Build Your Own Raspberry Pi Weather Station with OpenHAB 2

One of the most popular projects besides home automation and robots is the Raspberry Pi weather station. This can be used in both indoor and outdoor circumstances and can be expanded as required. We either display the data from other devices via a web interface or use the Raspberry Pi touchscreen.

In this tutorial, we will create a functional and expandable weather station that can be called up and controlled using a touchscreen.

Required Hardware Parts For the Raspberry Pi Weather Station

You will need the following hardware parts for the weather station. Individual components can of course also be omitted or added. However, the code must then also be adjusted accordingly.

• Raspberry Pi including a micro SD card and USB power plug
  • alternatively: Raspberry Pi Starter Kit or Sensor Kit (already contains the most important sensors and a display)
• DHT22 sensor for temperature & humidity
• BMP180 air pressure sensor
• Raspberry Pi Touchscreen
  • alternative: LCD Display
• Jumper Cable
• Breadboard

In addition, other sensors such as gas sensors, brightness sensors or wind strength sensors are also an option which can be integrated.

Another option is to use an ESP8266 NodeMCU or Raspberry Pi Zero W as an outpost for the weather station. The display on an LCD is not explicitly dealt with in this tutorial. How to display data on it is explained in more detail in a previous tutorial and can be adjusted if necessary.

 

 

Construction & Wiring

Let’s start with the wiring of all modules. The easiest way is with the official Raspberry Pi touchscreen. This can be connected to the DSI port of the Raspberry Pi using the ribbon cable. It gets power either via the 5V pin or via USB connection. A detailed description can be found here.

Then the sensors are on. These were also discussed in more detail in previous tutorials, but here is the structure again:

The DHT11 sensor is connected to 3.3V and GND as shown in the picture. Now the data pin goes to GPIO23 and at the same time to 3.3V via a 10k Ω resistor.

The BMP180 is only connected to the I2C bus and also gets a connection to 3.3V and GND.

 

Preparation: Installing OpenHAB & packages

We use OpenHAB as the interface, which is generally a very good introduction to home automation. Since it offers different graphical interfaces, it is not necessary that we create our own GUI. We can customize these later.

Therefore, we start to install OpenHAB 2 on the Raspberry Pi. When this is complete, we open http://openhabianpi:8080/paperui/index.html#/extensions and look for the “Exec Binding” package under “Binding”, the “RRD4j Persistence” package under the “Persistence” tabs and under “Transformations” “the” RegEx Transformation “package. All are installed.

Now we log in via SSH and install the required packages for the DHT and BMP180 sensors:

sudo apt-get update
sudo apt-get install build-essential python-dev python3-dev python3-openssl python3-smbus python3-pip i2c-tools git
git clone https://github.com/adafruit/Adafruit_Python_DHT.git && cd Adafruit_Python_DHT
sudo python3 setup.py install
cd ..
git clone https://github.com/adafruit/Adafruit_Python_BMP && cd Adafruit_Python_BMP
sudo python3 setup.py install

If you want to use Python2 instead of Python3, you have to adapt the packages and installation calls accordingly.

Then we have to activate I2C:

sudo raspi-config

We activate it under “Interface Options” -> “I2C” (this can vary from the Raspbian version, but is always included in the raspi-config).

If the BMP sensor is already connected, we can test whether it has already been recognized:

i2cdetect -y 1

The result should look like this:

 0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- 77

 

 

Setting Up the Raspberry Pi Weather Station

The functions that we will use need tools that deliver the data to us. The easiest way to do this is with Python, for which there are many libraries (including those that we have already used and installed). So we start with the main script::

sudo nano /etc/openhab2/scripts/weatherstation.py

It gets the following content:

Save with CTRL + O and return to the shell with CTRL + X (in the next steps as well).

We also have to give this script and the I2C module admin permissions, which we need for the GPIO calls:

sudo chmod +x /etc/openhab2/scripts/weatherstation.py
sudo chmod a+rw /dev/i2c-*

To ensure that the rights for I2C are set permanently, we have it executed every time you reboot. This is done via Crontab:

sudo crontab -e

If you have not yet set up an editor, select 2. nano. Now add the following line at the end and save the file:

@reboot sudo chmod a+rw /dev/i2c-*

 

Now it goes on with the things: For each value (temperature, humidity, air pressure, etc.) we have to create a thing. For this we use the previously installed Exec Add-On, with which we can start shell calls. For the storage we also need “RRD4j Persistence” (under Add-ons -> Persistence). Our Python script takes various parameters and returns corresponding values. We use this:

sudo nano /etc/openhab2/things/weatherstation.things

Next, our items come into play:

sudo nano /etc/openhab2/items/weatherstation.items

In order for the data to be stored permanently (every minute) in the database, we have to indicate this by writing it to a .persist file:

sudo nano /etc/openhab2/persistence/rrd4j.persist

So far we have created two items each. One as a text value from the script and the other as a numerical value, which we can change if necessary. This works with rules:

sudo nano /etc/openhab2/rules/weatherstation.rules

A change via regex values and debug logging is also possible here. In general, other events can be triggered here – for example, that if the temperature becomes over 30 degrees, the fan (if connected) turns on. If you are interested, we can go through and explain such scenarios in future tutorials.

Now we create a nicer view. However, this is not visible with the PaperUI, so we have to use it in the BasicUI:
http://openhabianpi:8080/basicui/app
For this we create a sitemap in which the previous items can be inserted:

sudo nano /etc/openhab2/sitemaps/weatherstation.sitemap

Then update the BasicUI page and select the sitemap “Waiter station”. Here all values and the previous values are now displayed in a table. Since the values are quite different (air pressure ~ 1000 [hPa], temperature 0-30 [° C], air humidity ~ 20-70 [%]), we can also create different graphs/charts or, for example, the unit instead of hPa Use bar.

 

In addition, we could of course also measure the temperature with the BMP180. He can also measure the height (in meters) and the sea level pressure. With the given examples it should be a breeze to expand the files if necessary.

If contrary to expectations, something does not work as it should, a look at the logs often helps. How you can access it is explained in this article (e.g. via Karaf console).

 

Addition: Setting up the Weather forecast via Yahoo!

Our Raspberry Pi weather station should get an additional feature: In addition to the currently measured data, we also want to make predictions for the next day. This feature is optimal, but it does make a difference. We can choose between different providers like Forecast.io, OpenWeatherMap, Yahoo! and much more. Depending on the location, some are more accurate or better suited. Since you need an API key everywhere except for the forecasts from Yahoo, we use this service for the sake of simplicity. Of course, it can also be replaced by another one.

For this, we use the OpenHAB weather binding. Go to “Add-Ons” -> “Bindings” in the PaperUI and install the “Weather Binding”.

We also need a so-called WOEID. You can get the required WOEID number for your city on this website. Find your location and copy the number.

Now we create a configuration file:

sudo nano /etc/openhab2/services/weather.cfg

The following content comes in:

 

Now we have to create corresponding items. To do this, we edit the previously created Things file and add the following lines (forecast = 1 indicates that the values are retrieved for the next day, 2 for the day after next, etc.). We can also create different locations in the configuration file (we only define “home”) and then create items for different locations:

The sitemap also needs to be adjusted:

No other files need to be adjusted because we don’t want to save predictions. If you want to use other icons in the sitemap, you can either upload your own or use the standard icons.

In order to be able to use the entire range of values (wind, clouds, precipitation, snow, perceived outside temperature, fog/visibility, etc.), you can take a look at the other examples.

 

Show Raspberry Pi Weather Station Data on the Touchscreen

Before we start with the installation, the display must be connected and supplied with power.

Since openHAB is based on Raspbian Lite, it has no graphical user interface. To automatically display the web panel on the touchscreen, we first have to install it. We choose the PIXEL surface and the Chromium browser. The installation runs via SSH.

sudo apt-get install --no-install-recommends xserver-xorg --yes
sudo apt-get install --no-install-recommends xinit --yes
sudo apt-get install raspberrypi-ui-mods --yes
sudo apt-get install chromium-browser --yes

We first activate automatic login to the desktop:

sudo raspi-config

Under “Boot Options” -> “Desktop / CLI” -> “Desktop”.

Now we set the automatic login in the GUI:

sudo nano /etc/lightdm/lightdm.conf

We are looking for the line “# autologin-user =” (search is easy with CTRL + W) and remove the diamond at the beginning and set the user “openhabian” at the end so that it looks like this:

autologin-user=openhabian

Save with CTRL + O and go back to the console with CTRL + X.

Now we make sure that the browser with the corresponding page also starts

sudo nano /home/openhabian/.config/lxsession/LXDE-pi/autostart

The following line comes at the very end of the file.

@xset s noblank
@xset s off
@xset -dpms 
@sudo chmod a+rw /dev/i2c-*
@/usr/bin/chromium-browser --kiosk --disable-restore-session-state http://http://openhabianpi:8080/basicui/app?sitemap=weatherstation

We also have to edit another file:

sudo nano /etc/kbd/config

Here the values of the following two entries change to zero:

BLANK_TIME=0
POWERDOWN_TIME=0

After saving, we restart the Raspberry Pi:

sudo reboot

Now the browser is started, but it takes a moment until OpenHAB is started and the panel becomes visible.