1. INTRODUCTION TO PROGRAMMABLELOGICCONTROL

2. PROGRAMMABLE LOGIC CONTROL (PLC): “ A digital electronic device that uses a programmable memory to store instructions and to implement specific functions such as logic, sequence, timing, counting and arithmetic to control machines and process. “PLCPLC

3. What is CONTROL? “ CONTROL is the process in a system in which one or several input variables influence other variables “ Definition of Control

4. CONTROLSYSTEM PLANT INFORMATION COMMANDS ACTUATORS SENSORS A Simple View of a Control System

5. CONTROL SYSTEM Types of Control System OPEN-LOOP CONTROL SYSTEM CLOSED-LOOP CONTROL SYSTEM

6. In open-loop control systems, output variables are influenced by the input variables. Open-loop Control System LN

7. It is characterized by continuous comparison of the desired value (or set point) with the actual value of the controlled variable. C Xs Xi Xi > Xs Xi < Xs LN Xi - Required value Xs - Actual value Closed-loop Control System

8. The essential difference between programmable control and traditional control technology may be summed up as follows: »The functions are no longer determined by the wiring, but rather by the program »Programming is simplified to enable symbols familiar to the control engineer to be used (contacts or logic graphic symbols) PLC and Conventional Control System

9. L N S1 S2 K1 S1 S2 PLC K1 HardwirePLC 0 V 24 VDC Hardwire and PLC Wiring Diagrams K1

10. ComparisonComparison Hardwired control systems »The functions are determined by the physical wiring. »Changing the function means changing the wiring »Can be contact-making type (relays, contactors) or electronic type (logic circuits) Programmable control system »The functions are determined by a program stored in the memory. »The control functions can be changed simply by changing the program. »Consist of a control device, to which all the sensors and actuators are connected.

11. CONVEYOR LINE WORKSTATION #1 WS #2 WS #3 FLOW OF MATERIAL PLC Application Example

12. »Input devices  Sensors  Switches etc. »Output devices  Relays  Lamps etc »PLC WS #1 WS #2 WS #3 M 0032 PLC PLC Control System

13. POWERSUPPLY CENTRALPROCESSING UNIT (CPU) INPUTMODULES OUTPUTMODULES MEMORY(EPROM/RAM) PG/PC Basic Structure of a PLC

14. PLC USERPROGRAM(LOGIC)USERPROGRAM(LOGIC) InputDevices OutputDevices PLC Inputs / Outputs (I/Os)

15. I N P U T S O U T P U T S WS #1 WS #2 WS #3 M 0032 PLC Logic Input/output Connections

16. Input / Output Modules »Digital input modules adapt digital signals e.g. from proximity sensors »Digital output modules convert the internal signal level of PLC into digital process signals e.g. relays »Analog input modules adapt analog process signals e.g. from transducers »Analog output modules convert internal digital values of the PLC to analog process signals e.g. temperature controller

17. Central Processing Unit (CPU) What is a CPU? »The “brain” of a PLC »Controlled by a program called the executive or operating system (OS) »The executive is a collection of supervisory programs permanently stored in memory

18. CPUCPU Four basic types of CPU operations: »Input and output operation »Arithmetic and logic »Reading or changing contents of memory locations »Jump operations

19. Program Memory Program memory RAM (Random Access Memory) the memory contents can be read and written (modified) memory contents will be lost when the supply voltage fails ROM (Read Only Memory) the memory contents can be read, but cannot be modified