Product Overview
The Allen-Bradley 1756-L55M12 is a ControlLogix 5555 controller from Rockwell Automation. This processor module delivers 750 kilobytes of RAM for data and logic, with 208 kilobytes of I/O memory. It supports up to 128,000 maximum I/O points, including 4,000 analog inputs and 2,000 analog outputs. With a program scan time of 0.08 milliseconds, it handles high-speed control tasks efficiently.
Technical Specifications Breakdown
Key parameters for the 1756-L55M12 are listed below for quick reference:
| Feature | Specification |
|---|---|
| Manufacturer | Rockwell Automation |
| Brand | Allen-Bradley |
| Part Number | 1756-L55M12 |
| Series | ControlLogix |
| Module Type | Processor Module |
| RAM | 750 Kilobytes |
| Maximum I/O | 128,000 |
| Maximum Analog I/O | 4,000 Input, 2,000 Output |
| Program Scan Time | 0.08 milliseconds |
| Backplane Current (5V DC) | 1.23 Amps |
| Backplane Current (24V DC) | 14 milliamps |
| Weight | 0.78 pounds (0.35 kilograms) |
| Operating Temperature | 32-140 Fahrenheit (0-60 Celsius) |
| Vibration | 10-500 Hertz |
| Relative Humidity | 5-95 percent |
| Battery | 1756-BA1 or 1756-BATM |
Industry Applications
This controller excels in discrete manufacturing and process control environments. Its 128,000 maximum I/O capacity suits large-scale assembly lines and material handling systems. The 0.08 ms scan time enables precise motion coordination in packaging machinery. For continuous processes, the analog I/O capability (4,000 inputs, 2,000 outputs) supports accurate temperature and pressure monitoring.
Installation & Setup Guidance
Mount the module in a ControlLogix chassis using the backplane. Ensure the backplane current draw does not exceed 1.23 A at 5V DC and 14 mA at 24V DC. Use compatible serial cables (1756-CP3 or 1747-CP3) for communication. The open-style enclosure requires installation in a clean, dry environment. Verify the operating temperature stays within 0 to 60 degrees Celsius.
Maintenance & Reliability
Operate the controller within the specified relative humidity range of 5% to 95% (noncondensing). The vibration tolerance of 10-500 Hz ensures reliable operation in industrial settings. Replace the lithium battery (1756-BA1 or 1756-BATM) only when needed to maintain memory retention during power loss. Inspect the module periodically for dust accumulation and secure connections.
Compatibility & Integration
The 1756-L55M12 integrates with ControlNet, EtherNet/IP, DH+, DeviceNet, and universal remote I/O networks. It can be used in redundant controller systems when paired with other 1756-L55 controllers on a ControlNet network. This flexibility allows seamless integration into existing Rockwell Automation architectures.
Selection Guide & Purchasing Advice
When selecting a processor module, consider the memory and I/O requirements of your application. The 1756-L55M12 offers 750 KB RAM and 128,000 I/O points, making it suitable for mid-to-large control systems. SpareTechPLC stocks this module and can assist with availability and lifecycle status. Please verify current lifecycle status and availability with SpareTechPLC before ordering.
Troubleshooting & Common Issues
If the controller fails to communicate, check the backplane connections and network cables. Verify the battery voltage if memory loss occurs. Ensure the operating temperature stays within 0-60 degrees Celsius. For scan time issues, review program logic complexity. Always refer to the official Rockwell Automation documentation for detailed diagnostics.
