Application Scenarios
In a municipal water treatment facility, a ControlLogix system manages the sequencing of intake pumps, chemical dosing, and filter backwash cycles across a distributed network of remote I/O racks. The original processor is nearing end-of-life, and the maintenance team needs a drop-in replacement that preserves the existing ladder logic and communication configuration without a full re-engineering project. The 1756-L55M24 addresses this need directly: its 3.5 MB non-volatile memory holds the complete program and data tables without relying on a battery, eliminating the periodic battery replacement task that had been a recurring maintenance item on the older controller . Because the module supports 128,000 discrete I/O points and up to 4,000 analog inputs, it comfortably covers the facility’s current I/O count with headroom for future expansion, allowing the plant to standardize on a single processor model across multiple treatment sites .
Parameter
| Main Parameters | Value / Description |
|---|---|
| Product Model | 1756-L55M24 |
| Manufacturer | Allen-Bradley (Rockwell Automation) |
| Product Category | ControlLogix Processor Module |
| Series | ControlLogix5555 |
| User Memory (RAM) | 3.5 MB |
| Non-Volatile Memory | 3.5 MB (supports battery-free operation) |
| Maximum Discrete I/O | 128,000 points |
| Maximum Analog I/O | 4,000 inputs / 2,000 outputs |
| Program Scan Time | 0.08 ms |
| Integrated Communication | 1× RS-232 serial port |
| Backplane Current | 1.25 A @ 5.1 V DC; 0.014 A @ 24 V DC |
| Operating Temperature | 0°C to 60°C |
Technical Principles and Innovative Values
- Innovation Point 1: Battery-Free Non-Volatile Memory Architecture. The 1756-L55M24‘s 1756-M24 memory board stores both the user program and data in non-volatile memory, meaning the controller retains its program through power cycles without a lithium battery . This eliminates a consumable maintenance item and removes the risk of program loss from a dead battery—a failure mode that has stranded many legacy ControlLogix installations during extended plant shutdowns.
- Innovation Point 2: Slot-Agnostic, Hot-Swappable Installation. The 1756-L55M24 can be installed in any available slot of a ControlLogix chassis, and it supports removal and insertion while chassis power is on (except in hazardous locations) . This flexibility means a failed processor can be replaced in minutes without de-energizing the entire rack, minimizing downtime for the associated process area.
- Innovation Point 3: Multi-Language Programming Support. The 1756-L55M24 supports relay ladder, Sequential Function Chart (SFC), Function Block Diagram, and Structured Text programming languages, allowing engineers to select the most appropriate paradigm for each section of the application . A single project can mix ladder for discrete interlocking, SFC for batch sequencing, and structured text for complex calculations, reducing the need for separate specialty controllers.
- Innovation Point 4: Redundancy-Capable Platform Compatibility. The 1756-L55Mxx family, including the 1756-L55M24, is supported within ControlLogix redundancy systems (with appropriate redundancy firmware revisions), enabling paired-controller architectures where a secondary chassis takes over seamlessly if the primary faults . For critical processes that cannot tolerate a controller failure, this provides a path to high availability without migrating to a different platform.
Reviews
There are no reviews yet.