pe 6441 advanced manufacturing lab ch4 wks 12 14

Programmable Logic Controllers

Professor Charlton S. InaoDefence UniversityBishoftu ,EthiopiaGuest Professor, Adama Science and Technology UniversityAdama, Ethiopia

Professor Charlton S. InaoDefence UniversityBishoftu ,EthiopiaGuest Professor, Adama Science and Technology UniversityAdama, Ethiopia

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General Objectives To explain and understand the following PLC concept:

Programmable logic controller; Structure of PLC and system components; Programming Languages;( LAD,STL,FBD)Logic Gates application for PLCCounterShift RegisterJumpProgramming Applications

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Programmable Logic Controllers

• Defined by NEMA as a digital electronic apparatus with a programmable memory for storing instructions to implement specific functions (logic, sequencing, timing, counting, and arithmetic) to control machines and processes.

• Considered as the first industrial-based computer

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Advantages of Using PLC

Shorter Project Shorter Project ImplementationImplementation

Easier Modification Easier Modification Without Cost PenaltyWithout Cost Penalty

Design Easily Change Design Easily Change Using SoftwareUsing Software

Project Cost Can be Project Cost Can be Accurately CalculatedAccurately Calculated

Shorter Training Time Shorter Training Time Required Required

A Wide Range of A Wide Range of Control OperationsControl Operations

Easy Easy Maintenance Maintenance

Able to Withstand Able to Withstand Harsh Plant Harsh Plant

EnvironmentEnvironment

High High ReliabilityReliability

Standardization of Standardization of Controller HardwareController Hardware

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Functions of PLC

Sequence Control

Conventional Relay Logic Replacer

Timer and Counter Functions

Auto / Semi / Manual Control of Machines and Processes

Sophisticated Control

Arithmetic Operations

Analog Control (Temperature, Pressure, etc.)

PID (Proportional Integral Derivation)

Stepper / Servo Motor Control

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Functions of PLC

Supervisory Control

Process Monitoring and Alarm

Interfacing with Computers

Factory Automation network

Wide Area Network

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Basic Control System

Open Loop System

INPUT LOGIC OUTPUT

-Pushbuttons

-Limit Switches

-Level Switches

-Flow Switches

-Relays

-Timers

-Counters

-Motors

-Solenoid valves

-Lamps

-Alarm/annunciator

-Relays/contactorsPLC

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Basic Control System

Closed Loop System

ControllerFinal Control

ElementProcessVariable

Transmitter

Set value

Error

Process Variable Primary

Element / Transducer

Temperature

Flow+

_

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Hardware Components

Central Processing Unit (CPU)

Micro PLC – less than 100 I/O’s

Small PLC – 0 to 128 I/O’s

Medium PLC – 0 to 256 I/O’s

Large PLC – 0 to 512 I/O’s

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Power Supply

100 – 240 Volts AC

100 / 110 Volts AC

200 / 220 Volts AC

24 Volts DC

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Inputs

DC – 24 Volts

AC – 110 / 220 Volts

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Outputs

Transistor type (24 Vdc )

Relay / Contact type (24Vdc / 220 Vac)

TRIAC type (110 / 220 Vac)

PNP-type Transistor Input

• Source

•Generates power

NPN-type Transistor Input

• Sink

•Transmits power04/10/23 31

Relay

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Example: Omron Relay

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Peripheral Devices

Programming Console

CX-Programmer Software

Conversion Cables

Connecting Cables

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Software Components1. Ladder Diagram Language – a symbolic instruction type

language

2. Boolean Language- Basic level language that composed of three (3) Boolean logic operation: AND, OR, NOT

Mnemonic Instruction – written in abbreviated form using 3 or 4 letters that generally imply the the operation of the instruction

3. Functional Blocks Language – high level instructions that permit the user to program more complex functions using the ladder diagram format

- Instruction set is composed of blocks that executes or performs specific function04/10/23 37

4. English Statement Language – considered derivative of computer language such as BASIC.

-also known as Control Statements

Note:

OMRON PLC’s uses both Ladder Diagram Language and Boolean Language.

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Key Points to Know in Selecting or Using PLC

I. Know the process to be controlled

II. Determine the type of control

Distributed control

Centralized control

Individual machine control

III. Determine I/O interface requirements

Estimate digital and analog I./Os

Check for I/O specifications

Determine if remote I/O is required

Allow for future expansion

IV. Define peripheral devices04/10/23 39

Steps in PLC Programming

Draw the Schematic Diagram

Draw Control Diagram

Develop PLC Ladder Diagram

I/O Assignment

Convert to Mnemonic (Boolean)

PLC Layout

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Basic Structure of PLC

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PL

C S

pecf

icat

ions

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Programming Format

1) Ladder diagram

2)Mnemonic List

3) Function Block Diagram

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NOR,NAND,EX-OR

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Timer: On delay and Off delay

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Cascaded timer/ On-OFF Cycle Timer

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Two Input control; Resetting a Latch

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Counter

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Shift Register -Mitsubishi

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Shift Register

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i  

M 0.0

Q 0.1

Q 0.2

Q 0.3

Q 0.4

Q 0.5

Q 0.6

Q 0.7

Q 0.0

I0.1

0UT

I0.0

I 0.2

M 0.0

M 0.2

M 0.3

M 0.4

M 0.6

M 0.5

M 0.7

SFT

RST

M 0.1

Shift Register Siemens Configuration

END

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Problem: Belt Sanding Machine

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Transfer Station

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End

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