20
Cables
There are CAN bus cables on the market with their conductors assembled as twisted pairs, for example those
from Lapp Cables, as well as cables with the conductors stranded, such as those offered by Helukabel.
If twisted pairs are used, one pair must be used for poles
1
and
4
, and the other pair for poles
2
and
3
.
With stranded conductors, any one of them can be used for any connection.
Suitable CAN bus cables:
Manufacturer
Installation method
Lapp Cables
Helukabel
Fixed installation
up to 30 m in length
UNITRONIC
®
BUS CAN UL/CSA (CMX)
2
×
2 × 0.22, Article No. 2170 261
CAN BUS 4 × 1 × 0.22
Article No. 81287
Fixed installation
up to 40 m in length
UNITRONIC
®
BUS CAN UL/CSA (CMX)
2
×
2
×
0.34, Article No. 2170 264
CAN BUS 4 × 1 × 0.34
Article No. 801573
Highly flexible installation
up to 40 m in length
UNITRONIC
®
BUS CAN UL/CSA (CMX)
2
×
2
×
0.25, Article No. 2170 273
CAN BUS 4 × 1 × 0.50
Article No. 800685
NOTE!
The data transmission rate of the CAN bus is 1 Mbit/s. According to ISO 11989, this means that if
a suitable uninterrupted cable with core cross sections of 0.25 mm
2
is used, the maximum length
of the bus will be 40 m.
The use of unsuitable cable types can disrupt data transmission. It is also possible that no
functioning data link can be established between the devices.
5.1.5.1 Requirements for the bus cabling
A bus topology (i.e. single line) must be used.
All devices must be wired in series in the bus.
Drop lines and star topologies are not permitted.
The total length of the bus must not exceed 40 m. See
Section 5.1.5.2 Cable types,
below for the cable
types to be used and their limitations.
At the beginning and end of the bus, the terminating resistors incorporated in the devices must be
activated. With the other devices that are not located at either end of the bus, the internal terminating
resistors must be deactivated.
NOTE!
To ensure fault-free operation, it is important that the twisted pairs in the cable be
correctly connected:
One twisted pair is connected to the outer poles 1 and 4, the other to the inner poles 2
and 3.
With conductors that are all stranded together, any one of them can be used for any
connection.
The maximum bus length of 40 m for suitable cable must not be exceeded.
A maximum of 7 devices plus one EM-FD 2500 Display or 6 devices plus two
EM-FD 2500 Displays may be connected to the same bus segment, however no more
than one EM-FD 2500 Display per EM-PQ 2300 or EM-MC 2200 may be connected.
If these instructions are not complied with, data transmission may be disrupted. It is also possible
that no functioning data link can be established between the devices.
5.1.5.2 Cable types
The following cable types or others with equivalent specifications must be used.
Surge impedance 120
:
For fixed installation up to 30 m
Lapp UNITRONIC
(R)
BUS CAN UL/CSA (CMX) 2 × 2
×
0.22, Article No. 2170 261
Helukabel CAN BUS 4 × 1 × 0.22, Article No. 81287
For fixed installation up to 40 m
Lapp UNITRONIC
(R)
BUS CAN UL/CSA (CMX) 2
×
2
×
0.34, Article No. 2170 264
Helukabel CAN BUS 4 × 1 × 0.34, Article No. 801573
