Projeto de sistema de controle de temperatura e monitoramento da umidade em equipamento de secagem de alimentos.

Abstract

Thermal systems are used in food drying process, in which may exist storage and/or heat flux. This phenomenon can be observed in three kinds of transmission: conduction, convection and radiation. The drying control systems are used in many industrial processes and demand very precise measurements. In food industry, it is fundamental that temperature, humidity and pressure are accorded to certain standards, seeing that variations above tolerances can jeopardize quality. Focused on this problem, this paper proposes to develop a control system using PID controllers to replace on-off systems and manage to monitor humidity in food products dryers. O drying system is coupled to a fixed bed dryer, a fluidized bed and a jet bed, installed in the Biochemistry Engineering Laboratory in Chemical Engineering Department in UFCG. Through the experiments and model techniques, it was possible to find the transfer function of the system. With the project specifications in hands like maximum temperature variation and spots in which it is desired to measure humidity it was possible to methods for tuning PID controller to obtain constants for the controller. Therefore, it was possible to simulate using Matlab software and from that to choose a controller that match the specifications. The next steps were to choose components that can perform temperature e humidity measurements, specify tools that can manage communication men-machine, to project the acquisition circuit of tension signals in order to determine the passage through zero point in each cycle and definition of actuator. An Atmel’s microcontroller ATmega328 was chosen for signal handling, data processing and implementation of PID controller. After fabrication of the structure of the circuits, a code was developed using programing language C++ in Arduino’s integrated development environment. Finally, it was made tests to validate the project observing temperature behavior, which were satisfactory, since proposed goals were reached.