Hi,
I am trying to get this air quality sensor to work with a photon. These are my connections. It compiles and flashes, but the readings are just 0. Has anyone used one before and can help. It it for university and I can’t get any help because my university is closed and I am working from home. thanks
Particle Photon ==> PPD42NJ sensor (placed in vertical direction)
GND ==> Pin1 (GND)
D6 ==> Pin2 (Output)
Vin ==> Pin3 (5V)
GND ==> Pin5 (Input)
int SensorPin = D6; // reads data from the sensor
int REDled = D1; // RED
int GREENled = D2; //GREEN
int BLUEled = D3; //BLUE
unsigned long starttime;
unsigned long sampletime_ms = 30000; //Length of sampling time before it reports. 30,000=30 sec. You can change this
unsigned long triggerOnP2;
unsigned long triggerOffP2;
unsigned long pulseLengthP2;
unsigned long durationP2;
boolean valP2 = HIGH;
boolean triggerP2 = false;
double ratioP2 = 0; // start the code with the ratio set to 0. This clears any previous data
double PM25 = 0; // start the code with the PM25 set to 0. This clears any previous data
String colour; // tells the color
String category; // tells the category of air
//used to control the wifi if being used in an area where there is no wifi
const uint32_t msRetryTime = 30000; // stop trying to connect to the internet after 30sec of boot up
SYSTEM_MODE(SEMI_AUTOMATIC)
SYSTEM_THREAD(ENABLED)
// end of Wifi checking
TCPClient client;
#define THINGNAME "AirQualDev" // Name you give to your device on dweet.io Don't use spaces.
void setup()
{
pinMode(REDled, OUTPUT);
pinMode(GREENled, OUTPUT);
pinMode(BLUEled, OUTPUT);
pinMode(SensorPin,INPUT);
starttime = millis();//millis() is the on chip timer that starts running when the program starts running.
//Tells you how many milliseconds since the program started
Particle.connect(); //if it can't connect to the internet in 30 seconds of booting up it will turn the Wifi off and keep running
if (!waitFor(Particle.connected, msRetryTime))
WiFi.off(); // if the wifi comes back it will not turn the wifi on the photon. You must reset it to get it back on wifi.
delay(120000); //this delays the sensor for 2 minutes while it warms up
}
void loop(){
valP2 = digitalRead(SensorPin);
if(valP2 == LOW && triggerP2 == false){
triggerP2 = true;
triggerOnP2 = micros();
}
if (valP2 == HIGH && triggerP2 == true){
triggerOffP2 = micros();
pulseLengthP2 = triggerOffP2 - triggerOnP2;
durationP2 = durationP2 + pulseLengthP2;
triggerP2 = false;
}
if ((millis() - starttime) > sampletime_ms) { //if the difference between what time it is right now and when this sample started is greater than our sample time
//than end this sample and report the data.
ratioP2 = durationP2/(sampletime_ms*10.0); // percentage 0=>100 Percent of time this pin was triggered during sampling.
//a higher ratio tells dirtier air.
PM25= ratioP2 * ratioP2 * .1809 + 3.8987 * ratioP2; //This is the calibration between the ratio and PM25 in ug/m3
//this section controls what color the LED is at on different PM25 levels.
if (PM25 < 10)
{
digitalWrite(REDled, LOW);
digitalWrite(GREENled, HIGH);
digitalWrite(BLUEled, LOW);
colour = "Green";
category = "Good";
}
if (PM25 < 20 && PM25 > 10)
{
digitalWrite(REDled, LOW);
digitalWrite(GREENled, HIGH);
digitalWrite(BLUEled, HIGH);
colour = "Cyan";
category = "Satisfactory";
}
if (PM25 < 30 && PM25 > 20)
{
digitalWrite(REDled, LOW);
digitalWrite(GREENled, LOW);
digitalWrite(BLUEled, HIGH);
colour = "Blue";
category = "Moderately satisfactory";
}
if (PM25 < 40 && PM25 > 30)
{
digitalWrite(REDled, HIGH);
digitalWrite(GREENled, LOW);
digitalWrite(BLUEled, HIGH);
colour = "Magenta";
category = "Poor";
}
if (PM25 < 100 && PM25 > 40)
{
digitalWrite(REDled, HIGH);
digitalWrite(GREENled, LOW);
digitalWrite(BLUEled, LOW);
colour = "Red";
category = "Very poor";
}
if (PM25 > 100)
{
digitalWrite(REDled, HIGH);
digitalWrite(GREENled, HIGH);
digitalWrite(BLUEled, HIGH);
colour = "Black";
category = "Severe";
}
//ends the LED control section
Particle.publish("colour", String(colour));
delay(2000);
Particle.publish("PM25", String(PM25));
delay(2000);
Particle.publish("ratioP2", String(ratioP2));
delay(2000);
Particle.publish("category", String(category));
delay(2000);
// Starts the section that will publish the results to DWEET
if (client.connect("dweet.io", 80))
// Go to http://dweet.io/follow/thingname to see the results in your browser. change "thingname" to your thingname in the web address.
{
client.print("GET /dweet/for/");
client.print(THINGNAME);
client.print("?ratioP2="); // Don't use spaces for data names
client.print(ratioP2);
client.print("&PM25="); // Don't use spaces for data names
client.print(PM25);
client.println(" HTTP/1.1");
client.println("Host: dweet.io");
client.println("Connection: close");
client.println();
}
// ends publishing to DWEET
durationP2 = 0; //resets the lowpulseoccupancy back to zero to start the next sample
starttime = millis(); // set the start time to what time it is now.
// go back to the top of the loop and start sampling again
}
}
