Allen-Bradley SLC 500 Modules – 1746-OB16E

Technical Dossier

Product Details And Specifications

Allen-Bradley SLC 500 Series Technical Notes

The Evolution of SLC 500 Architecture

The SLC 500 platform was introduced in the early 1990s as a mid-range successor to the PLC-2 and PLC-3 families, targeting applications requiring more I/O density than the MicroLogix line but not the full overhead of the PLC-5. The architecture centers on the 1746 backplane, available in 4-slot (1746-A4), 7-slot (1746-A7), 10-slot (1746-A10), and 13-slot (1746-A13) configurations. Processors communicate with I/O modules via a proprietary backplane bus at fixed scan rates.

Early SLC 5/01 and 5/02 processors (1747-L511, 1747-L524) supported only DH-485 communications. The SLC 5/03 introduced RS-232 DF1, and the SLC 5/04 added DH+ for integration into larger Allen-Bradley networks. The SLC 5/05 (1747-L551, 1747-L552, 1747-L553) introduced native Ethernet/IP, enabling integration with modern SCADA and MES layers without protocol converters. This generational progression created significant compatibility segmentation: 1746 I/O modules are backplane-compatible across all processor generations, but communication and programming software requirements differ. RSLogix 500 (now Studio 5000 Logix Designer legacy mode) is required for all SLC 500 programming. The platform reached end-of-life announcement from Rockwell Automation, with last-time-buy periods now closed for many catalog numbers, making secondary market sourcing the primary procurement channel for maintenance operations.

SLC 500 Full Catalog & Functionalities (SKU List)

Digital Output Modules

1746-OB16E: 16-point isolated sourcing DC output, 10–50 VDC, electronically fused per point — the subject of this listing. Designed for applications requiring per-point short-circuit protection without external fusing hardware. Commonly deployed in solenoid valve banks and motor starter pilot circuits.

1746-OB16: 16-point sourcing DC output, 10–50 VDC, non-isolated, group-fused. Standard discrete output for general-purpose actuator control.

1746-OB32: 32-point sourcing DC output, 10–50 VDC. High-density output module for applications with large actuator counts in a single slot.

1746-OB8: 8-point sourcing DC output, 10–50 VDC. Low-density output for smaller control panels or mixed I/O racks.

1746-OV16: 16-point sinking DC output, 10–50 VDC. Used where load common is positive rail (NPN-compatible field devices).

1746-OV32: 32-point sinking DC output, 10–50 VDC. High-density sinking output for NPN-type actuator arrays.

1746-OA16: 16-point AC output, 74–265 VAC, triac-based. Standard AC discrete output for contactors and solenoids on AC power rails.

1746-OA8: 8-point AC output, 74–265 VAC. Lower-density AC output for smaller panel configurations.

1746-OW16: 16-point relay output, Form A (SPST-NO), 5–265 VAC / 5–125 VDC. Relay isolation for mixed-voltage field devices and high-inrush loads.

Digital Input Modules

1746-IB16: 16-point sinking DC input, 10–30 VDC. Standard 24 VDC field device input, compatible with PNP proximity sensors and pushbuttons.

1746-IB32: 32-point sinking DC input, 10–30 VDC. High-density input for large sensor arrays.

1746-IA16: 16-point AC input, 74–132 VAC. For field devices powered from 120 VAC control circuits.

1746-IV16: 16-point sourcing DC input, 10–30 VDC. NPN-compatible input for sinking-type field sensors.

Analog I/O Modules

1746-NI4: 4-channel analog input, configurable 4–20 mA / 0–10 VDC / ±10 VDC / thermocouple / RTD per channel. 12-bit resolution. Used for process variable acquisition (pressure, temperature, flow).

1746-NO4I: 4-channel isolated analog output, 4–20 mA, 12-bit resolution. Isolated outputs for driving control valves and variable-speed drives with analog setpoints.

1746-NO4V: 4-channel analog output, 0–10 VDC / ±10 VDC, 12-bit resolution. Voltage output variant for positioners and other voltage-input actuators.

Specialty & Communication Modules

1746-HSCE2: High-speed counter/encoder module, dual-channel, up to 1 MHz input frequency. Used for encoder feedback in web tension and positioning applications.

1747-SDN: DeviceNet scanner module. Enables SLC 500 to act as DeviceNet master for distributed I/O and smart device networks.

1747-KE: DH-485 to RS-232 interface module. Protocol bridge for legacy HMI and programming terminal connectivity.

Quality Control for the SLC 500 Range

SLC 500 modules present specific test challenges due to their backplane-dependent operation: modules cannot be fully exercised without a live 1746 backplane and a functioning processor. DriveKNMS operates dedicated SLC 500 test rigs comprising 1746-A10 chassis, SLC 5/04 and 5/05 processors, and calibrated I/O load banks. The test protocol for the 1746-OB16E includes: (1) backplane communication handshake verification, (2) per-point output activation under rated resistive load (10–50 VDC, 0.5 A per point), (3) electronic fuse trip-and-reset cycle test on all 16 points, (4) thermal soak at 55°C for 30 minutes under full load, and (5) final backplane data integrity check. Analog modules (1746-NI4, 1746-NO4I) undergo additional calibration verification against NIST-traceable reference standards. All tested units are issued a DriveKNMS inspection report with point-by-point test results prior to shipment.