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https://github.com/miguel5612/MQSensorsLib.git
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104 lines
4.3 KiB
C++
104 lines
4.3 KiB
C++
/*
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MQUnifiedsensor Library - reading an MQ4
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Demonstrates the use a MQ4 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 26 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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This example code is in the public domain.
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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 A4 //Analog input 4 of your arduino
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#define type "MQ-4" //MQ4
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#define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
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#define RatioMQ4CleanAir 4.4 //RS / R0 = 4.4 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 MQ4(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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/***************************** MQ CAlibration ********************************************/
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// Explanation:
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// In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
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// and on clean air (Calibration conditions), setting up R0 value.
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// We recomend executing this routine only on setup in laboratory conditions.
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// This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
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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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MQ4.update(); // Update data, the arduino will read the voltage from the analog pin
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calcR0 += MQ4.calibrate(RatioMQ4CleanAir);
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Serial.print(".");
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}
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MQ4.setR0(calcR0/10);
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Serial.println(" done!.");
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if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
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if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
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/***************************** MQ CAlibration ********************************************/
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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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MQ4.setRL(10);
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*/
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/***************************** MQ Init ********************************************/
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//Input: setup flag, if this function are on setup will print the headers (Optional - Default value: False)
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//Output: print on serial port the information about sensor and sensor readings
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//Remarks: Configure the pin of arduino as input.
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/************************************************************************************/
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MQ4.init();
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Serial.println("** Values from MQ-4**********");
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Serial.println("| LPG (Linear EQ) | LPG (Exponential EQ) |");
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}
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void loop() {
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MQ4.update(); // Update data, the arduino will read the voltage from the analog pin
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//https://jayconsystems.com/blog/understanding-a-gas-sensor
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//Set math model to calculate the PPM concentration and the value of constants
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MQ4.setRegressionMethod(0); //_PPM = pow(10, (log10(ratio)-b)/a)
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MQ4.setA(-0.318); MQ4.setB(1.133); // A -> Slope, B -> Intersect with X - Axis
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float LPG1 = MQ4.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
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//Set math model to calculate the PPM concentration and the value of constants
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MQ4.setRegressionMethod(1); //_PPM = a*ratio^b
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MQ4.setA(1012.7); MQ4.setB(-2.786); // Configure the equation to to calculate CH4 concentration
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float LPG2 = MQ4.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
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// exposure to 2000 ppm of LPG gas is immediately dangerous to life and health. In this section
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if(LPG1>=2000 || LPG2>=2000) Serial.println("Warning - Very high concentrations detected!");
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Serial.print("| "); Serial.print(LPG1);
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Serial.print(" | "); Serial.print(LPG2);
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Serial.println(" |");
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delay(500); //Sampling frequency
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} |