Modbus Module User Guide
13
Issue 1
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7.
Modbus Control via Remote Keypad
To control a soft starter via an RS485 serial communications network using the Remote Keypad, connect the Remote Keypad to the
network as described in the following sections.
7.1
Grounding and shielding
Twisted pair data cable with ground shield is recommended. The cable shield should be connected to the GND device terminal at both
ends and one point of the site protective ground.
7.2
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 RS485 cable. This resistance should match the cable impedance (typically 120
Ω
). Do not use wire wound resistors.
Figure 7-1 Installation with termination resistors
03250.
B
1
2
3
Network master RS485
Remote Keypad RS485
Soft starter RS485
7.3
RS485 data cable connection
Daisy chain connection is recommended. This is achieved by parallel connections of the data cable at the actual device terminals.
7.4
Remote Keypad RS485 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
)
