Programmable Logic Controllers Presentation Edited

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8/10/2019 Programmable Logic Controllers Presentation Edited

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BASIC PLC COURSE

Objectives:

– To be able to define PLC and its functions.

– To understand the advantages of PLC.

– To be able to know PLC Hardware Components

– To be able to develop PLC Ladder Diagram.

– To learn proper wiring of inputs and outputs

to the PLC.

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

Functions of PLC

Sequence Control

Conventional Relay Logic Replacer

Timer and Counter Functions

Auto / Semi / Manual Control of

Machines and Processes

SophisticatedControl

Arithmetic Operations

Analog Control (Temperature,

Pressure, etc.)

PID (Proportional Integral

Derivation)

Stepper / Servo Motor Control

Functions of PLC

Supervisory Control

Process Monitoring and Alarm

Interfacing with Computers

Factory Automation network

Wide Area Network

Basic Control System

Open Loop System

INPUT LOGIC OUTPUT

-Pushbuttons

-Limit Switches

-Level Switches-Flow Switches

-Relays

-Timers

-Counters

-Motors

-Solenoid

valves

-Lamps

Basic Control System

Closed Loop System

ControllerFinal Control

Element

Process

Transmitter

Set value

ProcessVariable Primary

Element / Transducer

Temperature

Pressure

Hardware Components

Central Processing Unit (CPU)

Micro PLC – less than 100 I/O’s

Small PLC – 0 to 526 I/O’s

Medium PLC – 0 to 1028 I/O’s

Large PLC – 0 to 5120 I/O’s

Power Supply

100 – 240 Volts AC

100 / 110 Volts AC

200 / 220 Volts AC

24 Volts DC

Inputs

DC – 24 Volts

AC – 110 / 220 Volts

DC – 12 Volts

Outputs

Transistor type (24 Vdc )

Relay / Contact type (24Vdc / 220 Vac)

TRIAC type (110 / 220 Vac)

PNP-type Transistor

• Source

•Generates power

NPN-type Transistor

• Sink

•Transmits power

Peripheral Devices

Programming Console

CX-Programmer Software

Conversion Cables

Connecting Cables

Software Components

1. 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 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 function

4. English Statement Language – considered derivative of

computer language such as BASIC.

-also known as Control Statements

OMRON PLC’s uses both Ladder Diagram

Language and Boolean Language.

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 devices

5 Steps in PLC Implementation

Draw the Schematic Diagram

Draw Control Diagram

Develop PLC Ladder Diagram

I/O Assignment

PLC Layout

STEP I. SCHEMATIC OR POWER DIAGRAM

Exercise 1 FORWARD/ REVERSE SCHEMATIC DIGRAM OF 3-PHASE MOTOR

L1 L2 L3

FWD REV

EXERCISE 2 ELECTRO-PNEUMATIC DOUBLE ACTING CYLINDER

DOUBLE ACTING CYLINDER

4/2 WAY DIRECTIONAL CONTROL VALVE.

DOUBLE SOLENOID VALVE

STEP I. SCHEMATIC OR POWER DIAGRAM

STEP II. CONTROL DIAGRAM (RELAY DIAGRAM) OF EXERCISE 1

PB FORWARD

PB STOP

STEP IV. PLC DIGRAM

0.01 0.3 10.02

10.011001

0.30.02

STEP III. INPUT/OUTPUT ASSIGNMENT OF

EXERCISE 1

PB FWD – 0.01 FWD-10.01

PB REV - 0.02 REV-10.02

PB STOP- 0.03

STEP V. PLC LAY-OUT

CENTRAL

PROCESSING UNIT

INPUT MODULE OUTPUT MODULE

+ 24V -

Stop PB

CH0 CH10

220VAC

PLC I/O WIRING(INPUT WIRING)

PLC I/O WIRING(OUTPUT WIRING)

CX PROGRAMMER

• PLC ADDRESS T0- T127

COIL : TIM_TIM#_SET VALUE

CONTACT: T#

a contact point

b contact point

delay period

CONTACT

Timer No.

Set Value

COUNTER

In the control circuits, besides detection of objects and response operation or

timing control, there is a function which is called “counter”. For example counters

are often used in counting material numbers being carried by conveyor, or making

operation stop after a certain period is counted.

PLC ADDRESS C0- C127

Coil : CNT_CNT#_SET VALUE

Contact : C#

PULSER

Counter No.

Set Value

Pulser

FORCING OF STATUS

• Forcing is used for testing. To temporarily Turn ON the status of a certaininput, output or internal relay.

Note: PLC must be in monitor mode

To change operating mode:

PLC => Operating Mode => Monitor Mode

To begin forcing

PLC => Force => ON

To begin forcing

PLC => Force => OFF

Problem I.

Packages arriving on a roller-conveyor are lifted by a pneumatic cylinder and pushed onto

another conveyor by a second cylinder. Cylinder B may then perform a return stroke only after

cylinder A has reached the car position. The start signal should be provided by means of a manual

button, each signal initiating one cycle.

Positional sketch and determination of working elements:

Problems and Exercises

Displacement Step Diagram

Problem II.

Two clips are to be riveted together on a semi-automatic press.

Components and rivet are positioned by hand and then removed by hand on completion of the

riveting operation. The automated part of the working cycle consist of the holding and clamping of the components

(cylinder A) and also the riveting (cylinder B), and the cycle should be performed ending at the starting position

after operating a start button.

Positional sketch and determination of working elements:

Problem III.

Provide switches to operate this valve. Provide interlock so that only one can open at a time (It is undesirable to mix

the chemicals of several tanks.)

Note: Switches which drive active high valves must be driven with active low.

Problem IV.

REMOTE MONITORING OF 3 MOTORS

Design a control circuit that will start the three motors one at a time. Motor 1 should start first. After 10s Motor 2

will start and after another 10s, motor 3 will start. Provide a stop button to stop the operation at any time.

Problem V.

Flints are contained in a hopper and they are to be distributed to two only assembly

stations in a certain rhythm. Cylinder 1.0 (A) opens and closes the hopper seal. When the start

switch is operated, cylinder 1.0 (A) opens the seal. The flints slide into receptacle 1. When the

hopper has been closed, cylinder 2.0 (B) moves receptacle 2 under the hopper. In the meantime,receptacle 1 has arrived on the conveyor at the first assembly station. Another empty receptacle is

located on the sliding table when cylinder 1.0 (A) has closed the hopper. Cylinder 2.0 (B) moves

into its initial position and receptacle 2 is transported to the second assemble station on a

conveyor. If the start switch is operated again, the control performs a new cycle.

LADDER DIAGRAM DESIGNING

Condition: Level MonitoringThree float switch will be used to detect the level of the tank.Float switch 1 for Low Level, Float Switch 2 for Medium Level,and Float Switch 3 for High Level. Output lamps will give signalto the Operator upon actuation of the float switch. One lamp

will indicate when there is no signal given by the float switchyet.

Design the circuit.

Programmable Logic Controllers Presentation Edited

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