Low-cost remote distance and height sensing analog device for laboratory agriculture environments

Abstract

This paper introduces a novel simple readout system for infrared (IR) distance measurement and transmission in closed environments, for instance small-area agriculture, employing transformation of distance on settable duty cycle variation. This simple analog system utilizes active devices fabricated in 0.35 μm 3.3 V I3T25 ON Semiconductor CMOS process. Analog system generates and transmits the information in form of the duty cycle of square wave signal with frequency of 3 kHz up to 46.6 kHz in full range (approximately between 10% and 90%) or half range (above 50%) due to requirements of various types of receivers. There is no requirement for any special processing software. The transmitted waveform is received by a low-cost phototransistor in distance at least 30 mm (case when the transmitter and receiver are placed directly on both sides of dividing glass plate). The proposed concept was tested for distance measurement (up to 70 mm) by commercially available distance sensor connected to the communication system and can be utilized for different use cases (e.g. monitoring of growth of small plants or mushrooms). The measuring range (sensitivity and dynamical range) of the sensing system can be easily adjusted. The experiments indicate error between the transmitted and received value below 5%. The overall error of the system between the evaluated and real measured distance is below 10%. All presented tests confirmed operationability of the proposed system.