Allen-Bradley 1756 ControlLogix Modules: 1756-OB16I,

Technical Dossier

Product Details And Specifications

Allen-Bradley 1756 ControlLogix Series: Comprehensive Module Range and Technical Overview

The Allen-Bradley 1756 ControlLogix platform is one of the most widely deployed programmable automation controller (PAC) architectures in global heavy industry. Installed across petrochemical refineries, nuclear power generation facilities, offshore oil & gas platforms, pulp and paper mills, and large-scale water treatment infrastructure, the 1756 backplane-based system has served as the backbone of process and discrete control since its commercial introduction in the late 1990s. Its modular chassis architecture — supporting 4, 7, 10, and 17-slot configurations — allows engineers to construct highly scalable control nodes with deterministic I/O scanning, redundant controller support, and multi-network communication from a single rack. The 1756-OB16I is a 16-point isolated digital output module within this platform, rated for 10–30V DC operation with individual point isolation, making it the standard selection for applications requiring output channel independence and protection against ground loops in field wiring.

The Evolution of 1756 ControlLogix Architecture

The ControlLogix platform was introduced by Rockwell Automation in 1997 as a successor to the PLC-5 and SLC 500 families, designed to unify discrete, process, motion, and safety control under a single controller architecture. The original 1756-L1 and 1756-L20 controllers established the Logix5000 instruction set, which remains backward-compatible through current-generation 1756-L8x controllers. Early I/O modules used a parallel backplane bus; subsequent generations migrated to a high-speed serial backplane (ControlBus) that supports up to 65,535 I/O points per controller. The introduction of the 1756-EN2T and 1756-EN3TR EtherNet/IP adapters enabled distributed I/O over standard Ethernet infrastructure, replacing earlier ControlNet (1756-CNB) and DeviceNet (1756-DNB) topologies in many greenfield installations. The 1756-OB16I itself has remained a catalog-stable module across multiple firmware generations, with its isolated output architecture making it compatible with both legacy and current ControlLogix chassis without modification. As the broader 1756 platform transitions toward the 5380 and 5580 controller families, older I/O modules including the OB16I remain in active production support, though procurement lead times for certain variants have extended, increasing reliance on certified aftermarket supply channels.

1756 ControlLogix Full Catalog & Functionalities (SKU List)

Digital Output Modules

• 1756-OB16I: 16-point isolated 10–30V DC output module, individual point isolation, 0.5A per point
• 1756-OB16D: 16-point diagnostic 10–30V DC output, fault detection per point, electronic fusing
• 1756-OB32: 32-point 10–30V DC sourcing output, high-density discrete control
• 1756-OB8: 8-point 10–30V DC sourcing output, standard density discrete output
• 1756-OA16: 16-point 74–265V AC triac output, zero-cross switching, industrial AC loads
• 1756-OA8D: 8-point diagnostic AC output, 74–132V AC, per-point fault reporting
• 1756-OW16I: 16-point isolated relay output, 10–265V AC/DC, dry contact switching

Digital Input Modules

• 1756-IB16I: 16-point isolated 10–30V DC input, individual point isolation, high-noise immunity
• 1756-IB32: 32-point 10–30V DC sinking input, high-density discrete sensing
• 1756-IA16I: 16-point isolated 74–132V AC input, isolated channel architecture
• 1756-IC16: 16-point 48V DC TTL-compatible input, low-voltage logic interfacing

Analog I/O Modules

• 1756-IF16: 16-channel analog input, 4–20mA / 0–10V, 16-bit resolution, single-ended
• 1756-OF8: 8-channel analog output, 4–20mA / ±10V, 16-bit resolution
• 1756-IF8: 8-channel differential analog input, 16-bit, high-accuracy process measurement
• 1756-IR6I: 6-channel isolated RTD/resistance input, Pt100/Pt1000/Ni120 compatible

Controller & Communication Modules

• 1756-L73: ControlLogix 5573 controller, 8MB user memory, standard process control
• 1756-L83E: ControlLogix 5583 controller, EtherNet/IP embedded port, 20MB memory
• 1756-EN2T: EtherNet/IP communication module, dual-port, 100Mbps, DLR capable
• 1756-CNB: ControlNet bridge module, coax/fiber media, scheduled messaging
• 1756-PA72: 120/240V AC power supply, 10A backplane current, standard chassis power
• 1756-PB72: 18–32V DC power supply, 10A backplane current, DC-powered installations

Sourcing Hard-to-Find & Obsolete 1756 ControlLogix Parts

DriveKNMS maintains a dedicated inventory program for 1756 ControlLogix modules across all lifecycle stages — active production, mature, and discontinued. For facilities operating legacy ControlLogix chassis where original Rockwell Automation supply channels have extended lead times or have issued end-of-life notices, DriveKNMS provides certified surplus and refurbished units with full functional verification. This includes early-generation controllers such as the 1756-L55 and 1756-L60 series, legacy communication bridges including the 1756-DNB DeviceNet scanner, and high-density I/O modules that have been superseded by Compact 5000 equivalents. All sourced units are cross-referenced against Rockwell's catalog revision history to confirm hardware revision compatibility with the target chassis firmware. Customers operating under long-term maintenance agreements (LTMA) or extended support contracts are encouraged to submit their full BOM for batch availability assessment.

Quality Control for the 1756 ControlLogix Range

Each 1756-series module processed by DriveKNMS undergoes a structured verification protocol adapted to the module's functional category. Digital output modules including the 1756-OB16I are tested under load across all 16 output points, with isolation resistance measured between each point and chassis ground to confirm the isolated architecture is intact. Backplane connector pins are inspected under magnification for fretting corrosion — a common failure mode in modules removed from high-vibration environments. Analog modules are calibrated against NIST-traceable references with linearity and offset error recorded per channel. Communication modules are tested for EtherNet/IP or ControlNet connectivity using live network simulation, with CIP messaging latency logged. All modules are powered through a controlled 1756 chassis test fixture running current-generation Logix firmware to confirm module identity, revision reporting, and I/O tree recognition before dispatch.

© 2026 DriveKNMS. All trademarks belong to their respective owners. Specifications are for reference only and subject to change without notice. Verify all parameters against official documentation before installation.