Development and testing of hygrometers with Arduino low-cost electronic components
Soil moisture and its availability to encourage plant growth is a key factor in agricultural productivity. There are automated irrigation systems to make the agricultural labour easier and give the crops the daily water needed. But these irrigation systems work without regard to the needs of the soi...
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| Formato: | tesis de maestría |
| Fecha de publicación: | 2020 |
| País: | España |
| Recursos: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/333706 |
| Acesso em linha: | https://hdl.handle.net/2117/333706 |
| Access Level: | acceso abierto |
| Palavra-chave: | Arduino (Programmable controller) Arduino (Controlador programable) Àrees temàtiques de la UPC::Enginyeria electrònica |
| Resumo: | Soil moisture and its availability to encourage plant growth is a key factor in agricultural productivity. There are automated irrigation systems to make the agricultural labour easier and give the crops the daily water needed. But these irrigation systems work without regard to the needs of the soil. There exist low-cost sensors that determine what the soil moisture is which can help farmers to make more accurate irrigation and get better soil yield and water resources. The project test three low-cost Arduino sensors (resistive basic sensor code B071LH5Z9D, coated resistive IC Station B076DDWDJK, and capacitive SongHe B07SYBSHGX), to understand their behavior and introduce improvements to have more accurate readings. To perform the experiments, three types of soils (loamy, sand, clay) were used. First, the calibration curve of each sensor was performed for each soil. It was found that the Resistive sensor has a different curve depending on the type of soil. However, for the Resistive coated sensor and the Capacitive sensor, the calibration curves did not vary greatly depending on the type of soil. The only difference between these two sensors was that the Capacitive is capable of reading a wider range of VWC (0% -30%) than the Resistive coated (0% -15%). Beyond the calibration curves, other experiments were performed on continuous readings of VWC under ambient conditions in order to see which external factors influence the sensor readings. It was found that Resistive sensors are linear influenced by soil temperature (R2 > 0.874). This is why the Resistive sensor was tested by another experiment to see the effect of temperature: For each soil, 3 samples were prepared of the 15%, 20% and 25% VWC (total 9 samples for each type of soil) and then, a sample of each VWC was put in different environments (refrigerator, another in the sun and the last at room temperature). By this way, it was possible to perform an accurate VWC readings using 3 different temperatures. The result of this experiment demonstrates the close relationship between the temperature of the floor, the VWC and the reading of the sensor allowing thus to correct the readings in function of the temperature and obtain more precise results. Resisitve sensor is easily corroded that is why a second type of Resistive sensor was used with an anticorrosion coat. Although the temperature effect for the Resistive sensors can be corrected, the accuracy is still higher for the Capacitive one. The same tests as for the Resistive sensors were done using the Capacitive sensor and it was found out that it is not so influenced by the temperature, which can be dispensed with. That is why, once its calibration curve was obtained, this last sensor is the one used to design an automated irrigation system with Arduino. To sum up, resistive sensors could be used punctually, that is, they are not useful for continuous monitoring of soil moisture, whereas, capacitive sensors serve for prolonged soil moisutre controls through time. However, capacitive sensors are influenced by more structural soil factors, ie soil compaction and the depth at which the sensor is located. The proposed low-cost automatic irrigation system can cost between 42 and 124 euros, depending on where the necessary items are purchased. |
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