Sistema de controle e automação aplicável a secadores em camada fina utilizando-se instrumentos digitais endereçáveis / Automation and control system applicable to thin-layer grain dryer by using digital addressable instruments

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Many grain-dryers models with different configurations and applications are encountered worldwide. Among those a thin-layer dryer makes it possible to perform detailed analysis of the drying process. With the results from this analysis results, the drying curves can be modeled and the deep bad grain drying process can be predicted. The thin layer grain dryer used in this work has an electrical resistance system to heat the drying air, and fan driven by a 368 W motor to push the air trough the dryer and grain samples. A device based on DS2406 digital switches - the 1-wireTM technology developed by Dallas Semiconductor - and others electronics devices based on power semiconductors were developed to control the fan and dryer heating system operation. This system was called ACIONA AC. The dryer control is based on the drying process characteristics of the grain samples been tested. The relative humidity and temperature sensors use a device called UMETER 1.1, based on a HIH-3610 humidity sensor developed by Honeywell, and on a DS2438 A/D converter developed by Dallas semiconductor. The verification process of the grain samples moisture content reduction is performed by using a scale with a load cell (manufactured with resistive strain gauges). To construct the scale the sample tray was supported by three points (two fixed points and the other one over the load cell). The bottom of the tray that receives the grains samples is made up of a ten mesh screen, where the drying air passes. These devices were networked, and installed in bus topology configuration, and were controlled by a master device. Software is responsible to power up the system, turn on or off the fan and the heating system, as well as, record the measurements and commands, emit graphics and reports, and turn off the systems when the final conditions are achieved. To validate the system, several drying tests were carried out using shelled corn samples to obtain the drying curves. It was possible to demonstrate one more possibility for use the 1-WireTM technology. In this work it was possible to use temperature sensors and A/D converters in the signal identification and associate theses devices with others circuits, showing their versatility and a good flexibility in their operation bands. The feasibility of the 1-WireTM network was extensively proved because the devices were subject on electro-mechanical disturbs. Frequently the system was submitted to starts process and motors operation, promoting electromagnetic disturbs, always harmful to the data communications networks.

ASSUNTO(S)

addressable instruments dispositivos endereçáveis equipamento de secagem automation and control secadores de grãos controle e automação drying equipment engenharia agricola grain dryer

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