Manufacturer	Rockwell Automation (Allen-Bradley)
Product Line	1791 Block I/O
Part Number	1791-24B8
UPC	612598124794
Weight	1.02 kg (2.25 lbs)
Voltage	24 VDC
Inputs per Block	24
Input On-state Voltage Range	10 to 30 VDC
Input On-state Current	11 mA at 30 V max
Input Off-state Voltage	5 VDC max
Input Off-state Current	1.5 mA min
Outputs per Block	8
Output Voltage Range	10 to 30 VDC
External Power	19.2 to 30 VDC
Product Lifecycle Status	Discontinued/Obsolete
Dimensions	176.5 mm x 68.8 mm x 98 mm (6.95 in x 2.7 in x 3.85 in)
Operating Temperature	0 to 60 °C (32 to 140 °F)
Relative Humidity	5 to 95% non-condensing
Input Signal Delay	1 ms ON, 5 ms OFF (fast); 1 ms ON, 18 ms OFF (slow)
Output Current Rating	500 mA/1 A at 30 to 60 °C (vertical); 250 to 500 mA at 30 to 60 °C (horizontal)
Output Surge Current	3 A for 50 seconds, recurring after 2 seconds
Output Off-state Current	1 mA at 1 V drop; 0.5 mA leakage
External Power Current	300 mA
Thermal Dissipation	58.1 BTU/hour
Power Dissipation	17.1 W
Mounting	DIN rail mount

What are the input and output specifications for the Allen-Bradley 1791-24B8?

The 1791-24B8 is a 24V DC block I/O module featuring 24 inputs (organized in 3 groups of 8) and 8 outputs. The input on-state voltage range is 10 to 30 VDC, with an on-state current of 11 mA at 30 VDC max. The output voltage range is also 10 to 30 VDC.

What external power supply is required for the 1791-24B8?

The module requires an external power supply providing 19.2 to 30 VDC. The internal power supply has a current rating of 300 mA.

What are the physical dimensions and weight of the 1791-24B8?

The module measures 6.95 x 4.35 x 3.85 inches (176.5 x 68.8 x 98 mm). Weight specifications vary by source, with one listing 2.00 lbs (0.91 kg) and another listing 1.70 lbs.

What is the current lifecycle status of the 1791-24B8?

The 1791-24B8 is discontinued/obsolete by the manufacturer. It is no longer in active production, which may impact long-term availability and support.

What are the operating temperature and humidity limits for this module?

The 1791-24B8 operates at temperatures between 0 and 60 degrees Celsius (32 to 140 degrees Fahrenheit) with a relative humidity of 5 to 95% non-condensing.

What are the input signal delay times for the 1791-24B8?

The input signal delay is 1 millisecond ON and 5 milliseconds OFF in fast mode, or 1 millisecond ON and 18 milliseconds OFF in slow mode.

Does the Allen-Bradley 1791-24B8 come with a warranty?

Yes. The 1791-24B8 is backed by our 24-Month Replace Industrial Warranty, with no rush fees or hidden warranty charges. If a unit fails under normal use within the warranty period, we repair or replace it.

Is this 1791-24B8 a genuine Allen-Bradley part?

The 1791-24B8 is sourced and verified independently. Replace Industrial, LLC is not a Rockwell Automation Authorized Distributor, and all warranties are provided directly by Replace Industrial.

Is the Allen-Bradley 1791-24B8 new or used?

We offer the 1791-24B8 in multiple conditions, from unused surplus to professionally reconditioned units. Every option is sourced and verified independently and covered by our 2-year replacement warranty.

What are the key ratings of the 1791-24B8?

The 1791-24B8 operates across 0 to 60 °C (32 to 140 °F) and draws 500 mA/1 A at 30 to 60 °C (vertical); 250 to 500 mA at 30 to 60 °C (horizontal).

What is the Allen-Bradley 1791-24B8?

The 1791-24B8 is part of the Allen-Bradley Block I/O line.

Allen-Bradley

1791-24B8

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PLCs Block I/O

The Allen-Bradley 1791-24B8 PLC from Rockwell Automation is a compact 24 volt DC block I/O module with 24 inputs and 8 outputs, supporting a voltage range of 10-30V DC. It's designed for easy integration in control systems, but is now discontinued/obsolete, reinforcing the need for future-proof solutions.

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Overview of Allen-Bradley 1791-24B8

The Allen-Bradley 1791-24B8 is a 24V DC discrete block I/O module from the 1791 series, designed for remote input and output connections in programmable controller systems. This self-contained module integrates power supply, controller interface, and signal conditioning circuitry to facilitate easy integration into existing control architectures.

Currently listed as discontinued or obsolete by the manufacturer, the 1791-24B8 remains a critical component for maintaining legacy automation systems. It provides a compact solution for applications requiring a high density of digital inputs relative to outputs.

Key Features

This module features 24 discrete inputs organized in three groups of eight and eight discrete outputs in a single group of eight, totaling 32 I/O points. It is designed for 24V DC operation with an input on-state voltage range of 10 to 30 Volts DC and an output voltage range of 10 to 30 Volts DC.

The unit includes an internal power supply with protection that accepts an external DC voltage range of 19.2 to 30 Volts DC. It supports DIN rail mounting and is designed for vertical or horizontal installation, with specific current ratings dependent on the mounting orientation.

Performance and Capacity

The 1791-24B8 handles input on-state currents up to 11mA at 30 Volts DC, with an off-state voltage maximum of 5 Volts DC. Input signal delay is 1 millisecond for ON and 5 milliseconds for OFF in fast mode, or 1 millisecond ON and 18 milliseconds OFF in slow mode.

Output capacity is rated at 500mA to 1A at 30 to 60 degrees Celsius for vertical mounting, and 250 to 500mA for horizontal mounting. The module has a maximum power dissipation of 17.1 Watts and a thermal dissipation of 58.1 BTU/hour, operating within a temperature range of 0 to 60 degrees Celsius (32 to 140 degrees Fahrenheit) at 5 to 95% non-condensing relative humidity.

Installation and Compatibility

Measuring 176.5 mm x 68.8 mm x 98 mm (6.95 in x 2.7 in x 3.85 in) and weighing approximately 1.02 kg (2.25 lbs), the 1791-24B8 is designed for compact installation in control cabinets. It is compatible with the 1791 Block I/O system and is intended for use with Allen-Bradley programmable controllers.

As a discontinued part, buyers should verify specific revision compatibility, such as Series A or Series B, when sourcing replacements or maintenance units. The module requires an external DC power source within the 19.2 to 30V range to operate its internal circuitry and outputs.

Applications and Industries

The 1791-24B8 is suitable for industrial automation applications that require a high number of digital inputs for sensor monitoring and a smaller number of outputs for actuator control. Its 24V DC design makes it appropriate for machine control, process automation, and discrete manufacturing environments.

Industries utilizing legacy Allen-Bradley control systems, such as automotive, packaging, and material handling, may rely on this module for maintaining operational continuity in existing equipment. Its compact form factor allows for efficient use of space in crowded control panels.