Electronics

We are creating installations (Cybryonts) that each combines ceramics sculptures, microclimate remote monitoring devices and moss gardens and aim at exploring/imagining the world lived by the mosses in different polar regions (among them, Kilpisjärvi), in particular facing the shifting of their ecosystems conditions.

Every of those unit is centered around a ceramics structure that is both a robust enclosure for the digital devices that compose the microclimate monitoring system and a welcoming substrate for the mosses growth. It is as well an aesthetic assembly in itself. The technical challenges and experiments that are to be adressed concern how do we exactly collect and transmit data about the microclimates experienced by the mosses on the site of each sculpture.

As of now, our plan is to place a single microcontroller in each sculpture, wired to an array of environmental sensors. Periodically, this microcontroller collects data from the sensors and send them via radio waves to a server, such that the data is available from our local server in Montreal. We are planning to install between 2 and 4 sculptures (or at least, microclimate monitoring systems) around the Kilpisjärvi research station. Their exact location is still unknown, since we want to place them where rather specific kind of mosses already grow (we are interested in species that lives both in both circumpolar regions).

Regarding the collection and transmission of microclimates measurements, we are using Moteino M0 microcontrollers, a SAMD21 Cortex M0+ based device using the standard Arduino Zero bootloader. It is designed for low-power applications (since we want our devices to run out of batteries that are to be changed as rarely as possible on years-long period of time, this is quite important) and already includes a LoRa radio transceiver. Indeed, we plan to emit the sensors data from the installation towards the outside (and ultimately, our storage in Montreal) using the LoRa radio technique, given its long-range ability (we are expecting a 3-5km range from the base, but this will have to take into account and adapt to the hilly landscape), its relative low-power needs and its ease of use when integrated to the Moteinos. The MCU can be programmed to use either 915 [MHz] or 868 [MHz] as center frequency for the LoRa transmissions, according to the ISM bands regulations of the places where they are placed (868[MHz] for Finland, if I’m correct). Each set of environmental measurements is to be represented, stored and transmitted as numerical data (around a total of 10 bytes of data per readings, according to the sensors we currently use), and could be readily encrypted before its transmission if this seems relevant for any security concerns of the networks we are to be interfacing with (using any of the cryptographic methods available from the Arduino crypto library). Erich Berger, director of the BioArt Society, mentionned to us that he had successfully used LoRa at the Kilpisjärvi research station in the past, and that its frequency range wasn’t especially crowded here, such that we expect that our transmission range will be mostly constrainted by the combination of landscape and exact location of our devices and their transmitting hardware (we are currently testing if we are to use basic dipolar half-wavelenght antennas or quarter-wave monopole antennas and if they are to be enclosed in the clay sculptures or sticking out of it) . Ideally, we would like to schedule measurements (and transmissions) hourly, but their frequency could be lower (possibly daily) if energy storage or data storage constraints reveal to be more strict than expected. An array of sensors, all to be wired to the microcontroller, have been selected on the basis of being readily available to us and related to the most important abiotic signs/stimuli that compose the mosses experience of their microclimate (and their world). Each installation includes 2 atmospheric sensors (each measuring air relative humidity, temperature and barometric pressure at different point of the sculpture), a soil moisture sensor, a UV ambient light intensity sensor and a spectral visible light sensor (to access wavelength ranges that are specifically important to the mosses photosynthesis process). The exact devices we are using are listed and documented at the end of this document. Right now, this whole sensors and microcontroller node device is being assembled and tested as a breadboard circuit. The power concumption and transmission range are still under investigation. We are also still experimenting with the construction of ceramics enclosures that can protect the electronics from the harsh weather while also allowing the sensors to access the environment microclimate they are to monitor (that is not a trivial task, but until now it seems to unfold ok).

Overall, the data collected by the nodes in the sculpture have to be transmitted to our local server in Montreal. Until our last meeting, we were unaware of any global LoRa network coverage in Finland and were expecting to install a small server hosted on a microcomputer located in the station building. That small relay server would have been equiped with a RFGateway M4 board in order to emit and receive LoRa messages directly with the sculptures nodes placed in the area. Those message would have been stored locally, but also forwarded to our main server in Montreal, presumably over the Internet (something like a SSH connection was imagined). We were considering connectng the relay server either to the already existing local network of the research station or to a new internet access of our own, depending of the availability of your infrastructures and their security requirements. We are looking forward to learn about any global LoRa coverage in the region of the research station, perhaps we can avoid having to set up a relay server. We’ll research about the Finnish LoRa coverage, but any help would be of course appreciated.

One thing that was interesting about setting up a local LoRa server with internet access was that it allowed us to consider remote reprogramming of the nodes. Indeed, the Moteino M0 can be programmed over-the-air with LoRa, and being able to send them LoRa messages would have allowed us to eventually remotely correct any unforseen bug or add features to the minimal software they will be running.

Here’s a list of all the devices (a MCU and a few sensors) we plan to use (and are used in the prototypes we are currently testing), as well as links to their respective documentations. Until know, we use off-the-shelf breakout boards wired to the microcontroller for connecting all the sensors. All sensors are communicating over I2C connections.