Electronics_Projects_2018/Air_Quality_Sensor_PPD42/code/sensortest/sensortest.ino

#include <math.h>

int DustSensePin = 13;

//let's start with 100 readings. (copy and paste)
unsigned int airreading[100] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
unsigned long starttime = 0;
unsigned long sampletime_ms = 60000;//sample 60s == 60000 ;
unsigned long lowpulseoccupancy = 0;
float ratio = 0;
float concentration = 0;
unsigned int x = 0;
unsigned int toplimit = 0;
unsigned long sum = 0; //highest number possible - 32 bit unsigned, so 4 billion
unsigned int average = 0;


void setup() 
{
    Serial.begin(9600);
    Serial.println("Starting Air Sensor, please wait for readings...");
    pinMode(DustSensePin,INPUT);
    starttime = millis();//get the current time;
}

void loop() 
{

    airreading[x] = pulseIn(DustSensePin, LOW, 500000);
    
    /*lowpulseoccupancy = lowpulseoccupancy+duration;

    if ((millis()-starttime) > sampletime_ms)//if the sample time == 30s
    {
        ratio = lowpulseoccupancy/(sampletime_ms*10.0);  // Integer percentage 0=>100
        concentration = 1.1*powf(ratio,3)-3.8*powf(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();
    }
    */
    //if ((millis()-starttime) > sampletime_ms){
      
      //KISS. Relative readings only.
      //Something else keeps the time.
      if (airreading[x] != 0){
        Serial.println(airreading[x]);
        x=x+1;
          if(x>100){
            x = 0;
          }
      }
     
      //starttime = millis();
    //}
    
    
    //KISS. Average for a minute, and store that data in a webpage (that part will be in ethernet sensor test 3). 
    //
    if ((millis()-starttime) > sampletime_ms){
      toplimit = x; // don't read the zeros
      
      
      if(toplimit == 0){
      toplimit = 1; //to avoid divide by zero, in case sum / toplimit is both zero
      }
      
      for (x=0; x<toplimit; x++){
        sum = sum + airreading[x];
        
      }
      average = sum / toplimit;
      Serial.print("Average Get!:  ");
      Serial.println(average); //average when 0 is 65535, so it's invalid (dividing by zero  - sum divided by top limit which are both zero)
                                 //but we don't even want the average. It's just for testing here.
      Serial.print("Sum Get!:  ");
      Serial.println(sum); //this is what we care about
      
      //reset everything after a minute
      sum = 0;
      average = 0;
      x = 0;
      toplimit = 0;
      for (x=0; x<toplimit; x++){
        airreading[x] = 0;
      }
      starttime = millis();
    }
}