RS485 to RS485 Repeater

RS485 repeater or an optically isolated RS485 repeater. The device extends the communication distance of RS485-based equipment in industrial environments where the communication signals may be subjected to electrical noise and other interference.

The repeater supports one-way RS485 communication and operates in asynchronous half-duplex mode, allowing two-way communication between the master and slave devices. The device is transparent to the data transmission, meaning that the data transmitted through the repeater is not altered or modified in any way.

The built-in DC-DC power isolation module helps to protect the RS485 network from the ground loop and common mode voltage issues, which can affect the quality of the communication signals. The optocoupler further isolates the master and slave devices, ensuring that the data communication remains unaffected by electrical noise and other interference.

Product Overview

Product introduction

RS485 to RS485 repeater is an industrial grade high performance RS485 photoelectric isolation repeater that is compatible with EIA/TIA RS485 standards and realizes RS485 signal amplification and long communication distance of bus network, it is used to solve the problem of relay and isolation of RS-485 communication in a complex electromagnetic field. The interface adopts photoelectric isolation, and the interior adopts an industrial super anti-interference chip to realize the distinguishing intelligent circuit, automatically sensing the direction of data flow, stable signal, safe and reliable communication data, and aVOID RS-485 transceiver delay.


  • Designed for industrial automation communications, for range extension of RS485 communication equipment in complex and harsh industrial sites
  • 1 RS485 to 1 RS485, asynchronous half duplex, two-way communication, data transmission completely transparent
  • Built-in DC-DC power isolation module, isolation voltage 1500V
  • The optocoupler isolates RS485 master-slave network to ensure that data
  • communication is not affected by the common-mode voltage difference
  • TVS transient suppression protection + self-recovery fuse current limiting protection
  • Increase communication distance by 1200m (at 9600bps)
  • Real-time display of data transmission indicator light
  • The power supply circuit adopts an anti-reverse connection design
  • It is widely used in signal acquisition and control of industrial field equipment

1 RS485 to 1 RS485, asynchronous half duplex, two-way communication, data
transmission completely transparent

Application Scenarios

RS485 to RS485 repeater is suitable for: Industrial Automation, Power Collection, security monitoring, building intercom, high-speed charging, Brush Carmen ban, PLC, parking system, Modbus and other 485 bus protocol needs to extend the communication distance of the scene.

Technical parameters

Interface standardEIA / TIA compliant RS485 terminal block
Baud rate0 ~ 115200bps (adaptive)
Communication protocolnot restricted by the software protocol
Communication distanceonly one repeater is used to extend 1200 (at 9600bps)
CascadeRS485 interface supports a maximum of 32 nodes (distance between nodes should be ≤10m)
Operating voltage9V ~ 24V, active design with anti-reverse connection design
Static Power Consumption0.6W
Working temperature-20 ℃ ~ + 70 ℃
Storage temperature-40 ℃ ~ + 85 ℃
Relative humidity5% ~ 95%
Transmission mediumtwisted pair or shielded cable
Installation method35mm DIN rail

Product specification

Installation Dimensions

RS485 Amplifier

Terminal Function Description

FunctionNameAccount for
Input/InputA+Input RS485 positive signal
B-Input side RS485 negative signal
GNDInput RS485 ground
Indicator LightRXDThe input-receiving data indicator
TXDInput send data indicator
PWRPower Indicator
Output/OutputA+Output RS485 positive signal
B-Output RS485 negative signal
GNDOutput RS485 ground
Power/Power24V+DC 24V Power Positive Pole
GNDDC 24V power supply negative pole
AC power plug and SocketDC-00512V/1a, 5.5/2.1 mm power adapter socket

Diagram of The Connection

For RS485 to RS485 repeater RS485 signal output, maximum support 128 nodes (485 equipment), The branch length between nodes is not more than 10 meters, the bus length is not more than 1200 meters, the bus connection between nodes is hand-in-hand Mode does not allow forking to star connections (for hubs as a whole), as shown in figure 4.1.

1) single repeater: point-to-point connection of a 485 output device extends the communication distance by 1200m; point-to-multipoint connection of 32485 output devices with adjacent 485 devices not exceeding 10m extends the total bus length by 1200m.

2) Cascade (tree connection): Connect N 485 repeaters, indefinitely extend RS485 communication distance, and extend more 485 devices, a total of 128 devices are supported.

3) parallel: up to 16485 repeaters are supported and connected to the same 485 input devices, and up to 128 devices are supported.

Recommend debugging methods

After ensuring proper wiring of the equipment and strict compliance with specifications, the following recommended methods can be used for debugging:

  1. Common Ground Method: connect all 485 devices GND with a single line or shielded line, effectively avoiding the potential difference that affects communication between all devices.
  2. Terminal resistance method: improve communication quality by connecting 120 ω resistors to “A +” and “B-” on the last 485 devices of the bus.
  3. Middle section disconnection method: checking from the central end whether it is: equipment overload, communication distance is too long, device damage The impact on the entire communication line.
  4. Single wire method: simple and easy to pull a wire to the equipment temporarily, used to eliminate whether due to wiring communications failure.
  5. Converter replacement method: carry several converter replacement uses, and rule out whether the quality of the converter affects communication.
  6. Laptop debugging method: ensure that the personal computer laptop is a standard communication device, and replace the client computer for communication, if the communication is Normal, the customer’s computer serial port may be damaged.

Frequently asked questions

  1. are the data transfer transparent?
    Answer: Yes, RS485 to RS485 relay transmission is not limited by protocol, Modbus RTU/ASCLL, BAC NET, Profibus, DP, MPI/PPI.
  2. How Do I connect the terminal resistance?
    A: the beginning and end of the bus (no resistance is required if communication is normal).
  3. Does the repeater need to be configured to work?
    Answer: Repeater Plug and play, do not need to configure software settings can be used.
  4. What is the cause of data loss or error?
    Answer: check data rate, and format of data communication equipment on both sides are consistent.

Wiring matters needing attention

  • 485 communication lines must be Shielded Twisted Pair, preferably in reserve, with a total length of not more than 1200 meters
  • Wiring as far away from the high-voltage wire as possible, try not to parallel with the power line, can not tie together
  • 485 bus must be a hand-in-hand bus structure, resolutely put an end to star connection and bifurcation connection
  • More than 32 controllers or buses longer than 1200 m must use 485 repeaters
  • AC power supply equipment and chassis must be grounded, and a good grounding
  • Connect the GND of all 485 devices with a shielded cable
  • If it becomes unstable during communication, connect the last device’s A + a-to a 120-ohm terminal resistor

2 thoughts on “RS485 to RS485 Repeater”

  1. My PC adapter (Multipurpose optión) doesn’t work with the ppi protocol (s200) or with the mpi either (s300). Iy’s only world on profibus interface. What can I do to make the adapter work? Thanks un avance.


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