Modbus Control via Remote Operator
Modbus RTU Module
10 Modbus Control via Remote Operator
The Modbus Module can be used to connect a Remote Operator to the soft starter,
enabling control via an RS-485 serial communications network. See the Remote Operator
instructions for details on connecting the Remote Operator to the starter. Connect the
Remote Operator to the network as described in the following sections.
10.1 Grounding and Shielding
Twisted pair data cable with earth shield is recommended. The cable shield should be
connected to the GND device terminal at both ends and one point of the site protective
earth.
10.2 Termination Resistors
In long cable runs prone to excessive noise interference, termination resistors should be
installed between the data lines at both ends of the RS-485 cable. This resistance should
match the cable impedance (typically 120
Ω
). Do not use wire wound resistors.
03250.
B
1
2
3
1
Network master RS-485
2
Remote Operator RS-485
3
Soft starter RS-485
10.3 RS-485 Data Cable Connection
Daisy chain connection is recommended. This is achieved by parallel connections of the
data cable at the actual device terminals.
10.4 Remote Operator RS-485 Network Connection Specifications
Input impedance:
12 k
Ω
Common mode voltage range:
- 7 V to + 12 V
Input sensitivity:
± 200 mV
Minimum differential output voltage: 1.5 V (with max loading of 54
Ω
)
8
