RS232 TO RS485 (B)

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RS232 TO RS485
Metal case, wall mounted
RS232 TO RS485 (B).jpg

RS485, RS232
RS232 TO RS485 (B)
V0 flame-retardant case, DIN rail type




RS232 TO RS485 (B) is an active electromagnetic isolated RS232 TO RS485 asynchronous bi-directional converter.


  • Compatible with RS232/RS485 standard, converting the RS232 signal into balanced differential RS485 signal.
  • Stable transmission at the rate of 300~115200bps.
  • Onboard unibody power supply isolation, provides stable isolated voltage and needs no extra power supply for the isolated terminal.
  • Onboard unibody digital isolation, allows signal isolation, high reliability, strong anti-interference, and low power consumption.
  • Onboard TVS (Transient Voltage Suppressor), effectively suppresses surge voltage and transient spike voltage in the circuit, lightning-proof & anti-electrostatic.
  • Onboard resettable fuse and protection diodes, ensure the current/voltage stable outputs, provide over-current/over-voltage protection, and improve shock resistance.
  • Integrates optional RS485 output terminal 120R resistor, enabled/disabled via a switch.
  • The onboard screw terminal, allows 6V~36V DC wide-range input.
  • Industrial rail-mount ABS case design, small in size, easy to install, and cost-effective.


Product Type Active optoisolated RS232 to RS485 serial converter
Power Supply Interface Power Supply 6~36V DC
Interface Protection Anti-reverse
Reliable Communication Rate [1] 300~115200bps
Device Interface RS232/RS485 standard complaint
RS232 Interface Interface Form Screw terminal
Transmission Distance About 15m
Transfer Mode Point to point
RS485 Interface Interface Form Screw terminal
Direction Control Hardware automatic control
Interface Protection Provides 600W lightning protection, surge protection and 15KV electrostatic protection
Terminal Resistor 120R, can be enabled by switching [2]
Transmission Distance About 1200m
Transfer Mode Point-to-multipoint (up to 32 nodes, repeaters are recommended for more than 16 nodes)
Product Appearance Case Rail-mount ABS case
Dimensions L × W × H: 91.6 × 23.3 × 58.7 mm
Operating Environment Temperature Range -15℃~70℃
  1. Communication Rate: The baud rate can reach 921600bps, and the reliable baud rate is the recommended, and the communication within this range is more stable and reliable.
  2. 120R switch: RS485 interface reserves a 120R for balancing resistance switch. Customers can consider whether to join according to the number of communications. It is recommended to join at the start-stop end, that is, add a 120Ω resistance to match with the host and the last device.

Application Diagram

RS232 TO RS485 (B) Spec01.png

Application Distance

  • Connect to the host/PLC/other devices or hosts with RS232, and can expand external RS485 devices for point-to-point half-duplex communication.

RS232 TO RS485 (B) Spec02.png

  • Connect to the host/PLC/other devices or hosts with RS232, and can expand and cascade multiple RS485 devices for point-to-point half-duplex communication.

RS232 TO RS485 (B) Spec03.png

Interface Introduction

RS232 TO RS485 (B) Spec04.png

Note: Generally, RS485 interface only can be connected to A+ and B- . If you want to isolate the signal from the ground, you can connect it to the ground icon.


RS232 TO RS485 (B) Spec05.jpg

Hardware Test

Test Description

  • Testing environment: PC (windows)
  • Testing hardware:
    • RS232 TO RS485
    • USB TO RS485
    • PC (If there is no RS232 interface, you can choose USB TO RS232 (female socket) for adapting test.)

Hardware Connection Testing

The RS232 interface of RS232 TO RS485 (B) connects to the PC with a serial extension cable or USB TO RS232 cable. The RS485 interface is connected to RS232 TO RS485 (B). The USB interface of USB TO RS485 connects to the same PC and automatically tests.
RS232 TO RS485 (B) Specre06.png

Description: RS485 interface, generally can only connect A+ and B- , if you want the signals to isolate the ground, you should connect to the ground icon.

On the PC, open two SSCOMs, open the corresponding port number, set the same baud rate, and click on the timing send, you can send and receive normally, the software test screenshot is as follows:
RS232 TO RS485 (B) Spec07.jpg

Note: RS485 is a half-duplex communication, which cannot be used for sending and receiving tests at the same time. You can test the receiving after sending.




  • In some simple application scenarios, GND can be unconnected if there is no need for shared signals or a common reference ground between devices and there are no interference or safety issues with the circuit.
  • However, for complex communication systems and applications with high signal integrity requirements, it is recommended that GND be connected according to the specification.


  • RS232 connect to the correct power supply, to avoid reverse connection, please use a multimeter to confirm the voltage in the range of 6-36V;
  • RS232 must be connected to GND, signal GND, and power GND to the same interface, TXD-RXD; RXD-TXD, if not on the exchange of TXD and RXD comparison test!

RS232 TO RS485 (B)-faq02.png

  • RS485 must be connected like A-A B-B, the 120ohm resistor is not connected by default.


  • Directly bridging Modbus devices that do not directly support Modbus (read/write) functionality.
  • The module itself is a pure hardware module that converts between RS485 and RS232 voltage levels, and it does not inherently support Modbus.

Modbus read/write operations and parameter configurations are carried out between the host (such as a computer) and the slave device (RS485 sensors, etc.). The module is only responsible for transmitting data and bridging communication between the two devices.



Technical Support

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