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    سنسور گاز هیدروژن mq-8

    سنسور گاز هیدروژن MQ-8
    سنسورهای گاز سری MQ از هیتر داخلی کوچک به همراه سنسور الکتروشیمیایی بهره می گیرند. این سنسورها نسبت به طیف گسترده ای از گازها حساس اند.سنسور گاز هیدروژن MQ-8 مناسب برای سنجش غلظت هیدروژن موجود در هوا می باشد.این سنسور توانایی غلظت گاز هیدروژن را از 100ppm تا 1000ppm را دارد. حساسیت بالا نسبت به هیدروژن و حساسیت کم نسبت به الکل و پاسخ گویی سریع از خصوصیات این سنسور است. این سنسور برای راه اندازی به ولتاژ 5V و مقاومت بار نیاز دارد. خروجی این سنسور آنالوگ می باشد.این سنسور با آردوینو سازگار بوده و به راحتی قابل راه اندازی است.

    کاربردها
    شناسایی و تشخیص گاز هیدروژن در محیط های خانگی و صنعتی

    مثال
    در این مثال با اتصال سنسور به آردوینو می توانید آن را کالیبره کرده و غلظت هیدروژن در Serial Monitor مشاهده کنید.

    کد:
    [CPP]
    #define         MQ_PIN                       (0)     //define which analog input channel you are going to use
    #define         RL_VALUE                     (10)    //define the load resistance on the board, in kilo ohms
    #define         RO_CLEAN_AIR_FACTOR          (9.21)  //RO_CLEAR_AIR_FACTOR=(Sensor resistance in clean air)/RO,
                                                         //which is derived from the chart in datasheet
    
    
    
    
    
    /***********************Software Related Macros************************************/
    #define         CALIBARAION_SAMPLE_TIMES     (50)    //define how many samples you are going to take in the calibration phase
    #define         CALIBRATION_SAMPLE_INTERVAL  (500)   //define the time interal(in milisecond) between each samples in the
                                                         //cablibration phase
    #define         READ_SAMPLE_INTERVAL         (50)    //define how many samples you are going to take in normal operation
    #define         READ_SAMPLE_TIMES            (5)     //define the time interal(in milisecond) between each samples in 
                                                         //normal operation
    
    /**********************Application Related Macros**********************************/
    #define         GAS_H2                      (0)
    
    
    
    /*****************************Globals***********************************************/
    float           H2Curve[3]  =  {2.3, 0.47,-0.82};    //two points are taken from the curve in datasheet. 
                                                         //with these two points, a line is formed which is "approximately equivalent" 
                                                         //to the original curve. 
                                                         //data format:{ x, y, slope}; point1: (lg200, 0.47), point2: (lg10000, -0.92) 
    
    float           Ro           =  10;                  //Ro is initialized to 10 kilo ohms
    
    void setup()
    {
      Serial.begin(9600);                                //UART setup, baudrate = 9600bps
      Serial.print("Calibrating...\n");                
      Ro = MQCalibration(MQ_PIN);                        //Calibrating the sensor. Please make sure the sensor is in clean air 
                                                         //when you perform the calibration                    
      Serial.print("Calibration is done...\n"); 
      Serial.print("Ro=");
      Serial.print(Ro);
      Serial.print("kohm");
      Serial.print("\n");
    }
    
    void loop()
    {
       Serial.print("H2:"); 
       Serial.print(MQGetGasPercentage(MQRead(MQ_PIN)/Ro,GAS_H2) );
       Serial.print( "ppm" );
       Serial.print("\n");
       delay(200);
    }
    
    /****************** MQResistanceCalculation ****************************************
    Input:   raw_adc - raw value read from adc, which represents the voltage
    Output:  the calculated sensor resistance
    Remarks: The sensor and the load resistor forms a voltage divider. Given the voltage
             across the load resistor and its resistance, the resistance of the sensor
             could be derived.
    ************************************************************************************/ 
    float MQResistanceCalculation(int raw_adc)
    {
      return ( ((float)RL_VALUE*(1023-raw_adc)/raw_adc));
    }
    
    /***************************** MQCalibration ****************************************
    Input:   mq_pin - analog channel
    Output:  Ro of the sensor
    Remarks: This function assumes that the sensor is in clean air. It use  
             MQResistanceCalculation to calculates the sensor resistance in clean air 
             and then divides it with RO_CLEAN_AIR_FACTOR. RO_CLEAN_AIR_FACTOR is about 
             10, which differs slightly between different sensors.
    ************************************************************************************/ 
    float MQCalibration(int mq_pin)
    {
      int i;
      float val=0;
      
      for (i=0;i<CALIBARAION_SAMPLE_TIMES;i++) {            //take multiple samples
        val += MQResistanceCalculation(analogRead(mq_pin));
        delay(CALIBRATION_SAMPLE_INTERVAL);
      }
      val = val/CALIBARAION_SAMPLE_TIMES;                   //calculate the average value
      
      val = val/RO_CLEAN_AIR_FACTOR;                        //divided by RO_CLEAN_AIR_FACTOR yields the Ro 
                                                            //according to the chart in the datasheet 
     
      return val; 
    }
    /*****************************  MQRead *********************************************
    Input:   mq_pin - analog channel
    Output:  Rs of the sensor
    Remarks: This function use MQResistanceCalculation to caculate the sensor resistenc (Rs).
             The Rs changes as the sensor is in the different consentration of the target
             gas. The sample times and the time interval between samples could be configured
             by changing the definition of the macros.
    ************************************************************************************/ 
    float MQRead(int mq_pin)
    {
      int i;
      float rs=0;
    
      for (i=0;i<READ_SAMPLE_TIMES;i++) {
        rs += MQResistanceCalculation(analogRead(mq_pin));
        delay(READ_SAMPLE_INTERVAL);
      }
      
      rs = rs/READ_SAMPLE_TIMES;
     
      return rs;  
    }
    
    /*****************************  MQGetGasPercentage **********************************
    Input:   rs_ro_ratio - Rs divided by Ro
             gas_id      - target gas type
    Output:  ppm of the target gas
    Remarks: This function passes different curves to the MQGetPercentage function which 
             calculates the ppm (parts per million) of the target gas.
    ************************************************************************************/ 
    int MQGetGasPercentage(float rs_ro_ratio, int gas_id)
    {
      if ( gas_id == GAS_H2) {
         return MQGetPercentage(rs_ro_ratio,H2Curve);
      }  
      return 0;
    }
    
    /*****************************  MQGetPercentage **********************************
    Input:   rs_ro_ratio - Rs divided by Ro
             pcurve      - pointer to the curve of the target gas
    Output:  ppm of the target gas
    Remarks: By using the slope and a point of the line. The x(logarithmic value of ppm) 
             of the line could be derived if y(rs_ro_ratio) is provided. As it is a 
             logarithmic coordinate, power of 10 is used to convert the result to non-logarithmic 
             value.
    ************************************************************************************/ 
    int  MQGetPercentage(float rs_ro_ratio, float *pcurve)
    {
      return (pow(10, (((log(rs_ro_ratio)-pcurve[1])/pcurve[2]) + pcurve[0]))); 
    }
    
    [URL="http://server4.eca.ir/eshop/000/arduino/mq-8/"][COLOR=#0000cd][/COLOR][SIZE=5][COLOR=#0000cd]لینک دانلود پروژه[/COLOR][/SIZE][/URL]
    
    [/CPP]
    لینک دانلود پروژه
    جدیدترین ویرایش توسط ali_ezzati; ۱۰:۱۸ ۱۳۹۵/۰۷/۱۹.
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