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MQ-2 Smoke LPG CO Gas Sensor Module for Arduino or MCUs

$8.55

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Product Description

This sensor module has an MQ-2 as the sensor component and has a protection resistor and an adjustable resistor on-board. The MQ-2 gas sensor is sensitive to LPG, i-butane, propane, methane, alcohol, Hydrogen and smoke. It could be used in gas leakage detecting equipments in family and industry. The resistance of the sensitive component changes as the concentration of the target gas changes. For more details, please click HERE for product datasheet.

Features

Continuous Analog output
3-pin interlock connector
Low cost and compact size
In the Package

An assembled MQ-2 sensor module
A 3-pin 25cm cable (with interlock connector on one end, free on the other)
 
Technical Specification

A. Standard Working Condition

Symbol Parameter Name Technical Condition Remarks
VC Circuit voltage 5V±0.1 AC or DC
VH Heating voltage 5V±0.1 AC or DC
RL Load resistance adjustable  
RH Heater resistance 33Kohm±5% Room temperature
PH Heating consumption Less than 800mW  

B. Environment Condition

Symbol Parameter Name Technical Condition Remarks
TO Operating Temp. -20°C-50°C  
TS Storage Temp. -20°C-70°C  
RH Relative Humidity <95%  
O2 Oxygen Concentration 21%(standard condition) Oxygen concentration can affect sensitivity Minimum value is 2%

C. Sensitivity Characteristics

Symbol Parameter Name Technical Condition Remarks
RS Sensor Resistance 3Kohm-30Kohm (1000ppm iso-butane) Detecting concentration scope:
200ppm-5000ppm LPG and propane
300ppm-5000ppm butane
5000ppm-20000ppm methane
300ppm-5000ppm H2
100ppm-2000ppm Alcohol
? (3000ppm/1000ppm iso-butane) Concentration slope rate ?0.6
Standard detecting Condition Temp.: 20°C±2°C VC: 5V±0.1
Humidity:65%±5% VH:5V±0.1
Preheating Time Over 24 hours


Sample Code for Arduino

 Demo for MQ-2 Gas Sensor Module V1.0

Author:  Tiequan Shao: tiequan.shao[at]sandboxelectronics.com
         Peng Wei:     peng.wei[at]sandboxelectronics.com
        
Lisence: Attribution-NonCommercial-ShareAlike 3.0 Unported (CC BY-NC-SA 3.0)

Note:    This piece of source code is supposed to be used as a demostration ONLY. More
         sophisticated calibration is required for industrial field application.
        
                                                    Sandbox Electronics    2011-04-25
************************************************************************************/

/************************Hardware Related Macros************************************/
#define         MQ_PIN                       (0)     //define which analog input channel you are going to use
#define         RL_VALUE                     (5)     //define the load resistance on the board, in kilo ohms
#define         RO_CLEAN_AIR_FACTOR          (9.83)  //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_LPG                      (0)
#define         GAS_CO                       (1)
#define         GAS_SMOKE                    (2)


/*****************************Globals***********************************************/
float           LPGCurve[3]  =  {2.3,0.21,-0.47};   //two points are taken from the curve.
                                                    //with these two points, a line is formed which is "approximately equivalent"
                                                    //to the original curve.
                                                    //data format:{ x, y, slope}; point1: (lg200, 0.21), point2: (lg10000, -0.59)
float           COCurve[3]  =  {2.3,0.72,-0.34};    //two points are taken from the curve.
                                                    //with these two points, a line is formed which is "approximately equivalent"
                                                    //to the original curve.
                                                    //data format:{ x, y, slope}; point1: (lg200, 0.72), point2: (lg10000,  0.15)
float           SmokeCurve[3] ={2.3,0.53,-0.44};    //two points are taken from the curve.
                                                    //with these two points, a line is formed which is "approximately equivalent"
                                                    //to the original curve.
                                                    //data format:{ x, y, slope}; point1: (lg200, 0.53), point2: (lg10000,  -0.22)                                                    
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("LPG:");
   Serial.print(MQGetGasPercentage(MQRead(MQ_PIN)/Ro,GAS_LPG) );
   Serial.print( "ppm" );
   Serial.print("    ");  
   Serial.print("CO:");
   Serial.print(MQGetGasPercentage(MQRead(MQ_PIN)/Ro,GAS_CO) );
   Serial.print( "ppm" );
   Serial.print("    ");  
   Serial.print("SMOKE:");
   Serial.print(MQGetGasPercentage(MQRead(MQ_PIN)/Ro,GAS_SMOKE) );
   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_LPG ) {
     return MQGetPercentage(rs_ro_ratio,LPGCurve);
  } else if ( gas_id == GAS_CO ) {
     return MQGetPercentage(rs_ro_ratio,COCurve);
  } else if ( gas_id == GAS_SMOKE ) {
     return MQGetPercentage(rs_ro_ratio,SmokeCurve);
  }   
 
  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,( ((rs_ro_ratio-pcurve[1])/pcurve[2]) + pcurve[0])));
}


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  • Model: SH460415
  • Shipping Weight: 70 gram