PLC CPUs & Processors

What are PLC CPUs & Processors?

PLC CPUs (Central Processing Units) are the core hardware components of a Programmable Logic Controller. They are responsible for executing the control program, managing data memory, and coordinating communication between input/outputs (I/O), HMI interfaces, and networked drives. In modular systems, the CPU is typically a standalone module that slides into a chassis or mounts on a DIN rail, whereas in compact PLCs, the processor is integrated into the main unit.

Main Manufacturers

Palm Parts Solution stocks a comprehensive inventory of CPU modules from the industry’s leading automation brands:

• Allen-Bradley: High-performance processors for discrete and process applications.
• Siemens: Industry-standard CPUs for modular and PC-based control.
• Mitsubishi Electric: High-speed processing for complex motion and logic.
• Schneider Electric: Robust processors for infrastructure and industrial machine control.
• GE Fanuc / Emerson: Reliable logic controllers for power and utility sectors.
• Omron, ABB, Delta Electronics, B&R Industrial Automation, and Lenze: Specialized processors for high-speed packaging, robotics, and textile machinery.

Typical Applications

PLC processors are found in virtually every automated industrial environment. Standard applications include:

• Material Handling: Coordinating conveyors, sorters, and Palletizers using ControlLogix or SIMATIC S7-1500 processors.
• Motion Control: Synchronizing multi-axis servo systems with MELSEC iQ-R or Lexium controllers for precision packaging.
• Process Automation: Managing PID loops and analog data in chemical and water treatment plants using ABB AC800M or Schneider Modicon units.
• Machine Safety: Utilizing "GuardLogix" or "F-series" fail-safe processors to manage SIL3/PLe safety functions alongside standard logic.

Selection Guide

Choosing the correct processor requires matching the hardware to the application's complexity:

1. I/O Count: Determine the total number of local and remote points. A CompactLogix 5370 may suit a small machine, while a ControlLogix 5580 is required for plant-wide control.
2. Memory Requirements: Ensure the CPU has sufficient program and data memory (KB/MB) to handle the logic and data logging requirements.
3. Network Topology: Select a CPU with built-in ports for the required protocol (e.g., dual Ethernet ports for DLR or PROFINET MRP redundancy).
4. Environment: For extreme temperatures or corrosive atmospheres, source "XT" (Extended Temperature) or conformal-coated versions of Siemens or Allen-Bradley processors.