{URL}}
+
+/*
+  MQUnifiedsensor Library - reading an MQSensor using ESP8266 board
+
+  For this example wi will demonstrates the use a MQ3 sensor.
+  Library originally added 01 may 2019
+  by Miguel A Califa, Yersson Carrillo, Ghiordy Contreras, Mario Rodriguez
+ 
+  Updated library usage
+  modified 26 March 2020
+  by Miguel Califa 
+
+ This example code is in the public domain.
+
+*/
+
+//Include the library
+#include <MQUnifiedsensor.h>
+
+//Definitions
+#define placa "ESP8266" //NodeMcu, WeMos D1, TTGo, ESP32.. etc
+#define Voltage_Resolution 3.3
+#define pin A0 //Analog input 0 of your arduino
+#define type "MQ-3" //MQ3
+#define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
+
+//Declare Sensor
+MQUnifiedsensor MQ3(placa, Voltage_Resolution, ADC_Bit_Resolution, pin, type);
+
+void setup() {
+  //Init the serial port communication - to debug the library
+  Serial.begin(9600); //Init serial port
+
+  //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
+  /*
+    Exponential regression:
+  Gas    | a      | b
+  LPG    | 44771  | -3.245
+  CH4    | 2*10^31| 19.01
+  CO     | 521853 | -3.821
+  Alcohol| 0.3934 | -1.504
+  Benzene| 4.8387 | -2.68
+  Hexane | 7585.3 | -2.849
+  */
+
+  // Calibration setup
+  MQ3.setR0(3.86018237);
+
+  /* 
+    //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);
+}
+
+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 model and a and b values setted before or in the setup
+  MQ3.serialDebug(); // Will print the table on the serial port
+  delay(500); //Sampling frequency
+}