A programmable logic controller (PLC) is a solid-state device that controls the output of the process through the program given in ladder diagrams.
Advantages of the programmable logic circuit (PLC)
- Flexible in programming and one PLC can operate a number of machines
- Quickly reprogrammed for any change
- Offer easy troubleshooting and correcting any errors
- A large number of contact available
- Number of software timers, counters, relays are available
- Operation of PLC can be observed on display
- PLC is more reliable than relay logic
- Maintenance cost and downtime is less as compared to relay logic
- Security for ladder programming
- PLC is a hardness industrial computer
Disadvantages of the programmable logic circuit (PLC)
- The cost of PLC for small applications is high
- When a problem occurs, hold-up time is indefinite, usually long
- There are limitations of working PLCs under high temperature, vibration conditions.
- Some PLCs turns on when power is restored and may cause an accident
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