June 2007

Innovations in Comfort, Efficiency, and Safety Solutions.

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EMAIL INTERVIEW  Bill Lydon & Ken Sinclair

Bill Lydon, Director PLCopen North America

Bill has a broad background in Building Automation starting at Johnson Controls in the beginning of the Building Automation industry. He  has designed Building Automation Systems, DDC products, and was product manager for all Johnson BAS products. Subsequently Bill co-founded and ran an object oriented control software company. In addition to being PLCopen Director, Bill consults to the Building Automation and industrial controls industry and has been involved in CABA, ISA , OMAC, ODVA, PTO, and oBIX.

“New Tools & Ideas for Buildings 2.0”

Major activities of PLCopen are further developing open controls programming standards, extensions, and certifying products.

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Sinclair:  Recently PLCopen presented at BuilConn under the topic, “New Tools & Ideas for Buildings 2.0”, discussing how the IEC 61131-3 standard is a good fit for Building Automation. How do you think this fits in with Building Automation?

Lydon:  I should first provide some background on PLCopen and the IEC 61131-3 standard.

In the 1980’s the industrial controls community started developing a standard for programming of industrial controls. In 1993 the IEC 61131 Standard was approved and published by the International Electrotechnical Commission (IEC). The IEC has been setting standards for a wide range of electrical and control products since 1906 with their standards being recognized by 50 countries. A second edition of the standard was approved in 2003 and designated IEC 61131-3.

Up until this point there was no programming software standard for industrial controls, every process control and programmable logic control (PLC) vendor had their own standard. This should sound familiar since the Building Automation industry is in this situation today.

PLCopen was founded in 1992 as a not for profit, vendor independent, worldwide organization that focuses on improving the automation programming efficiency and productivity of control engineers. PLCopen is headquartered in the Netherlands with offices in China, Japan, and North America. Major activities of PLCopen are further developing open controls programming standards, extensions, and certifying products.

Today virtually every serious manufacturer of industrial controls and PLCs are member of PLCopen and have adopted the IEC 61131-3 standard for programming. There are over 50 vendor member companies including Siemens, Rockwell Automation (Allen-Bradley), Beckhoff, Mitsubishi, Schneider Electric, Omron, ABB, Danfoss, GE Fanuc, Honeywell, and Yokogawa.

Sinclair:  I can understand why users would like a standard but why would vendors be interested in a standard?

Lydon:  Users are certainly interested in standards and vendors have come to realize that standards can make them more efficient. The standardization of sensor network protocols has proven this. The computer industry had benefited from open standards for years. The cost to maintain a proprietary control language including software maintenance and training is very high over the lifecycle of a product. The value of an open standard for users is clear and the economics for vendors makes sense.

I believe that vendors who resist standards are basically making a statement to the industry that they are not confident they can compete on the value of their hardware and services.

contemporary Sinclair:  What is the IEC 61131-3 control software?

Lydon:  IEC 61131-3 defines a control software suite of five languages that all work together to meet the needs of any control application. The five languages are Instruction List, Ladder Logic, Function Block, Structured Text, and Sequential Function Chart.

Instruction list is a low level programming language used generally for highly embedded controls and is not used a great deal these days.

Ladder Logic is a standardized set of relay ladder programming symbols and terminology. Ladder logic is the primary way industrial programmable controllers were programming originally.

Structured Text is a High level language that has the function found in computer programming languages such as BASIC, C, C+, or C++. Structured text is being used more widely in the last few years because people are learning programming in grade school and high school.

Function Block programming is basically dragging and dropping logic blocks on a screen and “wiring” them together visually in software to create applications. This is most like Building Automation programming today.

A very powerful part of the IEC 61131 standard is the ability for users to create their own function blocks. Users create control logic in any of the languages and then “lock” them up in a block with inputs and outputs. This is encapsulation in object oriented programming which improves productivity, reliability, and quality of applications. In building automation applications I have created function blocks for each of the air handling unit types on a project, tested them and used them over and over. In a recent project we had 10 different types of DX and Heat Pump units with associated function blocks.

Sequential Function Chart is similar to flowcharting but more powerful. You define sequences and decision making for an application. The blocks in the chart are logic created with any of the other languages. In building automation for example you can describe the sequence of operation for an air handling unit in Sequential Function Chart and then give this to a control engineer to build the control logic creating a clear connection between specifying the function and implementation.

With IEC 61131-3 you can use all the languages in a single application and they work together. You pick what works best.

PLCopen has been extending the standard working with vendors and users to define and certify function blocks for various applications.

We just finished the XML interchange specification which will allow IEC 61131-3 applications created in one vendor’s product to be used in another vendor’s product.

Sinclair:  Many vendors have application specific controllers and functions, why do we need to program controls?

Lydon:  You and I have been in this business more years that we want to admit and have witnessed “cookie cutter” controls becoming normal operating procedure to reduce engineering and controls costs. I have observed this shift in controls and it has created bad temperature control, bad humidity control, and bad air quality in many facilities. It is also wasting a great deal of energy. This was echoed by a number of engineers and building owners at the March Building Automation Conference in Baltimore.

The fact is buildings designs are all different. HVAC systems are designed to serve the needs of the building design. Because of this “cookie cutter” controls do not provide adequate control. We can argue about why this has happened but the fact still remains that control systems need to be engineered and programmed to meet the requirements. (Could you envision building an office building with only three of four sizes of steel beams?)

Another reason we need better programming is that HVAC systems in buildings are generally not being coordinated today resulting in wasted energy and bad environmental control. The various HVAC systems are operating as separate islands. These need to be coordinated by the BAS.

There are a small group of good engineers using the proprietary programming methods available in BAS products to do good designs. There is a high learning curve to do this and every vendors programming language is different. An open standard makes this much easier and efficient so more engineers can implement better designs.

In Europe systems are being better engineered and there are a number of projects using IEC 61131-3 programmed controllers for BAS. Beckhoff Automation for example has a number of projects including: Microsoft Headquarters Building - Munich, Germany, Eurotheum (European Central Bank)- Frankfurt, Germany and IT-Port - Unterschleißheim near Munich, Germany

Sinclair:  How can people learn more about IEC 61131-3 and PLCopen?

Lydon:  The PLCopen North America WEB site has links to information. www.PLCopen-NA.org.

I am also interested in talking with people that are interested in helping PCLopen define HVAC and Building Automation functions that can be added to the standards and certified. This has been done for example in the packaging industry with great success where there are a set of functions blocks defined by users (Examples: Proctor & Gamble, Hershey; Unilever) for packaging machine functions. Now when packaging machines are delivered there is a common programming methodology.

Email blydon@PLCopen-na.org or phone 414-427-5853


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