The challenges of implementing a LoRaWAN-based smart agriculture solution
At Sensoterra we design and produce soil moisture sensors. We give farmers and landscapers the opportunity to look deeper into the soil at multiple places at the same time
Daan Roethof, Product Developer at Sensoterra and author of this article, gave his feedback on the challenges of sensor development and applications in the field. In addition, Daan talks about our partnership with TTN (The Things Network) and how LoRaWAN connectivity has been helping remote sensing.
"At Sensoterra we design and produce soil moisture sensors. We give farmers and landscapers the opportunity to look deeper into the soil at multiple places at the same time. This saves them a lot of time going into the fields and optimizing their irrigation decisions. Following the moisture level patterns can save you a lot of water and increase your yield by irrigating at the right time with the right amount of water", says Roethof.
A lot of challenges came up throughout sensors' design-phase and the number of requirements increased during the years, especially after getting feedback from the field.
The main challenge: battle the elements
These sensors are used by all types of growers, frequently throwing their equipment in the back of a truck in a multi-task environment. After the sensors survive the trip into the field they are placed in the soil out in a wet field with rain, wind, sun, in other words, left exposed to the elements. This brought us to the main challenge: how to make a sensor that is simple and user-friendly, fail-proof, rugged and watertight?
We stripped the sensors down to the bare minimum.All buttons were removed, switches, LEDs and created a closed box. This didn't come without many trade offs, then the question became: How do we switch it on? We needed to be smarter.
Sensoterra single-depth soil moisture sensors
The next challenge: turn it on and off
In this sense, the question to switch it on was bounced back with: do we need to switch it off? Modern electronics are super energy efficient in a deep sleep. So when the product is not in use it could and should go into the deep sleep mode. Our device has an hourly pattern: measure the soil, encode a payload, send it out, sleep for an hour, wake up, measure the soil, etc.
The energy consumption of the measurement is negligible compared to the LoRaWAN radio communication, so if the sensor cannot take a measurement, it isn't installed in the soil, which means it can go back to sleep and skip the battery consuming communication. In short, when in stock or in storage, the sensors are in a very energy-efficient mode, called “stock mode”.
When the user installs the sensor in the soil it will notice on its first wake up that it is in the soil and start up-linking. It takes up to an hour before the customer has its first feedback. Therefore, an accelerator was added to trigger sensors awakening; when growers shake the sensor from upside down and up again, the sensor will wake up immediately. The user will get the measurement available on their smartphone right away and can leave the field knowing the sensor is working properly.
Sensoterra multi-depth sensor
Another challenge: switching modes
When the sensors get their battery for the first time they start their life in the “factory mode”. This mode is made so we can do the checks during manufacturing and have good quality control. The results of the checks are stored in our backend and connected to the serial number. In the final step, it is set to the standard mode and the products are customer ready.
When the sensors are out of the factory we can switch modes with a downlink. For example when we would like to switch to a test mode or changing the uplink interval. A LoRaWAN network is needed to send down-links and that is where The Things Network comes.
How we use The Things Network (TTN) in these challenges
LoRaWAN network is needed everywhere: at the customers, the office and the warehouse. For the warehouse, we have a couple of specific reasons to set up a LoRaWAN system. Firstly, to control stock levels by the number of sensors online. Secondly, we can better manage sensors' energy consumption. Finally, we can control the down-link configurations before we send a sensor out to a customer.
TTN has the great advantage of allowing an unlimited number of sensors for free per user. This gives us the ability to register all the sensors coming from production. In addition, our API can register the sensors automatically to TTN, de-register it, or leave it connected when sent to a customer.
Our sensors are also extensively tested in the office and laboratory. TTN doesn’t limit us in our uplink usage, which is great when testing and we collect as much information as possible in a short time. We regularly hit LoRaWAN specification limits.
There are features, that we leave to the customer. For example, sometimes a public network is preferred, leaving out the high costs of setting up your own network. Unfortunately, this is not as common as we see with KPN with a nationwide network in the Netherlands. In this case, a gateway is configured to our customers, which all they should do is power it up. The advantage is that TTN provides easy gateway setups, keeping it easy for us as well.
TTN enables us to test and break our prototypes, bringing Sensoterra to the point where we are now. It allowed us to make our sensors behave in smart, energy-efficient ways, and ensure a smooth process from production to placing the sensors in the soil.
Daan Roethof, Product Developer, with Sensoterra multi-depth sensors.
About The Things Network:
The Things Network is about enabling low-power devices to use long-range gateways to connect to an open-source, decentralized network to exchange data with several applications such as smart cities, agriculture, landscaping, horticulture, and smart devices.
With thousands of Sensoterra sensors in the ground, generating over 60 million data points globally, Sensoterra was founded in 2014 and is based in Amsterdam, the Netherlands. Connected by LoRaWAN, sensors are wireless and farm-tough designed for urban and rural areas.
For more information, please send us an email to [email protected]
Caroline is a Soil Data Manager at Sensoterra. Previously, she worked as a laboratory analyst, responsible for data analysis of roots and soil, identifying pesticide contamination and plant accumulation. Her background is in Environmental Science, with a Masters's degree in Water & Environment from Radboud University.Get in touch