BECKHOFF BC2000 - Manual (Page 6)

Basic Principles
5 BC2000
Basic Principles
Description of the BC2000
The BC2000 is a slave with PLC functionality. It has a fieldbus interface,
the Lightbus. The bus terminal controller is programmable, and is
programmed using the TwinCAT software in the IEC61131-3 programming
languages. Applied in combination with the C1220 or FC200x Lightbus PC
card and the TwinCAT PLC software, the BC2000 permits decentralisation
of the control tasks. This is a way of removing parts of the application out
of the central control system to relieve the CPU and the field bus.
Distributed counters, controllers and switches are typical applications for
the bus terminal controller. The reaction times are dependent upon the bus
communication and the overall control system, and maintenance of
function is possible even when the bus or control system fails (e.g. an
orderly transfer of the processes into a secure condition).
The Beckhoff Bus Terminal System
Up to 64 bus terminals
each having 2 I/O channels
for each signal form
De-centralised wiring of
each I/O level
IPC as controller
Standard C - rail assembly
Modularity The bus terminal system is the universal interface between a fieldbus
system and the sensor / actuator level. A unit consists of a bus terminal
controller as the head station, and up to 64 electronic series terminals, the
last one being an end terminal. For each technical signal form, terminals
are available each having two I/O channels, and these can be mixed in any
order. All the terminal types have the same mechanical construction, so
that difficulties of planning and design are minimised. The height and depth
match the dimensions of compact terminal boxes.
Fieldbus technology allows more compact forms of controller to be used.
The I/O level does not have to be brought to the controller. The sensors
and actuators can be wired de-centrally, using minimum cable lengths. The
controller can be installed at any location within the plant. The use of an
industry PC as the controller means that the operating and observing
element can be implemented in the controller’s hardware. The controller
can therefore be located at an operating panel, in a control room, or at
some similar place. The bus terminals form the de-centralised input/output
level of the controller in the switching cabinet and the subsidiary terminal
boxes. The power sector of the plant is also controlled over the bus system
in addition to the sensor/actuator level. The bus terminal replaces the
conventional series terminal as the wiring level in the switching cabinet.
The switching cabinet can have smaller dimensions.
The Beckhoff bus terminal system unites the advantages of a bus system
with the possibilities of the compact series terminal. Bus terminals can be
driven within all the usual bus systems, thus reducing the controller parts
count. The bus terminals then behave like conventional connections for
that bus system. All the performance features of the particular bus system
are supported.
The easy, space-saving assembly on a standard C-rail, and the direct
wiring of actuators and sensors without cross-connections between the
terminals standardises the installation. The consistent labelling scheme
also contributes.
The small physical size and the great flexibility of the bus terminal system
allows it to be used wherever a series terminal is also used. Every type of
connection, such as analogue, digital, serial or the direct connection of
sensors can be implemented.
The modular assembly of the terminal strip with bus terminals of various