Grove-Dust-Sensor // Seeed Studio
**cat meowing is our pet in the background / it is not affecting the LEDs/circuit, rather this is testing the EPA tutorial with the Grove Dust Sensor. Each LED represents a certain threshold of particulate matter, red = a concerning density amount for long term exposure
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Review of unsigned long:
Parts needed:
Arduino code:
Dust Sensor + Arduino:
int PM=8;//tell the arduino which pin you are plugging the PM sensor into
//tell the arduino which pin you are pluggin the LEDs into
int LED1=3;
int LED2=4;
int LED3=5;//could easily modify to use more LEDs
//Amount of time the sensor collects data before displaying the results in milliseconds
//For PM sensor accuracy should be 30 s or greater (accuracy not important for this application)
unsigned long sampletime_ms = 5000;//unisigned long is the type of number you will be entering lets the computer know how much space it needs to store it (think decimals, whole numbers, etc)
//Define additional Variables
unsigned long duration;
unsigned long starttime;
unsigned long lowpulseoccupancy = 0;
unsigned long timediff;
float ratio = 0;
void setup(){
Serial.begin(9600);//start communication with computer
//(not necessary just for error checking or code modification)
pinMode(LED1,OUTPUT);//Define the LEDs as outputs
pinMode(LED2,OUTPUT);
pinMode(LED3,OUTPUT);
pinMode(PM,INPUT);
starttime = millis(); //set the start time of the PM measurement
//(millis() gives the time since the program started)
Serial.println(“BUILD YOUR OWN SENSOR INITIALIZING“);//Prints to the computer screen
}
void loop (){
//duration: waits for pin to go LOW, starts timing, then waits for the pin to go HIGH and stops timing
//Returns the length of the pulse in microseconds, gives up and returns 0 if no pulse starts within a specified time out
//works well for pulses from 10 microseconds to 3 minutes in length
duration = pulseIn(PM, LOW);
lowpulseoccupancy = lowpulseoccupancy+duration; //the lowpulse occupancy is the sum of all the durations
if ((millis()-starttime) > sampletime_ms){//following code executed if the sampletime specified has passed
ratio = lowpulseoccupancy/(sampletime_ms*10.0); // Integer percentage 0=>100
Serial.println(ratio); //print value to computer screen
if (ratio<15){ //if “low concentration” PM light up 1 LED
//- numbers selected based on experimentation not actual concentration values
digitalWrite(LED1, HIGH);
digitalWrite(LED2, LOW);
digitalWrite(LED3, LOW);
}
else if(ratio<20){ //if “moderate concentration” PM light up 2 LEDs
digitalWrite(LED1, HIGH);
digitalWrite(LED2, HIGH);
digitalWrite(LED3,LOW);
}
else{//”high concentration” light up all 3 LEDs
digitalWrite(LED1, HIGH);
digitalWrite(LED2, HIGH);
digitalWrite(LED3, HIGH);
}
lowpulseoccupancy = 0;//reset lowpulse
starttime=millis();//reset the start time of this PM measurement
}
}
Testing Neopixels
30 KM/s 