The Programmable Logic Controller, PLC is basically a programmed interface in between the field input elements and the final control element.
Advantages of PLC
- Reduced space : PLCs are completely solid state devices and hence are extremely compact in comparison to hard-wired controller where electro-mechanical devices are used.
- Higher Life and Reliability : These devices are extremely rugged. The chances of defect/damage are very less as there is very lesser moving mechanisms here.
- Economical : As the defect probability is very less, One can consider it as one time investment. In this way, PLCs are undoubtedly most economical systems. Cost of PLC recovers within a short period.
- Energy saving : Average power consumption is just 1/10th of power consumed by an equivalent relay based control.
- Ease of maintenance :
- Modular replacement
- Easy trouble shooting
- Error diagnostics with programming unit.
- Tremendous flexibility : There is no requirement of rewiring if any change is required to be implemented. It can carry out complex functions like arithmetic operations, counting, comparing, generation of time delay etc. It has a very high processing speed and greater flexibility in both analog and digital process. “On Line”/ ‘Off Line’ programming is also possible in it.
- Shorter Project Time : The hard wired control system can be constructed only when the task is fully defined. However, In case of PLC , the construction of the controller and wiring are independent of control program definition.
- Easier Storage Archiving and Documentation : This is due to its compatibility with PC-AT, Printer and Floppy disk.
However, if we compare Programmable logic controller function with computers, it has following advantages and disadvantages :
- many inputs and outputs, excellent for controlling and monitoring many processes.
- designed for industrial environments, very robust and reliable.
- ideally suited to supervisory control.
- easy to set up and good for FMS environment.