Components Required – 

Fig. 3: Block Diagram of Particle Photon and Blynk based IOT Weather Monitoring System

Circuit Connections – 

Particle Photon – Photon is a popular IOT board available from the Particle platform. The board houses STM32F205 120Mhz ARM Cortex M3 microcontroller and has 1 MB flash memory, 128 Kb RAM and 18 mixed signal general purpose input output (GPIO) pins with advanced peripherals. The module has on-board Cypress BCM43362 Wi-Fi chip for Wi-Fi connectivity and Single band 2.4GHz IEEE 802.11b/g/n for Bluetooth. The board comes equipped with 2 SPI, one I2S, one I2C, one CAN and one USB interface. The particle Photon has the following pin configuration – 

The data is displayed on the app in real-time and gets updated in every 2 seconds. Check out the program code to learn how Photon reads temperature and humidity from DHT-11 sensor and send it to the Blynk App. 

//Program to 

// This #include statement was automatically added by the Particle IDE.

#include 


// This #include statement was automatically added by the Particle IDE.

#include 


#define BLYNK_PRINT Serial  // Set serial output for debug prints

//#define BLYNK_DEBUG       // Uncomment this to see detailed prints


#include 



#define DHTTYPE DHT11

#define DHTPIN 4

#define DHT_SAMPLE_INTERVAL 60000


LiquidCrystal lcd(6, 5, 0, 1, 2, 3);



void dht_wrapper(); // must be declared before the lib initialization


// Lib instantiate

PietteTech_DHT DHT(DHTPIN, DHTTYPE, dht_wrapper);


// globals

unsigned int DHTnextSampleTime;     // Next time we want to start sample

bool bDHTstarted;     // flag to indicate we started acquisition

int n;                              // counter


//this is coming from http://www.instructables.com/id/Datalogging-with-Spark-Core-Google-Drive/?ALLSTEPS

char resultstr[64]; //String to store the sensor data


// You should get Auth Token in the Blynk App.

// Go to the Project Settings (nut icon).

char auth[] = "0395c08357fd480ba67b172ccdfa7039";


// Attach a Button widget (mode: Switch) to the Digital pin 7 - and control the built-in blue led.

// Attach a Graph widget to Analog pin 1

// Attach a Gauge widget to Analog pin 2


char VERSION[64] = "0.04";


void setup()

{

    Serial.begin(9600);

    

    lcd.begin(16,2);


   lcd.setCursor(0,0);

   lcd.print("IoT Weather");

   lcd.setCursor(0,1);

   lcd.print("  Monitoring   ");

   delay(2000);

   lcd.clear();

   lcd.setCursor(0,0);

   lcd.print("ENGINEERS GARAGE");

   delay(2000);

   lcd.clear();

     

    delay(5000); // Allow board to settle

    

    DHTnextSampleTime = 0;  // Start the first sample immediately

    Particle.variable("result", resultstr, STRING);


    Particle.publish("DHT11 - firmware version", VERSION, 60, PRIVATE);


    Blynk.begin(auth);

}


void dht_wrapper()

{

    DHT.isrCallback();

}


void loop()

{

    Blynk.run();

    

     if (millis() > DHTnextSampleTime) {

      

if (!bDHTstarted) { // start the sample

    DHT.acquire();

    bDHTstarted = true;

}

    

    if (!DHT.acquiring()) { // has sample completed?


  float temp = (float)DHT.getCelsius();

  int temp1 = (temp - (int)temp) * 100;

  

    lcd.clear();

    lcd.setCursor(0,0);

    lcd.print("T:");

    lcd.print((int)temp1);

    lcd.write(1);

    lcd.print("C");


  char tempInChar[32];

  sprintf(tempInChar,"%0d.%d", (int)temp, temp1);

  Particle.publish("The temperature from the dht11 is:", tempInChar, 60, PRIVATE);


  //virtual pin 1 will be the temperature

  Blynk.virtualWrite(V1, tempInChar);


  //google docs can get this variable

  sprintf(resultstr, "{"t":%s}", tempInChar);


  float humid = (float)DHT.getHumidity();

  int humid1 = (humid - (int)humid) * 100;

  

    lcd.clear();

    lcd.setCursor(0,0);

    lcd.print("Humidty:");

    lcd.print((int)humid1);


  sprintf(tempInChar,"%0d.%d", (int)humid, humid1);

  Particle.publish("The humidity from the dht11 is:", tempInChar, 60, PRIVATE);


  //virtual pin 2 will be the humidity

  Blynk.virtualWrite(V2, tempInChar);


  n++;  // increment counter

  bDHTstarted = false;  // reset the sample flag so we can take another

  DHTnextSampleTime = millis() + DHT_SAMPLE_INTERVAL;  // set the time for next sample

 }


}

    delay(2000);

}