Abstract
A low power wireless sensor network based on LoRaWAN protocol was designed with a focus on the IoT low-cost Precision Agriculture applications, such as greenhouse sensing and actuation. All subsystems used in this research are designed by using commercial components and free or open-source software libraries. The whole system was implemented to demonstrate the feasibility of a modular system built with cheap off-the-shelf components, including sensors. The experimental outputs were collected and stored in a database managed by a virtual machine running in a cloud service. The collected data can be visualized in real time by the user with a graphical interface. The reliability of the whole system was proven during a continued experiment with two natural soils, Loamy Sand and Silty Loam. Regarding soil parameters, the system performance has been compared with that of a reference sensor from Sentek. Measurements highlighted a good agreement for the temperature within the supposed accuracy of the adopted sensors and a non-constant sensitivity for the low-cost volumetric water contents (VWC) sensor. Finally, for the low-cost VWC sensor we implemented a novel procedure to optimize the parameters of the non-linear fitting equation correlating its analog voltage output with the reference VWC.
Highlights
In recent years, the rapid development and broad application of the IoT (Internet of Things) concept pushed towards the improvement of best practices in Wireless SensorNetworks (WSNs) [1] in Precision Agriculture (PA) applications, relevant to Greenhouses [2,3]
Wireless SensorNetworks (WSNs) could be made of simple and cheap components: the results provided by complex technology systems are not necessarily significantly better than the results derived from a combination of descriptive statistics and simple sensors: intrinsic limitations of the sensing element could be overcome [8] providing the measurement readout in a digital format [9]
The modular design of the proposed approach splits the architecture into different layers (Figure 1): (i) wireless nodes, (ii) internet gateway/concentrator, and The Things Network (TTN) [59], a worldwide open-access LoRaWANTM network, (iii) uplink and downlink connection, the bitrate of the LoRa message, significantly depends on the number of sensors deployed in the field and on the transmission rate, given in packets/day
Summary
The rapid development and broad application of the IoT (Internet of Things) concept pushed towards the improvement of best practices in Wireless Sensor. In cloud computing approaches, the collected data are analyzed, processed, and used to undertake the correct decisions to optimize natural resources: it follows that the set of sensors, devices, and storage systems, by which the IoT is composed, is very similar to a huge, distributed measurement system, as clearly outlined in [12] The management of such complex systems is part of the present. The reliability of very low-cost soil water content sensors purchasable in the worldwide internet market is still a matter of scientific debate [8,32,33,34,35,36,37] as further highlighted In this scenario, the objectives of the present work can be summarized as follows:. Comparison of the performance of a very low-cost soil moisture sensor with a commercially available expensive system using two different types of soil with an original modeling approach which helps us to compare measurement results taken at different soil depths
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