Allen-Bradley 1756-OB16I/A ControlLogix 16-Ch DC Isolated Output Module

Allen-Bradley 1756-OB16I/A ControlLogix DC Isolated Output Module - 16-Channel Industrial Control Solution

The Allen-Bradley 1756-OB16I/A is a high-density DC isolated output module designed for the ControlLogix platform, delivering 16 independently isolated output channels for precise control of DC-powered field devices. This module provides robust electrical isolation between each output and the backplane, protecting your control system from ground loops, voltage spikes, and electrical noise in harsh industrial environments.

Technical Specifications

• Output Channels: 16 isolated DC outputs
• Output Voltage Range: 12-24VDC nominal
• Output Current: 1A per channel (continuous)
• Isolation Voltage: 1500VAC channel-to-backplane, 250VAC channel-to-channel
• Output Type: Electronically protected sourcing outputs
• Response Time: 1ms typical ON/OFF delay
• Diagnostic Indicators: Per-channel LED status, module fault indication
• Power Consumption: 3.5W @ 5VDC, 1.5W @ 24VDC from backplane
• Operating Temperature: 0°C to 60°C (32°F to 140°F)
• Conformal Coating: Available for enhanced environmental protection
• Removable Terminal Block: 36-pin spring-clamp or screw-terminal style

Application Scenarios

The 1756-OB16I/A excels in applications demanding electrical isolation to prevent ground-related faults and ensure signal integrity across distributed control architectures:

• Multi-Zone Process Control: Isolated outputs prevent ground loops when controlling devices across different electrical zones or buildings with separate ground references
• Hazardous Location Interfacing: Provides isolation barrier between safe-area controllers and field devices in classified areas when paired with appropriate intrinsic safety barriers
• Motor Starter & Valve Control: Drives solenoid valves, motor contactors, and pneumatic actuators with protection against back-EMF and inductive kickback
• Conveyor & Material Handling: Controls diverters, gates, and sortation mechanisms in high-speed packaging and distribution systems
• Water/Wastewater Treatment: Operates pumps, chemical dosing systems, and valve actuators in corrosive, electrically noisy environments
• Building Automation: Interfaces with HVAC dampers, lighting contactors, and access control systems requiring isolated control signals

Engineering Solutions & Design Advantages

The channel-to-channel and channel-to-backplane isolation architecture eliminates common-mode voltage issues that plague non-isolated output modules in large-scale installations. Each output features electronic overcurrent protection with automatic recovery, eliminating the need for external fuses and reducing maintenance overhead.

Diagnostic capabilities include per-channel short-circuit detection, open-load detection (when enabled), and module-level fault reporting through the ControlLogix backplane. These diagnostics integrate seamlessly with RSLogix 5000/Studio 5000 programming software, enabling predictive maintenance strategies and rapid fault localization.

The removable terminal block design supports hot-swapping for minimal downtime during module replacement. Spring-clamp terminals accept 14-22 AWG wire without tools, accelerating installation and reducing wiring errors in high-density control panels.

Frequently Asked Questions

Q: What's the difference between 1756-OB16I and standard 1756-OB16E modules?
A: The "I" suffix denotes isolated outputs with 1500VAC channel-to-backplane isolation and 250VAC channel-to-channel isolation. Standard OB16E modules share a common return and lack this isolation, making them unsuitable for applications with multiple ground references or high electrical noise.

Q: Can I control 24VDC devices from a 12VDC power supply?
A: No, the module requires field power matching the device voltage. For 24VDC devices, supply 24VDC to the field power terminals. The module supports 12-24VDC range but cannot boost voltage—it only switches the supplied voltage to outputs.

Q: How do I wire the isolated outputs correctly?
A: Each output requires a dedicated return path to the field power supply negative terminal. Do not share returns between channels or tie returns to chassis ground, as this defeats the isolation and can create ground loops.

Q: What happens during output overload or short-circuit?
A: Electronic protection limits current and sets a diagnostic fault bit in the module's status word. The affected channel shuts down until the fault clears and the controller resets the output. No physical fuse replacement is needed.

Q: Is this module suitable for safety-rated applications?
A: No, the 1756-OB16I/A is a standard I/O module, not safety-rated. For SIL-rated safety applications, use GuardLogix safety I/O modules like the 1756-OB16IS or 1756-OB8EI with appropriate safety controllers.

Warranty & Support

This Allen-Bradley ControlLogix module is backed by a 12-month manufacturer warranty covering defects in materials and workmanship. Our technical team provides configuration assistance, wiring diagrams, and integration support for ControlLogix systems throughout the product lifecycle.

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