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Session 3548

An Automatic Control System Design with Practical Implications

Ahmad M. Farhoud

Engineering Technology Department University of Toledo

Abstract

The automatic control system design course requires students to design and build a closed loop control system. In the design presented here, students are to design, build and troubleshoot a humidity control system which is used to manage soil moisture levels in a green house. Maintenance of proper soil moisture levels for different plants is crucial to farming. The idea is to water the plants when the soil becomes dry beyond a certain level. Students are expected to select, design and build each component based on required specifications. Students are encouraged to take initiative in examining all the available options. This works to incite curiosity and inquisitiveness in students. To monitor the moisture levels of the soil, students are to investigate the conductivity of electrodes constructed from different metals and then choose the one with the widest range of variations in resistance reflecting changes in soil wetness. A signal conditioning circuit is then designed to change output resistance of the sensor to voltage, which is then amplified and fed into the controller to be compared to a preset moisture level. A simple switching circuit with hysteresis can be designed using an LM139 operational amplifier. A transistor circuit is used to energize the relay switch, which in turn controls the water flow. An LCD display is used to display moisture levels. Students must investigate and compensate for the effect of noise on the sensing probe. Junior and senior students with basic knowledge of electronics and automatic control should be capable of performing this experiment. It has been implemented in my automatic control course and has proved to be a very successful learning and teaching experience.

Introduction

The primary function of any valuable experiment is to solidify the learning experience by demonstrating realistic applications. Through it, students can investigate the validity of concepts learned in the classroom. It should also enhance the student’s ability to troubleshoot systems to ensure optimum performance. In class, students learn how to apply theory in the design of selected projects. This experiment enables them not only to develop their design, but also to build it and troubleshoot for best performance .

Proceedings of the 2004 American Society for Engineering Education Annual Conference & Exposition Copyright  2004, American Society for Engineering Education

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FARHOUD, A. (2004, June), An Automatic Control System With Practical Implications Paper presented at 2004 Annual Conference, Salt Lake City, Utah. 10.18260/1-2--13992