The head station is on slot / module 0, all other PLC cards on slot / modules 2 to 17 and 19 to 34. Head station as PLC box ID Property Value 20161 Configuration project Not empty 20408 PLC station ID Not empty 20409 Station type ET200AL 20416 PLC type designation For example 6ES7 157-1AB00-0AB0 20427 Rack 0 20164 Bus coupler / head station. 4 PLCs A.programmable logic controller (PLC).also.referred.to.as. A.programmable controller.is.the.name.given.to.a.type.of. A Siemens PLC is connected to a Profinet network by a(n) cable between its Profinet port and a Profinet network or device. Ethernet The Siemens software is used to program Siemens automation systems. Dismantle the modules in slots 8-9 (Version A) or 4-5 in Version B! Install the input module in slot 8 (4) and the output module in slot 9 (5)! Check whether you can switch the front connector between the input module and the output module (interchange protection)!

SIMATIC is a series of programmable logic controller and automation systems, developed by Siemens. Introduced in 1958, the series has gone through four major generations, the latest being the SIMATIC S7 generation. The series is intended for industrial automation and production.

The name SIMATIC is a registered trademark of Siemens. It is a portmanteau of “Siemens” and “Automatic”.

Function[edit]

As with other programmable logic controllers,SIMATIC devices are intended to separate the control of a machine from the machine's direct operation,in a more lightweight and versatile manner than controls hard-wired for a specific machine. Early SIMATIC devices were transistor-based, intended to replace relays attached and customized to a specific machine. Microprocessors were introduced in 1973, allowing programssimilar to those on general-purpose digital computers to be stored and used for machine control.^[1] SIMATIC devices have input and output modules to connect with controlled machines. The programs on the SIMATIC devices respond in real time to inputs from sensors on the controlled machines, and send output signals to actuators on the machines that direct their subsequent operation.

Depending on the device and its connection modules, signals may be a simple binary value ('high' or 'low') or more complex. For example, a binary input going from a thermometer on a machine to a SIMATIC device might have the following meanings:

• “High” signal: Temperature exceeded an operating limit
• “Low” signal: Temperature is within expected limits

Based on this input, and other factors, the program on the SIMATIC device might send a binary output signal to the same machine with the following meanings:

• “High” signal: Run the motor
• “Low” signal: Stop the motor

More complex inputs, outputs, and calculations were also supported as the SIMATIC line developed. For example, the SIMATIC 505 could handle floating point quantities and trigonometric functions.^[2]

Product lines[edit]

Siemens has developed four product lines to date:

• 1958: SIMATIC Version G
• 1973: SIMATIC S3
• 1979: SIMATIC S5
• 1995: SIMATIC S7

SIMATIC S5[edit]

The S5 line was sold in 90U, 95U, 101U, 100U, 105, 110, 115,115U, 135U, and 155U chassis styles. The higher the number (except for the 101U), the more sophisticated and more expensive the system was. Within each chassis style, several CPUs were available, with varying speed, memory, and capabilities. Some systems provided redundant CPU operation for ultra-high-reliability control, as used in pharmaceuticalmanufacturing, for example.

Each chassis consisted of a power supply, and a backplane with slots for the addition of various option boards. Available options included serial and Ethernet communications, digital input and output cards, analog signal processing boards, counter cards, and other specialized interface and function modules.

SIMATIC S7[edit]

The first entries in the S7 line were released in 1994, available under three performance classes: S7-200, S7-300 and S7-400. The introduction of SIMATIC S7 saw also the release of a new fieldbus standard PROFIBUS, and the pioneer use of industrial Ethernet to facilitate communication between automation devices. The great success of the S7-300 CPU family in particular helped to cement the role of Siemens as one of the global leader in automation technology. These series are expected to be phased out in 2023.^[3]

The first generation of S7 CPUs were later succeeded by the S7-1200 and S7-1500, released in 2012.^[4] These models came with standard Profinet interface.

Software[edit]

Programs running on SIMATIC devices run in software environments created by Siemens. The environment varies by product line:

• The SIMATIC S5 product line is programmed in STEP 5.
• The SIMATIC S7 product line is programmed in STEP 7 (V5.x or TIA Portal).^[5]

Step 5[edit]

The S5 product line was usually programmed with a PC based software programming tool called STEP 5. STEP 5 was used for programming, testing, and commissioning, and for documentation of programs for S5 PLCs.

The original STEP 5 versions ran on the CP/M operating system. Later versions ran on MS-DOS, and then versions of Windows through Windows XP. The final version of STEP 5 was version 7.2 (upgradable to version 7.23 Hotfix 1 with patches).

In addition to STEP 5, Siemens offered a proprietary State logic programming package called Graph5. Graph5 is a sequential programming language intended for use on machines that normally run through a series of discrete steps. It simulates a State machine on the S5 platform.

Several third-party programming environments were released for the S5. Most closely emulated STEP 5, some adding macros and other minor enhancements, others functioning drastically differently from STEP 5. One allowed STEP 5 programs to be cross-compiled to and from the C programming language and BASIC.

Structured programming[edit]

STEP 5 allowed the creation of structured or unstructured programming, from simple AND/OR operations up to complex subroutines. A STEP 5 program may, therefore, contain thousands of statements.

To maintain maximum transparency, STEP 5 offers a number of structuring facilities:

• Block technique - A linear operation sequence is divided into sections and packed into individual blocks.
• Segments - Within blocks, fine structuring is possible by programming subtasks in individual segments.
• Comments - Both a complete program as well as individual blocks or segments and individual statements can be directly provided with comments.

Methods of representation[edit]

STEP 5 programs can be represented in three different ways:

• Statement List (STL) - The program consists of a sequence of mnemonic codes of the commands executed one after another by the PLC.
• Ladder Diagram (LAD) - Graphical representation of the automation task with symbols of the circuit diagram
• Function Block Diagram (FBD) - Graphical representation of the automation task with symbols to DIN 40700/ DIN 40719.

Siemens Plc Slot Numbering Software

Absolute or symbolic designations can be used for operands with all three methods of representation.

In LAD and FBD complex functions and function block calls can be entered via function keys. They are displayed on the screen as graphical symbols.

There are several program editors, from either genuine Siemens, or from other suppliers. After Siemens discontinued support, other suppliers started to develop new STEP 5 version which can run on Windows XP, or Windows 7.

Blocks[edit]

Five types of blocks are available:

• Organization blocks (OB) - for managing the control program
• Programming blocks (PB) - contain the control program structured according to functional or process-oriented characteristics
• Sequence blocks (SB) - for programming sequential controls
• Function blocks (FB) - contain frequently occurring and particularly complex program parts
• Data blocks (DB) - for storing data required for processing the control program.

Some S5 PLCs also have block types FX (Extended Function Blocks), and DX(Extended Data Blocks); these are not distinct block types, but rather are another set of available blocks due to the CPU having more memory and addressing space.

Operations[edit]

STEP 5 differentiates between three types of operations:

• Basic operations, (e.g. linking, saving, loading & transferring, counting, comparing, arithmetic operations, module operations) - These can be performed in all three representations.
• Supplementary operations and complex functions, (e.g. substitution statements, testing functions, word-by-word logic operations, decrement/increment and jump functions.) - These can only be executed in STL.
• System operations (direct access the operating system) - These can only be executed in STL.

Stuxnet[edit]

The Stuxnetcomputer worm specifically targets SIMATIC S7 PLCs via its STEP 7 programming environment.

References[edit]

1. ^'60 Years of Simatic'. Siemens. Siemens. Retrieved 4 March 2020.
2. ^'Siemens Simatic 505'. Computing History. Centre for Computing History. Retrieved 4 March 2020.
3. ^'SIMATIC S7-300'. Siemens. Retrieved 12 November 2020.
4. ^'What are the differences between SIMATIC S7-300 and S7-1500 PLCs?'. RealPars. Retrieved 12 November 2020.
5. ^'PLC Programming with SIMATIC STEP'. Siemens. Siemens. Retrieved 4 March 2020.

External links[edit]

• Hans Berger (2009) [2000]. Automating with SIMATIC. ISBN978-3-89578-333-3.
• Hans Berger (2011). Automating with SIMATIC S7-1200. ISBN978-3-89578-356-2.
• Jürgen Müller (2005). Controlling with SIMATIC. ISBN978-3-89578-255-8.

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.

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 the input modules or points used by a PLC depends upon the types of the 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 statuses of the inputs, outputs, and other variables as it executes a stored program. The CPU then sends signals to update the status of the outputs.

The output modules convert the 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 and change the PLC’s program, to monitor and change the 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 of some sort to simplify monitoring of the machine or process.

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 necessary components 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. 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. PLC programming can be done also with the help of Simatic Manager, which provides the possibility to write programs in three programming languages:

Ladder logic (LAD) is one programming language used with PLCs. Ladder logic incorporates programming functions that are graphically displayed to resemble the symbols used in hard-wired control diagrams.

Statement List (STL) – list of instructions. This editor allows you to create a program by entering the mnemonic commands. In this editor you can create programs that can not be created in the LAD and FBD editor. Programming in STL is very similar to the assembler language, but it’s more specific.

Function Block Diagram (FBD) – functional block diagram. This editor displays the program in the form of conventional logic circuits. There are no contacts, but there are equivalent functional units. This editor doesn’t use the term “power flow”, as in the LAD, it expresses a similar concept of the control flow through the FBD logic blocks.

Siemens Plc Slot Numbering Machine

Motor Starter Example

This example will show the practical aspect of programming in Step 7 with a real, existing part of a system. A motor starter coil (M) is wired in series with a normally open, momentary Start push-button, a normally closed, momentary Stop push-button, and normally closed overload relay (OL) contacts.

Siemens Plc Slot Numbering Tool

PLC Motor Control

The motor control application can also be accomplished with a PLC. In the following example, a normally open Start push-button is wired to the first input (I0.0), a normally closed Stop push-button is wired to the second input (I0.1), and a normally closed overload relay contacts (part of the motor starter) are connected to the third input (I0.2). These inputs are used to control normally open contacts in a line of ladder logic programmed into the PLC.

Initially, I0.1 status bit is a logic 1 because the normally closed (NC) Stop push-button is closed. I0.2 status bit is a logic 1 because the normally closed (NC) overload relay (OL) contacts are closed. I0.0 status bit is a logic 0, however, because the normally open Start push-button has not been pressed.

Normally the open output Q0.0 contact is also programmed on Network 1 as a sealing contact. With this simple network, energizing the output coil Q0.0 is required to turn on the motor. When the Start push-button is pressed, the CPU receives a logic 1 from input I0.0. This causes the I0.0 contact to close. All three inputs are now a logic 1. The CPU sends a logic 1 to the Q0.0 output. The motor starter is energized and the motor starts.

The output status bit for Q0.0 is now equal to 1. On the next scan, when the normally open contact Q0.0 is solved, the contact will close, and the output Q0.0 will stay on, even if the Start push-button is released.

When the Stop push-button is pressed, the input I0.1 turns off, the I0.1 contact opens, the output coil Q0.0 de-energizes and the motor turns off.

Advantages of PLCs

PLCs are not only capable of performing the same tasks as hard-wired control, but are also capable of covering a larger array of complex applications. In addition, the PLC program and electronic communication lines replace much of the interconnecting wires required by hardwired control.

Therefore, hard-wiring, though still required to connect the field devices, is less intensive, that’s why correcting the errors and modifying the application is much easier.

Here are the main advantages of the PLCs:

• Smaller physical size than the 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.

Evghenii
PLC Engineer