Food-Care: An Optoelectronic Device for Detection of Fertilizer Contamination in Fruits and Vegetables in Smart Agriculture Framework

In this work, a portable device for real-time de-tection of nitrate concentration for fruits and vegetables is developed. First, the identification of the target wavelength was carried out by measurement of standard nitrate solutions on a UV-Visible 730 spectrometer of spectrum range between 200nm and 800nm. The experimental results reveal a peak absorbance spectrum of 265nm at different nitrate concentrations. Then a novel device is developed consisting of UVC-LED, quartz, photodiode, trans-impedance amplifier, micro-controller, A to D converter, display unit, and a power supply. The quartz cuvettes of length 10mm are placed between LED and photodiode for measurement of standard nitrate solutions. When LED is turned on the attenuation of the light beam is measured in terms of photo diode current and further amplified through a trans-impedance amplifier for readout circuitry. The developed prototype shows good linearity over amplifier response for nitrate concentration of
$10-100\mu g/mL$
with a correlation coefficient
$R^{2}=0.998$
. As the device operates at a very low voltage (of the order 5 V), it can be easily powered by a rechargeable battery or a smartphone.