Allen-Bradley 1756-OB32 ControlLogix Output Module

Description

Product Introduction

The Allen-Bradley 1756-OB32 is a high-density 32-channel sourcing digital output module engineered for the ControlLogix system architecture. Slotting into any local or remote 1756 chassis, it provides maximum point density for switching 24V DC field actuators such as pilot valves, indicator lights, small relays, and alarm stacks.

By packing 32 output channels into a single slot, the 1756-OB32 cuts rack space requirements in half compared to standard 16-point cards like the 1756-OB16. However, because it drives double the points in the same physical footprint, care must be taken with total group current draw and terminal block wiring density.

Key Technical Specifications

Application Scenarios & The “Trench” Experience

A cabinet builder fits a complex packaging machine with 60 small pneumatic directional valves and 20 pilot lamps. Panel space is tight, and expanding the backplane to a larger 13-slot rack isn’t an option. Slapping in two 32-point 1756-OB32 cards gives the client 64 output channels while leaving open backplane slots for network communication bridges and motion cards.

Target Application Scenarios

• High-Density Packaging Equipment: Drives large arrays of low-wattage 24V DC pneumatic manifold valves on compact machinery.
• Material Handling & Sorting Hubs: Operates hundreds of small divert actuators, stack lights, and photo-eye emitters along conveyances.
• Assembly Automation Cells: Switches small locking solenoids, status indicators, and part-present clamping drivers.
• DCS Marshalling Cabinets: Acts as the main 24V DC sourcing output interface for high-point-count process skid control.

Field Case Study

An OEM automotive tier-1 supplier needed to add a secondary station to a door-trim assembly cell without expanding the existing 7-slot ControlLogix chassis. The current rack was fully populated with 16-point I/O cards. We supplied bench-tested 1756-OB32 modules to consolidate their 24V DC outputs. By replacing two 1756-OB16 cards with a single 1756-OB32, they freed up a full chassis slot for a 1756-EN2T Ethernet card to bring the new assembly section online without mounting an expansion rack.

1756-OB32

1756-

Transparency SOP: Quality Assurance & Testing

We don’t just ship boxes; we test them on actual Allen-Bradley racks. Every 1756- module moving through our shop undergoes a strict 5-step verification process:

1. Inbound Physical Inspection: Examining high-density backplane connector pins, side latching mechanisms, faceplate display windows, and checking board traces for thermal discoloration.
2. Live Rig Chassis Test: Inserting the card into an active 1756-A10 chassis running under power to verify backplane boot routines and diagnostic LED sequencing.
3. Full 32-Channel Load Bank Audit: Wiring all 32 channels across both 16-point groups to active 24V DC test loads to verify sourcing voltage, current delivery, and thermal performance under simultaneous switching loads.
4. Group Isolation Test: Verifying electrical isolation between Group 1 and Group 2 to ensure field power noise on one bank does not disrupt channel switching on the other.
5. ESD Isolation & Final Packaging: Neutralizing static charges on an ESD-grounded bench, fitting protective connector covers, and vacuum-sealing the module in anti-static shielding bags with desiccant.

The Veteran’s Tech Trap Guide (Crucial Value-Add)

⚠️ Watch Out for Terminal Block Compatibility: The 1756- uses a 36-pin Removable Terminal Block (RTB) such as the 1756-TBCH or 1756-TBS6H. Do NOT try to force a standard 20-pin RTB (like the 1756-TBNH used on 8-point and 16-point cards) onto this module—it will not fit and will break the alignment guides.

❗ Mind the 0.5A Current Limit: Each channel on the 1756- tops out at 0.5 Amps at 50°C (dropping to 0.35A at 60°C). Attempting to directly drive large hydraulic solenoid valves, heavy contactor coils, or motor brakes pulling >0.5A will burn out the output channel transistor. Use interposing relays or a heavy-duty card like the 1756-OB8 for heavy loads.

⚠️ 36-Pin Wiring Duct Saturation: Wiring 32 individual field leads plus power commons into a single 36-pin RTB gets crowded fast. Use thin-jacketed 18 AWG or 20 AWG wire. If you attempt to cram 14 AWG wire into a 36-pin screw terminal block, you won’t be able to close the module’s front door cover.

Frequently Asked Questions (FAQ for Conversion)

Q: Does the 1756- have per-point electronic fusing like the 1756-OB16E?

A: No. The 1756- features standard electronic short-circuit protection for the module, but it does NOT offer per-point individual electronic fusing. If you require channel-level electronic fusing and fault logging, consider using the 1756-OB16E (16-point) or adding external fused terminal blocks.

Q: Can I split the power supply between the two groups on a 1756-?

A: Yes. The 32 outputs are divided into two isolated groups of 16 channels (Group 1: Points 0-15; Group 2: Points 16-31). Each group has its own DC+ and DC- terminals, allowing you to feed them from separate 24V DC power supplies or safety circuit legs if needed.

Q: Is the 1756- hot-swappable in a live chassis?

A: Yes, it supports RIUP (Removal and Insertion Under Power). You can pull and insert the card without disrupting adjacent I/O modules or halting the ControlLogix backplane. Always turn off field power to the 36-pin RTB before removing the wiring harness.

Q: What wiring options exist besides manual terminal block wiring?

A: To save hours of cabinet panel wiring, you can use Rockwell’s IFM (Interface Module) pre-wired cable system. Simply plug a 1756-CBAxx cable into the 1756- and snap the other end into a DIN-rail mounted IFM terminal block matrix (e.g., 1492-IFD32).

Q: What warranty comes with this high-density module?

A: Every New Surplus and Refurbished 1756- module includes our full 12-month operational warranty. If the card experiences hardware failure under standard operating conditions within one year, we issue an immediate replacement or full refund.