Buses, Protocols and Systems for Home and Building Automation

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Evropský sociální fond. Praha & EU: Investujeme do vaší budoucnosti. important usage of the BACnet is an interconnection of incompatible building automation systems and components. First of disadvantages of the BACnet is that there exists no common configuration tool (in opposite to KNX for example). Therefore almost every producer has to develop his own new tool for its devices. Another big problem with BACnet in recent history was that some BACnet products were not 100% compliant, so the interoperability of the devices was not as good as it should be. This problem was the reason of founding of BACnet Testing Laboratories (BTL). Today, BACnet is supported in devices of more than 500 companies and also universities (February 2011: 191 vendor ids in the USA, 59 in Germany, 4 in the Czech Republic) including Siemens, Honeywell, Hyundai, Mitsubishi, ABB, WAGO, DOMAT Control systems or Teco Kolín. Further reading: (8) (9) (11) (12) 3.1.2. Konnexbus Fig. 3.1.2.1: KNX (13) Konnexbus (KNX) is the main building automation system (not only) in Europe. Eighty percent of companies on the market offer devices, which are capable to be connected into a KNX network. KNX is also known by its older name EIB Instabus. EIB is one of three older independent European building automation systems which were joined together in the year 2001 to create a new system called KNX. The other systems were EHS and BatiBus and a backward compatibility to these older systems is provided. Konnexbus is covered by five standards today: - ISO/IEC 14543-3 - CSA-ISO/IEC 14543-3 (Canada) - CENELEC EN 50090 (Europe) - CEN EN 13321-1 (Europe) - GB/Z 20965 (China) The KNX system is a typical example of a fully decentralized complex home and building automation system – every device has its own “intelligence” and knows what to receive/send from/to the bus and how to process the received data. As is usual in the case of standardized protocols, there exists an association (KNX association (13)) which cares about everything around the protocol – organizes a scientific conference every year, users meetings, trainings, publishes its own journal, develops and produces software for the users and manufactures... The KNX association has nowadays more than 220 members including companies ABB, Gira, Schneider, Wago, Hager, Siemens, Buderus, Viessman, Somphy, Bosch or Toschiba. There also exist more than 30000 installer companies in 100 countries and 150 training centers all over the world. Strong academic research is very important for the KNX – the scientific club of the Konnexbus comprises about 60 universities (for example prof. Kastner in TU Wien). These facts imply that customers can Ondřej Nývlt - Buses, Protocols and Systems for Home and Building Automation 14
Evropský sociální fond. Praha & EU: Investujeme do vaší budoucnosti. choose from a very large portfolio of KNX devices (more than 7000) which are the most suitable with a function, price and design for their project. Product lines include not only actors, sensors or visualization panels, but also gateways, which are capable to interconnect the KNX system with all other building automation systems (e.g. BACnet, LON, EnOcean, DALI, OpenTherm). The system can be used for automation of every type and size of a building – from family houses to office complexes and airports. A classical and basic application of the protocol is a sophisticated light control, but today it covers all main tasks in building automation: energy management; energy consumption measure; HVAC control (using KNX meteo-station); advanced shutter and jalousie control; control of electronic devices; security and safety tasks… Similarly to other typical complex standardized protocol KNX uses more than one physical layer: - Twisted pair wiring (inherited from the BatiBUS and EIB) - Powerline networking 230V (inherited from the EIB and EHS) - Wireless KNX-RF (carrier frequency 868.3 MHz) - Infrared - Ethernet (KNXnet/IP) The most frequently used medium is a twisted pair (called TP1) with a speed of 9600 bit/s, which enables an interconnection of basic sensors and actors (field level). TP1 is also used as a power supply for sensors. Ethernet physical layer is used mainly for a connection of “higher” devices (automation level) like gateways, touch-panels, computers or PLCs with the rest of the system. The communication itself is based on two types of addresses: individual and group address. Every device in a KNX net has a unique individual address. This address is used only for programming, configuration and monitoring of the device – not for transferring process data. For this purpose, there are dedicated group addresses. This type of address is not bundled with a device, but with a “shared” variable of a specified type (we can also call them net-variables). This variable forms the connection between sensors and actors, because it logically connects together a group of variables of the same type located in different devices. More than one device can listen to one group address and react on changes, but only one device can write data to the group address (1 producer and 1 or more consumers). So, for example, when a push-button is pressed, then it sends a packet with some group address. Then a light actor, which is listening to this group address on the bus, recognizes the change of the variable and switches the light on. Important fact is that there is no packet sent directly (a packet with destination address equals to the individual address of the device) from the push-button to the actor. The KNX system can be configured and parameterized very easily. For this purpose, there exists a tool called Engineering Tool Software (ETS) which is manufacturer independent and easy to learn. So the KNX system avoids typical problems of other standardized systems (e.g. BACnet) where exists a special configuration tool for every manufacturer quite often (you cannot use a tool from one producer for devices using the same protocol/bus from another producer). The ETS tool is managed by the KNX association and the manufacturers only have to add a plug-in into the ETS tool. This plug-in is designed for a detailed configuration of a device and its functions. The ETS tool exists in several modifications based on skills of a user. Of course, there are still some bugs in the ETS tool. If the possibilities of the Ondřej Nývlt - Buses, Protocols and Systems for Home and Building Automation 15
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Page 3 and 4: 1. Basic categorization Evropský s
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