PROGRAMMABLE LOGIC CONTROLLER

DNT 353/3

BY:Salsabila Ahmad

CHAPTER 1ELECTRICAL CONTROLLER

EQUIPMENT

BY:Salsabila Ahmad

ELECTRICAL CIRCUIT BASIC4 ELECTRICAL BASICS• POWER SUPPLY• INPUT DEVICE

– Input Controller Equipment

• CONDUCTOR• OUTPUT DEVICE

– Output Controller Equipment

POWER SUPPLY

Definition:A device which supplies energy

needed to create an electrical current

EXAMPLES OF POWER SUPPLY

• Battery• DC Power Supply• AC Power Supply

INPUT DEVICE

• DEFINITION• 2 TYPES OF INPUT DEVICE

– Mechanical input device– Solid state proximity device

• ELECTRICAL SWITCHING– Basic Principle of Electrical Switching– Types of Contacts– How do These Contacts Work?

DEFINITION:• A device which allows/ controls the

flow of current in a circuit• These devices are known as“ELECTRICAL CONTROLLER

EQUIPMENTS”• Provides Electrical Switching

MECHANICAL INPUT DEVICES

Definition:• An input device with a mechanical

contact

EXAMPLE OF MECHANICAL INPUT DEVICES

• Contact Relay• Push button• Limit Switch• Selector Switch• Toggle Switch• Temperature Switch• Pressure Switch• Solenoid Switch• Induction Motor Controller

CONTACT RELAY

• Relay Coil – output device

But• Relay Contact

– input device

RELAY

2 TYPES OF RELAY:• EMR• SSR

CHARACTERISTICS OF EMR & SSRRELAY SYMBOLS

ELECTROMAGNETIC RELAY (EMR)

Definition:• An EMR is an electromagnetic device

composed of a frame/core, electromagnet coil and contacts (move and fixed)

• Based on simple electromagnetic principle

SOLID STATE RELAY (SSR)

HOW IT OPERATES?

• Operates similarly to EMR, but with no mechanical contact.

• Employ semiconductor switching elements– thryristors – triacs – diodes – transistors.

• Employ optical semiconductors called photo couplers to isolate input and output signals.

• Photo couplers change electrical to optical signals and relay the signal through space.

CHARACTERISTICS OF EMR AND SSR

EMR SSR

•slow speed•wears out easily•noisy•cheap

•high speed, high frequency for switching operations•no failure due to wear out, since no mechanical contacts•little noise•expensive

• Commonly used in electrical machine diagram

Normally open (NO)

Normally close (NC)

Coil

RELAY SYMBOLS

BASIC PRINCIPLE OF ELECTRICAL SWITCHING

• A situation of breaking and open an electrical circuit

• Or to direct current from one conductor to another.

• The PLC is the solution to today’s electrical switching requirements – where it is able to solve complex switching

requirements.

2 TYPES OF CONTACT

NO NC

HOW DO THESE CONTACTS WORK?

• Once coil is energized, the contact will change state– NO NC– NC NO

PUSH BUTTON

• Definition• Concepts of Operation• Application of Push Button• Schematic Symbols

DEFINITION

• pushbutton-type operator• Have one set or more

contact/spring• Mostly have a set of normally open

(NO) and normally closed (NC) contact

CONCEPTS OF OPERATION

• Pushing the operator causes the contacts to change state

• Spring causes switch operator to automatically return to it’s natural state when it is released.

NO NC NONC NO NC

natural state change state automatic return

• a switch with this return spring action, is called a momentary switch.

• Frequently used in industrial applications to control functions such as – starting – and stopping

the machine’s operation

• With a safety nature. Why?

APPLICATIONS

SCHEMATIC SYMBOLS FOR PUSH BUTTON

Normally Open Contact

Normally Closed Contact

LIMIT SWITCH

SELECTOR SWITCH

• Definition• Application• Schematic Symbols

DEFINITION

• Similarly to pushbutton, but instead of pushing, you rotate a knob

• may be designed to stay in a selected position or may have a momentary action

• selector switch that stays in a certain position is called a maintained switch.

APPLICATION• Widely used in industrial applications

– for switching mode of operation• For example from automatic to manual

modes– to turn the main power on and off – to select between AC or DC output.

• Some requires key (authorized person) to turn on for safety reason.

SCHEMATIC SYMBOLS FOR SELECTOR SWITCH

Normally open contact

Normally close contact

Selector switch with two contacts

TOGGLE SWITCH

Toggle switch is a maintained switch

What is a maintained switch?

TEMPERATURE SWITCH

PRESSURE SWITCH

SOLENOID SWITCH

• Use concept of magnetic flux for armature/plunger to move

• Produces linear mechanical motion

INDUCTION MOTOR CONTROLLER

• Commonly used micro-controllers

PROXIMITY SENSORS

SOLID STATE PROXIMITY DEVICES

Definition:• An electronic input device which

needs power to be able to operate

Proximity Sensors Category

PROXIMITY SENSORS CATEGORY

Proximity sensors inductive

capacitive dielectric type

conductive type

ultrasonic

optical diffuse reflective type

retro reflective type

thru beam

fiber optic sensor

color mark sensor

encoder sensor

• Sense only metallic objects– e.g. steel, iron, aluminum, tin, copper

etc

• Has limited sensing range– range affected by the type of metal

sense

INDUCTIVE PROXIMITY SENSOR

An oscillator and a detection coil generate a magnetic field that produces Eddy currents in a nearby metallic object (the detectable object). These Eddy currents generate a magnetic field that influences the field produced by the sensor’s detection coil.

CAPACITIVE PROXIMITY SENSOR

• sense all material with mass.• operation for both dielectric and

conductive type are the same

CAPACITIVE PROXIMITY SENSOR

• The dielectric type works best for high density material– Low density material (e.g. paper, foam

etc) do not cause a detectable change in dielectric.

• The conductive type works best on electrically conductive material – e.g. metal or water-based material)

ULTRASONIC SENSOR

• Use ultrasonic technology• How does it works?

CONCEPTS OF ULTRASONIC SENSOR

• Use an ultrasonic “ping” sent from sensor to target– Sensing area is a funnel shape area– Therefore, target must be located directly in

front of sensor

• When echo is returned, sensor detects target by measuring time delay between transmitted ping and returned echo– sensor calculate distance between sensor

and target

CONCEPTS OF ULTRASONIC SENSOR (cont’)

• Do not work well on cloth, foam rubber

– since good absorber of sound waves

• Works best on high density material

– where sound waves reflects best

DIFFUSE REFLECTIVE

• Emitter and receiver located in same housing

DIFFUSE REFLECTIVE

• Light emitted is received when the object is present

• Works well on glossy target but not transparent

Emitter and receiver

• Emitter and receiver located in same housing.

RETRO-REFLECTIVE

• Light emitted is received when the object is absent.

• Does not work well with glossy target. Why?

– Because glossy target acts like a reflector

Emitter and receiver

reflector

RETRO-REFLECTIVE

EXERCISE:

If you have a shinny object as a target, which type of sensor do you choose; retro or diffuse?

THRU-BEAM

• Emitter and receiver is located in different housing

• Sense the object’s present when it passes through between emitter and receiver

– where it stops the light from hitting receiver

emitter receiver

THRU-BEAM

• Available in both thru beam and reflective

FIBER OPTIC

• Use plastic and glass fibers to carry lights

Thru-beam

Reflectorobject

FIBER OPTIC

• A special type of diffuse reflective optical sensor that can – differentiate between colors

• some can detect contrast between colors.

• Typically used to check labels and sort packages by color mark.

COLOR MARK

ENCODER

• Used for position feedback and some for velocity feedback

• Two main types– Incremental– absolute

CONDUCTOR

CONDUCTOR

Definition:• A medium that connects all the

components and allows current to flow.

Examples:• copper wire • bread board• What else???

OUTPUT DEVICE

•Definition•Example

DEFINITION

• A component that will produce a desired output. E.g.– Sound– Light– Movement etc

• It is also referred to as a load.

EXAMPLE

• Coil• Buzzer/Alarm• Lamp• Motor• Solenoid• Timer• Counter

COIL

Can represents various forms of output including

• Motor• Light• Pump• Counter• Timer• Relay

BUZZERLAMP

MOTOR

• Types of Motor• In PLC, motor can only be controlled

for– power (ON/OFF)– direction (CCW/CW)– preset speed

TYPES OF MOTOR

DC motor type wound fieldpermanent magnetelectronics commutation

dc motors

AC motor type induction motorssynchronous motor

SOLENOID VALVE

Function:• Used to delay actions

Common symbols

Timer Characteristics

How they are differentiate?

How they are programmed?

TIMER

DEFINITION

• Used to provide time delay.

COMMON SYMBOLS OF TIMER

• most common symbol for displaying timer function is in block diagram– uses a box shape to display the timer

function– Sometimes, timer is displayed in coil

format symbol

TMR TIMER0

T0

K40

INPUT

CHARACTERISTICS OF TIMER

• Timers typically have one or two input• Timer with one input has functions as a

timer enable input. When input ‘high’, the timer begins timing

• A timer with 2 inputs has additional functions which is used to reset the timer accumulated time to zero when the second input is ‘high’

• Every timer has a time base– Typically; 1 sec, 0.1 sec and 0.01sec.

HOW TIMERS ARE IDENTIFIED?

• Each timer will have number to identify it

• There are two parameters for timer– timer number

•Used to identify timer e.g. Timer 0, Timer 2.

– Preset value•Is the delay time set for the timer

TIMER’S PROGRAM

• There are still many similarities in the way the timers are programmed– even when PLC are different brand

• Let say the time base of a timer is 0.1 second– Therefore, if a programmer entered 50 for

the number of delay increments– What is the timer’s delay?

• the timer would have a 5-second delay.• 50 x 0.1 sec = 5 sec

COUNTER

• What is it?• What is its characteristics?

• used to capture and store number of occurrence

• Common applications of counters– include keeping track of the number of

items moving past a given point– determining the number of times a

given action occurs

DEFINITION

CHARACTERISTICS

• set to some preset number value– when this value of input pulses has been

received, it will operate its contacts• Let say the counter is set for 10 pulses,

then when 10 pulse impulses have been received, the counter contacts will close

• When there is a input transition for X0 from OFF to ON, counter starts counting

• When the RESET is ON, the counter resets to 0