Configured for high-density modular I/O integration in PLC-5 system architectures, the Allen-Bradley 1771-A4B (1771A4B Universal Input/Output Chassis) provides direct physical backplane execution for 16-slot module configurations.

Model Matrix

• 1771-A4B: Standard catalog number for the 16-slot universal I/O chassis.

• Universal Design: Engineered to accommodate various 1771 series I/O modules, communication adapters, and processor configurations.

Hardware Specifications

Industrial Control Integration

The 1771-A4B chassis utilizes a backplane bus communication velocity architecture optimized for deterministic PLC-5 operations. It supports I/O density scaling via 1/2-slot addressing and accommodates diverse module types, including analog, digital, and high-speed motion controllers. Firmware flash compatibility is governed by the specific adapter or processor module installed in the leftmost slot. The backplane design ensures signal integrity across all 16 slots, provided that cumulative load does not exceed the 24 A current limit at 5 VDC.

Ordering Information

• 1771-A4B 16-Slot I/O Chassis.

• Note: This unit does not include an integral power supply module; external power supplies must be sourced separately.

• Hardware includes 36 plastic keying bands for module-to-slot configuration security.

Field Installation Guidelines

• Grounding: Establish a central ground bus within the enclosure. Connect the chassis to this bus using 1-inch (2.54 cm) copper braid or 8 AWG copper wire.

• Contact Integrity: Scrape paint from the back-panel mounting surface to ensure a low-impedance electrical bond. Secure ground lugs using nuts and star washers to prevent loosening.

• Placement: The leftmost slot is reserved exclusively for the processor or I/O adapter module. Other modules may occupy any of the remaining 15 slots.

• Environment: Intended for Pollution Degree 2, Overvoltage Category II industrial environments at altitudes up to 2000 meters.

Frequently Asked Questions

• Can modules be hot-swapped while the chassis is powered? No, the 1771 series architecture generally requires the system to be de-energized to prevent electrical shorts or backplane damage.

• What is the total current limit for this chassis? The backplane supports a maximum of 24 A at 5 VDC.

• Can I use a power supply rated at 10 A? Yes, external power supplies for this chassis must be rated between 6.5 A and 16 A, depending on the I/O load.

• What if I exceed the 2000-meter altitude limit? Operation above 2000 meters may require output power derating; consult the engineering manual for specific curves.

• Are the keying bands required for operation? Yes, 36 keying bands are necessary to prevent the insertion of incompatible modules into configured slots.

• Is the chassis compatible with PLC-5/40 processors? Yes, the chassis supports various PLC-5 processors, provided the processor occupies the leftmost slot.

• How do I prevent EMI between slots? Maintain proper spacing and ensure the chassis is firmly bonded to a common cabinet ground bus.

• Does this chassis support communication modules? Yes, communication modules can occupy any slot except the leftmost dedicated slot.