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RS485 RJ45 Interface Board for Laurel Electronics 1/8 DIN Instruments

RS485 RJ45 interface board

Key Features

  • Includes dual RJ45 connectors for daisy chaining of meters without a hub.
  • Allows up to 247 meters to be addressed using the Modbus RTU protocol.
  • Allows up to 31 meters to be addressed using Laurel's Custom ASCII protocol.
  • Selectable full-duplex or half-duplex operation.
  • Suitable for all 1/8 DIN Laureate DPMs, counters, timers & remote displays.
  • Selectable baud rates to 9600.
  • Isolated from meter and power grounds.
Description

The Laureate RS485 RJ45 interface board allows multiple Laureate meters, counters, timers and remote displays to be connected to the same RS485 line. Dual RJ45 jacks wired in parallel allow multiple instruments to be daisy-chained using data cables or patch cords with RJ45 plugs. In the absence of a computer, a single Laureate meter with an RS485 board can drive multiple Laureate 6-digit remote displays.

Operation can be configured for full-duplex or half-duplex operation using jumpers on the RS485 board. Transmission distances up to one mile are possible. In case of long line lengths, a jumper can be plugged in the RS485 board at the end of the line to insert a 120-ohm termination resistor to minimize signal reflections.

RS485 RJ45 connector wiring

Two serial protocols are user-selectable for RS485: Modbus RTU and Custom ASCII. For detailed information on our protocols, please see our communication user manuals.

  • The Modbus RTU protocol is an international standard and allows Laureates to share the same RS485 data lines with non-Laurel devices. It supports up to 247 digital addresses. Use of more than 31 Laurel RS485 Modbus boards requires repeaters for impedance reasons. Modbus RTU works in a master-slave (or query-response) mode, and its use requires an external Modbus master, which is typically a PC.
  • Laurel's Custom ASCII protocol is the simpler of the two protocols and uses ASCII strings. It is recommended if the only devices on the RS485 data line are Laureate meters. It supports up to 31 digital addresses. It can be set to a command mode under control of an external master, or to a continuous streaming mode where data is output at specified intervals at rates up to 60 per second.

The Laureate RS485 RJ11 interface board is similar to the RS485 RJ45 interface board which is the subject of this web page, except that it providess dual RJ11 connectors instead of RJ45 connectors. Both board support the Modbus RTU and Custom ASCII protocols equally.

Laurel RS485 network connected to PC via USB-to-RS485 server
Laurel RS485 network connected to Internet an Ethernet router or switch

The Laureate RS485 RJ11 interface board provides two 6-pin RJ11 jacks, whose pins are wired in parallel. This allows multiple Laureates to be daisy-chained using readily available 6-wire CBL03 data cables, with no need for an RS485 hub. It also allows meters with RS485 communications to be connected to a LAN via Laurel's Ethernet-to-RS485 converter, or to a host PC via Laurel's USB-to-RS458 converter. These Laureate converter boards provide an RJ11 connector, not an RJ45 connector.

The signal levels of the Laureate RS485 boards are compliant with the EIA/TIA-485 standard. Devices by different manufacturers can share the same RS485 data line, provided that their connectors are wired appropriately.

Specifications

Electrical Specifications

RS485 RJ11 Board Specifications
Laurel Part Number LMOD
Connection Full duplex (ATX, ARX, BTX, BRX) or
half duplex (ATX / ARX, BTX / BRX)
Data rates 300, 600, 1200, 2400, 4800, 9600 baud
No. of devices on data line Up to 31 without a repeater, 247 Modbus addresses
Connectors Dual RJ11 jacks for daisy chaining without a hub
Line length, max Up to 5000 feet (1500 meters) at 9600 baud depending on cable
Isolation 250V rms working, 2.3 kV rms per 1 min test
ESD Protection 15 kV per IEC 1000-4-2
EMI Immunity 10 V/m per IEC 1000-4-3
EFT Protection 2 kV per IEC 1000-4-4s
Short Circuit Protection Continuous
Selectable Protocols Modbus RTU, Custom Laurel ASCII

Protocol Specifications (protocols reside on Main Board)

Modbus RTU Protocol
Standards Compliance Modbus over Serial Line Specification V1.0 (2002)
Protocol Type Master-slave, query-response command mode
Data Streaming Mode Not supported by Modbus specification
Data Formats (selectable) 1. No parity, 8 data bits, 2 stop bits
2. Odd parity, 8 data bits, 1 stop bit
3. Even parity, 8 data bits, 1 stop bit
Main Board Revision Level Level 5 or above
Custom ASCII Protocol
Standards Compliance Laurel proprietary protocol
Data Format No parity, 8 data bits, 1 stop bit
Protocol Type Text string based command mode or continuous data streaming mode
Data Streaming Mode User selectable for up to 60 readings/sec
Main Board Revision Level Any
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