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How to add a RS232 to RS485 converter to a ACE PLC?


It is sometimes useful to be able to connect the ACE PLC to an RS485 network.

As examples:

  • connect hundreds ACE PLC on the same RS485 network
  • connect a HMI to a ACE PLC far away from the each other where the RS232 is not enough (10 meters about)
  • connect an ACE PLC to an external sensor or device: Small display, variable-frequency drive, smart sensor,..

The ACE 1430 and 1450 already have a built-in RS232/485 port, but for the others a small RS232 to RS485 signal converter must be added. It’s not the ideal solution, but it can be useful as our industrial ACE are very powerful and cheap.

It has on one side a terminal board for the RS485. Only 485+ A+ and 485- B+ need to be connected.

On the other side, for RS232 the classic SUB-D9. Optional RS232 cable.

The RS232/485 converter is powered via the RS485 network. It is not necessary to power it except if you have many converters on RS485.

RS-232 Side
RS-485 Side
ACE PLC connector pin 1 <> Sub-D9 Converter Pin 4 485+ (A+) <> Your device A+
ACE PLC connector pin 2 <> Sub-D9 Converter Pin 3 485- (B-) <> Your device B-
ACE PLC connector pin 3 <> Sub-D9 Converter Pin 1 GND only connected on the master device side
Optional +5 to +12 VDC
(Only if serverals converters on network)

RS232 to RS485 converter connected to the ACE connector that is supplied with the ACE

Note: Cable sold without ACE connector

Connector Viewed from the wire side


Connect a HMI to a ACE PLC via RS232/485 converter

Download HMI project

  • The HMI project reads a ui16 value from the ACE PLC at address 4×0
  • We use the HMI port COM 1 (RS485 pins 9 & 8)
  • For HM-070MW (can be changed)

Download PLC program

  • It increments the value every second in the Modbus register
  • We use the port COM 1 (RS232)
  • For ACE-7096 PLC (can be changed)


ACE PLC to the RS-232 cable

White = RX
Red = TX
Green = GND

One twisted pair from the converter to the HMI

Red = A+
White = B-

 Sub-D9 wiring HMI side

Pin 9 = A+
Pin 8 = B+