plcs(1).pdf

Table of Contents

Introduction...............................................................................2

PLCs..........................................................................................4

Number.Systems......................................................................8

Terminology............................................................................. 2

Basic.Requirements................................................................ 8

S7-200.Micro.PLCs..................................................................20

Programming.a.PLC................................................................33

Discrete.Inputs/Outputs..........................................................4

Analog.Inputs.and.Outputs.....................................................48

Timers.....................................................................................5

Counters..................................................................................58

High-Speed.Instructions..........................................................6

Specialized.Expansion.Modules..............................................65

Review.Answers.....................................................................72

Final.Exam...............................................................................73

quickSTEP.Online.Courses...................................................... 76

Introduction

Welcome.to.another.course.in.the.STEP.series,. S iemens.

T echnical. E ducation. P rogram,.designed.to.prepare.our.

distributors.to.sell.Siemens.Energy.&.Automation.products.

more.effectively..This.course.covers. Basics of PLCs .and.related.

products..

Upon.completion.of. Basics of PLCs .you.should.be.able.to:

•. Identify.the.major.components.of.a.PLC.and.describe.

their.functions

•. Convert.numbers.from.decimal.to.binary,.BCD,.and.

hexadecimal

•. Identify.typical.discrete.and.analog.inputs.and.outputs

•. Identify.key.differences.of.the.various.S7-200.models

•. Identify.the.types.of.expansion.modules.available.for.

S7-200.PLCs

•. Describe.the.types.or.programming.available.for.S7-200.

PLCs

•. Describe.the.operation.of.commonly.used.program.

functions.such.as.timers.and.counters

•. Identify.the.proper.manual.to.refer.to.for.programming.or.

installation.of.an.S7-200.PLC

This.knowledge.will.help.you.better.understand.customer.

applications..In.addition,.you.will.be.better.able.to.describe.

products.to.customers.and.determine.important.differences.

between.products..

You.should.complete. Basics of Electricity before.attempting.

Basics of PLCs ..An.understanding.of.many.of.the.concepts.

covered.in. Basics of Electricity .is.required.for. Basics of

PLCs ..In.addition,.you.may.wish.to.complete. Basics of

Control Components ..Devices.covered.in. Basics of Control

Components .are.used.with.programmable.logic.controllers.

If.you.are.an.employee.of.a.Siemens.Energy.&.Automation.

authorized.distributor,.fill.out.the.final.exam.tear-out.card.and.

mail.in.the.card..We.will.mail.you.a.certificate.of.completion.if.

you.score.a.passing.grade..Good.luck.with.your.efforts.

Siemens.is.a.trademark.of.Siemens.AG..Product.names.

mentioned.may.be.trademarks.or.registered.trademarks.of.their.

respective.companies..Specifications.subject.to.change.without.

notice.

PLCs

A. programmable logic controller (PLC) ,.also.referred.to.as.

a. programmable controller ,.is.the.name.given.to.a.type.of.

computer.commonly.used.in.commercial.and.industrial.control.

applications..PLCs.differ.from.office.computers.in.the.types.of.

tasks.that.they.perform.and.the.hardware.and.software.they.

require.to.perform.these.tasks..While.the.specific.applications.

vary.widely,.all.PLCs.monitor.inputs.and.other.variable.values,.

make.decisions.based.on.a.stored.program,.and.control.

outputs.to.automate.a.process.or.machine..This.course.is.

meant.to.supply.you.with.basic.information.on.the.functions.

and.configurations.of.PLCs.with.emphasis.on.the. S7-200 . PLC .

family..

Motor

Indicator Light

SF/D IAG

Pump

Sensor

Pushbutton

Basic PLC Operation .

The.basic.elements.of.a.PLC.include. input modules .or points ,.

a. central processing unit (CPU) ,. output modules .or. points ,.

and.a. programming device ..The.type.of.input.modules.or.

points.used.by.a.PLC.depends.upon.the.types.of.input.devices.

used..Some.input.modules.or.points.respond.to.digital.inputs,.

also.called.discrete.inputs,.which.are.either.on.or.off..Other.

modules.or.inputs.respond.to.analog.signals..These.analog.

signals.represent.machine.or.process.conditions.as.a.range.of.

voltage.or.current.values..The.primary.function.of.a.PLC’s.input.

circuitry.is.to.convert.the.signals.provided.by.these.various.

switches.and.sensors.into.logic.signals.that.can.be.used.by.the.

CPU..

The.CPU.evaluates.the.status.of.inputs,.outputs,.and.other.

variables.as.it.executes.a.stored.program..The.CPU.then.sends.

signals.to.update.the.status.of.outputs..

Output.modules.convert.control.signals.from.the.CPU.into.

digital.or.analog.values.that.can.be.used.to.control.various.

output.devices.

The.programming.device.is.used.to.enter.or.change.the.PLC’s.

program.or.to.monitor.or.change.stored.values..Once.entered,.

the.program.and.associated.variables.are.stored.in.the.CPU.

In.addition.to.these.basic.elements,.a.PLC.system.may.also.

incorporate.an.operator.interface.device.to.simplify.monitoring.

of.the.machine.or.process.

Input

Module

Central Processing Unit

(CPU)

Output

Module

Programming

Device

Operator

Interface

In.the.simple.example.shown.below,.pushbuttons.(sensors).

connected.to.PLC.inputs.are.used.to.start.and.stop.a.motor.

connected.to.a.PLC.output.through.a.motor.starter.(actuator)..

No.programming.device.or.operator.interface.are.shown.in.this.

simple.example.

Motor Starter

Motor

Output

SF/D IAG

PLC

Inputs

Start

Pushbutton

Stop

Pushbutton

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