เซนเซอร์วัดฝุ่น PM 2.5 ยี่ห้อ SAMYONG รุ่น DSM501A

/* 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(8,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("concentration = ");
Serial.print(concentration);
Serial.println(" pcs/0.01cf");
Serial.println("\n");
lowpulseoccupancy = 0;
starttime = millis();
}
}