18-08-2012, 03:36 PM
GREENHOUSE MANAGEMENT THROUGH CAN NETWORK AND PLC ON A TOUCH SCREEN SYSTEM
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Abstract
This paper describes a distributed control
system for an agriculture plant made up of three
greenhouses, each one controlled through a single
PLC. Each PLC must control the temperature and
humidity inside a greenhouse through the suitable
activation of a fan, irrigation system, heater and the
opening/closing of some windows. PLCs are
connected through a CAN bus to a central monitoring
station with a graphic interface. The design and
development of the interactive interface
"Greenhouses Management" has been the more
intense and difficult part of the job. Four principles
have been adopted for a user-centered design:
understanding the user, interactive design, constant
measurement of the results achieved, iterative
planning. The main objectives have been: to speak
the language of the user, to minimize the quantity of
memory required, to provide a continuous feedback
and to help the users to recognize, diagnose and
recover the errors.
INTRODUCTION
This papers analyzes and emulates all the
operations which are required for the remote
managements of three Greenhouses which are
represented by three cards interconnected through a
Can network. A graphical interface allows to control
and monitor remotely the three greenhouses and set
appropriate parameters. Every card has been
connected to a PLC and the entire system
communicates with a master node through a touchscreen
PC TC1000. Each PLC, uses a firmware
written in FBD language, and has the function to
manage the systems which control the greenhouse,
i.e. the heating, ventilation, opening and closing
doors and the dehumidification system. The
implementation of the GreenHouse System has
required the use of PLCs, Microcontroller boards
with communication capability, an industrial PC with
touch-screen monitor, various sensors and actuators,
and some spare electronic components.
CONCLUSIONS: THE HUMAN
MACHINE INTERFACE
I have developed a system for managing three
greenhouses in order to provide people which operate
in the agricultural area a safe and efficient system. A
fundamental component of the system is the humanmachine
interface whose task is to allow an easy
interaction with the system. The design and
development of the interactive interface for
"Greenhouses Management" has been the more
intense and difficult part of job. During the
development, over the 50% of the code has been
devoted to the interface. The complexity of the
design of the interface has depended on the variety of
choices and design decisions to perform all possible
tasks, often unpredictable.