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105 lines
4.3 KiB
C++
105 lines
4.3 KiB
C++
/*
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MQUnifiedsensor Library - reading an MQ3
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Demonstrates the use a MQ3 sensor.
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Library originally added 01 may 2019
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by Miguel A Califa, Yersson Carrillo, Ghiordy Contreras, Mario Rodriguez
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Added example
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modified 23 May 2019
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by Miguel Califa
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Updated library usage
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modified 29 March 2020
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by Miguel Califa
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Wiring:
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https://github.com/miguel5612/MQSensorsLib_Docs/blob/master/static/img/MQ_Arduino.PNG
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Please take care, arduino A0 pin represent the analog input configured on #define pin - For this example this doesn't matter
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You will connect your sensor to your external A2D Sensor
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This example code is in the public domain.
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Important:
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1. Although it doesn't matter what pin you put in when initializing your MQ sensor function it is important that you don't
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for any reason invoke the MQ.init() method because that method configures the selected pin as input and you may need it for
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other use in the program.
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2. You must ensure that your analog/digital converter will perform the conversion taking into account the output voltage
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levels of the MQ sensor module.
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3. You must ensure that when invoking the setADC(value) method the value you are passing is within the expected parameters,
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for example if it is a 10-bit ADC converter, we expect a value between 0 and 2^10 = 1024
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*/
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//Include the library
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#include <MQUnifiedsensor.h>
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//Definitions
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#define placa "Arduino UNO"
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#define Voltage_Resolution 5
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#define pin A0 //Analog input 0 -> This value can have any number, we recomend use A0
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#define type "MQ-3 With A2D External connected" //MQ3
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#define ADC_Bit_Resolution 10 // Resolution of your external A2D
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#define RatioMQ3CleanAir 60 //RS / R0 = 60 ppm
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//#define calibration_button 13 //Pin to calibrate your sensor
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//Declare Sensor
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MQUnifiedsensor MQ3(placa, Voltage_Resolution, ADC_Bit_Resolution, pin, type);
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void setup() {
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//Init the serial port communication - to debug the library
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Serial.begin(9600); //Init serial port
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//Set math model to calculate the PPM concentration and the value of constants
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MQ3.setRegressionMethod(1); //_PPM = a*ratio^b
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MQ3.setA(4.8387); MQ3.setB(-2.68); // Configurate the ecuation values to get Benzene concentration
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/*
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Exponential regression:
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Gas | a | b
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LPG | 44771 | -3.245
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CH4 | 2*10^31| 19.01
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CO | 521853 | -3.821
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Alcohol| 0.3934 | -1.504
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Benzene| 4.8387 | -2.68
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Hexane | 7585.3 | -2.849
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*/
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/*
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//If the RL value is different from 10K please assign your RL value with the following method:
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MQ3.setRL(10);
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*/
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/***************************** MQ CAlibration ********************************************/
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// Explanation:
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// In this routine the sensor will measure the resistance of the sensor supposing before was pre-heated
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// and now is on clean air (Calibration conditions), and it will setup R0 value.
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// We recomend execute this routine only on setup or on the laboratory and save on the eeprom of your arduino
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// This routine not need to execute to every restart, you can load your R0 if you know the value
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// Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
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Serial.print("Calibrating please wait.");
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float calcR0 = 0;
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for(int i = 1; i<=10; i ++)
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{
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int yourA2DValue = random(0, 1024); // 10-bit emulation
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MQ3.setADC(yourA2DValue);// Update data, the arduino will be read the voltage on the analog pin
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calcR0 += MQ3.calibrate(RatioMQ3CleanAir);
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Serial.print(".");
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}
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MQ3.setR0(calcR0/10);
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Serial.println(" done!.");
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if(isinf(calcR0)) {Serial.println("Warning: Conection issue founded, R0 is infite (Open circuit detected) please check your wiring and supply"); while(1);}
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if(calcR0 == 0){Serial.println("Warning: Conection issue founded, R0 is zero (Analog pin with short circuit to ground) please check your wiring and supply"); while(1);}
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/***************************** MQ CAlibration ********************************************/
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MQ3.serialDebug(true);
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}
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void loop() {
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int yourA2DValue = random(0, 1024); // 10-bit emulation
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MQ3.setADC(yourA2DValue); // Update data, the arduino will be read the voltage on the analog pin
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MQ3.readSensor(); // Sensor will read PPM concentration using the model and a and b values setted before or in the setup
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MQ3.serialDebug(); // Will print the table on the serial port
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delay(500); //Sampling frequency
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} |