Allen-Bradley SLC 500 Modules: 1747-L551/C Processor,

Name: Allen-Bradley SLC 500 Modules: 1747-L551/C Processor,
Brand: Allen-Bradley

Model: 1747-L551/C

Brand Allen-Bradley

Series SLC 500

Model 1747-L551/C

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Product Details And Specifications

Allen-Bradley SLC 500 Series Technical Notes

The Allen-Bradley SLC 500 (Small Logic Controller 500) is a fixed and modular programmable logic controller platform developed by Rockwell Automation. Since its commercial introduction in the early 1990s, the SLC 500 has accumulated one of the largest installed bases in global discrete and process manufacturing. It is deployed across chemical processing plants, oil refineries, nuclear auxiliary systems, pulp and paper mills, automotive assembly lines, and water treatment facilities. The platform's 1747 (processor/chassis/comms) and 1746 (I/O) catalog numbering system remains a reference standard for spare parts procurement worldwide. Despite Rockwell Automation's end-of-life announcements for several processor models, the SLC 500 continues to operate in thousands of facilities where full migration to ControlLogix or CompactLogix is deferred due to capital constraints or process continuity requirements.

The Evolution of SLC 500 Architecture

The SLC 500 platform was introduced as a successor to the Allen-Bradley SLC 100 and SLC 150 fixed controllers. The original modular chassis design used the 1746 backplane, supporting up to 30 I/O slots across multiple chassis sizes (4-slot 1746-A4, 7-slot 1746-A7, 10-slot 1746-A10, 13-slot 1746-A13). Processor generations evolved from the 1747-L511 (16KB memory, DH-485 only) through the 1747-L553 (64KB user memory, DH+, RS-232, full instruction set). The SLC 5/05 processors (1747-L551 through 1747-L553) added native Ethernet/IP capability, enabling integration with modern SCADA and MES systems without a separate communication bridge. Compatibility across generations is constrained by memory size and instruction set: programs written for 5/03 processors require validation before loading onto 5/04 or 5/05 hardware. The RSLogix 500 programming environment (now maintained as a legacy product) supports all SLC 500 processor variants. Migration paths to Studio 5000 / Logix Designer require full program conversion and hardware replacement.

SLC 500 Full Catalog & Functionalities (SKU List)

Controllers / Processors

1747-L511: SLC 5/01 processor, 1K memory, DH-485 port, fixed I/O configuration support.
1747-L514: SLC 5/01 processor, 4K memory, DH-485 port, expanded program capacity.
1747-L524: SLC 5/02 processor, 4K memory, DH-485, enhanced instruction set vs 5/01.
1747-L532: SLC 5/03 processor, 8K memory, DH-485 + RS-232 (DF1/DH-485), online editing.
1747-L541: SLC 5/04 processor, 16K memory, DH+ network port, high-speed counter support.
1747-L542: SLC 5/04 processor, 32K memory, DH+ port, extended data table capacity.
1747-L543: SLC 5/04 processor, 64K memory, DH+ port, maximum capacity for 5/04 family.
1747-L551: SLC 5/05 processor, 16K memory, Ethernet/IP + RS-232, web server interface.
1747-L551/C: SLC 5/05 processor Series C revision, 16K memory, Ethernet/IP, firmware Rev. 10+.
1747-L552: SLC 5/05 processor, 32K memory, Ethernet/IP + RS-232, dual-port comms.
1747-L553: SLC 5/05 processor, 64K memory, Ethernet/IP + RS-232, maximum SLC 500 capacity.

Digital I/O Modules (1746 Series)

1746-IA16: 16-point 120VAC digital input module, screw terminal, IEC Group 1 isolation.
1746-IB16: 16-point 24VDC sinking digital input module, standard density.
1746-OA16: 16-point 120/240VAC digital output module, triac output type.
1746-OB16: 16-point 24VDC sourcing digital output module, 0.5A per point.
1746-OW16: 16-point relay output module, Form A contacts, 2A per point, mixed voltage.

Analog I/O Modules (1746 Series)

1746-NI16I: 16-channel analog current input module, 4–20mA, 16-bit resolution.
1746-NI8: 8-channel analog input module, configurable voltage/current, 12-bit resolution.
1746-NO4I: 4-channel analog current output module, 4–20mA, 12-bit resolution.
1746-NO4V: 4-channel analog voltage output module, 0–10V / ±10V selectable.

Communication Adapters

1747-SDN: DeviceNet scanner module, master node, supports up to 64 slave devices on DN network.
1747-SN: Remote I/O scanner module, connects SLC 500 to 1771 remote I/O racks.
1747-KE: DH-485 to RS-232 interface module, protocol conversion for legacy serial devices.

Power Supplies

1746-P2: 24VDC / 120-240VAC power supply, 5A at 5VDC, supports up to 10-slot chassis.
1746-P4: 120-240VAC power supply, 10A at 5VDC, for high-density I/O chassis configurations.

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