basic sales tech training information

8/7/2019 Basic Sales Tech Training Information

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PLC What is PLC

PLC is an abbreviation and stand

forProgrammable LogicController.

A Programmable LogicController is a device that a usercan program to perform a seriesor sequence of events.

PLC performs relays, timers andcounters equivalent functions

Designed for industrialenvironment

Common brand use in market :Omron, Siemens, Mitshubishi,Allen-Bradley, GE, Modicon,Telemecanique/Schneider, etc.


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PLC How it work

PLC is like a small computer containing :

CPU (central processing unit), Memory, Input module and Outputmodule

Application for controlling machine or certain process thru pre-programmed set of instructions for implementing specific throughdigital or analog inputs and outputs.

The inputs will provide machine condition and status at the specific

time.The CPU with pre-programmed instruction will analyze and computeall the inputs condition as well as operation requirement and willtake necessary actions thru outputs channel.

The outputs are used to do specific action on the machine orprocess according to program logic sequence.

The program logic sequence is a set of instructions, sequencing,timing, counting and arithmetic that is written for specific application.

Programming PLC can be done thru few different programminglanguage, depending on type of PLC and what feature available tospecific model.

The most popular and easy to use is called a Ladder Logic Diagram


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PLC Connection


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PLC Programming Language

Statement list Function block

Ladder diagram

The instructions are represented

by graphic symbols:

Contacts, Coils & Boxes

The ladder diagram is the most

popular programming language


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Digital signals are discrete, have 2 values like 0 or 1, ON

and OFF.Analog signals are continuous, and varying in value.

Typical analogue signals from 0-10 VDC or 4-20 mA.

Ued to represent changing values such as speed,

temperature, weight and level

PLC Digital and Analog

PLC Input and Output (I/O = eye-oh)

Input is kind of analog or digital signal from input devices

(photo sensor, limit switch, pushbutton, transducer, etc)to PLC input module

Output is kind of analog or digital signal sent-out from

PLC output module to output devices (solenoid,

contactor, relay, frequency inverter, lamps, etc)


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PLC Conventional Design Comparition

Disadvantage Many wirings to relays and timers

Modification can be quite difficult

Troubleshooting can be quitedifficult to trace for problem

Power consumption can be quitehigh as relay coils consumespower

Machine downtime is usually longwhen problem occur

Drawing are not easily updatedover the years due to changes,this causes longer downtime inmaintenance and modifications

Advantage: Components replacement

compatibility usually easy to findeventhough has been absolute


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Advantages : Cost effective for controlling

complex system Flexibe and be re-applied to

control other system quickly andeasily

Computational abilities allow moresophisticated control application

Trouble-shooting aids make

programming easier and reducedown-time

Reliable components is higherthan mechanical relays and timers

High speed PLC operationincreases productivity

Cost much less compare to

conventional system in situtionwhen number of I/Os is very largeand control functions are complex

Spare part for relays andhardware timers are greatlyreduced as compared toconventional control panel

Disadvantages:Due to long years operation

capability, in long termreplacements could be difficult ifthe model has been absolute inthe market, may required aspecialist who know details ofmachine operation andprogramming, will take high costto upgrade.

Need certain skill level oftechnician for trouble-shooting

PLC Advantage vs Disadvantage


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PLC When need it

Mainly used in complex process control, that may

require algorithm and performance.Now there are many small and compact PLCsavailable in market that significantly help to reducecost to build a simple process automation, soconventional control system with relays, timers andcounters has been drastically left behind.


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Term of Control Board here is

referring to customized controlboard, designed for specificmachine process orsequencing.

Control Board controlled bymicrocontroller, programmed

to execute certain instructions.Provide software protectionagainst pirate copy by othercompetitor, as well as supplierdependent for spare

Relatively faster execution ofinstruction comparing to PLCexecution time.

Widely used for more complexand fast machine processapplication

PLC vs Control Board


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Advantage Faster respond

DisadvantageSensitive against

temperatureDifficult totroubleshoot

High cost for sparedue to supplied only

by machine supplier

Control Board Advantage vs Disadvantage

Program written and stored in

this IC Microcontroller


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PLC - Operator Interface

Man Machine Interface = Human Machine Interface =

User Interface = Operator Interface consider termused for similar function/purpose althought in definitianslightly different each other.

User interface is a place (device) where interactionbetween humans and machines occurs, for effectiveoperation and control of the machine, and

feedback/status/alarm/fault indication from themachine which aids the operator in making operationaldecisions.

Built-in hardware and software components.

In machine industries application, usually used in

combine with PLC, it will help to reduce cost forhardware input and output devices like push-button,indication lights, status, switches, input and output forvalues, etc.

(contd next.....)


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PLC - Operator Interface (contd)

Help to reduce extra wirings for more complex

machine applicationFor more advance model, can be used to aids formaintenance trouble-shooting.


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Data Communication - 1

Serial RS232, RS422, RS485

Serial transmission involves the sending of data onebit at a time over a single communication line.

Low speed data transfer compare with other type ofcommunication.

Can be used for long distance data transfer (forcurrent-loop type), sometime up to several

kilometers, comparing with voltage type with only upto 50 meters.

Profibus A single multi-drop cable is used to connect all

devices, with high speed, bi-directional, serial

messaging used for transfer of information Offer huge savings on cabling cost when compare

with older methods, particularl for large plant sites.

Allow simple linking of devices from many differentvendors


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Ethernet

The most common type of connection computersuse in a local area network (LAN)

Looks much like regular phone jack, has 8 pins,called RJ45

2 widely-used form of Ethernet are 10BaseT(10mbps) and 100BaseT (mbps=megabit per-

second)

USB Allow high speed data transfer, easy connection of

peripheral to a PC. When plugged in, everythingconfigures automatically.

Use for short length of distance, not suitable forlonger distance data transfer process as thevoltage will significantly drop over the longdistance.

USB has completely replace parallel ports in mostmodern PC now


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Parallel

Parallel communication requires atleast as many lines as there arebits in a word being transmitted (foran 8-bit word, a minimum of 8 linesare needed).

For short distances or when highertransmission rates are required.

Mainly used for connectionbetween test instruments orcomputer and printer.

Less use in modern PC now sincethe USB found to be much fasterand more simple connection.


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Interfacing Devices Sensors & Actuators

A Sensoris an input device, transducer that converts a

physical stimulus from one form into a more useful form tomeasure the stimulus

An Actuatoris an output device that convert a controllercommand signal into a change in a physical parameter

Actuators

Controller or

PLC

Transformation Process

Sensors

DAC ADC

Input DevicesOutput Devices

Continuous and Discrete

VariablesContinuous and Discrete

Parameters


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Sensors - Function

Feedback on task completion

Information on the status of the process

Inspection and measurement data

Collect product or process data for quality monitoring

Sensors Types (1)

Contact versus Non-contact

Contact sensor : there is a physical contact between

the sensor and parameter to be measured Non-contact sensor: also called proximity sensors.

Proximity indicates that the object is near, but contact isnot required


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Sensors Non-contact

Non-contact sensors do not operate mechanically and

are more reliableLess likely to fail than mechanical ones

They are much faster than mechanical devices


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Sensors Digital vs Analog

Digital sensor:

Have two states : ON or OFF

Presence or absence of object

Counting such as used in a rotary encoder

Analog sensor:

It senses continues variables (such temperature,pressure) and provides a continuous (usually linear)voltage or current

More complex than digital and can provide moreinformation


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Sensors Digital Type

Switches

Optical (photoelectric) sensors

Encoders

Ultrasonic sensors

Inductive sensorsCapacitive sensors


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Sensors Digital Type - Switches

Pushbuttons andmanual switches(manual operators)

Limit switches


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Sensors Digital Type Switches

Manual Operatos

Push Buttons

Normally Open /Normally Closed

Spring returned versus

maintained

Selectror Switches

Specify number ofpositions : 2, 3, 4, etc

Can be spring returnedor maintained

Limit Switches

Advantages

Robust, made for harshenvironments

Can directly drive a load

(contact 15A+)

Disadvantages

Mechanical wear out

Large sizeMay require contact withproduct

Operating force may besignificant


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Sensors Digital Type Switches

Other Mechanical Switches

Level/Float Switch

Mechanical switch that is actuated by the level of a liquid

Pressure Switch

Mechanical switch that is actuated by the pressure influid system

Flow Switch

Mechanical switch that is actuated by the flow rate of afluid

Temperature Switch

Mechanical switch that is actuated above a settemperature (such a bimetallic element)


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Sensors Digital Type Optical/Photoelectric

All optical sensors use light to sense objects

Operating method: Lasers, Incandescent bulbs, or Light emitting diodes

(LED) are used as light source

The light source is turned off and on (modulation) at ahigh frequency (several kHz)

A photodetector senses the pulsed light

The light emitter and receiver are tuned to themodulation frequency

Refers to the normal state of the sensor, optical sensor

are either : Light sensing (light-ON): the output is energized (ON)

when the sensor receives modulated beam

Dark sensing (dark-ON): the output is energized (ON)when the sensor does not receive modulated beam


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Sensors Digital Type Optical/Photoelectric

All optical sensors function in the same basic

manner, the differences are in the way in which thelight source and receiver are package

Type of Optical Sensors

Reflective Sensors

Polarizing Photo SensorsRetroreflective Sensors

Thru-Beam Sensors

Convergent Photo Sensors

Fiber-Optic SensorsColor Mark Sensors

Laser Sensors


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Sensors Digital TypeOptical/Photoelectric : Reflective (Diffuse) Sensors

Transmitter and receiverare combined into oneunit

Relies on the reflectivesurface of the target to

bounce the light from thetransmitter to the receiver

Target must be somewhatperpendicular to thesensor axis

Used when it is notfeasible to mount areflector

Less sensing range (relyon the reflected light)


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Sensors Digital TypeOptical/Photoelectric : Polarizing Photo-Sensors

They sense only shiny objects using special reflector

The reflector vertically polarizes the light from the sensor

Reflections from shiny objects will be ignored

Only reflections from the polarizing reflector will trigger

this sensor


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Sensors Digital TypeOptical/Photoelectric : Retroreflective Sensors

Transmitter and receiver are combined into one unit

Makes use of a reflector to bounce the light from thetransmitter to the receiver

Have more sensing distance than reflective sensors

Have less sensing distance than thru-beam sensors


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Sensors Digital TypeOptical/Photoelectric : Thru-beam Sensors

Has a separate transmitter and receiver

Capable of sensing very small object by narrowing thelight beam

Fiber optics can be used to position the beam

transmitter and receiversTargets can be opaque but not transparent


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Sensors Digital TypeOptical/Photoelectric : Convergent Photo Sensor

Also called focal length sensor

The sensor emits the light to a specific focal length

The light must be reflected from the focal length to besensed

Only objects near the focal point are detected


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Sensors Digital TypeOptical/Photoelectric : Thru-beam Sensors

Has a separate transmitter and receiver

Capable of sensing very small object by narrowing thelight beam

Fiber optics can be used to position the beam

transmitter and receiversTargets can be opaque but not transparent


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Sensors Digital TypeOptical/Photoelectric : Fiber Optic Sensor

Same as the other types of photo sensors except fiber isused to transmit and receive the light

Allows the sensor to be used in very small tight areas


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Sensors Digital TypeOptical/Photoelectric : Color Mark Sensor

These sensors can differentiate between different colors

Used to check labels and to sort packages by color mark

Charts are used for propoer selection


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Sensors Digital TypeOptical/Photoelectric : Laser Sensor

Optical sensors can use laser as their light source

Laser sensors can be used for precise measurements(as small as few microns), example is a bar code reader

Outputs can be analog or digital

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