- Fixed PLCs and
- Modular PLCs
are two primary types of programmable logic controllers (PLCs) that are employed in industrial automation applications and differ in their properties and utilization.
Fixed PLCs
Couch or clinical model PLCs are the descriptor PLCs that have the abilities of input and output integrated into a single package known as the fixed PLC.
This implies that the I/O points are limited and any additional is not possible since it is designed and limited by the manufacturer.
Key features include:
Integration
It is an integrated device that contains all peripherals and circuits, CPU, power supply, and communication interfaces as a single block.
Limited Scalability
Due to the fixed I/O, these PLCs are ideal for small applications where the control demand is not expected to expand or alter in the future.
Cost-Effectiveness
Fixed PLC is usually cheaper than the modular PLC and the latter is recommended for use where the requirements in terms of I/O is low.
Maintenance
When the element of a fixed PLC becomes damaged, it is sometimes more problematic as the whole Fixed piece may require replacement due to the issue, this will take longer time.
Modular PLCs
Rack mounted PLCs are other types of modular PLCs and these PLCS have individual modules of CPU, power supply and I/O interfaces.
This design proves to be more soluble as well as flexible and Scalable.
Key features include:
Expandability
Expansibility of the system is very easy because users can either upgrade or downgrade the I/O modules depending on the growing application needs. This is why modular PLCs are particularly suited for complex systems in the industrial manufacturing environments.
Easier Fault Detection and Maintenance
The elements of each module are separate, which helps in identifying the location of a problem.
In the case where one of the modules would be a problem, it is usually contained and easy to change, which minimizes the down time.
Higher Performance
Modular PLCs have higher capacity to control more I/O points and more sophisticated processes since they are scalable by adding more modules to the system, thus recommended for complex processes in industries.
Cost Considerations
Comparing to the traditional PLCs, modular PLCs are more costly during the first time by increasing the elements and capacities encompassed in the PLC, but it is definitely more cost effective in the long run by its flexibility of expansion and ease in repair.
Therefore, it can be concluded that the decision to integrate a fixed or modular PLC mainly boils down to several factors such as the size of the line, cost considerations, and anticipated scalability. Fixed PLCs are suitable to the application that is very simple and not likely to change over time while the modular are preferred for complex environments in large industries.