CHAPTER 3 INTRODUCTION TO PLC SYSTEM BAKISS HIYANA

CHAPTER 3 INTRODUCTION TO PLC SYSTEM BAKISS HIYANA ABU BAKAR

COURSE LEARNING OUTCOMES (CLO) • Explain clearly blocks, parts, components and instructions found in the automation systems. (C 3) • Construct simple automation sequential control of hardware or PLC system based on IEC 61131 and NEMA standards. (C 4)

Objective : 1. Understand basic characteristics of PLC v PLC terminologies v PLC function/ background v Type / advantages of PLC 2. Understand building structure of PLC v CPU, memory unit, display and indicator unit, input and output interface 3. Understand PLC hardware unit v Housing unit, programming unit, power supply unit, printer unit 4. Explain input and output device

Introduction PLC (Programmable Logic Control) • A digital device (microprocessor based controller) that uses a programmable memory to store instructions and to implement functions such as logic, sequencing, timing, counting and arithmetic in order to control machines and processes and has been specifically designed to make programming easy. • PLCs are similar to computers but have certain features which are specific to their use as controllers: i. They are rugged and designed to withstand vibrations, temperature, humidity and noise. ii. The interfacing for inputs and outputs is inside the controller. iii. There are easily programmed.

3. 1. 1 Define PLC What is Programmable Logic Controller (PLC) ? Definition: National Electrical Manufacturers Association US (NEMA) A PLC is a digital operating electronic apparatus which uses a programmable memory for internal storage of instruction for implementing specific function such as logic, sequencing, timing, counting and arithmetic to control through analog or digital input/output modules various types of machines or process.

3. 1. 1 Define PLC • An electronic system working digitally for the use in industrial environment with a programmable memory for the internal storage of user -orientated control instructions for the implementation of specific functions. • For example: logic operation control, process control, timer, counting-and arithmetic functions, in order to control various machines and processes through digital or analog input , and output variables. • The logic programmable controls as well as the peripheral installations (PLC-system) are designed so that they can be easily integrated in an industrial control system and be implemented in all their desired functions. - International Standard IEC 61131 -1

3. 1. 1 Define PLC üSeveral different terms used to described programmable controllers: i. PLC –Programmable Logic Controller (UK origin) ii. PC – Programmable controller (US origin) üMost referring to the functional operation of the machine. üPLC has been used in this text to avoid confusion with the personal computer. **Before the 1980’s, programmable controllers were called PCs.

3. 1. 2 PLC Background PLC Development factors: i. Needs for low-cost ii. Flexible iii. Easily commissioned/ smart usage

3. 1. 2 PLC Historical Background: The first Programmable Logic Controller (PLC) was developed by a group of engineers at General Motors in 1968 The company was looking for an alternative to replace complex relay control systems. The PLC must be: v Must be programmable / Easy to program. (and reprogrammable) v Designed to operate in an industrial environment v Must accept 120 V ac signals from pushbuttons, switches v Outputs must switch and continuously operate loads such as motors and relays of two amps rating v Not need rewiring the control system if change the program. v Smaller in size, cheaper and high reliability. v Simple construction and low maintenance v Cost- competitive

3. 1. 3 Explain PLC functions q PLC performs the functions of conventional relays, timers, counters. q Capable of storing instructions, such as sequencing, timing, counting, arithmetic, data manipulation, and communication, to control industrial machines and processes.

3. 1. 3 Explain PLC functions CONTROL TYPE: FUNCTIONS i. Sequence Control ii. iv. Advanced/ Sophisticated Control i. iii. iv. v. vi. Conventional Relay Control Logic replacer Timers/ Counter PCB Card controller replacer Auto/Semi-auto/Manual control of machine and process. Arithmetic operation (+, -, × , ÷) Information Handling Analog Control (Temperature, Pressure ) P. I. D (Proportional Integral Derivation) Servo Motor Control Stepper Motor control

3. 1. 3 Explain PLC functions CONTROL TYPE: Supervisory Control FUNCTIONS i. iii. Process monitoring and alarm. Fault Diagnostic and monitoring Interfacing with Computer (RS-232 C/RS 422) iv. Printer/ ASCII Interfacing v. Factory Automation Networking vi. Local Area Network (LAN) vii. Wide Area Network (WAN) viii. Factory Automation (F. A), Flexible Manufacturing System (F. M. S) & Computer Integrated Manufacturing (C. I. M).

3. 1. 4 List types of PLC Size: • Small : - It covers units with up to 128 I/O’s and memories up to 2 Kbytes. - Capable of providing simple to advance levels or machine controls. • Medium : - Have up to 2048 I/O’s and memories up to 32 Kbytes. • Large : - The most sophisticated units of the PLC family. They have up to 8192 I/O and memories up to 750 Kbytes. - Can control individual production processes or entire plant.

3. 1. 4 List types of PLC Types of PLC Construction: i. iii. Compact PLC Modular PLC Plug-in Card Manufacturer: OMRON, Allen Bradley, Mitsubishi, NAIS, Siemens, Toshiba, Festo etc.

3. 1. 4 List types of PLC • Type of PLC - compact TECOMAT TC 600 Mitsubishi Omron Zelio Compact PLC – MELSEC FX 3 U

3. 1. 4 List types of PLC • Type of PLC - modular Omron

3. 1. 4 List types of PLC • Type of PLC - plug in card

3. 1. 5 Advantages of PLC • • • Shorter project implementation time. Easier modification Project cost can be accurately calculated. Shorter training time required. Design easily changed using software ( changes and addition to specifications can be processed by software. A wide range of control application Easy maintenance. High Reliability Standardization of Controller hardware. Able to withstand Harsh plant/process environments (Operate normally under severe conditions of temperature, humidity, voltage fluctuations and noises).

3. 2 Building Structure of PLC Basic PLC Structure Data BUS ROM RAM Output Input Microproce ssor/ CPU Address Bus Control Bus Design of Basic Microcomputer Basic internal structure of PLC consists essentially of : -processing unit (CPU) -memory -input/output units

3. 2. 1 Functions and Operation of each Block a. Central Processing Unit (CPU) • The CPU controls, monitors and supervises all operations within PLC. • It is also caries out programmed instructions stored in the memory. • An internal communications highway also known as a bus system, carries information to and from the CPU, memory and I/O units under the control of the CPU.

3. 2. 1 Functions and Operation of each Block b. • Memory Unit For storage of programs. • The user’s ladder logic program, the state of I/O in the memory of PLC. • The main program and the other programs necessary for the operation of PLC. • The organization of the data and information in the memory is called memory map. 2 types of Memory ROM RAM

3. 2. 1 Functions and Operation of each Block b. Memory Unit (types of memory): RAM Random Access Memory ROM Read Only Memory (read) This memory can be read from and written to. This memory can be read only Storing all user’s programs Storing all system’s program Entire contents will be lost if power is Memory content remain when the switched off. power is switched off.

3. 2. 1 Functions and Operation of each Block c. Display and Indicator Unit Referring to PLC standard display Internal Relay: Console’s LCD Display if user use Mnemonic Code Programming. Monitor Screen if user use software programming method. Monitor Screen LCD Display

3. 2. 1 Functions and Operation of each Block I/O Unit The I/O Unit is the interface unit has function to convert the input signal and output signal so that the CPU can communicate with the external apparatus like the switch, stepping motor, solenoid, sensor, etc. The I/O Unit has two type; Discrete I/O and Analog I/O. d. Input Interface Unit Input Unit: Function as a medium that connects the external input devices (Switch, sensor & timer) e. Output Interface Unit Output Unit: Function as a medium that connects the external output devices to the CPU within PLC. ( Lamp, motor & solenoid )

3. 3 PLC Hardware Units Hardware of the PLC ØHardware of the PLC are only consist of several components; such as Power Supply Unit, CPU Unit, Memory Unit and I/O Unit. ØAt the small PLC; Power Supply, CPU, Memory and I/O stay in the same Unit but at the big PLC; Power Supply, CPU, Memory and I/O in the separate Unit.

3. 3. 1 Identify and Describe PLC Hardware Units Hardware of the PLC a. Housing Unit Protect PLC circuit and internal component b. Programming Unit Use to process operation and system status that will be display by PLC. i. Programming Console ii. Computer iii. Video Display Unit (VDU) iv. Program Loader Unit v. Output Interface Unit

Programming Unit • Programming Console q Hand-held programming devices are sometimes used to program small PLCs q They are compact, inexpensive, and easy to use, but are not able to display as much logic on screen as a computer monitor q It is often used on the factory floor for troubleshooting, modifying programs, and transferring programs to multiple machines

Programming Unit • Computer q A personal computer (PC) is the most commonly used programming device q. The software allows users to create, edit, document, store and troubleshoot programs q. The personal computer communications with the PLC processor via a serial or parallel data communications link

3. 3. 1 Identify and Describe PLC Hardware Units Hardware of the PLC c. Secondary Storage Unit This unit related to CPU where all program and information were kept. d. Power Supply Unit: • Supplies DC power to the Central Processing Unit, Input Unit and Output Unit. The most PLC works with power 24 VDC or 220 VAC. • The big PLC has the separate power supply and the small PLC has power supply which is one. • The Power Supply is also provided by the battery back up, when happened the failure of power, automatically battery will replace the power supply to supply the CPU, so that the program of memory user do not lose. Printing Unit Used to print control system programming that controlled by PLC whether graphically or text.

3. 4 Explain Input & Output Device 3. 4. 1 Input Devices • PLCs can receive input from either automated or manual devices. • The PLC could receive data from the user via a pushbutton switch, keyboard, or similar device. • Automated input could come from a variety of devices: micro switches, timers, encoders, photo sensors, and so on. • Some devices, like the Limit Switch shown below, turn ON or OFF when the equipment actually makes contact with it. • Other devices, like the Photoelectric Switch and Proximity Switch shown below, use other means, such as light or inductance, in order to get information about the equipment being monitored.

3. 4. 1 Input Devices Push Button Limit Switch Thumbwheel SW Level SW Flow SW

3. 4. 2 Output Devices • A PLC can output to a myriad of devices for use in automated control. • Almost anything that you can think of could be controlled (perhaps indirectly) by a PLC. • Some of the most common devices are motors, Solenoids, Servomotors, Stepping Motors, valves, switches, indicator lights, buzzers, and alarms. • Some of these output devices; such as the motors, Solenoids, Servomotors, Stepping Motors, and valves; affect the controlled system directly. • Others; such as the indicator lights, buzzers, and alarms; provide output to notify personnel

3. 4. 2 Output Devices Motor Solenoid LED Display Heater Coil Lamp