Grove_Dust_Sensor.ino

/* 
 Grove - Dust Sensor Demo v1.0
 Interface to Shinyei Model PPD42NS Particle Sensor
 Program by Christopher Nafis 
 Written April 2012
 
 http://www.seeedstudio.com/depot/grove-dust-sensor-p-1050.html
 http://www.sca-shinyei.com/pdf/PPD42NS.pdf
 
 JST Pin 1 (Black Wire)  => Arduino GND
 JST Pin 3 (Red wire)    => Arduino 5VDC
 JST Pin 4 (Yellow wire) => Arduino Digital Pin 8
*/

int pin = 8;
unsigned long duration;
unsigned long starttime;
unsigned long sampletime_ms = 30000;//sampe 30s ;
unsigned long lowpulseoccupancy = 0;
float ratio = 0;
float concentration = 0;

void setup() 
{
    Serial.begin(9600);
    pinMode(pin,INPUT);
    starttime = millis();//get the current time;
}

void loop() 
{
    duration = pulseIn(pin, LOW);
    lowpulseoccupancy = lowpulseoccupancy+duration;

    if ((millis()-starttime) > sampletime_ms)//if the sampel time == 30s
    {
        ratio = lowpulseoccupancy/(sampletime_ms*10.0);  // Integer percentage 0=>100
        concentration = 1.1*pow(ratio,3)-3.8*pow(ratio,2)+520*ratio+0.62; // using spec sheet curve
        Serial.print(lowpulseoccupancy);
        Serial.print(",");
        Serial.print(ratio);
        Serial.print(",");
        Serial.println(concentration);
        lowpulseoccupancy = 0;
        starttime = millis();
    }
}