A reconfigurable IoT system for the measurement of greenhouse variables

There are various methods and equipment for the measurement of greenhouse variables with IoT, however, most of them have disadvantages such as expensiveness, limited coverage, or lack updating capacity through new technologies. Hence, this article aims to explain the development of a greenhouse variable measurement system, whose magnitudes will be recorded in a database to later be accessed from a device connected to the internet, with the possibility of reconfiguring it in order to measure other variables, and/or adapt it to other sensors and/or applications. A methodology for the use of a FPGA based data acquisition and processing card, in addition to a Raspberry-Pi IoT system are described, with which communication will be established with the following measurement sensors: TMP006 (infrared, IR, temperature), TSL230 (solar radiation), SHT75 (air temperature and relative humidity), and FC-28 (soil humidity). This system will not only allow real-time in situ acquisition and processing, but also will store the information gathered in a database located on local and external servers using open-source code. The system includes both IoT and in situ interfaces. Communication protocols are used to measure the variables. Statistical tests were performed for the monitored data, verifying its accuracy. The sensors' performance reached correlations over
$r=0.9$
in most of the cases. Lower correlations and significant measurement errors depend specifically on the selected sensor.