sharp_pm2_5_wrapup.ino

#include <Arduino.h> 


/* -------------------------------------------------------------------------- */
/*                               PM2.5 Variable                               */
/* -------------------------------------------------------------------------- */


    // Choose program options.
    //#define PRINT_RAW_DATA  //uncomet if you wont raw data displayed in serial monitor
    #define USE_AVG //calculate average value in N mesared values

    // Arduino pin numbers.
    const int sharpLEDPin = 7; // Arduino digital pin 7 connect to sensor LED.
    const int sharpVoPin = A0; // Arduino analog pin 5 connect to sensor Vo.

    // For averaging last N raw voltage readings.
    #ifdef USE_AVG
    #define N 100
    static unsigned long VoRawTotal = 0;
    static int VoRawCount = 0;
    #endif // USE_AVG

    // Set the typical output voltage in Volts when there is zero dust.
    static float Voc = 0.6;  //Voc is 0.6 Volts for dust free acordind sensor spec
    static float VocT = 0.6; //Self calibration overvrite the Coc with minimum measered value - this variable you need to have the treshold for the sensor  (facturi calibration)

    // Use the typical sensitivity in units of V per 100ug/m3.
    const float K = 0.5;

    /////////////////////////////////////////////////////////////////////////////

 
void setup()

{

  Serial.begin(115200);

  /* ---------------------------- Start sharp pm2.5 --------------------------- */

    pinMode(sharpLEDPin, OUTPUT);
    VocT = Voc; //corect the VocT (to have alwas data for the initioal Voc

 
  /* ------------------------------ Start system ------------------------------ */

    Serial.println("Dust(ug/m3)");  
}



void loop()

{


  /* --------------------------- Correct data PM2.5 --------------------------- */
 
    
    digitalWrite(sharpLEDPin, LOW);       // Turn on the dust sensor LED by setting digital pin LOW.
    delayMicroseconds(280);               // Wait 0.28ms before taking a reading of the output voltage as per spec.
    int VoRaw = analogRead(sharpVoPin);   // Record the output voltage. This operation takes around 100 microseconds.
    digitalWrite(sharpLEDPin, HIGH);      // Turn the dust sensor LED off by setting digital pin HIGH.
    delayMicroseconds(9620);              // Wait for remainder of the 10ms cycle = 10000 - 280 - 100 microseconds.

  
    // Use averaging if needed.
    float Vo = VoRaw; 
    VoRawTotal += VoRaw;
    VoRawCount++;
    if (VoRawCount >= N)
    {
      Vo = 1.0 * VoRawTotal / N;
      VoRawCount = 0;
      VoRawTotal = 0;
    }
    else
    {
      return;
    } 

    // Compute the output voltage in Volts.
    Vo = Vo / 1024.0 * 5.0;

    //------------ Dust density calculated by Voc set in the begining - like in sensor spec  ------------
    // Calculate Dust Density in units of ug/m3 for the initial Voc (as in sensor specs)
    float dV = Vo - VocT;
    if (dV < 0)
    {
      dV = 0;
    }
    float dustDensity = dV / K * 100.0; 
  

    dV = 0;                                         // Reset the dV to 0 for the next calculation
    dustDensity = 0;                                // Reset the dustDensity to 0 for the next calculation

    //------------ Dust density calculated by lowest output voltage during runtime  ------------
    // Convert to Dust Density in units of ug/m3.
    // During runtime, the Voc value is updated dynamically whenever a lower output voltage is sense.
    // this cover the dust sensing below the sensors specefied range from 0 to Voc (0,6V) as specified in the beginin
    dV = Vo - Voc;
    if (dV < 0)
    {
      dV = 0;
      Voc = Vo;
    }
    dustDensity = dV / K * 100.0;
  







  /* --------------------------------- Output --------------------------------- */

    String dataPack="";
    dataPack = String(dustDensity)+"\n";
  
    Serial.print(dataPack);

}