Classification of PLCs

 

Classification of PLCs

PLCs are classified based on their hardware structure and expandability into two main types: Fixed PLCs and Modular PLCs.

1. Fixed PLCs

• Structure: All components (CPU, power supply, input/output modules) are built into a single compact unit.

• I/O Capacity: Limited number of inputs and outputs (usually small).

• Flexibility: Cannot be expanded; suitable for simple applications.

• Cost: Lower cost, economical for small-scale automation.

• Applications:

  • Small machines (packaging, labeling).

  • Simple process control (lighting, pumps).

2. Modular PLCs

• Structure: Built from separate modules (CPU, power supply, I/O modules, communication modules) mounted in a rack.

• I/O Capacity: Can be expanded by adding more modules.

• Flexibility: Highly flexible; supports analog/digital I/O, communication, and special functions.

• Cost: Higher cost but scalable for complex systems.

• Applications:

  • Large industrial plants.

  • Complex automation (chemical, power, automotive industries).