Purchase now: Allen Bradley 1747-L531 SLC 5/03 Processor
Purchase now: Atlantechdrives provides you the 1747-L531, the foundational CPU processor of the highly celebrated Allen Bradley SLC 5/03 family. This module represents a massive architectural leap over the older 5/01 and 5/02 series. Equipped with 8K of user memory, the 1747-L531 is engineered to control medium-complexity industrial applications such as advanced packaging wrappers, automated assembly stations, and fluid mixing skids. The defining feature of the SLC 5/03 series is the introduction of a dual-port communication design (DH-485 and RS-232) and the ability to execute highly advanced mathematical functions, making it a rugged and versatile workhorse for factories demanding precise, high-speed automation.
Technical Specifications of the 1747-L531
The 1747-L531 drastically reduces processor scan times compared to legacy models. It occupies slot 0 of any 1746 chassis and features a physical key switch on the front panel for strict security over operational modes (RUN, PROG, REM).
- Part Number: 1747-L531
- Processor Class: SLC 5/03 CPU
- Total User Memory: 8K Words (Instructions and Data)
- Channel 1 Port: DH-485 via RJ45 jack
- Channel 0 Port: RS-232 (Supports DF1 Full/Half-Duplex, ASCII, DH-485)
- Maximum Local I/O Capacity: 4096 inputs / 4096 outputs
- Maximum Local Chassis: 3 (Up to 30 slots total)
- Backplane Current Draw: 500 mA at 5V DC, 175 mA at 24V DC
Expert Installation Advice: The Power of Online Editing
The greatest advantage of upgrading to a 1747-L531 is the operational uptime it provides. Expert Tip: Unlike the 5/01 or 5/02 processors which require you to completely halt the machine to download a program change, the SLC 5/03 architecture introduces Online Editing. Using RSLogix 500, with the processor key switch set to «REM» (Remote), a programmer can insert new rungs, modify timer presets, and alter logic on the fly while the machine continues to run production. You simply test the edits in RAM, assemble them, and finalize them without ever switching the CPU out of Run mode. This feature alone saves thousands of dollars in downtime during the commissioning and optimization phases of a manufacturing line.
Maintenance and the 1747-BA Battery
The 8K of memory in the 1747-L531 is backed up by a 1747-BA lithium battery. A flashing red «BATT» LED on the front of the processor indicates the voltage has dropped below safe thresholds. Maintenance Warning: You must replace this battery while the chassis power is turned ON. If you turn off the main 120V AC power to the PLC rack and pull the dead battery out, the internal volatile RAM will instantly drain, and your entire 8K program will be permanently deleted, requiring a full download from your engineering laptop to restore operation.
Frequently Asked Questions (FAQs)
Q: Can I use the RJ45 port for Ethernet?
A: No. The RJ45 port (Channel 1) on the 1747-L531 is strictly for the DH-485 token-passing network. Plugging an Ethernet cable into this port will permanently damage the communication circuitry due to the 24V DC power present on the pins.
Q: How do I connect my laptop to the RS-232 port?
A: You must use a null-modem serial cable, specifically the Allen Bradley 1747-CP3, connected from the bottom 9-pin D-sub port to your computer’s serial port or a high-quality USB-to-Serial adapter.
Do you need more references from this brand? Explore our full catalog of Allen Bradley here.
This SLC 5/03 OS301 processor features an integrated RS-232 port for direct connection via a 1747-CP3 cable.
