Allen-Bradley SLC 500 Modules – 1746-IB16

Technical Dossier

Product Details And Specifications

Allen-Bradley SLC 500 Series Technical Notes

The Allen-Bradley SLC 500 (Small Logic Controller 500) series, manufactured by Rockwell Automation, is one of the most widely deployed programmable logic controller platforms in global heavy industry. Installed across petrochemical refineries, nuclear auxiliary systems, pulp and paper mills, automotive assembly lines, and water treatment facilities, the SLC 500 platform has accumulated decades of field-proven reliability. Its modular 1746 backplane architecture supports a broad range of discrete I/O, analog I/O, specialty, and communication modules, making it a standard reference platform for plant engineers and maintenance teams worldwide. The installed base remains substantial, with millions of I/O points still active in production environments across North America, Europe, and Asia-Pacific.

The Evolution of SLC 500 Architecture

The SLC 500 platform was introduced by Allen-Bradley in the late 1980s as a mid-range successor to the SLC 100 and SLC 150 fixed controllers. The architecture is built around the 1746 I/O chassis and the 1747 processor family. Early processors such as the 1747-L20 and 1747-L30 offered limited memory and fixed I/O counts. Subsequent generations introduced the 1747-L40, 1747-L511, 1747-L514, 1747-L524, and 1747-L531 through 1747-L553 series, progressively expanding user memory from 1K to 64K words, adding DH+ and RS-232 communication ports, and supporting online editing.

The 1746 I/O module family expanded in parallel, covering 24VDC and 120/240VAC discrete inputs and outputs, analog current and voltage modules, thermocouple and RTD inputs, high-speed counter modules, and DeviceNet/Profibus communication adapters. The SLC 500 platform reached end-of-life announcement from Rockwell Automation, with the majority of processor and I/O modules now classified as discontinued or RFQ availability review. This lifecycle status makes third-party sourcing and certified refurbishment critical for facilities committed to long-term SLC 500 operation.

Compatibility across the platform is governed by the 1746 backplane bus. All standard 1746 I/O modules are slot-compatible within any 1746 chassis (4-slot through 13-slot), provided the processor's I/O capacity and addressing limits are observed. Communication modules such as the 1747-SDN (DeviceNet Scanner) and 1747-AENTR (EtherNet/IP Adapter) extend the platform's connectivity to modern industrial networks without requiring a full migration to ControlLogix or CompactLogix.

SLC 500 Full Catalog & Functionalities (SKU List)

Discrete Input Modules (DI)

• 1746-IB16: 16-point 24VDC sink discrete input module, 1746 backplane, standard density
• 1746-IB32: 32-point 24VDC sink discrete input module, high-density, single-slot
• 1746-IA16: 16-point 120VAC discrete input module, optically isolated
• 1746-IA8: 8-point 120VAC discrete input module, standard density
• 1746-IN16: 16-point 24VDC source (NPN) discrete input module

Discrete Output Modules (DO)

• 1746-OB16: 16-point 24VDC source discrete output module, 0.5A per point
• 1746-OB32: 32-point 24VDC source discrete output module, high-density
• 1746-OA16: 16-point 120/240VAC triac output module, optically isolated
• 1746-OW16: 16-point relay output module, Form A contacts, 2A per point
• 1746-OV16: 16-point 24VDC sink discrete output module

Analog I/O Modules (AI/AO)

• 1746-NI4: 4-channel analog input module, 4–20mA / 0–10VDC selectable
• 1746-NI8: 8-channel analog input module, current/voltage configurable per channel
• 1746-NO4I: 4-channel analog current output module, 4–20mA
• 1746-NO4V: 4-channel analog voltage output module, 0–10VDC / ±10VDC
• 1746-NT4: 4-channel thermocouple/mV input module, types J/K/T/E/R/S/B
• 1746-NR4: 4-channel RTD/resistance input module, Pt100/Pt1000/Ni/Cu

Processor Modules (CPU)

• 1747-L511: SLC 5/01 processor, 1K user memory, DH-485 port
• 1747-L524: SLC 5/02 processor, 4K user memory, DH-485 port
• 1747-L531: SLC 5/03 processor, 8K user memory, DH+ and RS-232 ports
• 1747-L541: SLC 5/04 processor, 16K user memory, DH+ and RS-232 ports
• 1747-L553: SLC 5/05 processor, 64K user memory, EtherNet/IP and DH+ ports

Communication & Specialty Modules

• 1747-SDN: DeviceNet Scanner module, master node, up to 63 slave devices
• 1747-AENTR: EtherNet/IP adapter module, remote I/O over standard Ethernet
• 1746-HSCE: High-speed counter/encoder module, up to 1MHz input frequency

Quality Control for the SLC 500 Range

Discrete I/O modules (including the 1746-IB16) are tested under live 24VDC or 120VAC stimulus conditions, with each input point verified for correct state reporting via a reference SLC 5/04 or SLC 5/05 processor. Output modules are load-tested at rated current per point. Analog modules are calibrated against NIST-traceable references and verified across the full input/output range at multiple setpoints. Processor modules are powered, firmware-verified, and subjected to a communication port loopback test on both DH+ and RS-232/EtherNet/IP interfaces as applicable. All modules are inspected for capacitor condition, backplane connector integrity, and conformal coating status before packaging.