1. PLC introduction1 Discrete Event Control Concept Representation DEC controller design DEC controller implementation

2. PLC introduction2 DEC Implementation Hardware DEC system Software DEC system PLC system

3. PLC introduction3 1. PLC - Introduction What does PLC stand for? n PLC - programmable logic controller n PLC implements logic control functions by means of a program

4. PLC introduction4 1. PLC - Introduction Features

5. PLC introduction5 1. PLC - Introduction Features

6. PLC introduction6 1. PLC - Introduction An application example 1: Gate Control n PLC can sense a vehicle at the entrance or exit, and open and close the gate automatically n The current vehicle count is easily determined by programming a simple counter

7. PLC introduction7 1. PLC - Introduction An application example 2: Conveyor System n PLC can be used to start/stop latching logic for motor control n Counters can be used for monitoring product amounts

8. PLC introduction8 1. PLC - Introduction Comparing traditional and programmable control systems - 1

9. PLC introduction9 1. PLC - Introduction Comparing traditional and programmable control ystems - 2 n In traditional control, the switches S1, S2 and S3 must close for K1 to be turned on - the wiring makes the rule n In PLC systems, the program is written to perform the logic “when S1 is closed AND S2 is closed AND S3 is closed, THEN turn on K1” - the program makes the rule It is much simpler to change program then wiring!

10. PLC introduction10 1. PLC - Introduction How does a PLC differ from a computer? n A computer is optimized for calculation and display tasks n A computer is programmed by specialists n A PLC is designed for (logic) control and regulation tasks n A PLC is programmed by non-specialists n A PLC is well adapted to industrial environment

11. PLC introduction11 1. PLC - Introduction Why are PLCs so common? n They are cost-effective n They are flexible, reliable and compact n They have significant advantages over traditional control systems based on relay or pneumatics

12. PLC introduction12 1. PLC - Introduction Where are PLCs used? n In every industry where automation is involved, from individual machines to whole processes

13. PLC introduction13 1. PLC - Introduction What tasks do PLCs perform? n The logic control tasks such as interlocking, sequencing, timing and counting (previously undertaken with relays or pneumatics) n In addition, PLCs can perform a variety of calculation, communication and monitoring tasks

14. PLC introduction14 Inputs Outputs & Power Supply Communication Ports (RS-485) 1. PLC - Introduction

15. PLC introduction15 1. PLC - Introduction Structure of a PLC

16. PLC introduction16 1. PLC - Introduction The PLC processor

17. PLC introduction17 1. PLC - Introduction PLC Input/Output Devices

18. PLC introduction18 1. PLC - Introduction PLC Input Devices n Push buttons n Switches (limit switches, level switches, etc.) n Sensors n...

19. PLC introduction19 1. PLC - Introduction PLC Output Devices n Relay contacts n Solenoid valves n Signal devices (such as lamps, alarms, etc.) n Motors n...

20. PLC introduction20 1. PLC - Introduction Programming terminal

21. PLC introduction21 1. PLC - Introduction n Programming is done through programming terminal n Programming terminal translates engineering language (logic control) to machine language (binary code)

22. PLC introduction22 1. PLC - Introduction Programming through standard computer n Most PLC manufacturers offer software packages that allow a standard computer to be used as a programming terminal

23. PLC introduction23 1. PLC - Introduction Programming through standard computer

24. PLC introduction24 1. PLC - Introduction Relating the program to inputs and outputs n The CPU reads the data from the inputs n The program in the CPU uses the inputs to evaluate the control logic. As the program runs, the CPU updates the data n The CPU writes the data to the output

25. PLC introduction25 1. PLC - Introduction Relating the program to inputs and outputs

26. PLC introduction26 1. PLC - Introduction Data Flow in the PLC

27. PLC introduction27 1. PLC - Introduction n One of the advantages of PLC is that it can be programmed by non-specialists n Program can be written either in the form of a statement list: a set of mnemonic instructions representing a function of the CPU or a ladder diagram: a graphical language resembling the electrical relay diagrams

28. PLC introduction28 1. PLC - Introduction statement list

29. PLC introduction29 1. PLC - Introduction Ladder diagram