Description

The 1746-OBP8​ is an eight-output high-current DC output module manufactured by Allen-Bradley, a brand of Rockwell Automation, for the SLC 500 family of programmable controllers. It switches up to 2 A per point at voltages from 10 to 60 V DC — with a 72 V DC absolute maximum — and is the module to reach for when the load is too heavy for a standard 24 V DC output card but still within the SLC 500’s single-slot form factor.What defines the 1746-OBP8​ is the current rating rather than the voltage. At 2 A per point and 8 A per module, it drives contactor coils, solenoid valves, small motors, and indicator banks directly, without an interposing relay. The eight outputs are arranged in two fused groups of four, each protected by a 4 A slow-blow fuse, so a shorted load takes out four points rather than all eight — and the status LEDs show immediately which group dropped. The module is sinking (current-sourcing), switches in 2.5 ms OFF→ON and 1.5 ms ON→OFF, and carries 500 V DC of isolation between the output group and the backplane (but not between outputs). It is not socketed, has no conformal coating, and carries no hazardous-location approval, so it belongs in a clean, dry cabinet. Discontinued on 31 August 2016, the 1746-OBP8​ now circulates as new-surplus and tested spare stock — which makes a verified unit and a migration plan the sensible purchase.

Application Scenario

A grain terminal in the Canadian prairies runs a 1990s-vintage SLC 500 on its conveyor and loader skids, switching a mix of 48 V DC solenoid valves and 24 V DC contactor coils. The original output cards were standard 0.5 A modules, and every heavy load needed an interposing relay — a cabinet full of relays, a parts list nobody could keep straight, and a failure rate that rose with every relay contact that pitted or welded. During a harvest-season breakdown, the terminal lost a loader to a failed interposing relay and discovered it had no spare for the output card either.The panel was rebuilt around the 1746-OBP8. The eight high-current outputs drove the solenoids and coils directly, and the interposing relays were removed — fewer parts, fewer contacts, fewer things to stock. The two fused groups of four meant a shorted solenoid disabled its own group but not the whole skid, and the status LEDs turned fault-finding into a glance at the rack. The terminal now carries a tested 1746-OBP8​ on the critical-spare list and reports fewer after-hours callouts — the kind of gain that barely shows up in a spec sheet but dominates the maintenance budget during harvest.

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