ABB C250 User manual - 2.5
5
2.5
Termination Resistor – Fig. 2.3
For long transmission lines, a 120
Ω
termination resistor must be fitted to the last slave
in the chain – see Fig. 2.3.
2.6
Serial Connections – Figs. 2.1 to 2.4
Notes.
•
Up to 10 slaves can be connected to a single RS422 adaptor card on
a PC.
•
Up to 32 slaves can be connected to a single RS485 adaptor card on
a PC.
The number of slaves can be increased if the driver’s serial port permits.
Connections to the MODBUS serial board must be made as shown in Figs. 2.1, 2.2
or 2.4. Connections on links with multiple slaves must be made in parallel, as shown
in Fig. 2.3. When connecting cable screens, ensure that no ‘ground loops’ are
introduced.
The maximum serial data transmission line length for both
RS422
and
RS485
systems is
1200m. The types of cable that can be used are determined by the total line length:
Up to 6m
–
standard screened or twisted pair cable.
Up to 300m
–
twin twisted pair with overall foil screen and an integral drain wire,
e.g. Belden 9502 or equivalent.
Up to 1200m
–
twin twisted pair with separate foil screens and integral drain
wires, e.g. Belden 9729 or equivalent.
2
Electrical installation…
Fig. 2.4 OPTO22 Board Connections
32
33
34
35
36
Rx+
Rx–
C250
V250
Tx+
GND
Rx+
Rx–
Tx+
Tx–
GND
OPTO22 Adaptor
Board Connections
Screen
Tx–
8
9
4
5
3
Refer to
page 2