Siemens Simatic S7 Series User manual

Siemens
Simatic S7
Manuals and Guides
Presented By: Siemens Supply
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Table of Contents
Introduction ..............................................................................2
PLCs .........................................................................................4
Number Systems......................................................................8
Terminology ............................................................................ 12
Basic Requirements................................................................18
S7-200 Micro PLCs.................................................................20
Programming a PLC................................................................33
Discrete Inputs/Outputs .........................................................41
Analog Inputs and Outputs.....................................................48
Timers.....................................................................................51
Counters .................................................................................58
High-Speed Instructions .........................................................61
Specialized Expansion Modules .............................................65
Review Answers.....................................................................72
Final Exam .............................................................................. 74
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Introduction
Welcome to another course in the STEP series, Siemens
Technical Education Program, designed to prepare our
distributors to sell Siemens Industry, Inc. 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
this course.
After you have completed this course, if you wish to determine
how well you have retained the information covered, you can
complete a final exam online as described later in this course. If
you pass the exam, you will be given the opportunity to print a
certificate of completion.
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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.
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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.
SF/DIAG
Motor
Pump
Pushbutton
Sensor
Indicator Light
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.
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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.
Programming
Device
Operator
Interface
Central Processing Unit
(CPU)
Input
Module
Output
Module
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
Start
Pushbutton
Stop
Pushbutton
Inputs
Output
PLC
Motor
SF/DIAG
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Hard-Wired Control Prior to PLCs, many control tasks were performed by
contactors, control relays, and other electromechanical devices.
This is often referred to as hard-wired control. Circuit
diagrams had to be designed, electrical components specified
and installed, and wiring lists created. Electricians would then
wire the components necessary to perform a specific task. If
an error was made, the wires had to be reconnected correctly.
A change in function or system expansion required extensive
component changes and rewiring.
OL
M
CR
CR
L1
T1
T2
T3
L2
L3
OL
OL
OL
M
M
CR
M
Motor
Start
Stop
460 VAC
24 VAC
1
2
Advantages of PLCs PLCs not only are capable of performing the same tasks as
hard-wired control, but are also capable of many more complex
applications. In addition, the PLC program and electronic
communication lines replace much of the interconnecting wires
required by hard-wired control. Therefore, hard-wiring, though
still required to connect field devices, is less intensive.This also
makes correcting errors and modifying the application easier.
Some of the additional advantages of PLCs are as follows:
• Smaller physical size than hard-wire solutions.
• Easier and faster to make changes.
• PLCs have integrated diagnostics and override functions.
• Diagnostics are centrally available.
• Applications can be immediately documented.
• Applications can be duplicated faster and less expensively.
Siemens Modular PLCs Siemens SIMATIC PLCs are the foundation upon which our
Totally Integrated Automation (TIA) concept is based.
Because the needs of end users and machine builders vary
widely, SIMATIC PLCs are available as conventional modular
controllers, embedded automation products, or as PC-based
controllers.
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Modular SIMATIC controllers are optimized for control tasks
and can be adapted to meet application requirements using
plug-in modules for input/output (I/O), special functions, and
communications. Examples of products in this category include:
LOGO!, S7-200, and S7-1200 micro automation products,
S7-300 and S7-400 modular system PLCs, C7 combination
controller and panel, and ET 200 distributed I/O system with
local intelligence.
SIMATIC S7-400 SIMATIC S7-300
SIMATIC S7-200 LOGO!
SF/DIAG
SIMATIC
S7-1200
SIMATIC S7-1200
Other SIMATIC Controllers SIMATIC embedded automation products are available in
a microbox, panel PC, or multi-functional PC-based system.
All products utilize rugged, fan-free, diskless hardware
platforms with an operating system optimized for each
platform. Examples of products in this category include:
Microbox 420-RTX, Microbox 420-T, Panel PC 477-HMI/RTX, and
WinAC MP.
SIMATIC PC-based controllers are available as software that
can run on standard PC systems or in a plug-in card (slot PLC)
for increased reliability.This category includes WinAC software
and WinAC slot PLC.
SIMATIC Software SIMATIC software is the universal configuring and
programming environment for SIMATIC controllers, human
machine interface systems, and process control systems.
SIMATIC software with STEP 7 and numerous engineering
tools supports all phases of product deployment, from
hardware configuration of the system and parameterization
of modules to service of the installed system. A variety
of programming options are available.This includes basic
programming languages (Instruction List, Ladder Diagram,
and Function Block Diagram), high-level languages (Structured
Text and Sequential Function Chart), and engineering tools
(S7 Structured Control Language, S7-Graph, S7-PLCSIM, S7-
HiGraph, and Continuous Function Chart).
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Number Systems
Because a PLC is a computer, it stores information in the form
of on or off conditions (1 or 0), referred to as bits. Sometimes
bits are used individually and sometimes they are used
to represent numerical values. Understanding how these
bits can be used to represent numerical values requires an
understanding of the binary number system.
Decimal System In order to understand the binary number system, it is
first useful to recall some of the basics of the decimal
number system. All number systems have the same three
characteristics: digits, base, weight. For example, the decimal
system has the following characteristics:
Ten digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
Base 10
Weights Powers of base 10 (1, 10, 100, 1000, ...)
Binary System The binary system has the following characteristics:
Two digits: 0, 1
Base 2
Weights Powers of base 2 (1, 2, 4, 8, 16, ...)
The binary system has a base of 2 and uses only two
characters, 1 and 0. Each bit is associated with a power of 2
based on its position in the number. The further to the left,
the higher the power of 2.The number in the far left-hand
column is referred to as the most significant bit or MSB and
the number in the far right-hand column is referred to as the
least significant bit or LSB. A 1 is placed in a position if that
power of 2 is used in the number. Otherwise, a 0 is placed in a
position.
128 64 32 16 8 4 2 1
0 0 0 1 1 0 0 0
Most Significant Bit (MSB) Least Significant Bit (LSB)
2726252423222120
00011000 in binary = 24 in Decimal
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The process of converting a binary number to an equal decimal
value is as simple as adding the equivalent decimal value
for each position in the binary number where a 1 is shown.
Positions with a 0 do not add to the number value.
128 64 32 16 8 4 2 1
0 0 11 0 0
2726252423222120
1 0
Decimal Value = 32 + 8 + 1 = 41
Bits, Bytes, and Words Each position in a binary number is called a bit. The number
of bits used to represent numbers varies with the device.
However, instructions and data are usually grouped in bytes and
eight bits make up one byte.Two bytes, or 16 bits, make up one
word.
Word
Byte
Bit
Logic 0, Logic 1 While PLCs are capable of sensing and generating analog
values, programmable controllers internally use signals that are
on or off. These on and off conditions correspond to the binary
values 1 and 0. For example, a binary 0, also called logic 0, can
be used to indicate that a switch is off, and a binary 1 (logic 1)
can be used to indicate that a switch is on.
PLC
Input 1
24 VDC
Off
Logic 0
On
Logic 1 PLC
Input 1
24 VDC
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