Goals and Benefits of the IEC 61131 Standard (PLCs – Programmable Logic Controllers)

Goals and Benefits of the IEC 61131 Standard (PLCs – Programmable Logic Controllers) - photo by Advanced Electric and Controls Inc.; http://advanced-electric.ca

PLC Hardware/Programming System

The five parts of the standard IEC 61131 summarise the requirements of modern PLC systems. These requirements concern the PLC hardware and the programming system.

The standard includes both the common concepts already in use in PLC programming and additional new programming methods.

IEC 61131-3 sees itself as a guideline for PLC programming, not as a rigid set of rules.

The enormous number of details defined means that programming systems can only be expected to implement part but not all of the standard. PLC manufacturers have to document this amount: if they want to conform to the standard, they have to prove in which parts they do or do not fulfil the standard.

For this purpose, the standard includes 62 feature tables with requirements, which the manufacturer has to fill in with comments (e.g. “fulfilled; not implemented; the following parts are fulfilled:…”).

The standard provides a benchmarkwhich allows both manufacturers and customers to assess how closely each programming system keeps to the standard, i.e. complies with IEC 61131-3.

For further proof of compliance, PLCopen (see Section 1.3) defines further tests for compliance levels which can be carried out by independent institutions. The standard was established by working group SC65B WG7 (originally: SC65A WG6) of the international standardisation organisation IEC (International Electrotechnical Commission) which consists of representatives of different PLC manufacturers, software houses and users.

This has the advantage that it is accepted as a guideline by most PLC manufacturers.

Goals and Benefits of the IEC 61131 Standard

Because of the constantly increasing complexity of PLC systems there is a steady rise in costs for:

  1. Training of applications programmers
  2. The creation of increasingly larger programs
  3. The implementation of more and more complex programming systems.

PLC programming systems are gradually following the mass software market trend of the PC world. Here too, the pressure of costs can above all be reduced by standardisation and synergy. Because the standard brings previously manufacturer specific systems closer together, both manufacturers and customers stand to gain from IEC 61131-3.

Manufacturers (PLC hardware and software)

Several manufacturers can invest together in the multi-million dollar software required to fulfil the functionality necessary in today’s market.

The basic form of a programming system is determined to a large extent by the standard. Basic software such as editors, with the exception of particular parts like code generators or “online“-modules, can be shared. Market differentiation results from supplementary elements to the basic package which are required in specific market segments, as well as from the PLC hardware.

Through the introduction of the standard a lively exchange of experience and products is currently taking place between hardware and software manufacturers.

Development costs can be substantially reduced by buying ready-made products. The error-proneness of newly developed software can be greatly reduced by the use of previously tested software.

The risk of an inappropriate development (the system does not satisfy the market needs) is smaller. The standard sets the rules which the customer already knows from other IEC 61131-3 products.

The development costs of contemporary programming tools have increased significantly as a result of the required functionality. By buying ready-made software components or complete systems the “time to market” can be significantly shortened, which is essential in order to keep pace with the rapid hardware evolution.


Customers

Customers often work simultaneously with PLC systems from different manufacturers. Up to now this has meant that employees have needed to take several different training courses in programming, whereas with IEC 61131-3-compliant systems training is limited to the finer points of using the individual programming systems and additional special features of the PLCs.

This cuts down on the need for system specialists and training personnel, and PLC programmers are more flexible.

The requirements of the standard ease the selection of suitable programming systems because systems that conform to the standard are easily comparable.

Though it is not expected that complete application programs will be able to be exchanged between different PLC systems in the foreseeable future, language elements and program structure are nevertheless similar among the different IEC systems. This facilitates porting onto other systems.


Introduction to PLC Part 01 – Programmable Logic Controller Basics

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Introduction to PLC Part 02 – Programmable Logic Controller Basics

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Reference: IEC 61131-3 – Programming Industrial Automation Systems – Karl-Heinz John, Michael Tiegelkamp (Get this book from Amazon)


author-pic

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV high power busbar trunking (<6300A) in power substations, buildings and industry fascilities. Designing of LV/MV switchgears. Professional in AutoCAD programming and web-design. Present on Google+.



One Comment


  1. bhanuprakash reddy
    Jun 04, 2014

    please explain me plc programming for the water treatment plant in granite industery

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