A Programmable Logic Controller can be defined in many ways.
It can be defined as a program controlled electronic equipment with a reprogrammable memory for storing a set of commands which is used for executing exact tasks like logical, arithmetic, timer, counter, and furthermore controlling different processes or machines with the help of analog/digital through digital or analog inputs/outputs.
In other words, it can also be defined as :
The Programmable Logic Controller is fundamentally a programmable interfacing that links the i/p components (such as sensor, transducer, push-button, limit-switch etc) and o/p components (such as actuator, driver, solenoid-valve, transducer etc).
These interfacing links (PLCs) contains :
- I/P component
- Central processing unit
- Reprogrammable memory
- Standard electrical supply
The block diagram for Programmable Logic Controller is mentioned below.
If we compare Programmable logic controller with conventional devices, then it has the following advantages :
- It has more flexibility.
- It occupies Less space and is more compact as compared to conventional devices.
- Higher reliability (less mechanical parts).
- Modular, can be easily connected to computer systems and to hardware.
for further details and elaboration of advantages, visit https://electricalfundablog.com/blog/advantages-of-programmable-logic-controller/690/
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.
- do not use the full capabilities of the microprocessor.
- ladder logic programming style is cumbersome and prone to mistakes.
- only good for yes/no decision.
- do not handle continuous inputs and outputs. It is not good for “direct control” purposes.
- inflexible (if compared to microprocessors)
The function of these Programmable Logic Controller blocks is a tricky and lengthy part which will be discussed in my next post.