Allen-Bradley 1791-24A8 Block I/O Module: Compact Remote I/O Solution

Core Technical Specifications

• Brand & Manufacturer: Allen-Bradley
• Model Number: 1791-24A8
• Product Line: 1791 Block I/O
• Discrete Input Channels: 24 channels (grouped as 3 sets of 8)
• Input Voltage Rating: 120V AC
• On-State Input Range: 79 to 132V AC
• Discrete Output Channels: 8 channels (1 group of 8)
• Output Voltage Range: 20 to 132V AC
• External Power Supply: 85-132V AC, 150 mA
• Module Power Dissipation: Maximum 18.76 Watts

Communication & Environmental Features

• Interface Compatibility: Built-in Remote I/O (RIO) scanner interface for adapter mode.
• Controller Support: Connects to PLC-2, PLC-3, PLC-5, and SLC 500 (via 1747-SN scanner) families.
• Communication Baud Rates: Supports 57.6K, 115.2K, and 230.4K baud for flexible network speed.
• Maximum Cable Distance: Up to 10,000 feet at 57.6K baud, decreasing with higher speeds.
• Recommended Cable: Use Belden 9463 (Blue Hose) three-wire shielded cable for reliable connections.
• Network Termination: Requires an 82 Ohm or 150 Ohm terminating resistor at the last network node.

Installation & Application Guidelines

• Mounting Options: You can mount the module vertically or horizontally for installation flexibility.
• Typical Use Case: Ideal for distributing I/O points closer to machines in a remote I/O setup, reducing wiring costs.
• Connection Planning: Ensure your controller supports the RIO protocol and plan cable runs within the rated distance limits.
• Power Considerations: Provide a clean 120V AC source within the 85-132V AC range for the external power terminals.

FAQ - Frequently Asked Questions

• What controllers work with the 1791-24A8? It works with Allen-Bradley PLC-2, PLC-3, PLC-5, and SLC 500 controllers using RIO.
• What is the purpose of the terminating resistor? It prevents communication errors by properly ending the RIO network chain.
• Can I mix input and output signals? No, the 1791-24A8 has 24 fixed inputs and 8 fixed outputs.
• What happens if input voltage is below 79V AC? The input may not turn ON reliably, as 79V is the minimum on-state voltage.

Packaging & Shipping Details

• Shipping Weight: Approximately 1.88 lbs (0.85 kg).
• Packaging: The module comes in a secure individual box for protection.
• Available Shipping Methods: We ship globally via FedEx, UPS, and DHL for fast delivery.

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