78 • CANopen
Network
Architecture
WAGO-I/O-SYSTEM
750
CANopen
4.2.1.3 Required Conductor Cross Section
The conductor cross section depends on the conductor length and has to be se-
lected according to the number of nodes connected.
Fig. 4-1: Conductor cross section depending on the conductor length and the number of nodes
4.2.2 Cabling
The connection of a WAGO fieldbus node to the CANopen bus cable is made
by the appropriate supplied plug (5-pole plug MCS or 9-pole plug D-SUB).
For cabling with a shielded copper cable (3x0.25 mm²), the plug is assigned
with the CAN_High, CAN_Low and CAN_GND connections.
CAN_High and CAN_Low are two physically different bus levels.
CAN_GND is the common reference potential.
The conductor shield of the cable can be routed on the connection drain,
which is terminated with 1 M
Ω
as against the ground or PE (carrier rail con-
tact). A low ohmic connection of the shield to the PE can only be made exter-
nally (i.e. by means of a supply module). The aim is for a central PE contact
for the entire CANopen bus conductor screening.
Note
WAGO offers the screen connection system (series 790) for an optimum con-
nection between fieldbus cable screening and functional earth.
Each CAN node forms the differential voltage U
Diff
with: U
Diff
= U
CAN_High
-
U
CAN_Low
. from the bus levels CAN_High and CAN_Low.
The different signal transmission offers the advantage of being immune to
common mode interference and ground offset between nodes.
0,75
1
0,34
0,25
0,5
0,25
0,5
0,75
1
100 150 200 250 300 350 400 450 500
Conductor length L/m
32 nodes
64 nodes
100 nodes
