1791-8BR | Allen-Bradley Block I/O Module - Petro Auto Tech

Product Overview

The 1791-8BR is an Allen-Bradley Block I/O combination module designed for distributed industrial automation. This compact unit integrates eight 24VDC input channels and eight relay output channels, supporting Remote I/O (RIO) protocol for seamless communication with PLC controllers. It operates as a stand-alone distributed I/O station, reducing long cable runs by mounting near field devices.

Technical Specifications Analysis

The 1791-8BR features 8 inputs per block with an on-state voltage range of 10-30VDC and an on-state current of 11mA at 30V max. The input off-state voltage is 5V dc max, with an off-state current of 1.5mA min. Outputs per block are 8, with a voltage range of 20-30V dc at 1A resistive max. The module requires 24VDC external power (19.2-30V dc) and weighs 1.00 lbs (0.45 kg). It supports vertical and horizontal mounting and is compatible with PLC-2, PLC-3, PLC-5/20, and PLC-5 controllers.

Application Scenarios & Usage Methods

In manufacturing lines, the 1791-8BR monitors proximity switches and limit switches while controlling solenoid valves or motor starters. For material handling, it interfaces with pushbutton switches and auxiliary contacts to manage conveyor systems. Use the module near field devices to minimize wiring. Connect incoming power to terminals +24 (1), RET +24 (3), and GND (2). For RIO connections, use terminals BLU (6), CLR (8), and SHD (7).

Installation Guide & Packing List

Mount the 1791-8BR on a standard DIN rail or directly panel mount in vertical or horizontal orientation. Use 14-gauge stranded wire with 3/64 maximum insulation thickness for signal termination. Do not parallel output connections to avoid lowering circuit resistance. The package includes the 1791-8BR module and mounting hardware. No certificate, warranty, or shipping details are included.

Purchasing Advice

When selecting the 1791-8BR, verify compatibility with your PLC system (PLC-2, PLC-3, PLC-5/20, or PLC-5). Ensure the external power supply delivers 19.2-30V dc. Consider the surge current requirements of connected loads, as the module lacks internal fusing. Petro Auto Tech offers this module with reliable sourcing for industrial automation needs.

Repair & Maintenance Tips

Inspect the 1791-8BR regularly for loose connections or debris on terminals. Clean with a dry cloth; avoid solvents. Store in a dry environment within the specified voltage range. Check external fuses for output protection. Verify input on-state voltage remains between 10-30VDC to prevent damage.

Frequently Asked Questions (FAQs)

Q: What is the input voltage range for the 1791-8BR?

A: The input on-state voltage range is 10-30VDC, as specified in the technical data.

Q: How many outputs does the 1791-8BR have?

A: It has eight relay output channels with a voltage range of 20-30V dc at 1A resistive max.

Q: Can the 1791-8BR be mounted horizontally?

A: Yes, it supports both vertical and horizontal mounting orientations.

Q: Does the module include internal fusing?

A: No, the 1791-8BR does not come with internal fusing. Use external protection as needed.

Q: What protocols does the 1791-8BR support?

A: It supports Remote I/O (RIO) protocol for connecting to RIO scanners and controllers.