Version 3.05
| Optidrive Eco User Guide |
57
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10. Serial Communications
10.1. RS-485 Communications
Optidrive Eco has an RJ45 connector located within the wiring enclosure of the drive. This connector allows the user to set up a drive
network via a wired connection. The connector contains two independent RS485 connections, one for Invertek’s Optibus Protocol
and one for Modbus RTU / BACnet MSTP. Both connections can be used simultaneously.
The electrical signal arrangement of the RJ45 connector is shown as follows:
1
Not used
2
Not used
3
0 Volts
4
-RS485 (PC)
5
+RS485 (PC)
6
+24 Volt
7
RS 485- Modbus RTU / BACnet MSTP
8
RS 485+ Modbus RTU / BACnet MSTP
Warning:
This is not an Ethernet connection. Do not connect
directly to an Ethernet port.
Warning:
When using Modbus RTU or BACnet, ensure that the
0V signal (T3) is also used to avoid comms errors
and potentially damaging common mode voltages.
The Optibus data link is only used for connection of Invertek peripherals and inter-drive communication.
The Modbus interface allows connection to a Modbus RTU network as described in section
10.2. Modbus RTU Communications
.
10.1.1. RS-485 Communications Electrical Connections
Modbus RTU and BACnet MSTP connection should be made via the RJ45 connector. The pin assignments are as shown in section
11.1. RS-485 communications
.
Modbus RTU and BACnet MSTP networks require three conductors for best operation and to eliminate common mode voltages
on the drive terminals:
o RSR85+
o RS485-
o 0 Volt Common
Connection should be made using a suitable dual twisted pair, shielded cable, with a wave impedance of 120R.
Use one of the twisted pairs to connect to the RS485+ and RS485- of each drive.
Use one conductor of the remaining pair to connect together all the 0 volt common connection terminals.
The cable shield should be connected to a suitable clean ground point to prevent interference with the screen maintained as close
as possible to the cable terminations.
Do not connect the 0 Volt Common, RS485- or RS485+ to ground at any point.
Network terminating resistor (120R) should be used at the end of the network to reduce noise.
10
Serial Communications
