5
The heart of the system is the
CPU
board, which is in charge of all the decision making of the
controller. The decision making procedure is based on the logic included in the firmware, the
configuration defined by the installer, the programs defined by the user and the current status
of the devices connected to the controller, inputs and outputs.
The input devices consist of sensors that supply information to the
CPU
and the output devices
are those that are activated by the commands generated by the
CPU
. However the
CPU
does
not interact directly with the input/output devices comprising the irrigation network, for that
purpose various kinds of
I/O
(Inputs/Outputs)
Interfaces
are used
.
The
I/O Interfaces
will
usually use the services of various
I/O boards
or
RTU
s that really execute the output
commands and read the input sensors.
The
CPU
communicates with all the
I/O
Interfaces
second by second, sending them the
desired status of outputs and receiving back the status of the inputs. The schematic drawing
above shows the various kinds of
Interfaces
recognized by the
DREAM 2
system. A control
system will include an arbitrary combination of these
Interfaces
; some controllers may include
several
Interfaces
of the same type. The communication channel between the
CPU
and the
Interfaces
uses the
RS485
protocol which enables communication up to a distance of several
kilometers on a two wired line; this enables placing interfaces distantly from the
CPU
when
needed.
Another function of the
CPU
is the communication with the external world. This is done through
the internet, utilizing the
SERVER
which is located somewhere in the cloud. The way to set up
the communication channel will be described below.
1.1
Looking inside the DREAM 2 case
Location of the
backup battery
AC power
supply board
Transformer
Motherboard
Local I/O
interface
Local I/O
board 16/8
RF interface
