1769CRL3 Allen Bradley AB 1769-CRL3 Right To Left Bus Expansion Cable "FACTORY SEALED"

1769-CRL3 | CompactLogix 1769 Right-to-Left Bus Expansion Cable — 1m / Multi-Bank I/O Architecture / Termination Caps

Expanding the 1769 I/O System Beyond One Bank

The 1769-CRL3 is the right-to-left bus expansion cable for the CompactLogix 1769 series I/O platform — the physical cable that links two separate 1769 I/O banks, enabling the system to accommodate more modules and power supplies than a single bank allows.

In a standard 1769 I/O installation, all modules sit in one linear bank connected by the shared 1769 backplane. When the application requires more I/O modules than one bank can hold, or when separate power supplies are needed for different I/O groups, the 1769-CRL3 extends the bus connection from the right end of one bank to the left end of the next bank — creating a physically separate but electrically unified I/O expansion.

Key Specifications

Right-to-Left Architecture — Understanding the Expansion Direction

The 1769 backplane defines "right" and "left" relative to the controller or power supply:

Right-to-Left (1769-CRL3): The cable connects from the rightmost position of one bank to the leftmost position of the next bank — extending the bus from right to left, with the right bank's I/O modules visible to the left bank's power supply and controller.

Three-Bank Maximum: The 1769 platform supports a maximum of two expansion cables, creating up to three separate I/O banks. The 1769-CRL3 is one of those two cables — a maximum system of three banks can accommodate significantly more I/O modules than any single bank allows.

Independent power supplies: Each bank receives its own 1769 power supply — the expansion cable carries bus communication between banks, but each bank's modules are powered independently. This allows different voltage requirements or power ratings for different I/O groups within the same system.

Applications

CompactLogix PLC I/O expansion: Production machines using CompactLogix controllers that require more than one I/O bank to accommodate the full complement of digital and analogue I/O modules — the 1769-CRL3 enables the expansion without changing the controller platform.

Multi-bank power distribution: Applications requiring separate 24V power supplies for different I/O groups (e.g., separating safety-critical outputs from standard I/O) using independent banks with individual power supplies.

DriveLogix 5730 systems: The 1769-CRL3 is specified for the DriveLogix 5730 controller's 1769 I/O expansion — connecting I/O banks for drive-integrated PLC applications.

Panel space optimisation: Control panels where a single linear I/O bank would not fit, but two or three shorter banks can be arranged in the available panel space — the 1769-CRL3 links them into a single I/O system.

FAQ

Q1: What is the maximum number of 1769-CRL3 cables that can be used in one CompactLogix system?

The 1769 platform permits a maximum of two expansion cables, creating at most three I/O banks. Only one cable configuration is used per expansion link — one 1769-CRL3 between bank 1 and bank 2, and one between bank 2 and bank 3. Using more than two expansion cables or more than three banks is not supported.

Q2: Can the 1769-CRL3 be used for left-to-right expansion?

No — the 1769-CRL3 is specifically a right-to-left cable. The connector keying is directional and the cable cannot be reversed. For left-to-right expansion, the 1769-CLR3 (left-to-right, same 1m length) is the appropriate cable. Ensure the correct expansion direction is selected based on the panel layout and the physical placement of the I/O banks relative to the controller.

Q3: Does each 1769 bank connected via 1769-CRL3 need its own power supply?

Yes — each 1769 bank requires its own 1769 power supply module. The expansion cable carries the backplane communication signals between banks but not the power supply rail. All modules in bank 2 receive power from the bank 2 power supply, while bank 1 modules are powered by the bank 1 supply. Omitting the power supply from an expanded bank will cause all modules in that bank to fail to power up.

Q4: What happens if the termination caps are missing from the 1769 system end connectors?

Without proper termination, signal reflections occur on the 1769 backplane bus — the same communication fault that affects any terminated serial bus without its terminator. Symptoms range from intermittent I/O communication errors and unexpected module faults to complete inability for the controller to discover I/O modules across the expansion. Always fit termination caps on all open (unused) connector positions on the first and last bank in the I/O chain.

Q5: What environmental ratings apply to 1769-CRL3?

The 1769-CRL3 operates at 0–60°C and is rated for operating vibration of 10–500 Hz at 5G with 0.030 in peak-to-peak displacement — appropriate for panel-mounted industrial control cabinet installation. Operating altitude is rated to 6,561 ft (2,000 m). The cable is an open-style component and requires installation inside an enclosure providing the appropriate IP protection for the installation environment.