Allen-Bradley 1756-OB16D | 16-Point DC Diagnostic Output

Allen-Bradley ControlLogix 16-Point Diagnostic DC Output Module 1756-OB16D

The Allen-Bradley 1756-OB16D is an advanced diagnostic output module for ControlLogix systems. It provides 16 sourcing DC outputs with per-point electronic fusing and comprehensive health monitoring. This module is designed for applications requiring high reliability and detailed fault detection.

Core Specifications

• Brand & Model: Allen-Bradley 1756-OB16D
• Series: ControlLogix Diagnostic I/O Module
• Type: 16-Point Sourcing DC Output
• Voltage Category: 12/24V DC Source
• Operating Voltage Range: 19.2 – 30V DC
• Output Current (Per Point): 2 A Max @ 30°C, derated to 1 A @ 60°C
• Output Current (Module Total): 8 A Max @ 30°C, 4 A Max @ 60°C
• Backplane Current: 250 mA @ 5V DC, 140 mA @ 24V DC
• Power Dissipation: 3.3 Watts Max @ 60°C
• Isolation Voltage: 50V Continuous (250V AC max)

Key Features

• Advanced Diagnostics: Per-point detection for short circuits, no-load (open wire), and output verification.
• Electronic Fusing: Individual point protection (trips at 8A for 180 ms min, 10A for 120 ms min).
• Configurable Fault States: Set each point to Off, On, or Hold Last State in Program or Fault mode.
• Pulse Test Function: User-configurable pulse width for output verification testing.
• Data Echo: Reads back actual output state for confirmation and diagnostics.

Performance & Timing

• Output Delay (OFF to ON): 55 µs typical / 1 ms max
• Output Delay (ON to OFF): 630 µs typical / 5 ms max
• On-State Voltage Drop: 1.2V DC max @ 2 A
• Off-State Leakage: 1 mA max per point
• Minimum Load Current: 3 mA per point for no-load detection
• Surge Current: 4 A for 10 ms per point, repeatable every second

Installation & Compatibility

• Terminal Block: Requires 36-pin RTB: 1756-TBCH (screw) or 1756-TBS6H (spring clamp).
• Chassis: Installs in any slot of a compatible 1756 ControlLogix chassis.
• Wiring: Follow 24V DC sourcing output practices. Ensure external power supply is within 19.2-30V DC.
• Grouping: 16 points divided into 2 isolated groups of 8.

Physical & Environmental

• Operating Temperature: 0° to 60°C (32° to 140°F)
• Storage Temperature: -40° to 85°C (-40° to 185°F)
• Isolation Test: 2546V for 1 second (group-to-group, user-to-system)
• Enclosure: None (for chassis mounting)
• Slot Width: 1 Slot

Packaging & Shipping

• One Allen-Bradley 1756-OB16D diagnostic output module.
• Secure industrial packaging.
• Shipped via FedEx, UPS, or DHL.

FAQ

• What is "no-load" detection?
  It detects an open wire or missing load when the output is commanded ON, helping to identify wiring faults or disconnected devices.
• Can I replace a blown fuse on this module?
  No. Protection is provided by electronic fusing which resets automatically after the fault is cleared; there are no physical fuses to replace.
• How is this module different from a standard output module?
  It adds advanced per-point diagnostics (short, open, verification) and electronic fusing, which are not available on standard modules like the 1756-OB16.