Photocapacitance discharge of LEDs applied in remote sensing detectors

Abstract

Abstract This paper describes the application of light emitting diodes (LEDs) as light detectors for remote sensing systems, used for the measurement of normalized differential vegetation index, one of the most common parameters monitored by these systems. The light intensity measurement was carried out through correlation of discharge time of photocapacitance of LEDs, and the performance of this configuration was compared with the same LEDs used as detectors in photovoltaic mode. One measurement system was implemented for each configuration of LEDs, using the STM32F401CBU6 microcontroller. The normalized differential vegetation index was measured in samples of liquid suspensions of microalgae Spirulina platensis with different biomass concentrations. The measurements were taken at an outdoor location and under sunlight illumination. The results obtained with measurement of normalized differential vegetation index through photocapacitance discharge effect demonstrated that this is an effective technique with an improved repeatability in measurement, in comparison with photovoltaic mode of LEDs used as detectors.