Technische Alternative CAN-EZ2, Manual

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Installation and connection – CAN bus
16
CAN Bus network
Terminal diagram, CAN Bus cable
Guidelines for the topology of CAN networks
Technical principles
The CAN bus comprises the cables CAN-High,
CAN-Low, GND and one +12 V supply cable for
bus components without their own power sup -
ply. The combined total load of all devices with
12 V and 24 V supply must not exceed 6 W.
Design CAN networks in a linear fashion and set
a terminator at each network termination. This
is ensured by the termination of the end devic -
es.
In the case of larger networks (covering several
buildings), problems can occur through electro -
magnetic interference and potential differenc -
es.
To avoid or to the greatest extent manage such
problems, take the following measures:
• Cable screening
The bus cable screen must be connected well at every node to provide continuity. For larger
networks we recommend including the screen in the equipotential bonding, in line with the
examples shown.
• Equipotential bonding
As low an ohm connection as possible to the earth potential is particularly important. Where
cables enter buildings, ensure that the cable entries are in the same location where possible
and that all are connected to the same equipotential bonding system (SingleEentryPoint prin -
ciple). The purpose is to create potentials that are as similar as possible, in order to achieve
the smallest possible potential difference to adjacent lines in case one line suffers a voltage
surge (lightning strike). Also ensure a corresponding clearance between the cable and light -
ning protection systems.
The equipotential bonding also has positive properties to counteract interferences emitted
from linked cables.