1756-OB8 | Allen-Bradley ControlLogix 19-30V DC 8-Ch Digital Output Module
1756-OB8 | Allen-Bradley ControlLogix 19-30V DC 8-Ch Digital Output Module
1756-OB8 | Allen-Bradley ControlLogix 19-30V DC 8-Ch Digital Output Module
    1756-OB8 | Allen-Bradley ControlLogix 19-30V DC 8-Ch Digital Output Module
1756-OB8 | Allen-Bradley ControlLogix 19-30V DC 8-Ch Digital Output Module

1756-OB8 | Allen-Bradley ControlLogix 19-30V DC 8-Ch Digital Output Module

Part #: 1756-OB8 Manufactured by: Allen-Bradley
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$672.00
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Product Overview
Allen Bradley ControlLogix DC Output Module with 8-Point Outputs
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Product Description P/N: 1756-OB8

Description / Specifications

Description 

The Allen-Bradley 1756-OB8 is a ControlLogix discrete output module. It features Eight (8) 24VDC output channels in Two (2) groups of Four (4) channels each. Each channel delivers an output voltage range of 10-30VDC with nominal signal voltage of 24VDC. It is compatible for use with any ControlLogix chassis and uses the 1756-TBNH and 1756-TBSH Removable Terminal Block (RTB).

 

Technical Specifications 

Brand Allen-Bradley
Manufacturer Rockwell Automation
Part Number 1756-OB8
Signal Delay, OFF Transition 2 ms max
Signal Delay, ON transition 1 ms max
Current per module, max 8 A @ 60 °C (140 °F)
Current per point 2 A @ 60 °C (140 °F)
No. of channels per group 2
No. of output groups 2
Output Voltage range 10-30VDC
Output Voltage 24VDC
No. of Outputs 8
Backplane Current, 5.1VDC 165 mA
Backplane Current, 24VDC 2 mA
Total Backplane power 0.89 W
Series ControlLogix
Module Type Digital DC output module
Removable Terminal Block (RTB) 1756-TBNH 1756-TBSH
Outputs 8-Point
Voltage 12-24 Volts DC Source
Operating Voltage Range 10-30 Volts DC
Maximum Output Current Rating-Point 2 Amps at 60 degrees Celsius
Maximum Output Current Rating-Module 8 Amps at 60 degrees Celsius
Power Dissipation (Max) 2.5 Watts at 60 Celsius
Removeable Terminal Block(s) 1756-TBNH, 1756-TBSH
Isolation Voltage 50 Volts Continuous
Enclosure None

  

 

Information About 1756-OB8

The Allen-Bradley 1756-OB8 is a ControlLogix discrete output module. This module delivers an output voltage range of 10-30 VDC with nominal value of 24VDC. It is used to energize electrical loads that operate in DC voltages as well as AC loads, used with an interposing circuitry.

The 1756-OB8 is a single slot module that occupies any available slot of the chassis except the left-most slot which is intended for the ControlLogix processor or ControlLogix communication adapter / scanner module. It is compatible acting as a local I/O component or as part of a distributed I/O system. It may be installed to any available 1756- ControlLogix chassis and operate along standard or power supply modules.

The 1756-OB8 has a backplane current draw of 165 mA at 5.1 VDC and 2 mA at 24VDC while the total backplane power is 0.89 W and power dissipation of 2.5 W @ 60 °C (140 °F) and thermal dissipation of 8.53 BTU/hr. Each channel of this output module can deliver up to 2 Amperes @ 60 °C (140 °F) and 8 Amperes @ 60 °C (140 °F) per module.

This module uses a Removable Terminal Block (RTB) for connecting each channel of the module to the electrical loads. Compatible RTBs are 1756-TBNH and 1756-TBSH while appropriate RTB keying is user-defined, mechanical keying.

It is entered in the hardware configuration where module parameters and properties can be further modified/ Some of these parameters are Request Packet Interval (RPI), filter time, module inhibition and many others.

This module uses a Removable Terminal Block (RTB) which can either be the 1756-TBNH or the 1756-TBSH (20 pins RTB). This module has the following communication formats available: rack optimization, listen-only - rack optimization, output data, listen-only output data, and scheduled output data. Pilot duty is also available for the 1756-OB8 module.

The 1756-OB8 module has a voltage category of 12/24 volts DC source and an operating range of 10 to 30 volts DC. Its current draw is 165 mA at 5.1V and 2 mA at 24V. It has a backplane power of 0.89 W, with a maximum dissipation of 2.5 W at 60 Degrees Celsius (140 degrees Fahrenheit), and a thermal dissipation of 8.53 BTU/hr. The maximum off-state leakage current of this module is 1 mA per point and during an on-state, it has a maximum voltage drop of 1.2V DC at 2 A. It also has a maximum current of 2 A per point at 60 Degrees Celsius and a maximum current of 8 A at 60 Degrees Celsius per module. Its surge current per point is 4 A for 10 ms each that is repeatable every 1 s at 60 Degrees Celsius and its minimum load current is 2 mA per point. The module's isolation voltage is continuous at 250V. This module also allows you to modify states in Fault Mode per point and states in Program Mode per point. The choices for both are Hold Last State, On, or Off, with 'Off' set as default. Temperature ranges for the 1756-OB8 module are 0 to 60 Degrees Celsius when in operation and -40 to 85 Degrees Celsius when not in operation. It also has a maximum surrounding air temperature of 60 Degrees Celsius and a non-condensing relative humidity of 5% to 95%.





Manufacturer information

Allen-Bradley, a brand of Rockwell Automation, specializes in manufacturing industrial automation equipment. The product range includes programmable logic controllers (PLCs), motion control systems, safety devices, motor control equipment, automation software, and HMI panels. Allen-Bradley products are known for their reliability and integration with other systems.

Frequently Asked Questions about 1756-OB8
Question: What is the 1756-OB8 used for?
Date Update:20/06/2025
Answer:

The 1756-OB8 is an 8-point DC digital output module designed for ControlLogix systems. Its main purpose is to switch external DC loads such as relays, solenoids, and indicators by sourcing current from each output channel. It delivers 24VDC nominal output across a voltage range of 10–30VDC. Each channel can handle up to 2 A of output current, while the total module current is limited to 8 A at 60°C. The module can be configured in distributed or local I/O systems and supports various output data modes. This makes it ideal for precise and reliable control in industrial automation applications.

Question: Is 1756-OB8 hot-swappable?
Date Update:20/06/2025
Answer:

Yes, the 1756-OB8 module is hot-swappable when used within a properly configured ControlLogix system. This means the module can be inserted into or removed from the chassis while power is applied, without shutting down the entire system. However, hot-swapping should be done with caution — you must ensure that the controller is in a safe state, and it is strongly recommended to inhibit the module in the programming software (like Studio 5000) before removal or installation. Also, the system’s configuration must allow for electronic keying or be set to allow compatible keying to avoid faults. Hot-swap capability increases uptime and flexibility in maintenance and troubleshooting operations.

Question: What are voltage and current specs?
Date Update:20/06/2025
Answer:

Each output channel of the 1756-OB8 supports a voltage range of 10–30 VDC, with a nominal output of 24 VDC. The maximum current per point is 2 A, and the entire module can handle up to 8 A at 60°C ambient temperature. Surge current up to 4 A for 10 ms is supported, repeatable every second. The module’s backplane current consumption is 165 mA at 5.1 VDC and 2 mA at 24 VDC. Minimum load current per point is 2 mA, ensuring compatibility with low-consumption devices. Off-state leakage is limited to 1 mA, and voltage drop during on-state is a maximum of 1.2 V at 2 A.

Question: What are its isolation and temp specs?
Date Update:20/06/2025
Answer:

The 1756-OB8 is rated for operation in environments from 0°C to 60°C and storage from -40°C to +85°C. It tolerates relative humidity from 5% to 95%, non-condensing, and must be installed in environments free of corrosive gases and dust. Its isolation voltage is 50 V continuous between field-side and logic-side circuits. It provides basic protection against voltage spikes but should be used in conjunction with external fusing and surge suppression in critical applications. Proper grounding and shielding are also recommended to ensure stable operation in electrically noisy environments.

Question: Is 1756-OB8 still produced or replaced?
Date Update:20/06/2025
Answer:

Yes, the 1756-OB8 is currently still manufactured and supported by Rockwell Automation. It is part of the standard ControlLogix platform and widely used in both legacy and modern systems. However, for high-speed or safety-related applications, Rockwell also offers newer models with advanced diagnostics or output protection. Alternatives like the 1756-OB8EI provide enhanced electronic protection features. Migration to newer ControlLogix 5580 series I/O is also recommended for high-performance systems. When replacing or upgrading, ensure software and firmware compatibility with the controller.

IQElectro is not an authorized distributor.
QElectro LLC (IQElectro) is NOT an Authorized Distributor or in any way affiliated with Rockwell Automation, Siemens, or any other Manufacturers. IQElectro is NOT an Authorized Dealer of this product. The product may be of older version, date codes, or design than that available from authorized dealers. As IQElectro is not an authorized dealer of this product, the Original Manufacturer's Warranty and Support DO NOT apply. IQElectro sells SURPLUS only and DOES NOT SELL SOFTWARE or FIRMWARE licenses For more detailed information, please refer to the full version of our disclaimer policy Disclaimer Policy.
Description / Specifications

Description 

The Allen-Bradley 1756-OB8 is a ControlLogix discrete output module. It features Eight (8) 24VDC output channels in Two (2) groups of Four (4) channels each. Each channel delivers an output voltage range of 10-30VDC with nominal signal voltage of 24VDC. It is compatible for use with any ControlLogix chassis and uses the 1756-TBNH and 1756-TBSH Removable Terminal Block (RTB).

 

Technical Specifications 

Brand Allen-Bradley
Manufacturer Rockwell Automation
Part Number 1756-OB8
Signal Delay, OFF Transition 2 ms max
Signal Delay, ON transition 1 ms max
Current per module, max 8 A @ 60 °C (140 °F)
Current per point 2 A @ 60 °C (140 °F)
No. of channels per group 2
No. of output groups 2
Output Voltage range 10-30VDC
Output Voltage 24VDC
No. of Outputs 8
Backplane Current, 5.1VDC 165 mA
Backplane Current, 24VDC 2 mA
Total Backplane power 0.89 W
Series ControlLogix
Module Type Digital DC output module
Removable Terminal Block (RTB) 1756-TBNH 1756-TBSH
Outputs 8-Point
Voltage 12-24 Volts DC Source
Operating Voltage Range 10-30 Volts DC
Maximum Output Current Rating-Point 2 Amps at 60 degrees Celsius
Maximum Output Current Rating-Module 8 Amps at 60 degrees Celsius
Power Dissipation (Max) 2.5 Watts at 60 Celsius
Removeable Terminal Block(s) 1756-TBNH, 1756-TBSH
Isolation Voltage 50 Volts Continuous
Enclosure None

  

 

Information About 1756-OB8

The Allen-Bradley 1756-OB8 is a ControlLogix discrete output module. This module delivers an output voltage range of 10-30 VDC with nominal value of 24VDC. It is used to energize electrical loads that operate in DC voltages as well as AC loads, used with an interposing circuitry.

The 1756-OB8 is a single slot module that occupies any available slot of the chassis except the left-most slot which is intended for the ControlLogix processor or ControlLogix communication adapter / scanner module. It is compatible acting as a local I/O component or as part of a distributed I/O system. It may be installed to any available 1756- ControlLogix chassis and operate along standard or power supply modules.

The 1756-OB8 has a backplane current draw of 165 mA at 5.1 VDC and 2 mA at 24VDC while the total backplane power is 0.89 W and power dissipation of 2.5 W @ 60 °C (140 °F) and thermal dissipation of 8.53 BTU/hr. Each channel of this output module can deliver up to 2 Amperes @ 60 °C (140 °F) and 8 Amperes @ 60 °C (140 °F) per module.

This module uses a Removable Terminal Block (RTB) for connecting each channel of the module to the electrical loads. Compatible RTBs are 1756-TBNH and 1756-TBSH while appropriate RTB keying is user-defined, mechanical keying.

It is entered in the hardware configuration where module parameters and properties can be further modified/ Some of these parameters are Request Packet Interval (RPI), filter time, module inhibition and many others.

This module uses a Removable Terminal Block (RTB) which can either be the 1756-TBNH or the 1756-TBSH (20 pins RTB). This module has the following communication formats available: rack optimization, listen-only - rack optimization, output data, listen-only output data, and scheduled output data. Pilot duty is also available for the 1756-OB8 module.

The 1756-OB8 module has a voltage category of 12/24 volts DC source and an operating range of 10 to 30 volts DC. Its current draw is 165 mA at 5.1V and 2 mA at 24V. It has a backplane power of 0.89 W, with a maximum dissipation of 2.5 W at 60 Degrees Celsius (140 degrees Fahrenheit), and a thermal dissipation of 8.53 BTU/hr. The maximum off-state leakage current of this module is 1 mA per point and during an on-state, it has a maximum voltage drop of 1.2V DC at 2 A. It also has a maximum current of 2 A per point at 60 Degrees Celsius and a maximum current of 8 A at 60 Degrees Celsius per module. Its surge current per point is 4 A for 10 ms each that is repeatable every 1 s at 60 Degrees Celsius and its minimum load current is 2 mA per point. The module's isolation voltage is continuous at 250V. This module also allows you to modify states in Fault Mode per point and states in Program Mode per point. The choices for both are Hold Last State, On, or Off, with 'Off' set as default. Temperature ranges for the 1756-OB8 module are 0 to 60 Degrees Celsius when in operation and -40 to 85 Degrees Celsius when not in operation. It also has a maximum surrounding air temperature of 60 Degrees Celsius and a non-condensing relative humidity of 5% to 95%.





Manufacturer information

Allen-Bradley, a brand of Rockwell Automation, specializes in manufacturing industrial automation equipment. The product range includes programmable logic controllers (PLCs), motion control systems, safety devices, motor control equipment, automation software, and HMI panels. Allen-Bradley products are known for their reliability and integration with other systems.

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