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104 lines
4.4 KiB
C++
104 lines
4.4 KiB
C++
/*
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MQUnifiedsensor Library - reading an MQ9
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Demonstrates the use a MQ9 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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Please make sure arduino A0 pin represents the analog input configured on #define pin
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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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/************************Hardware Related Macros************************************/
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#define Board ("Arduino UNO")
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#define Pin (A9) //Analog input 4 of your arduino
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/***********************Software Related Macros************************************/
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#define Type ("MQ-9") //MQ9
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#define Voltage_Resolution (5)
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#define ADC_Bit_Resolution (10) // For arduino UNO/MEGA/NANO
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#define RatioMQ9CleanAir (9.6) //RS / R0 = 60 ppm
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/*****************************Globals***********************************************/
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//Declare Sensor
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MQUnifiedsensor MQ9(Board, 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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MQ9.setRegressionMethod(1); //_PPM = a*ratio^b
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/***************************** MQ Init ********************************************/
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//Remarks: Configure the pin of arduino as input.
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/************************************************************************************/
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MQ9.init();
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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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MQ9.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 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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MQ9.update(); // Update data, the arduino will read the voltage from the analog pin
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calcR0 += MQ9.calibrate(RatioMQ9CleanAir);
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Serial.print(".");
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}
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MQ9.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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Serial.println("** Values from MQ-9 ****");
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Serial.println("| LPG | CH4 | CO |");
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}
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void loop() {
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MQ9.update(); // Update data, the arduino will read the voltage from the analog pin
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/*
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Exponential regression:
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GAS | a | b
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LPG | 1000.5 | -2.186
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CH4 | 4269.6 | -2.648
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CO | 599.65 | -2.244
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*/
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MQ9.setA(1000.5); MQ9.setB(-2.186); // Configure the equation to to calculate LPG concentration
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float LPG = MQ9.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
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MQ9.setA(4269.6); MQ9.setB(-2.648); // Configure the equation to to calculate LPG concentration
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float CH4 = MQ9.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
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MQ9.setA(599.65); MQ9.setB(-2.244); // Configure the equation to to calculate LPG concentration
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float CO = MQ9.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
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Serial.print("| "); Serial.print(LPG);
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Serial.print(" | "); Serial.print(CH4);
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Serial.print(" | "); Serial.print(CO);
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Serial.println(" |");
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delay(500); //Sampling frequency
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} |