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Type: Artigo
Title: A Self-powered And Autonomous Fringing Field Capacitive Sensor Integrated Into A Micro Sprinkler Spinner To Measure Soil Water Content
Author: da Costa
Eduardo Ferreira; de Oliveira
Nestor E.; Morais
Flavio J. O.; Carvalhaes-Dias
Pedro; Duarte
Luis Fernando C.; Cabot
Andreu; Siqueira Dias
J. A.
Abstract: We present here the design and fabrication of a self- powered and autonomous fringing field capacitive sensor to measure soil water content. The sensor is manufactured using a conventional printed circuit board and includes a porous ceramic. To read the sensor, we use a circuit that includes a 10 kHz triangle wave generator, an AC amplifier, a precision rectifier and a microcontroller. In terms of performance, the sensor's capacitance ( measured in a laboratory prototype) increases up to 5% when the volumetric water content of the porous ceramic changed from 3% to 36%, resulting in a sensitivity of S = 15.5 pF per unity change. Repeatability tests for capacitance measurement showed that the theta(v) sensor's root mean square error is 0.13%. The average current consumption of the system ( sensor and signal conditioning circuit) is less than 1.5 mu A, which demonstrates its suitability for being powered by energy harvesting systems. We developed a complete irrigation control system that integrates the sensor, an energy harvesting module composed of a microgenerator installed on the top of a micro sprinkler spinner, and a DC/ DC converter circuit that charges a 1 F supercapacitor. The energy harvesting module operates only when the micro sprinkler spinner is irrigating the soil, and the supercapacitor is fully charged to 5 V in about 3 h during the first irrigation. After the first irrigation, with the supercap fully charged, the system can operate powered only by the supercapacitor for approximately 23 days, without any energy being harvested.
Subject: Autonomous Sensors
Soil Water Content Sensors
Capacitive Soil Water Content Sensor
Energy Harvesting
Micro Sprinkler Spinner Generator
Ultra-low-power Circuits
Editor: MDPI AG
Citation: Sensors. Mdpi Ag, v. 17, p. , 2017.
Rights: aberto
Identifier DOI: 10.3390/s17030575
Date Issue: 2017
Appears in Collections:Unicamp - Artigos e Outros Documentos

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