In the CONA project, the School Center Nova Gorica, Vocational College received the task of manufacturing 12 devices that would measure the current and cumulative amount of precipitation and transfer data via the Internet to the control rooms of treatment plant. The project partners determined the locations of the measuring stations, and the students of informatics and mechatronics had to find a way with their mentor how to make the device and how to solve the data transfer problem.
To perform the measurements, they chose a "rain gauge" or "pluviometer", namely one with a "tipping bucket", because it allows the measurement of both set quantities - current and cumulative rainfall. Students made the »rainmeter« with a help of a mentor. In the 3D modeling program, they drew the components of the »rainmeter«, which they printed with the help of a 3D printer and assembled the meter. Then it was necessary to look for solutions that would allow the transfer of collected data to the Internet.
The relatively new LoRaWAN technology has proven to be an ideal solution. The abbreviation LoRaWAN consists of the English words Long Range Wide Area Network. This is a protocol designed to network low-power devices over long distances. The LoRaWAN network consists of gateways and end devices.
Passages are radio stations that are connected to the Internet. Terminal devices are usually battery-powered "smart" low-power radios that communicate wirelessly with one or more passages. Communication can take place in both directions. The technology enables the slow transfer of small amounts of data over long distances, reaching 10 km in the open.
Due to the extremely low power consumption when using this protocol, the devices can operate for many years on battery power. This eliminated the cost of solar cells. Since the freely available 868MHz frequency band is used for communication, there are no royalties. When the project started, two crossings were active in the wider area of Nova Gorica. They anticipated that they would need at least 5. In 2019, there are 12 active crossings on the Slovenian side of the border and 5 crossings on the Italian side, which are completely sufficient to cover the locations of measuring stations.
They also made the electronic circuit of the device themselves. It consists of a microcontroller that consumes only 1 µA of current and a radio transmitter module in economy mode. The microcontroller program was written to send data every two minutes in the event of rainfall. If there is no precipitation, the device sends data on the temperature and relative humidity measured at its location every half hour.
Operation co-funded by the European Regional Development Fund
