OpenWeatherStation (OWS)

The Open Weather Station (OWS) is a do-it-yourself weather station solution that aims to be affordable, stable, easy to build and tested in the wild. Measure, monitor, store months of data and send it to your server as well as Wunderground, Thingspeak, Windguru or OpenWeatherMap via Wifi or GPRS/GSM/4G. It evolved from other approaches I have been testing and using in the field since late 2012 to this day

Eng. Francisco Clariá

OpenWeatherStation Presentation (OWS)

Don't miss the YouTube tutorials!

Take a look at the Youtube tutorials that will walk you through all the steps to get the station ready :)

Table of contents

Latest code release

Access the latest stable release from here (recommended):

To access the most up-to-date (yet not fully tested) project version access the develop branch here:

The Open Weather Station App (Android only) is ready for use for free just install it from the Google Play as any other app. Read more about the app here

Weather data

The information generated by the OWS every minute is the following:


The current implementation is my personal approach to the challenges I have faced during several years of dealing with a lot of unexpected scenarios in the field. Having said that lets understand how this works.

OWS Concept

An Arduino Uno module reads data from sensors and every minute sends a payload of data via bluetooth to a connected device. The “connected device” is an android smartphone running an app that receives this information, stores it in memory, displays the data on the screen and if needed it can send the measures to an external service using out of the box presets supporting Wunderground, Thingspeak, Windguru, OpenWeatherMap or another custom cloud service of your preference either via wifi and/or mobile network - this is one of the primary advantages of using the smartphone. You could also write a Raspberry Pi program to connect to the Arduino via bluetooth to receive the data if the Android app is not suitable for you (at this point the Pi implementation is not in the scope of the project).

Next you can read more about the concepts behind this implementation. Otherwise click here to jump to the assembly instructions.

Motivation and goals

Before the current approach I have programed and tested other alternatives like: raspberry, pic, arduino + wifi shield, arduino + ethernet shield, arduino + GPRs shield, arduino uno + arduino mega, wifi boards, routers, integrated arduino with sd/microsd modules, etc etc etc and finally the current approach turned out to be the most effective for my goals:


I tried to make the price as low as possible so it is not a barrier especially for those in countries where electronics are expensive, currently the total cost is around 300USD to 500USD including sensors, smartphone, housing, etc depending on your location and mostly the smartphone you get

Compact and unattractive to burglary

Usually the station would end up in a rooftop, tower, etc from someone who allowed me to install the device, being it very compact makes it less attractive to thieves, easier to install, looks better and the elements such as wind, rain, hailstones will make less damage. Also as the arduino module connects via bluetooth the smartphone it is connected to can be placed in a safer place like inside the house to prevent theft.

Simple and repeatable to build

Some solutions I evaluated before involved a lot of testing, pre configuration or calibration, complex assembly or even difficulty to get the parts for EVERY station i had to build, current OWS approach reduces that headache a lot

Wifi and cell phone network

By using an android smartphone I have the possibility to connect via wifi and cell phone network as needed to keep updating external services in the cloud. And even more, if the wifi connection is lost it will automatically switch to the cell network without any hassle, no AT commands and weird handshakes to achieve a simple HTTP connection…

Power loss

Electricity goes away many times, specially during storms: the Arduino module can stay on for around a day with a 5000mAh power bank and the cellphone has already batteries on it, so, depending on the model it will work probably for a day or so too, while still being able to send data if the cell network is working (wifi will probably will die in this scenario)

Software stability

Arduino module software is really robust, if it reboots it will restart from scratch without any stuff hanging around, I even added a watchdog to make it reboot if for some reason some process takes more than 4 seconds. In this matter I have tested over long periods of time the sd shields, ethernet, wifi and GPRs shields and ALL of them hang after some weeks or even less, requiring a manual reset and in the case of the SD/memory I even needed to extract the card and insert it back… In the other hand I found after long periods of testing in the wild that Android is rock solid and smartphones (like a moto E/moto G) endurance is amazing, coping with temperatures below 0Cº and over 50Cº, experiencing repeated power loss (until battery drained completely) as well as connectivity loss without hanging at all.

Data visualization and diagnosis

The app allows to both serve as an offline visualization screen or when performing a new installation or maintenance in the field to see what is going on. Sometimes I need to make sure the OWS is working properly especially during a new installation or maintenance, and most of the time I perform this task alone, in a tower or rooftop where its not suitable to take a laptop with me, therefore having the Arduino module connected via bluetooth allows easier diagnosis and with the app running on the smartphone visualization is very easy, comfortable and I don’t need to get the data to the external service to diagnose if its working… its all in the screen

Data log and storage

As mentioned before adding memory to the arduino module was one of the things that increased maintenance requirements for the solution as SD hangs and EEPROM wears out, not to mention that the storage and retrieval of large amounts of data (many days of 1 sample per minute) is a slow and complex process for arduino to properly handle. For this reason the arduino module stores samples for about 15 minutes (configurable) which is the time that eventually android may take to restart if it was off for some reason, and then the android app handles data logging, visualization and upload in a more efficient and stable way while at the same time allowing to store larger periods of time.

Reduced maintenance

It all comes down to reducing implementation and maintenance as much as I could since most stations I installed are located in remote places, where I need to request access to the owner and everything has to be done as fast as possible

Why arduino?

The core reasons I decided to use Arduino are:

Android App

Arduino module connects to an android app via bluetooth. The app can be downloaded for free from Google Play

OpenWeatherStation app

Some of the main OpenWeatherStation App features are:

Initial app setup

Follow the next steps to get started (there is also a video tutorial for this):

If you are using the android device for telemetry you may want to root your device and also install the Remote Reboot app ( This app will act as a watchdog allowing you to reboot Android remotely via SMS or using a URL endpoint so everything can start fresh again.

Connecting other devices

Since the sensing Arduino module transmits the data every minute you could build your own solution that connects to it via bluetooth and process the data as you wish instead of using the proposed android app. For instance a Raspberry implementation could be a great alternative to achieve this, or you could write a Windows 10 application and connect to the module with your computer, just to mention couple examples. This alternatives however are outside the scope of the current project for the time being.

Arduino module assembly

Next I depict some guidelines so you can build your own module step by step.

OWS assembly

Youtube tutorials

In the following videos I walk you through the details to build the station from 0 to 100%:

Schematics diagram

OWS schematics

List of materials

The following is the full list of materials needed to implement the station with all its features. In the next sections I will instruct how to assembly the OWS arduino module considering the ideal scenario with all the components, however the module will still work if you don’t connect all sensors, so, if you only want to measure wind speed for instance you can simply ignore the rain, light or pressure sensors.

Item Quantity Use
Red or Green led 1 status light
18 kOhm resistor 2 anemometer and rain debounce circuit
12 kOhm resistor 2 anemometer and rain debounce circuit
10 kOhm resistor 1 windvane
220 Ohm resistor 1 status led
2.2 kOhm resistor 1 bluetooth
1 kOhm resistor 2 bluetooth
dual rj11 jack (example) 1 anemometer, wind vane and rain cables
diode 2 anemometer and rain debounce circuit
1μF capacitor 2 anemometer and rain debounce circuit
NPN transistor 1 bluetooth
Single side copper PCB 5cm x 7cm or bigger (example) 1 pcb shield to connect components
Arduino Uno R3 along with its USB cable 1 procesing unit
BH1750 Light sensor 1 llight
BME280 pressure, temperature, humidity sensor 1 pressure, temperature, humidity
HC05 Bluetooth module 1 bluetooth communications
WS 1080 replacement anemometer sensor (example) 1 wind speed
WS 1080 replacement wind vane sensor (example) 1 wind direction angle
WS 1080 replacement rain gauge sensor (example) 1 rain
standard male header pins pack (example) 1 connecting sensor wires
standard female header pins pack (example) 1 connecting bluetooth module
female to female jumper wires pack (example) 1 wiring sensors
portable power bank charger 5000mAh or similar that operates without user intervention - must NOT need a button push for it to work 1 OWS power backup for Arduino
15x10x10cm or similar, outdoor plastic housing 1 protect the OWS module from elements
110/220v dual usb wall socket charger module (example) 1 OWS usb power source
110v/220v power cable (example) 1 power
WS 1080 anemometer and wind vane plastic support (example) 1 support for wind sensors
WS 1080 rain gauge plastic support (example) 1 support for rain sensors

Please recall that I have included all components needed for a full OWS Arduino module assembly, you can purcharse only those related to the sensors you want to implement or even build your own if you want to reduce some costs (like the wind and rain plastic supports). The Arduino code implementation will still work if only some sensors are connected.

Soldering and wiring

I have a detailed step by step image galleries that you can use a reference to produce the OWS from zero to 100%:

I will explain aswell how to assembly and arrange the components as a reference for you to start building your own station in the following sections.

PCB Etching

There are several techniques to produce the board circuit, from manually drawing the circuit with a permanent marker to a tone transfer method ( Since there are plenty of videos and tutorials on how to do it I will let you choose the method of your preference. In case you go for the tone transfer method, recall it’s very important to use a photo quality glossy paper.

Any case you can use this PDF sheet or use the next copper circuit image to produce the pcb. Both have a size reference in the left side (50mm) you can use to make sure the printer did not alter its original dimensions and recall also that the circuit has already been mirrored for your convenience.

OWS pcb

PCB Drilling

Once you have the board ready drill the holes (I use a 1mm drill). From the diagram and circuit layout the required holes are pretty much self explanatory.

OWS pcb drilling

Solder surface components

Use the following diagram and the list of components to solder each element to the PCB. There are couple things to keep in mind:

OWS pcb

Item assembly code
18 kOhm resistor R6, R2
12 kOhm resistor R8, R4
10 kOhm resistor R9
220 Ohm resistor R10
2.2 kOhm resistor R11
1 kOhm resistor R12, R13
1μF electrolytic capacitor C1, C2
diode D1, D2
NPN Transistor NPN
male header pins to connect to arduino (solder facing down, to the arduino uno) D2,D3,D9,D10,D12,D13,A2,A4,A5,GND,VCC
male header pins to connect to sensors (solder facing up) anem, pluv, stat, bmp, bht, vane
female header pins to connect to bluetooth (solder facing up) blue

Wire and connect sensors

Once you have soldered all the elements it is time to connect to the sensors.

Wind speed, wind direction and rain

These sensors, which are replacement parts for the WS1080 weather station, use a telephone line (RJ11 plug) that we will interface to the Arduino OWS module using a dual RJ11 jack.

The anemometer and wind vane use one RJ11 connector where the 2 central pins (red and green cables) connect the anemometer and the 2 outer ones (black and yellow) belong to the wind vane. The rain gauge uses its RJ11 central pins (red and green) to connect to the sensor.

In order to connect the RJ11 Jack to the arduino module use the female jumper wires (cut one of the tips to leave the cable exposed) as illustrated in the step by step gallery images.

Pressure, temperature & humidity

These three parameters are obtained using the BME280, beware that there are many places selling the BMP280 as if it was the BME, but the BMP will NOT measure humidity so pay close attention to the chip specs before buying.

Connect the BME chip using the female to female jumper wires to the “bme” male header pin on the module board.


Light amount measured in lux is obtained using the BH1750 sensor. Connect the chip using the female to female jumper wires to the “bht” male header pin on the module board.


The arduino module, as explained before, sends the data using the HC05 Bluetooth module. To connect it to the board simply plug the HC05 to the “blue” female header pins as shown in the gallery.

Status Led

The status led is just a red or green led that blinks to indicate that the station is working. Therefore I recommend placing the led where it is visible. Wire the led with a female jumper to the “stat” male header pin on the module board (recall to connect the shortest leg of the led to the board pin that is connected to ground).

Powering arduino module

To power the module connect the Arduino Uno USB cable to the portable power bank, and the power bank to one of the 2 available USB outputs on the wall socket charger module, the remaining output can be used later on to connect the Android usb cable to power the smartphone. If you dont want to use a power bank to keep the module on in the event of power loss then you can simply plug the arduino usb cable directly to the wall socket module. The power bank must comply with the following features:

The wall socket charger module connects to 110/220v to feed power to the module. I recommend wiring it with the 110/220v power cable so it is easier later on to connect it to any power outlet. You could also accomplish the same using a regular usb wall charger, but please be sure to protect it inside the housing as usually chargers will not work well exposed outdoors for a long period of time. I have used this approach when I couldnt find a decent 2A output dual wall socket charger module and used a regular dual usb charger instead (with 2A output).

Housing recommendations

Step by step gallery images illustrate how I arrange the module and all the elements inside the outdoor plastic housing, although you may try your own approach. Just keep in mind that you need to protect all the electronics from the elements (such as strong winds, hailstorms, rain, etc.). Sunlight is very harmful for plastics that are not UV protected so try to use materials that are prepared to be outdoor.

Some prefer to use the Stevenson screen for this purpose (

The BME280 have to be exposed (but protected) to properly measure temperature, pressure and humidity, so it is not advisable to enclose it in a sealed box (likewise the BH1750 to measure light). Also keep in mind the heat that direct sun will produce on the housing and on the sensors as it can raise electronics temperatures a lot. I have tested the OWS exposed to direct sun for several days with an internal housing temperature rounding 60ºC without any issues.

Load the code and run

First off you need to load the arduino program. Inside the “arduino” project folder you will find another folder called “open-weather-station” where the .ino program file is located. Also, inside the “arduino” folder I have placed the libraries that you will need for the specific sensors, include those libraries in your arduino project ( and it should be ready to compile.

I did my best to organize, add comments the code and keep the code simple to make it understandable so please read through the code to learn more about how it works. Nevertheless let me provide you some basic hints.

About arduino program constants

The rest of the constants are pretty much self explanatory.

Partial and full data samples

The module will send by default every 5 seconds the partial wind samples, useful for instance to show more “real time” wind data, and then, every minute the module sends all the data with the averaged wind samples, gust, temperature, etc. The partial samples are sent from the “sendWindPartialSample” function and the full samples are sent from the “sendFullSamples” function. Each sensor data is separated by a separator (configured in the constants) and each transmission is terminated with a new line. Take a look at those functions in the arduino code to understand how the samples are labeled and sent. I strongly recommend to enable the debug output constant so you can see the data in the arduino serial output monitor otherwise you will need to connect via bluetooth to see any data.

Connect to the OWS module via bluetooth

To connect to the module there are several alternatives. I will not enter into details on how to pair and connect to a bluetooth device from your PC, Mac, laptop, Iphone or Android device since there many tutorials that explain that with greater detail (nevertheless in the step-by-step gallery you will find some images where I connect using my PC and Android phone).

Just keep in mind that the bluetooth device you are using for the Arduino OWS module will be listed as HC05 when being discovered and if a code is requested to pair to the device the HC05 usually uses 1234 or 0000. If you are connected via an Android bluetooth app (e.g. for instance or even via Putty to your laptop using a bluetooth COM port (, you will see in your screen the same payload of data you see in the Arduino IDE serial monitor (providing the debug output flag is set to true).

Sending commands to the OWS module

You can send commands (single uppercase ascii character) to make the module do some things. The arduino function called “readCmdFromBluetooth” implements this feature. For instance it allows to: