Description
Product Introduction & Engineering Value
High-density control enclosures often run out of physical mounting space long before they run out of control logic tasks. The Allen-Bradley 1746-OB32E solves this footprint constraint by cramming 32 sourcing 24V DC transistor outputs into a single SLC slot, effectively doubling the density of standard 16-point cards.
Crucially, Rockwell equipped this high-density module with onboard electronic fusing (“E” designation). If a field wire short-circuits on channel 27, the card trips that specific point without blowing a physical fuse or taking down the other 31 active output points across your process line.
Technical Specifications
- Number of Outputs: 32 sourcing points (electronically fused)
- Operating Voltage Range: 10 to 30V DC
- Continuous Current per Channel: 0.5 A at 30°C (0.25 A at 60°C)
- Continuous Current per Group: 4.0 A max per 8-point group (16.0 A module total max)
- Electronic Protection Trip Point: 1.0 A to 2.0 A per channel
- Off-State Leakage Current: 1.0 mA max
- On-State Voltage Drop: 1.2 V DC max at 0.5 A
- Backplane Current (5V DC): 190 mA
- Field Wiring Connector: 40-Pin MIL-C-83503 style ribbon or terminal block connector
- Isolation: 1500V AC field-to-backplane
Field Application & The “Trench” Experience
During an emergency line restoration at a high-speed pharmaceutical packaging facility, a sorting wheel assembly pinched a harness containing 12 solenoid control wires. On standard 32-point output cards without electronic protection, a single pinched ground wire would incinerate internal traces or drop an entire 16-point common bank. Thanks to the 1746-OB32E, the electronic trip isolated only the damaged divert gate solenoids, allowing the rest of the 32-point packaging indexer to complete its batch cycle safely while operators isolated the faulty wiring harness.
- High-Speed Postal Parcel Sorting: Controlling 32 individual pneumatic diverter shoes across continuous high-speed sorting conveyors.
- Semiconductor Automated Test Racks: Driving pilot indicator arrays, safety interlock relays, and vacuum solenoids in compact testing skids.
- Multi-Lane Beverage Can Inspection: Actuating high-rate rejection air blast valves across 32 parallel inspection lanes.
Transparency SOP: QA & Testing
- Connector & Edge Pin Audit: Inspecting the 40-pin header connector pins for bending or fretting corrosion, along with gold edge fingers on the backplane interface.
- Backplane Current Verification: Placing the 1746-OB32E into an active 1746 chassis to ensure 5V DC backplane power draw stays precisely within the 190 mA factory rating.
- 32-Point Overcurrent Trip Stress Test: Systematically shorting every single output point (0 through 31) under live load in RSLogix 500 to verify that every channel’s electronic short-circuit protection trips and latches correctly.
- Thermal Chamber Load Testing: Running all 32 channels under maximum rated current loading (4.0A per group) inside an environmental chamber for 12 hours to verify thermal dissipation stability.
- 1746-OB32E
- 1746-OB32E
The Veteran’s Tech Trap Guide
- ⚠️ Wiring Interface Connection: Unlike 8-point and 16-point SLC cards that use standard Screw-Terminal Blocks (RTB), the 32-point 1746-OB32E utilizes a 40-pin high-density connector. You MUST use pre-wired cable assemblies (such as Allen-Bradley 1492-CABLE series) or 1492 interface breakout terminal modules. Trying to hand-solder or force standard connectors onto these pins will break the internal header.
- PRO TIP: Resetting Tripped Outputs: When an overcurrent occurs, the channel’s electronic protection latches the output in an OFF state. Clearing the physical short circuit on the machine is step one; step two requires toggling the output bit in logic or cycling 24V DC field supply power to reset the electronic fuse.
- ⚠️ Strict 4.0A Group Limit: The 32 channels are arranged into four groups of 8 points. Even though each output can handle 0.5A individually, energizing all 8 points in a single group to 0.5A simultaneously hits the 4.0A group limit. If your field solenoids draw high continuous power, balance the loads across different point groups to avoid thermal trips.
Dynamic FAQ
Q: Can I use the 1746- in a standard SLC 500 rack without special power supplies?
A: Yes, provided your overall 24V DC external field power supply can handle the combined load of your 32 field devices. The backplane draw is modest (190 mA @ 5V DC).
Q: How does the electronic protection on the 1746- differ from standard fusing?
A: Standard fused cards rely on physical glass fuses that must be manually replaced when blown. The 1746- uses solid-state current sensing that trips electronically in milliseconds without permanent damage, resetting as soon as the fault is cleared and power is toggled.
Q: What cable family is compatible with the 1746- front connector?
A: It pairs directly with Allen-Bradley 1492 IFM (Interface Modules) and 1492-CABLE pre-wired harnesses for fast terminal rail wiring.
Q: Are these high-density replacement cards fully tested across all 32 points before shipping?
A: Yes. Every 1746- undergoes a complete 32-channel bench audit where each individual channel is load-tested and short-circuit verified on a live SLC 500 test rack.
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