Advantage of PLC :
#1. simple and less wiring
#2. Fast and design for the rugged industrial environment
#3. Another advantage of the PLC system is easy to troubleshooting.in other term i say good programmer easily read plc program and figure out what is working and what is not working
#4. One of the best future of plc system is versatility with programming and expandability compare to relay system. for example, just imagine you want to add one-timer
to make a motor run after 10s .what you do just add one-timer instruction and it’s done
#5. The program can run or simulated without actual input connection or Hardware.
Advantage of plc over relay :
#6. In some Industry, there is a redundant system for example if one pump fails the second pump will automatically start. acknowledge failure means that you get warning that one has failed
#7. A wide range of control application
#8. speed of operatio.scan time in mili second
#9. PLC has a low power consumption
#10. PLC have High processing speed
#11. smaller physical size then relay or hardwire solution
#12. flexible and can be reapplied to control other systems very easily.
#13. plc cost is like 4 to 5 relay but can replace hundred of relay
#14. some complex task not possible with relays for example Calculation Information exchange text & Graphic display data processing networking
#15. Diagnostics are centrally available.PLC Interface directly to the wired system
#16. large production of PLC and Advanced technology makes it cheaper than the other controller or relay-based systems.