DIY Arduino Weather Station

( Thanks to @jefpatat for the suggestion of adding this pic!!)

Repository

https://github.com/fillerInk/Arduino-Weather-Station

Overview

At times when the weather is constantly changing every moment, it would be really useful to have your favourite microcontroller board telling you the weather and the weather to come.

In this article, we will go through how to make your own weather station, which updates you with temperature and humidity, which shows you the humidity, temperature and heat index, in both Celsius and Fahrenheit.

How it works?

We will use a DHT11 humidity sensor along with our Arduino and oled screen. There will be a push button which is programmed to switch the information in the display between Celsius and Fahrenheit. The humidity and the temperature values can be read from the humidity sensor.

For the module to work, you’ll need to install a library (the link to the GitHub repository is given below). After the library is installed, you can create an object of the DHT class and use the pre-defined functions of those class such as readTemperature() and readHumidity().

Components needed

1.Arduino Uno / Pro-Mini

I used a Pro-Mini to pack up the entire circuit into a smaller package, but more on that later.

(The Arduino Pro-Mini and a USB-Serial converter which I used to program it)

2.OLED Display

3.DHT11 Humidity Sensor

4.10k resistor

5.Momentary pushbutton switch

Additional components

You will also need these components if you want to compactify the project and make it as a standalone model.

7.SPDT toggle switch ( for turning the module on and off)

8.A Li-Po battery or even some 3v coin cells

(If a LiPo cannot provide the required voltage, you may have to use a larger one, or even another power source. Choose a power source suitable for the board you are using.)

9.An enclosure for the circuit

You can either 3D print this, or as I did, make a cardboard enclosure.

Wiring Diagram

Connect a 10k ohm resistor between the power and signal pins.

Explanation for the code

#include "DHT.h" 
#define DHTPIN 2 
#define DHTTYPE DHT11
DHT dht(DHTPIN,DHTTYPE);

Here we declare the DHT class.
We define the pin to which we connect the signal pin of the humidity module as DHTPIN.
I am using a DHT11 module. So I declare that as DHTTYPE and declare the DHT object.

 dht.begin();  

Inside the setup() function, we need to start the DHT module.
We do this with the objectName.begin() command.

boolean state;

In order to have the push button switch between Fahrenheit and Celsius, we first declare a variable of boolean type, outside the setup and loop methods.

In the next part, we'll see how to use this variable along with some ifs and else-ifs to switch between the formats.

int buttonPin = 7;
pinMode(buttonPin,INPUT_PULLUP);

When we declare the button as INPUT_PULLUP, we activate the internal pullup resistor. Now, when the button is pressed, it will return a value of LOW.

 int mode = digitalRead(buttonPin);

First read the button and store the state in a variable.

if(mode == LOW)                        
  {
    state = !state;
  }

Now if the button is pressed, the state variable gets changed from true to false.

When you push it again, the state variable reverts again.

Now we can easily implement an if-else chain to check the value of the state variable and run two different pieces of code for each state.

 if(state == HIGH)                          
 {
      t = dht.readTemperature();               
      hi = dht.computeHeatIndex(t, h, false);  
 }

  else if(state == LOW)                 
  {
     t = dht.readTemperature(true);       
     hi = dht.computeHeatIndex(t, h);    
  }

In this snippet of code, we check the value of the state variable and execute the code for displaying celsisus and fahrenheit values of the temperatures and heat indices.

The entire code :-

#include<SPI.h>
#include<Adafruit_GFX.h>
#include<Adafruit_SSD1306.h>

#include "DHT.h" 
#define DHTPIN 2 
#define DHTTYPE DHT11
DHT dht(DHTPIN,DHTTYPE);

int buttonPin = 7;


//If you are using an SPI oled module, uncomment this block of code and connect accordingly
/*
#define oled_mosi 11
#define oled_clk 10
#define oled_dc 13
#define oled_reset 12
#define oled_cs 2
Adafruit_SSD1306 oled(oled_mosi,oled_clk,oled_dc,oled_reset,oled_cs);
*/

//If you are using an I2C oled module, uncomment this block of code and connect accordingly
/*
 * Connect the SCl and SDA pins to the respective SCL and SDA pins of your board
 * 
 * #define OLED_RESET 4
   Adafruit_SSD1306 oled(OLED_RESET);
 */


boolean state;



void setup() {
  
 
 oled.begin(SSD1306_SWITCHCAPVCC);
 oled.clearDisplay();
 oled.setTextColor(WHITE);
 oled.setTextSize(1);

 pinMode(buttonPin,INPUT_PULLUP);
 
 dht.begin();                        // this command initializes the dht module

 

}

void loop() {
 
  
  oled.clearDisplay();
  
  float h = dht.readHumidity();
  float t;
  float hi;
 
  int mode = digitalRead(buttonPin);    //read the pushbutton

 if(mode == LOW)                        //change the state variable if there is a change in pushbutton
  {
    state = !state;
  }

  if(state == HIGH)                          //if state is high, display in celcius
 {
    t = dht.readTemperature();               //this function displays temperature in celsius
    hi = dht.computeHeatIndex(t, h, false);  //this function displays heat index in celsius

  }
  else if(state == LOW)                 //if state is low, display in fahrenheit
  {
   t = dht.readTemperature(true);       //if true is passed as an argument, returns temperature in fahrenheit
    hi = dht.computeHeatIndex(t, h);    // if false is not passed as an additionalargument, returns heat index in fahrenheit
  }

  oled.setCursor(1,1);
  oled.print("Humidity    : ");
  oled.print(h);
  oled.print(" %");
  oled.setCursor(1,11);
  oled.print("Temperature : ");
  oled.print(t);

  if(state == HIGH)                    // the same conditionals as above, to display the units of temperature
    oled.print(" C");
  else if(state == LOW)
    oled.print(" F"); 

  oled.setCursor(1,21);
  oled.print("Heat Index  : ");
  oled.print(hi);  

  if(state == HIGH)                   // the same conditionals as above, to display units of heat index
   oled.print(" C");
  else if(state == LOW)
    oled.print(" F"); 

  oled.display();

  delay(1000);
 
}

Result

The circuit wired up in the breadboard.

This is an early implementation of the project where I had not included the switching function and the heat index variable.

Unfortunately my oled screen was burnt while I was doing some soldering work after completing the project.

Conclusion

Overall, it was really a fun project. I made a few mistakes in the beginning, but cleared them up later. I was able to learn a lot. I finally uploaded the code into my Arduino Pro-Mini, a toggle switch to power it on and off, and shrinkified my project. It also looks cute now.

Resources

1.GitHub repository for the DHT Library

https://github.com/adafruit/DHT-sensor-library

2.GitHub repository for the Adafruit_Sensor Library, to be installed with the DHT library

https://github.com/adafruit/Adafruit_Sensor

3.The DHT Guide from Adafruit

https://learn.adafruit.com/dht/overview

Sources -

All the images provided and the code is my own creation.
The wiring diagram was made with fritzing.