Allen-Bradley SLC 500 Modules: 1746-OV16

Technical Dossier

Product Details And Specifications

Allen-Bradley SLC 500 Series Technical Notes

The Allen-Bradley SLC 500 (Small Logic Controller 500) platform, manufactured by Rockwell Automation, is one of the most widely deployed modular PLC architectures 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 series established a benchmark for rack-based I/O modularity in the 1990s and 2000s. The 1746-OV16 is a 16-point transistor (sinking) DC digital output module within this platform, rated for 5–26.4V DC loads at up to 0.5A per point. Its continued presence in legacy installations across Asia-Pacific, the Middle East, and North America makes it a high-demand spare part for facilities operating extended lifecycle programs.

The Evolution of SLC 500 Architecture

The SLC 500 platform was introduced by Allen-Bradley (now Rockwell Automation) in 1989 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 1747 processor family, with a backplane communication bus operating at a fixed scan rate. Early processors such as the 1747-L20 (SLC 5/01, 1K memory) and 1747-L30 (SLC 5/02, 4K memory, DH-485) supported limited I/O counts. The mid-generation 1747-L531 (SLC 5/03) introduced DH+ networking. Later generations including the 1747-L541 (SLC 5/04) and 1747-L553 (SLC 5/05) expanded to 4096 I/O points with Ethernet/IP, DH+, and RS-232 communication.

The SLC 500 platform entered Rockwell's End of Life phase in 2012, with final production of select modules ceasing between 2015 and 2022. Facilities that have not migrated to the CompactLogix (1769) or ControlLogix (1756) platforms continue to require original 1746-series modules for corrective maintenance. Compatibility across chassis generations — 4-slot 1746-A4, 7-slot 1746-A7, 10-slot 1746-A10, 13-slot 1746-A13 — is maintained across the full I/O module range, making cross-generation spare pooling viable. The SLC 500's long installed base means lifecycle support demand will persist through the 2030s in facilities with deferred migration schedules.

SLC 500 Full Catalog & Functionalities (SKU List)

Digital Output Modules

• 1746-OV16: 16-point transistor sinking DC output, 5–26.4V DC, 0.5A/point — primary listing SKU.
• 1746-OV32: 32-point transistor sinking DC output, 5–26.4V DC, 0.25A/point, high-density rack.
• 1746-OB16: 16-point transistor sourcing DC output, 10–50V DC, 1A/point, NPN load drive.
• 1746-OB32: 32-point transistor sourcing DC output, 10–50V DC, 0.5A/point, high-density sourcing.
• 1746-OA16: 16-point triac AC output, 74–265V AC, 0.5A/point, resistive and inductive loads.
• 1746-OW16: 16-point relay output, 5–265V AC/DC, 2A/point, isolated contacts for mixed voltage.
• 1746-OW8: 8-point relay output, 5–265V AC/DC, 4A/point, high-current relay switching.

Digital Input Modules

• 1746-IB16: 16-point DC sinking input, 10–30V DC, standard field device interface.
• 1746-IB32: 32-point DC sinking input, 10–30V DC, high-density sensor interfacing.
• 1746-IA16: 16-point AC input, 74–132V AC, 50/60Hz, legacy AC field wiring.
• 1746-IV16: 16-point DC sourcing input, 10–30V DC, PNP sensor compatibility.
• 1746-IN16: 16-point AC/DC input, 5–30V DC / 74–132V AC, universal field wiring interface.

Analog I/O Modules

• 1746-NI4: 4-channel analog input, 4–20mA / 0–10V DC, 12-bit resolution, process instrumentation.
• 1746-NO4I: 4-channel analog current output, 4–20mA, 12-bit resolution, valve and actuator control.
• 1746-NI8: 8-channel analog input, configurable current/voltage, 12-bit, multi-loop process control.
• 1746-NO4V: 4-channel analog voltage output, 0–10V DC, 12-bit resolution, speed reference drives.
• 1746-FIO4I: 4-channel fast analog I/O, 1ms update rate, high-speed closed-loop applications.
• 1746-NT4: 4-channel thermocouple input, J/K/E/T/R/S/B types, 16-bit resolution, furnace control.

Processor / CPU Modules

• 1747-L20B: SLC 5/01 processor, 1K user memory, DH-485, entry-level standalone control.
• 1747-L30B: SLC 5/02 processor, 4K user memory, DH-485, small network node.
• 1747-L531: SLC 5/03 processor, 16K user memory, DH+ + RS-232, mid-range standalone control.
• 1747-L541: SLC 5/04 processor, 64K user memory, DH+ + RS-232, plant-floor network backbone.
• 1747-L553: SLC 5/05 processor, 64K user memory, Ethernet/IP + DH+ + RS-232, full network integration.

Communication & Specialty Modules

• 1746-BAS: BASIC module, embedded BASIC interpreter for custom data handling and serial communication.
• 1746-HSCE: High-speed counter/encoder module, 1MHz input rate, position and velocity measurement.
• 1746-QS: Stepper/servo positioning module, pulse-and-direction output, single-axis motion control.

Sourcing Hard-to-Find & Obsolete SLC 500 Parts

For facilities operating under a Run-to-Failure or Extended Lifecycle Maintenance strategy, DriveKNMS provides: direct replacement units for immediate dispatch, tested exchange units with documented burn-in records, and multi-unit lot pricing for stocking programs. Procurement teams managing SLC 500 installed bases across multiple sites are encouraged to submit consolidated BOM lists for bulk quotation.

Quality Control for the SLC 500 Range

SLC 500 I/O modules present specific test challenges due to their backplane-dependent communication architecture. DriveKNMS applies the following test protocol to all 1746-series modules prior to dispatch: