Overview
The Allen-Bradley 1756-OB16D is a ControlLogix DC diagnostic output module designed for high-density diagnostic outputs in industrial control systems. It features 16 diagnostic outputs arranged in two groups of 8 points, each with individual electronic fusing and real-time diagnostics at the point level. This module supports 24V DC loads and is optimized for applications requiring discrete output control with comprehensive fault detection and monitoring.
Key Features
- 16 Diagnostic Output Points — Two groups of 8 points with per-point electronic fusing for enhanced reliability and protection
- Advanced Diagnostics — Configurable no-load detection, output verification, and fault/program mode state management
- Sourcing Outputs — Delivers current to 24V DC loads such as solenoids, lights, relays, and control devices
- Per-Point Fusing — Electronically fused on a per-point basis for circuit isolation without traditional cartridge fuses
- Field-Side Diagnostics — Output state visibility in fault mode, program mode, and transition states with latching options
- RTB Compatibility — Requires 36-position removable terminal block housing (1756-TBCH or 1756-TBS6H)
Technical Specifications
- Output Voltage: 19.2–30V DC (nominal 24V DC)
- Number of Outputs: 16 diagnostic points (8 per group)
- Output Current per Point: 2 A maximum at 30 °C (80 °F); 1 A maximum at 60 °C (140 °F)
- Module Output Current: 8 A maximum per group at 30 °C; 4 A per group at 60 °C
- Minimum Load Current: 3 mA per point
- Maximum Off-State Leakage: 1 mA per point
- On-State Voltage Drop: 1.2V DC maximum at 2 A
- Output Delay (On to Off): 630 µs nominal; 5 ms maximum
- Output Delay (Off to On): 55 µs nominal; 1 ms maximum
- Short-Trip Diagnostic: 8 A (180 ms minimum) or 10 A (120 ms minimum)
- Backplane Current: 140 mA @ 24V DC; 250 mA @ 5.1V DC
- Backplane Power: 4.64 W
- Operating Temperature: 0–60 °C (32–140 °F)
- Storage Temperature: –40–85 °C (–40–185 °F)
- Isolation Voltage: 100% tested at 2546V DC for 1 second; 250V AC maximum continuous (group-to-group)
- Module Location: 1756 ControlLogix Chassis (any available slot)
- Connector: 36-pin backplane connector
Typical Applications
- Industrial machinery control with solenoid valve actuation and relay switching
- Assembly line output control for motor starters, indicator lights, and alarm devices
- Conveyor systems with discrete point-level fault diagnostics
- Process automation requiring output verification and no-load detection
- Building automation and HVAC system integration via ControlLogix platforms
- OEM equipment requiring real-time output state monitoring and diagnostic reporting
Compatibility & Replacements
Compatible With
- 1756 ControlLogix Programmable Automation Controller (PAC) chassis
- CompactLogix 5370 controllers via optional adapters
- ControlLogix 5570 and earlier ControlLogix families
- Removable Terminal Block Housings: 1756-TBCH, 1756-TBS6H
- Studio 5000 Logix Designer software (all current and legacy versions supporting 1756 modules)
- Allen-Bradley EtherNet/IP and ControlNet networks (module communication via chassis)
Replaces / Drop-In Replacement For
- 1756-OB16D (Revision A and earlier revisions) — compatible with same RTB and chassis configurations
- Functionally similar to non-diagnostic 1756-OB16 (standard output module without diagnostics) in many applications, though diagnostic features differ
Works With
- Studio 5000 Logix Designer — native support for all diagnostic configuration and monitoring
- Allen-Bradley FactoryTalk View and HMI platforms for output state visualization
- PROFINET gateways for integration into Siemens environments (via EtherNet/IP bridge)
- OPC-UA servers for enterprise data integration
- Secure FTP firmware updates via Rockwell Automation connected services
