Overview
The Allen-Bradley 1785-KA3 is a PLC-2 communication interface module that integrates legacy PLC-2 controllers into Data Highway Plus (DH+) networks. This communication adapter module allows a PLC 2 programmable controller to communicate with other devices over the Data Highway Plus network. This communication adapter module needs to be installed in a slot in an Allen-Bradley Bulletin 1771 I/O chassis.
Key Features
- PLC-2 to DH+ Gateway: The 1785-KA3 PLC-2 Family Communication Adapter Module is a communication adapter installed on any slot (except the furthest left) of the 1771 I/O chassis, which links the PLC-2 family processors to a Data Highway Plus (DH+) Network.
- Configurable Network Parameters: The 1785-KA3 has 3 sets of switches: the Data Highway Plus baud rate switch assembly, the write options switch assembly and the node address group switch.
- Multiple Interface Support: It has an interface port for connection to the PLC-2 Programmable Controller using the Data Highway Plus Processor cable and a Data Highway Plus drop-line, and for connection to the 1784-T50 Industrial Workstation using the Program Panel Interconnect Cable.
- Wide Processor Compatibility: This unit supports most PLC-2 family processors, and the module is keyed to the backplane by connecting the band between pins 4 and 6, 22 and 24 of the top connector.
Technical Specifications
- Backplane Current Draw: The 1785-KA3 draws 1.2 A backplane current at 5 Volts DC.
- Operating Temperature: It has an ambient working temperature range between 0 to 60 degrees Celsius and is stored at a range of -40 to 85 degrees Celsius.
- Mounting: Single slot installation in Bulletin 1771 I/O chassis
- Network Protocols: Data Highway Plus (DH+), Data Highway
- Interface Ports: DH+ connector, DH+ drop-line port, 1784-T50 configuration terminal interface
Typical Applications
The 1785-KA3 serves as a critical bridge for legacy PLC-2 automation systems requiring network connectivity. Industrial applications include:
- Machine tool and assembly line control systems requiring remote I/O access
- Integration of distributed PLC-2 processors across multi-plant facilities
- Real-time monitoring and diagnostics of legacy manufacturing equipment
- Network expansion of existing Data Highway Plus installations with PLC-2 nodes
- Drop-in replacement for failed or obsolete communication modules in operational systems
Compatibility & Replacements
The 1785-KA3 is designed specifically for PLC-2 family processors operating on Data Highway Plus networks. For systems requiring alternate communication solutions, engineers may reference companion modules such as the 1785-KA (DH/DH+ bridge for PLC-5 systems) or 1785-KE (PLC-5 DH+ interface). When specifying a replacement or upgrade path, consult your system architecture documentation to verify DH+ network topology and node addressing requirements. Used modules are commonly available from surplus automation distributors and offer immediate delivery for emergency repairs.
