Introduction: Programming KNX Installations using ETS, Now and in the Future
By Vassilios Lourdas, KNX Association.
KNX is the leading global standard for home and building control and is complied with by numerous manufacturers. This means that you can mix and match products from different companies, and they will all work together. But what is the technology behind KNX, and what is the future of its only commissioning tool, ETS? The following short overview summarises some major points.
KNX system architecture
KNX is based on a bus technology. This means that all physical devices in a KNX system use the same transmission method and are able to exchange data via a common bus network. Access to the bus network is clearly regulated using the ‘bus access’ method.
An important feature of the KNX bus system is its decentralised structure. Every KNX device has its own microprocessor, which means that there is no need for a central control unit, because the ‘intelligence’ of the system is spread across all of its devices. Centralised units are possible, but these tend to be used for very specialised applications.
A major advantage of KNX’s decentralised structure is that, if one device fails, the others continue to function, since the configuration is done individually, at device level. Only those applications dependent on the failed device will be interrupted.
Generally, in a KNX system, devices fall into three categories: • Sensors. • Actuators. • System devices.
Sensors are devices that detect events or actions in the building. Sensors can include presence detectors, push buttons, touch panels, apps for mobile devices etc. Events or actions could include things such as someone pressing a button, someone moving, a temperature falling above or below a set value, etc. Sensors convert events into telegrams (data packets), and send them along the bus cable.
Actuators are devices that receive these telegrams and convert the commands embedded in them, into actions. They are basically switches and dimmers for lighting, shading, heating etc. Sensors issue commands, while actuators receive them.
System devices are products such as power supplies, programming interfaces, couplers, etc.
System devices are products such as power supplies, programming interfaces, couplers, etc.
Creating the KNX bus
KNX has been designed to be very flexible, so that it can be installed in all kinds of building and environment. If a new building is being created, it would be usual to create the KNX bus using a cable, but for retrofit in existing buildings, re-wiring is not always possible. KNX offers a number of ways to create the bus:
• KNX Twisted Pair (KNX TP) – communication via a twisted pair data cable (bus cable). • KNX Powerline (KNX PL) – uses the existing mains network. • KNX Radio Frequency (KNX RF) – wireless communication via radio signal. • KNX IP – communication via Ethernet.
Programming the KNX system
A KNX system can be programmed by one of the following two modes:
• S-Mode : the majority of KNX products today are designed to be configured and commissioned using S-Mode. To do this, a special software, namely ETS Professional, is required. This is Windows-based software that runs on a PC.
• E-Mode: products designed for E-mode are configured not using a PC, but a handheld unit, push buttons, or other means. This configuration method is suitable for electricians with a basic knowledge of bus technology, but no software skills. S-Mode devices can, however, always be added to an E-Mode installation at a later stage.