Product Overview
The 1771-P5 is a 24V DC input power supply module for Allen-Bradley‘s 1771 I/O chassis, used across PLC-5 and related programmable controller systems. As a two-slot module, the 1771-P5 installs directly into the 1771 chassis backplane and converts a nominal 24V DC source into regulated 5V DC backplane power, delivering up to 8 amperes to support the I/O modules resident in that chassis . The module is designed for installations where a DC power source is available or preferred over AC mains, such as battery-backed systems, DC-powered control panels, or remote I/O racks fed from a centralized DC bus.
The 1771-P5 occupies a distinctive position in the 1771 power supply family. Unlike the AC-input 1771-P4 series, the 1771-P5 accepts a 20.5–30V DC input range and is specifically engineered to operate in parallel with another 1771-P5 module, combining their outputs to provide up to 16A of backplane current when higher loads demand it . This parallel capability distinguishes it from AC-powered supplies and makes the 1771-P5 suitable for larger 1771 chassis configurations where a single supply’s 8A capacity is insufficient. Rockwell Automation officially discontinued the 1771-P5 on December 31, 2017, and the module is now supported through surplus and refurbishment channels for maintenance of legacy PLC-5 installations .
Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | 1771-P5 |
| Manufacturer | Allen-Bradley (Rockwell Automation) |
| Product Type | 1771 I/O Chassis Power Supply |
| Nominal Input Voltage | 24V DC |
| Input Voltage Range | 20.5–30V DC |
| Backplane Output Current | 8A @ 5V DC (16A when paralleled with another 1771-P5) |
| Maximum Real Input Power | 57W (approximately) |
| Fuse Rating | 5A, 32V, normal-blow |
| Parallel Operation | Yes, with another 1771-P5 only (using 1771-CT cable) |
| Chassis Slots Occupied | 2 slots |
| Isolation | 1500V AC RMS (input to chassis ground) |
| Operating Temperature | 0–60°C |
| Weight (Approx) | 1.16–1.18 kg |
Main Features and Advantages
DC input flexibility for specialized power architectures: The 1771-P5 accepts a 20.5–30V DC input, making it the appropriate choice for 1771 chassis installations where AC mains are unavailable, undesirable, or already converted to a centralized DC bus. In telecommunications facilities, remote pumping stations, or mobile equipment, a DC-powered 1771-P5 eliminates the need for a dedicated AC feed to each I/O rack while maintaining full backplane power capability. The wide input tolerance accommodates the voltage droop and ripple commonly present on 24V DC industrial power systems without triggering nuisance shutdowns.
Parallel capability for scalable current capacity: The 1771-P5 is explicitly designed to operate in parallel with a second 1771-P5 module, doubling the available backplane current from 8A to 16A . This feature allows system integrators to populate a chassis with a higher density of I/O modules than a single supply could support, without changing the chassis footprint or adding an external bulk power supply. When paralleling, both 1771-P5 modules must be energized simultaneously to prevent an overcurrent condition in one supply, and the dedicated 1771-CT parallel cable must be used to interconnect them .
Proven reliability in legacy PLC-5 infrastructure: The 1771-P5 shares the robust construction and circuit isolation characteristics of the broader 1771 power supply family, with 1500V AC RMS isolation between the input and chassis ground protecting backplane circuitry from DC bus transients and ground potential differences. The module’s soft-start feature limits inrush current during power-up, reducing stress on upstream DC distribution components. For organizations maintaining PLC-5 control systems beyond the platform’s active sales lifecycle, the 1771-P5 remains a critical spare to keep DC-powered I/O chassis operational.
