The Allen-Bradley 1756-OB16I/A, also cataloged as the 1756-OB16I Digital Output Module, provides 16 individually isolated 12/24 VDC output channels for switching field loads from a ControlLogix controller.

Model Reference

The 1756-OB16I is a ControlLogix DC digital output module with 16 individually isolated channels. The module supports configurable output states and uses electronic protection for abnormal output conditions. The supplied spare reference is 1756-OB16I/A.

Hardware Specifications

DC Output and Channel Isolation

The 1756-OB16I provides 16 output channels with individual channel isolation. This construction permits each output circuit to be wired as a separate field interface without treating the sixteen channels as a single electrically common group.

The output is intended for 12/24 VDC circuits. Maximum output current is 2 A per channel, subject to the module's total current and environmental limitations.

Electronic output protection limits the effect of short-circuit and overload conditions. A faulted output should be corrected according to the module diagnostic and field wiring requirements before normal operation is restored.

Industrial Control Interface

The module exchanges output commands and status information with the ControlLogix controller through the chassis backplane. Output transition time is determined by the module hardware response together with the controller scan and application logic.

The specified maximum output delay is 70 us for off-to-on operation and 1 ms for on-to-off operation. These values describe module-level switching response and do not represent the complete end-to-end controller response time.

The 1756-OB16I occupies one ControlLogix chassis slot and uses a removable terminal block interface. Compatible terminal block families include the 1756-TBNH and 1756-TBSH.

Backplane Loading and Firmware Compatibility

The module draws 250 mA from the 5.1 VDC ControlLogix backplane supply. The specified backplane power is 1.28 W, while maximum module power dissipation is 5.6 W.

The module configuration and diagnostic behavior are handled through the ControlLogix programming environment. Controller and I/O-module firmware compatibility should be checked before changing controller firmware or migrating an existing project.

Ordering Information

• 1 x Allen-Bradley 1756-OB16I ControlLogix 16 Point DC Digital Output Module
• 1 x 1756-OB16I module assembly
• 1 x Compatible removable terminal block, selected separately when required
• 1 x ControlLogix chassis position is required for installation
• Field wiring, terminal-block accessories, and external protection devices are separate system components unless specifically configured

Installation and Wiring Guidelines

Output wiring

• Verify the field circuit voltage before connecting the output terminals.
• Use conductors sized for the required load current and installation conditions.
• Keep output wiring away from high-voltage and high-current switching circuits where practical.
• Confirm the load current for each channel before energizing the module.

Channel isolation

• Treat each isolated output as an independent field circuit.
• Do not connect output commons together unless the external circuit design explicitly requires it.
• Observe the specified isolation limits when wiring separate voltage domains.

Load protection

• Use suitable suppression for inductive loads such as relays, contactors, and solenoids.
• Verify that any external suppression device is compatible with the load voltage and polarity.
• Do not use the module's electronic protection as a substitute for correctly rated external load protection.

Installation

• Install the module in a compatible ControlLogix chassis.
• Check the chassis power budget after adding the output module.
• Ensure the removable terminal block is fully seated before applying field power.
• Follow the ControlLogix grounding and cabinet wiring requirements for the complete installation.

Frequently Asked Questions

• How many outputs does the 1756-OB16I provide?
  The module provides 16 DC digital output channels. Each channel is individually isolated for separate field circuit connection.
• What voltage does the module switch?
  The 1756-OB16I is a 12/24 VDC digital output module. The actual applied voltage must remain within the specified field circuit limits.
• Are the output channels individually isolated?
  Yes. The module provides individual channel isolation, allowing separate output circuits without treating all channels as one common electrical group.
• What is the maximum output current?
  The specified maximum output current is 2 A per channel. The total module load must also remain within the manufacturer's overall current limitations.
• What is the backplane current draw?
  The module draws 250 mA from the 5.1 VDC ControlLogix backplane supply. Its specified backplane power is 1.28 W.
• What are the output switching delays?
  Module-level delay is specified at 70 us maximum for off-to-on switching and 1 ms maximum for on-to-off switching.
• Which terminal blocks can be used?
  Rockwell Automation identifies 1756-TBNH and 1756-TBSH as compatible removable terminal block options for this module family.
• Does the module require a separate ControlLogix chassis?
  Yes. The 1756-OB16I is a chassis-based I/O module and occupies one ControlLogix chassis slot for backplane communication.