mirror of
https://github.com/miguel5612/MQSensorsLib.git
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120 lines
4.3 KiB
C++
120 lines
4.3 KiB
C++
/*
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MQUnifiedsensor Library - reading an MQ7
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Demonstrates the use a MQ7 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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Updated example of MQ-7 AND MQ-309A
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modified 20 April 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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//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 of your arduino
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#define type "MQ-7" //MQ7
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#define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
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#define RatioMQ7CleanAir 27.5 //RS / R0 = 27.5 ppm
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#define PWMPin 5 // Pin connected to mosfet
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//Declare Sensor
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MQUnifiedsensor MQ7(placa, Voltage_Resolution, ADC_Bit_Resolution, pin, type);
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unsigned long oldTime = 0;
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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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pinMode(PWMPin, OUTPUT);
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//Set math model to calculate the PPM concentration and the value of constants
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MQ7.setRegressionMethod(1); //_PPM = a*ratio^b
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MQ7.setA(99.042); MQ7.setB(-1.518); // Configure the equation to calculate CO concentration value
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/*
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Exponential regression:
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GAS | a | b
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H2 | 69.014 | -1.374
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LPG | 700000000 | -7.703
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CH4 | 60000000000000 | -10.54
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CO | 99.042 | -1.518
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Alcohol | 40000000000000000 | -12.35
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*/
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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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MQ7.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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MQ7.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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MQ7.update(); // Update data, the arduino will read the voltage from the analog pin
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calcR0 += MQ7.calibrate(RatioMQ7CleanAir);
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Serial.print(".");
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}
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MQ7.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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MQ7.serialDebug(true);
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}
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void loop() {
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// 60s cycle
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oldTime = millis();
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while(millis() - oldTime <= (60*1000))
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{
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// VH 5 Volts
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analogWrite(5, 255); // 255 is DC 5V output
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MQ7.update(); // Update data, the arduino will read the voltage from the analog pin
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MQ7.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
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MQ7.serialDebug(); // Will print the table on the serial port
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delay(500); //Sampling frequency
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}
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// 90s cycle
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oldTime = millis();
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while(millis() - oldTime <= (90*1000))
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{
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// VH 1.4 Volts
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analogWrite(5, 20); // 255 is 100%, 20.4 is aprox 8% of Duty cycle for 90s
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MQ7.update(); // Update data, the arduino will read the voltage from the analog pin
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MQ7.readSensor(); // Sensor will read PPM concentration using the model, a and b values set previously or from the setup
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MQ7.serialDebug(); // Will print the table on the serial port
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delay(500); //Sampling frequency
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}
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// Total: 60 + 90s = 2.5 minutes.
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} |