TYPES OF PLC

TYPES OF PLC:-

1) Small type:- I/O module cpu all as a one unit. All module fixed with CPU.
2) Modular type:- I/O module can be expand but put to some limit.
3) Rack type:- componet include rack type plc.


1) Rack
2) Slot
3) Modules/card
4) Channels

Generally I/O module avaliabal 2,4,8,16,32, channel as per application.



PLC PROGRAMMING LANGUAGES:-

1) IL ( instruction list)
2) LD ( ladder diagram)
3) FBD ( function block diagram)
4) SFC ( sequential function chart)
5) ST ( structured text)



PLC SCAN:-

1) Input scan:- input terminals are read and I/P image tabal is prepred.
2) Program scan:- read I/P image tabal and apply I/P status to the user program usear program is executed & O/P image is prepred.
3) Output scan:- read O/P image tabal and provide o or1 logic to the O/P devives.
4) Scan time :- It is the time releted to read I/P process to logic cycle update O/P in one cycle.
5) Scane cycle of cpu :- scan cycle depends up to no of I/Os.
Sace Time:-

1. More I/O more scan time.
2. Application decides the scan time of a plc.
3. Scan time is normal application is 1ms to 2ms and in bigger application 100ms to 200ms.