KNX Basics the KNX Standard – the Basics

KNX Basics The KNX standard – the basics

Introducing bus systems

Intelligent bus systems make Bus technology buildings more cost-effec- A far better solution is to link tive to operate, safer, more all sensors and actuators in the flexible, more energy-effi- building with a “data cable”, cient and – above all – more and enable them to share infor- comfortable and conveni- mation with each other (Fig. 2). ent. The KNX standard oc- Each device can then commu- cupies a large share of the nicate with every other device, market for building automa- for example: a light switch can tion systems. “talk” to a dimmer and tell it how bright to set the ceiling Past, present light; a motion sensor can tell and future the actuator for the corridor People live differently from lighting that someone has en- how they did just a decade or tered the corridor, or tell the two ago. We get money from room thermostat that there is cash dispensers, buy and sell no one in the room any more, goods and services over the in- so it can turn down the tem- ternet, phone friends all over Figure 1. “Smart” houses that adapt to users’ needs? It sounds like something perature. The following are from a sci-fi novel, but it is already a reality. Intelligent buildings incorporating the world from our mobile networks of sophisticated devices that control the building as needed already examples of sensors that can phones, and start to moan if exist, and are making life easier for their occupants on a day-to-day basis. send information to the bus: an MMS or e-mail takes more • Light switches than 5 minutes to reach a des- • Dimmer switches tination in the USA. In our cars that. Before going away for More networking • Motion sensors we are guided around by sat the weekend, it is wise to turn The key to making a building • Presence detectors (which navs, and we lock and unlock down the temperature in our “intelligent” is to equip it with can detect whether there the doors remotely without hot water tanks and to turn off networked sensors and actua- is a person in a room even a key. The interior light goes all those electrical appliances tors. There are several differ- if they are not moving) on the moment we step inside, on standby. But no one actu- ent ways of doing this: • Window and door contacts then after a while slowly dims ally does – at least, not relia- (for security and heating down again. In short, for quite bly. It takes too long. Conventional methods control) some time we have been en- The immediately obvious so- • Doorbell buttons for front joying cutting-edge develop- Time to do lution is to employ a star to- doors ments in the areas of com- some catching up pology, i.e. an arrangement • Water, gas, electricity and munication, entertainment So electrical installations in where every socket outlet heat meters and automotive technology. buildings have some substan- circuit, ceiling or wall out- • Overvoltage sensors If we look at how technolo- tial catching up to do. Net- let, and light switch is linked • Temperature sensors for in- gy in buildings has developed worked sensors and actuators by its own (ideally five-core) door and outdoor air over the same period, it’s a have long since been a standard NYM cable to a central dis- • Temperature sensors in heat- very different story. We still feature of motor cars; build- tribution board in which the ing and hot water circuits open our flat doors with con- ings, on the other hand, are logical relationships are creat- • Modules for preselecting ventional keys; and if we can’t lagging some way behind. A ed by contactors, switch re- room temperature setpoints find our keys fast enough, the change of mindset is needed, lays, and a programmable logic • Brightness sensors for in- staircase light timer switch- not least because of the long controller (PLC). This works doors and outdoors, e.g. for es the lights off and plunges service life of an electrical in- well in reasonably small dwell- constant lighting control us into darkness. True, while stallation. Today’s new buildings. However, the size of the • Wind sensors for control- we’re out working all day, the ings will have to adapt to nu- house only needs to increase ling blinds heating automatically keeps merous changes over the next by a fairly small amount before • Fault and system status mes- our homes at a pleasant tem- few decades. Now, more than the extent of the wiring work sages for white goods (wash- perature – but it doesn’t no- ever, buildings need to be flex- and size of the power distribu- ing machine, clothes dryer, tice whether we left the living ible and capable of accommo- tion boards required becomes dishwasher, cooker, etc.) room window open when we dating networked building ser- excessive. In a star topology, • Leak sensors, e.g. in laundry went out. Only the electrici- vices. In technical terms, all of adding to or extending the sys- room ty meter, ticking away quiet- this is already entirely feasi- tem is also very time-consum- • Level measurements e.g. for ly in a switch cabinet, notices ble (Fig. 1). ing in terms of installation and rain water tank, oil tank, programming. wood pellet store

2 The KNX standard – the basics

• Radio receivers for door • Presence simulation locks • Displays and user interfaces • Receivers for infrared re- • Modules for connecting bus mote controls with telephone • Fingerprint modules and card • Modules for automatically readers for access control sending warning messages by text The following are examples • Modules for accessing build- of actuators that can be con- ing data from outside via the trolled via the bus: internet or a phone • Relays for switching room lights on and off Why KNX? • Dimmers and DALI-gate- There are several bus tech- ways nologies on the market. All • Electric thermostatic radia- of them are beneficial and tor valves appropriate for certain are- Figure 2. A bus system is a system of sensors and actuators joined together • Temperature displays as of application. But no oth- by a “bus cable”. • Drive mechanisms for awn- er bus system is supported by ings, blinds, curtains and ga- as many different manufactur- rage doors ers as KNX. This is because: • Drive mechanisms for win- • All strong brands in the build- • KNX is standardised in Eu- Do bus installations dows ing installation sector are rope, the USA, China and make sense financially? • Circulator pumps for heat- pushing KNX technology internationally, through e.g. This is one of the first ques- ing systems • KNX was developed spe- CENELEC EN 50090 (Eu- tions that building owners and • Valve control systems, e.g. cifically to meet the needs rope), CEN 13321-1/2 (Eu- tradespeople ask when con- for solar thermal installations of electrical installations in rope), ISO/IEC 14543-3 sidering bus technology. As • Alarms (lights and buzzers) buildings (International), GB/T 20965 so often – it depends. At first • Information displays and in- • KNX devices are installed, (China), and ANSI/ASHRAE glance, bus systems appear dicator LEDs programmed and parame- 135 (USA). More than 350 more expensive than conven- • Relays for making and break- terised by fully qualified sys- KNX members in 37 coun- tional installations. But appear- ing socket outlet circuits tem integrators tries manufacture products ances can be very deceptive! (standby cut-off) • KNX is well-established and according to the KNX stand- What need to be considered • Well pumps can accommodate a huge ard. Because the technology are the benefits offered by a • Air conditioning systems range of functions is standardised, KNX prod- system over its entire service • Ventilation systems (toilet/ • There are several thou- ucts are all mutually com- life. Depending on the build- bathroom extractor fans, sand KNX-certified prod- patible and KNX installa- ing type, the following may controlled ventilation for uct groups available, cover- tions can be easily modified be compelling arguments for living areas) ing every conceivable field or extended at a later stage. choosing a bus system: • Control of washing machine, of application dryer, dishwasher • KNX products are tested for • Consumer electronics conformity by an independ- • Trigger signals for alarm sys- ent third party test labora- tems tories Reduced energy consumption in % • Telephone systems • KNX products are compat- • Electric door openers and ible with products from all door locking systems manufacturers (interwork- 80 ing) 70 80 Examples of functional mod- • End customers benefit from 60 ules (may be self-contained or an extensive network of spe- 50 60 integrated in devices): cialist tradesmen with sol- 50 40 45 • Room temperature control- id KNX skills accredited by 40 lers KNX-certified training cen- 30 • Timer functions tres 20 • Freely-programmable logic • The PC software ETS can 10

modules be used to plan, design and • PLCs with KNX interface commission installations • Constant lighting control of KNX-certified products Individual of Heating of Lighting

modules from any manufacturer Automation Automation Automation Automation of Ventilation Room control • Alarming and alerting • KNX supports all communi- of Sun shading • Telephone switchboards cation media: TP (based on connected to the bus a standalone 2-wire bus ca- Figure 3. A study conducted by the Institute for Building and Energy Systems at Biberach University of Applied Sciences, entitled “The potential offered by • Media control ble), PL (Powerline), RF (Ra- modern electrical installations for saving energy”, has revealed that the use of • Heating control dio Frequency), and IP/Eth- a KNX-based, networked home and building control system can reduce energy • Pump control ernet/WLAN consumption by as much as 50 %.

3 The KNX standard – the basics

• In situations where the customer wants a large num- The KNX bus system ber of different functions, a bus system will be easier and cheaper to install than an equivalent conventional installation Intelligent bus systems make • In situations where the cus- buildings more cost-effective tomer wants a large number to operate, safer, and more of different functions, a bus flexible. The KNX standard system will also be less com- occupies a large share of the KNX Bus plex than a traditional instal- market for building automa- lation Sender Telegram Receiver tion systems. (e.g. sensor) (e.g. actuator) • Continuous energy savings and hence lower operating Where does the name costs KNX come from? Figure 4. Sensor/actuator principle • Greater comfort and con- The KNX building automation venience system was originally known as • Easier to operate for older the European Installation Bus • Most of the data transmitted How big can a people/conducive to senior- (EIB), and was developed and are not payloads (e.g. light KNX system be? friendly living marketed by the EIB Associ- on/light off signals), but ad- • Flexible, future-proof instal- Thanks to their decentralised ation (EIBA). In 1999, EIBA, dress information (i.e. where structure, KNX bus systems lations Batibus Club International have the data come from? • Safety/security (presence can be modified and added (BCI, France) and the Euro- Where are they going to?) to exactly as required. The simulation, alarms in case of pean Home Systems Asso- Another important feature of break-in attempts, freezer smallest possible KNX appli- ciation (EHSA, Netherlands) the KNX bus system is its de- cation is a system linking two door alarms, panic buttons amalgamated, the name KNX centralised structure: there is with telephone link, etc.) bus devices: a sensor and an was adopted, and the Brus- no need for a central control actuator. This basic system sels-based KNX Association unit, because the “intelligence” can later be upgraded with as Electrical installations are was set up. The technology of the system is spread across changing. Customers need to many devices as necessary to used in modern KNX devic- all of its devices. Centralised perform the desired control be shown the benefits of a fu- es is compatible with that of units are possible, however, ture-proof KNX installation, in tasks. Theoretically a KNX the old EIB system, so all de- for realising very specialised system can consist of more order to make an informed devices bearing either the KNX applications. Every device has cision about whether the ini- than 50,000 devices. When or the EIB logo are mutually its own microprocessor. A ma- extending a KNX system it is tial higher investment is justi- compatible. jor advantage of KNX’s decen- fied by the long-term reduc- necessary to adhere to a spe- tralised structure is that, if one cific topology. tion in operating costs. What is the device fails, the others contin- Already, new commercial and KNX system? ue to function. Only those ap- What communication institutional buildings, in oth- The KNX system is a bus sys- plications dependent on the media are available? er words schools, events ven- tem for building control. This failed device will be interrupt- ues, offices, hotels, doctors’ Various communication me- means that all devices in a KNX ed. Generally in a KNX sys- dia (and hence transmission surgeries, law firms and pro- system use the same transmis- tem, devices fall into three cat- duction sites, are generally methods) can be used for the sion method and are able to egories: system devices (pow- exchange of data between equipped with KNX bus in- exchange data via a common er supply, programming inter- stallations. In these buildings devices in a KNX system: bus network. This has the fol- face, etc.), sensors, and actua- • KNX Twisted Pair (KNX TP) bus technology often costs lowing consequences: tors. Sensors are devices that less than a conventional elec- – communication via a twist- • Access to the bus network detect events in the building ed pair data cable (bus cable) trical installation even in the needs to be clearly regulat- (e.g. someone pressing a but- wiring stage. The benefits of • KNX Powerline (KNX PL) ed (bus access method) ton, someone moving, a tem- – uses the existing 230 V bus technology are undenia- perature falling above or be- ble (Fig. 3). mains network low a set value, etc.), convert • KNX Radio Frequency these into telegrams (data (KNX RF) – communication packets), and send them along via radio signal the bus network. Devices that • KNX IP – communication receive telegrams and convert via Ethernet the commands embedded in them into actions are known as actuators. Sensors issue commands, while actuators receive them (Fig. 4).

4 The KNX standard – the basics

KNX communication media

Bus systems need to be very of the power supply, then gen- convenient to install, add To be transmit- 1 0 1 0 0 1 0 1 erates a positive compensat- to, and in general to work ted characters ing pulse (resonator). with. The wide selection of KNX communication media Signal voltage Telegram structure available means that what- superimposed Information is exchanged be- ever the requirements, KNX onto the Direct tween bus devices in the form can meet them – for exam- Current of so-called telegrams. A tel- ple when retrofitting bus de- Figure 5. Signal shape in KNX TP egram consists of a sequence vices in even the most laby- of characters, with each char- rinthine of buildings. acter consisting of eight zeros and ones, in other words eight KNX Twisted Pair (TP) bits, or one byte. Often sev- A two-core twisted pair data eral characters are combined cable (bus cable) is the most + + with one another to form a common communication me- – – field. KNX TP telegrams have dium for KNX installations. four fields (Fig. 7): Here all devices are connect- • The control field defines the ed with one another via the priority of the telegram and bus cable. Twisted pair cables whether or not transmission are cost-effective to buy and DVC Signal Interference DVC of the telegram was repeat- easy to install. radiation ed (if the receiver did not re- DVC = Device spond) Power supply • The address field specifies In KNX TP the bus cable sup- the Individual Address of plies all bus devices with both Figure 6. Symmetrical data transfer the sender and the destina- data and power. The rated tion address (Individual Ad- voltage of the bus system is dress or Group Address) of 24 V, while the voltage pro- KNX TP Telegram the receiver vided by the power supplies • The data field, which can be is 30 V. The bus devices work up to 16 bytes long, contains Control Address Data Checksum without error at voltages be- Datenfeld the telegram’s payload tween 21 V and 30 V, so a tol- field field field field • The checksum field is used erance range of 9 V is availa- 1 Byte 5 Byte 1 to 16 Bytes 1 Byte for parity checks ble to compensate for voltage drops in the cable, and contact Figure 7. Telegram structure in KNX TP Bus access method resistance. In the devices, the Access to the KNX bus, like DC supply voltage is first of out at the original voltage. This means that, without any signif- several other bus systems, is all separated from the data- is due to the inductor effect of icant additional hardware, sta- random and event-driven. A carrying AC voltage. The DC the choke. The transmission bility against coupled interfer- telegram can only be trans- supply voltage is created by a of logical ones corresponds ence signals increases signifi- mitted if no other telegram capacitor, while a transform- to the idle state of the bus cantly, because e.g. the inter- is being transmitted at the er decouples the data-carry- (Fig. 5). An important feature ference signals on both cores same time. To prevent col- ing AC voltage. In transmit- of communication via KNX counterbalance each other lisions during transmission, ting devices, the transformer TP is that the signals are cou- (differential). The transmitter the priorities of the various also serves to superimpose pled symmetrically onto the creates the AC voltage corre- sending devices are regulat- the outgoing data onto the bus, i.e. the data cable has no sponding to the logical zero by ed by the CSMA/CA (Car- bus voltage. fixed reference point against only sending a half-wave, which rier Sense Multiple Access/ earth. This kind of communi- it does by lowering the voltage Collision Avoidance) method Data rate and signal shape cation is known as symmetri- on the pair of cores in the data (Fig. 9). The data transfer rate is cal, non-earthed transmission. cable by around 5 V. After ap- Each transmitting device lis- 9,600 bit/s, and the data trav- The receiver does not regis- proximately half a bit period, tens in to every bit of data el serially, one byte at a time, ter the voltage to earth in an the sender cancels this volt- transfer along the bus. If two via asynchronous data transfer. individual data cable (like e.g. age drop again. The rest of the devices are sending a telegram When a logical zero is trans- in the USB port), but instead system – the bus cable, trans- at the same time, then inevi- mitted, the voltage drops brief- evaluates changes in the volt- formers and charging capaci- tably (and no later than at the ly and then, after no more than age difference between the tors of all bus devices, and – moment of transmission of the 104 µs, increases again to even two data cables (Fig. 6). This very importantly – the choke sender address in the address

5 The KNX standard – the basics

field), one sender will transmit couplers are used to ensure a 0 while the other wants to that data communication can Female connectors transmit a 1. The device send- take place via all three phases, for a KNX device ing the 1 “hears” that a 0 is be- while band-stop filters prevent ing transmitted along the bus, the propagation of data signals and detects the collision. It is through the building connec- obliged to abort its own data tion towards the mains grid. Bus connector transmission and give priori- Alternatively, instead of phase ty to the other transmission. couplers, system couplers can After the transmission tak- be used. ing priority is complete, the KNX cable aborted data transmission re- Data rate and signal shape commences. A telegram’s lev- In KNX PL the data transfer Figure 8. Bus terminal with incoming and outgoing bus cable el of priority can be defined in rate is 1,200 bit/s. Logical ze- its control field; this enables ros and ones are transmitted the designer of the system to via spread frequency shift key- specify which telegrams have ing (S-FSK). A signal of frequen- Abortion of transmission “right-of-way” in case of col- cy 105.6 kHz sent by a trans- of telegram 1 lision. If two telegrams have mitter corresponds to a logi- the same level of priority, cal zero, while a logical one is Telegram 1 1 0 1 1 0 1 0 1 which telegram is allowed to represented by a frequency of be sent first is determined by 115.2 kHz (Fig. 10). The signals Collision its physical address (0 has pri- are superimposed onto the ority over 1). mains voltage. Thanks to com- Telegram 2 1 0 1 0 0 1 0 1 parative techniques and an in- Connection of bus devices telligent corrective procedure, Bus devices are connected to signals received can be evaluat- Telegram visible on the bus the data cable via components ed even when interference is = Telegram 2 known as bus terminals – plug- present. The centre frequen- in terminals able to accom- cy of the two wave motions modate up to four KNX ca- is 110 kHz, which is why the Figure 9. Collision avoidance in KNX TP bles. The bus terminals make KNX PL system is also known it possible to disconnect devic- as PL110. The transmission es from the bus without inter- power of the superimposed To be transmit- 1 0 0 1 rupting the bus line. This rep- signals is often equal to the ted characters resents a key benefit of the level of noise on today’s high- KNX bus system: removing ly noise-polluted mains net- a single bus device from the works. As a result they can Signal voltage superimposed system does not stop the oth- only be evaluated using spe- onto the mains er devices from communicat- cial digital signal processing ing with one another (Fig. 8). methods, in which the transmission power and receptive Figure 10. Signal shape in KNX PL KNX Powerline (PL) sensitivity of the bus devices Using the existing electrici- are constantly adapted to the ty cables in a building as the network conditions. KNX communication medium KNX PL Telegram is a cost-effective way of ret- Telegram structure rofitting a building with KNX. KNX PL telegrams are essen- Training 2 Preamble Complete System ID In KNX Powerline (KNX PL) tially extended KNX TP tele- Sequence fields KNX TP Frame there is no need to lay a dedi- grams. KNX PL telegrams have 4 Bit 2 Byte 9 to 23 Byte 1 Byte cated bus cable: the electricity four fields (Fig. 11): cables already installed (one of • The training field synchro- Figure 11. Telegram structure in KNX PL the three phases + the neutral nises and sets the levels of wire) themselves become the senders and receivers communication medium. The • The preamble fields indicate separate, so that only devic- only be done by delaying the data signals are superimposed the start of transmission, con- es using the same system ID sending of telegrams by bus de- onto the mains voltage. trol access to the bus, and are can communicate with one vices. The default state of all needed to prevent telegrams another. bus devices is receive mode; Power supply from colliding only if certain conditions are No additional power supplies • The third field contains the Bus access method met are they able to switch to are needed for KNX PL; the KNX TP telegram Like KNX TP, KNX PL re- sending mode. If a device de- power required by the bus de- • The system ID field contains quires the use of a bus access tects the bit string of a pre- vices comes from the 230 V an ID for keeping the signals method to prevent collisions amble, this indicates to it that mains electricity grid. Phase of different KNX PL systems between telegrams. This can the bus is occupied by anoth-

6 The KNX standard – the basics er device. A differentiation is IACK) can be obtained from made between the two states an 1 0 1 1 0 Information signal up to 64 individual receivers. Bus occupied and Bus blocked. (Baseband signal) If no Fast IACK is received, If a device receives a Bus occu- transmission of telegrams is pied signal, the transmission of automatically repeated. its telegram is postponed until mT Carrier a later point in time, chosen In larger installations, retrans- at random from one of seven t mitters can be used to for- possible options. This hugely 0 T 2T 5T ward telegrams to distant in- reduces the likelihood of col- stallation locations. Media cou- m Frequency lisions occurring. F plers can be used for coupling shift keying KNX RF systems with KNX Connection of bus devices t TP systems. In KNX PL, bus devices are Telegram structure connected directly to the Figure 12. Frequency modulation and signal in KNX RF 230 V mains network. Like with all KNX communication media, in KNX RF the KNX Radio Frequency (RF) done by modulating either its (S1 and S2). The fast chan- useful data are sent via multi- Radio is always an appropriate amplitude (amplitude modu- nels are intended for appli- cast telegrams. This means that KNX communication medium lation), frequency (frequen- cations operated by humans, one telegram can be received in those situations where it is cy modulation), phase (phase e.g. lights, blinds, etc., while by several bus devices simulta- not possible to lay new cables modulation), or a combina- the slow channels are for de- neously and so e.g. switch on in the building (e.g. for sensors tion thereof. The modulated vices that do not need to be several lights at once. KNX in inaccessible areas). KNX signal is sent to the receivers permanently in receive mode, RF telegrams are made up of RF is also particularly suitable which then demodulate it, i.e. e.g. HVAC control systems. several data blocks separat- for extending existing KNX recover the information from Fast channels have a data rate ed by checksum (CRC) fields TP installations. Theoretically it. KNX RF uses frequency of 16.384 kbps, slow channels (Fig. 13). The data blocks con- KNX RF could allow all tech- modulation (Fig. 12). The log- only half of that. tain the actual payload as well nology in a building to be con- ical states zero and one are While the data transfer rate as bus-specific information for trolled wirelessly, but this will produced by slightly modify- (duty cycle) in F1 and F2 can addressing purposes. The first remain the exception rather ing the frequency of the car- only be 1 % or 0.1 % at a max- data block consists of three than the rule. rier wave, also known as the imum of 25 mW, for chan- fields (Fig. 14): the first – the centre frequency. nels F3 and S1 it can be in- control field – contains infor- Power supply creased to 100 % at a maxi- mation about the length of To enable RF sensors to be Choosing the correct centre mum of 5 mW (but between the telegram, the transmis- positioned where they do not frequency is an important fac- 5 and 25 mW again only 1 %). sion quality (reception per- have access to mains power, tor in determining the trans- The data transfer rate in chan- formance), the battery sta- they are generally fitted with mission performance. There nel S2 is limited to 10 % at a tus of battery-operated KNX batteries. This is only possible are two upwards-compatible maximum of 25 mW. RF devices , and whether the if these devices do not need versions of KNX RF – KNX Although devices are always device is unidirectional, while to be in a permanent ready- RF Ready and KNX RF Multi. capable of sending telegrams, the second field contains ei- to-receive state. To help here, they are switched to sleep ther the KNX serial number a unidirectional device model In KNX Ready the centre fre- mode to reduce their con- or the domain address. The has been defined in KNX that quency is 868.3 MHz, and only sumption by up to 80 % for serial number is assigned by only sends telegrams when one communication chan- fast channels and as much as the manufacturer and cannot needed, and does not contain nel is available. However, ra- 99 % for slow channels, wak- be changed. a receiver. Actuators, on the dio communication in which ing up only periodically in or- In commissioning in E- Mode, other hand, need to be able only one channel is available der to receive telegrams. the serial number is evaluat- to receive at all times, so need is vulnerable to interference To ensure compatibility be- ed in the receiver together to be bidirectional. RF actua- from non-KNX radio systems tween single and multi-chan- with the source address of tors therefore generally take in the same or adjacent band nel devices, a compatibili- the sender. their power from the 230 V that use different methods for ty scheme has been devel- In KNX RF S-Mode devices, mains. In KNX all receivers accessing the communication oped, whereby newly-devel- the domain address is assigned must also be able to transmit. medium. oped single-channel devices in ETS (version 5 or higher), The unique capabilities of KNX now need to use longer pre- and serves to keep neighbour- shine through when consider- KNX RF Multi overcomes this ambles. It must be possible for ing RF systems separate from ing the performance of the sys- interference by enabling de- multi-channel devices to be one another. tem as a whole. vices to switch from an occu- downgraded to single-chan- The third field, the checksum pied channel (e.g. F1, which is nel devices. field, allows the receiver to Data rate and signal shape identical to the channel used KNX RF Multi also makes it determine whether or not a Radio technology works by by KNX RF Ready) to a dif- possible to check that a tele- telegram has been sent with- modulating a carrier wave ferent radio channel, i.e. ideal- gram has been received cor- out error. In addition to fur- with the information that ly two other fast channels (F2 rectly: fast, direct acknowl- ther control fields and check- needs to be sent. This can be and F3), or two slow channels edgement of receipt (Fast sum bytes, the second data

7 The KNX standard – the basics

block consists of fields con- Connection of bus devices the internet. Throughout the family) introduced in 1984 – taining the individual source KNX RF components can world there are a wide varie- is currently very widely used. address (physical address), be flush-mounted, surface- ty of different network struc- Although usually discussed the destination address, and mounted, or built-in. Flush- tures. The Ethernet stand- in the form “TCP/IP”, TCP the payload. The payload is mounted devices are mainly ard defines the physical ar- (Transmission Control Proto- the actual information that is inserts onto which operating eas (network engineers call col) and IP (Internet Protocol) to be sent. Depending on the buttons are mounted to en- them layers) – i.e. for exam- are in fact two distinct proto- length of the payload, a KNX able lights to be switched on ple the following: cols. Strictly speaking, the in- telegram can also contain fur- and off or dimmed, or drive • What form the signals take ternet protocol suite TCP/IP ther data blocks. mechanisms for blinds to be in the cable also includes a third, equal- operated. The radio com- • What cables are used ly important protocol: UDP Bus access method munication components can • Cable pin configurations (User Datagram Protocol). Unidirectional devices only be integrated either in the • How the various devices can The base protocol, IP, serves send telegrams when nec- push-on interface or in the access a common system to ensure that the data pack- essary. Because of the very device insert. Various sen- • How the characters being ets are sent from one device small duty cycle (= the pulse sors, actuators and combina- sent are represented to another, and that in doing duration as a percentage of tion units are available as sur- • What data backup methods so they follow the optimal the complete period) of 1 %, face-mounted/built-in devices are used routes. This is made possible it is virtually impossible for suitable for mounting, gluing For sending data between two by so-called IP addresses. The telegrams to collide, even in or integrating in any desired devices, these definitions are TCP protocol is based on the KNX RF Ready. Bidirectional location and on any surface. generally not sufficient, how- IP protocol, and is used for devices check before sending ever. Numerous other de- a large number of common a telegram whether the radio KNX IP tails concerning the protocols network applications, e.g. e- channel is free. If the channel is Ethernet is an open (manufac- used also need to be defined; mail and surfing the internet. occupied, the device waits un- turer-independent), high-per- this is particularly important The TCP protocol establishes til it is free again before send- formance, local and wide area in large networks (internet). a permanent, error-checked ing the telegram. As already network compliant with the Protocols are needed in order connection and ensures that mentioned, in KNX RF Mul- international standard IEEE for computers to communi- all data packets are sent in ti the sender can request ac- 802.3 (Ethernet). Ethernet is cate with one another in the the correct order and suc- knowledgement of receipt of used for local networks, par- network. TCP/IP – a group of cessfully reconstructed by the the telegram. ticularly in conjunction with protocols or rules (protocol receiver (connection-orient-

KNX RF Telegram

Synchro- Synchro- Data Block 1 Checksum Data Block 2 Checksum Data Block ... Checksum nisation nisation

10 Byte 2 Byte 16 Byte 2 Byte 2 Byte

Figure 13. Telegram structure in KNX RF

Data Block 1

Serial No./Do- Control field Checksum main Address

Data Block 2

Individual Individual Address Synchronization Control field Data Checksum Address (Source) (Target) or Group Address

Figure 14. Data blocks in a KNX RF telegram

8 The KNX standard – the basics ed protocol). The UDP protocol is used for applications Header Header IP Header UDP KNXnet/IP (e.g. audio and video stream- Ethernet ing) in which it is acceptable for data packets to occasion- ally go missing. The connec- Application Layer HTTP KNXnet/IP tion is not error-checked, and the delivery of data packets is uncontrolled (connectionless Transport Layer protocol). UDP is considera- TCP UDP bly leaner and faster than TCP. In applications like the transmission of speech and video, Network Layer IP ICMP IGMP ARP it would also be counter-pro- ductive to resend – e.g. a second later – a packet that has Physical Layer Ethernet gone missing. The UDP protocol is often used in building automation. Linking KNX to Figure 15. KNXnet/IP in the OSI reference model the Ethernet has the following advantages: • The existing network infra- structure in the building can be used for the KNX main IP telegram), the transport lay- The KNXnet/IP Service Type KNXnet/IP routing and backbone lines (higher er (UDP), the network layer Identifier indicates the action Routing is needed for the si- speed, more cost effective, (IP), and Ethernet – the phys- that is to be carried out. multaneous, connectionless and more convenient) ical layer. Like with the TP • Total Length transmission of KNX tel- • Buildings can be monitored protocol, additional informa- This field indicates the total egrams to several partici- and controlled via Ethernet tion for the respective layer length of the KNXnet/IP tel- pants via a KNXnet/IP rout- from anywhere in the world (the header) is always added egram. er (Fig. 18). This is equivalent • Several individual sites can to the KNXnet/IP information. • KNXnet/IP-Body to group communication in be observed and maintained This field contains the pay- e.g. KNX TP. Routing is used from a central location over Telegram structure load. for e.g. coupling TP cables. A the internet The KNXnet/IP telegram con- KNXnet/IP router serving as • KNX customer installations tains some further information KNXnet/IP tunneling a line coupler for a KNX TP can be analysed and pro- in addition to that in the KNX Tunneling is needed where cable will only send a tele- grammed remotely over the TP telegram (Fig. 16): ETS is to be used to send KNX gram to the IP side if the cor- internet by the designer of • Header Length telegrams in a connection- responding group address ap- the KNX system The header length is always oriented manner within an IP pears in the filter table of the the same. This information framework (Fig. 17). In princi- KNXnet/IP router. All other Protocol is still sent, however, be- ple this is always the case if a KNXnet/IP routers serving as The KNX system uses two cause the header length may physical address is to be used line couplers for other KNX Ethernet communication change in a later version of as the destination address (e.g. TP lines will only transmit the methods – tunneling and the protocol. The purpose when programming the phys- telegram from the IP side to routing – both of which use of the header is to identify ical address/downloading the their KNX TP line provided the UDP protocol. Tunneling the start of the telegram. application software for KNX that the relevant group ad- is used to access the bus from • Protocol Version devices). In tunneling, commu- dress appears in the filter ta- a local network or the inter- This indicates what version nication always takes place via bles of the KNXnet/IP routers. net for purposes of e.g. proof the KNXnet/IP protocol the IP address of the KNXnet/ gramming the KNX installa- applies. IP device that is being used for tion, while routing is used for • KNXnet/IP Service Type Iden- tunneling. exchanging telegrams over an tifier Ethernet network, e.g. to couple two KNX TP systems via Ethernet. The KNX protocols for these two communication methods are called KNXnet/ KNXnet/IP IP routing and KNXnet/IP tunneling. IP communication Header Protocol Service type KNXnet/ in KNX can be explained us- Total Length ing the OSI reference model Length Version Identifier IP-Body (Fig. 15). Communication takes place via the application layer (which generates the KNXnet/ Figure 16. KNXnet/IP telegram

9 The KNX standard – the basics

KNX IP and KNX TP KNX PL and KNX RF can be compared clearly seen in their suitabili- Internet IP Couplers ty for linking together separate As communication via IP and or LAN Ethernet grows in significance, sensors and actuators. KNX is it is reasonable to ask wheth- the only bus system to offer er the popularity of Ethernet such a wide variety of com- will eclipse that of the cur- munication media. rent most popular, established Data transfer rates KNX medium, TP. The answer compared is no. The main reasons for this are, firstly, the substan- Despite its various different tial cabling costs involved – communication media availa- because each terminal would ble, KNX constitutes a single need its own network cable. KNX Installation bus system. KNX systems can PC with ETS Software Secondly, networking KNX be designed and commissioned DIN rail modules in a switch Figure 17. Example of KNXnet/IP tunneling: programming of bus devices via with just one piece of software cabinet via Ethernet would be Ethernet (ETS). KNX bus devices differ too time-consuming, because only in the type of connection of the very large number of they use; this does not affect network switches needed. the way the devices commu- Their high energy consump- nicate with each other (the tion furthermore means that same Group Addresses apply they are not energy-efficient. throughout the system, com- IP does not pose a problem, ponents from different manu- however, if – by virtue of its facturers are mutually compat- IP Couplers function – a device has a net- Internet ible, etc.). The various media work connection anyway (e.g. or LAN do differ considerably in their a KNX display). Thus, through data transfer rates, however. the integration of KNX sys- In normal data traffic, KNX TP tem software, any device with needs around 20 ms to send a a network connection can be telegram. Only during the pro- turned into a KNX device gramming of devices does this increase – to 40 ms. A KNX without any additional hard- KNX Installation KNX Installation ware costs. So while the hier- TP bus can send a maximum of 50 telegrams per second. archical topologies will clearly Figure 18. Example of KNXnet/IP routing: accessing several KNX installations continue to prevail, Ethernet at once via Ethernet KNX PL, in contrast, offers will become increasingly estab- a data rate of six telegrams lished as a high-performance per second, due to the low- backbone and a means of con- er baud rate, longer telegram necting complex (KNX IP) de- structure, and different access vices. The benefits of KNX TP, method of this medium.

10 The KNX standard – the basics

KNX topology

KNX systems can be added ed instead. On the one hand to as desired, and can consist this makes the system more DVC 1 DVC 4 DVC 3 of several KNX subsystems manageable, and on the oth- based on different commu- er hand it reduces the num- DVC 5 nication media (TP, PL, RF, ber of telegrams travelling IP). To ensure problem-free along each line (by taking ad- transmission of telegrams vantage of the filter function Power Supply and Choke between individual bus de- of the line couplers). A Line DVC 2 DVC 64 vices, KNX systems must ad- Coupler will not send a tele- here to a specific topology. gram to a line for which it is not destined. Up to 15 lines Figure 19. KNX TP line can be operated via Line Cou- KNX TP plers on a line – the main line peaters). Line Couplers on plies. The system as a whole the area line count as bus de- continues to work even if in- Topology – to form an area (Fig. 21). The main line can likewise accom- vices. In practice, area cou- dividual power supplies fail. The basic unit of a KNX TP modate up to 64 devices. Line pling is typically performed 2. Local data traffic on a line installation is a line (Fig. 19). Repeaters cannot be used on using Line Couplers parame- or area does not affect the A line includes a KNX power the main line. Line Couplers terised as area couplers. The data rate in other lines and supply (including choke), and in the main line count as bus area line is also called the back- areas. usually no more than 64 other devices. Each line needs its bone, so it also needs its own 3. The topology is logical and bus devices. The power supply own power supply (including power supply. manageable for commis- and twisted pair line (bus cable) choke). Up to 15 areas can be The separation of the system sioning purposes. perform two functions: they added to an area line via Area into lines and areas has the supply the bus devices with Couplers, to form a complete following substantial benefits: Cable lengths the power they need, and per- system (Fig. 22). Just like the 1. More reliable operation For signal formation reasons, mit the exchange of informa- main line, the area line can ac- thanks to galvanic separa- and due to the maximum per- tion – i.e. the sending of tele- commodate up to 64 bus de- tion – lines and areas all missible propagation delay, grams – between those devic- vices (not including Line Re- have their own power sup- distances in line segments are es. The bus cable can be laid as desired, and branches can be added at any point. The re- sulting topology is a free tree Power Supply and Choke DVC 4 structure, which allows a great Line repeater deal of flexibility in terms of DVC 63 layout. Line Repeaters can be used to extend a line if more than 64 devices are needed. DVC 1 DVC 2 DVC 3 Sections added in this way are Power Supply DVC 64 Power Supply DVC 128 Power Supply DVC 192 known as line segments. A line and Choke and Choke and Choke segment consists of a line repeater, a power supply (includ- DVC 127 DVC 191 DVC 255 ing choke), and no more than 64 further bus devices (line re- Figure 20. Maximum length of a line in KNX TP peaters count as bus devices in the line). No more than three repeaters can be operated in Power Supply Line 0 DVC 1 DVC 49 parallel in a line, meaning the Line Coupler and Choke maximum number of bus devices is 255 (Fig. 20). Another way of expanding the DVC 0 DVC 0 DVC 0 installation is to create new lines using Line Couplers. Be- Power Supply Power Supply Power Supply cause, in practice, line repeat- Line 1 and Choke and Choke Line 15 and Choke ers and Line Couplers (or Area Couplers) are often the same DVC 1 DVC 1 DVC 1 hardware, lines are not nor- DVC 63 DVC 63 DVC 63 mally extended to their maximum size using line repeaters; new lines are generally creat- Figure 21. An “area” in KNX TP: up to 15 lines can be coupled via a main line.

11 The KNX standard – the basics

limited as follows: • Distance from power sup- Area Coupler Backbone Power Supply and Choke ply to device: max. 350 m • Distance between any two devices in a line: max. 700 m Area 15 • Length of a line segment: Area 2 max. 1,000 m Area 1 • Distance between two power supplies (including choke) in a line: as per manufacturers’ specifications.

Individual Addresses Every device in a KNX system is assigned a unique, un- ambiguous number – its Indi- vidual Address. This consists Figure 22. Up to 15 areas can be coupled via area couplers in KNX TP. of three numbers separated by dots. The numbers depend on System couplers, like all oth- lations. It therefore needs to KNXnet/IP routers is an Eth- the position of the bus device er couplers, have filter func- be ensured that neighbouring ernet port and a KNX TP in the topology: tions, which make it possible installations cannot interfere connection. The routers for- • The first number denotes to reduce the number of tel- with one another. Telegrams ward KNX telegrams to other the number of the area egrams in the various subsys- sent by KNX radio transmit- KNXnet/IP routers using the • The second number denotes tems. Because the number of ters always include the serial routing method. The availa- the number of the line telegrams in a KNX PL instal- number/domain address of the bility of Ethernet as a further • The third number is a se- lation is considerably smaller device as a unique identifier. communication medium in- quential number indicating than in KNX TP, using KNX Only those receivers paired creases yet further the flexi- the device’s position in the PL can be a necessary meas- with the transmitter are able bility of KNX system topolo- line. ure for preventing congestion to process telegrams sent by it. gies. KNXnet/IP routers can Physical addresses are need- in the bus system. A KNX system can be purely be used both as Line Cou- ed in order to identify devic- a radio network, or can com- plers (Fig. 23) and Area Cou- es clearly, and also to program Individual Addresses bine radio with another com- plers (Fig. 24). Like all cou- them. A special point to note System couplers (like Area and munication medium (e.g. KNX plers, KNXnet/IP routers are is that, when attributing phys- Line Couplers) are assigned TP). Media Couplers are used also able to filter telegrams. ical addresses, area/line cou- the sequential number 0. for coupling purposes. KNXnet/IP routers also make plers must always be given the All other PL devices are as- it possible to program devices number 0 as their sequential signed a Individual Address Individual Addresses in different lines. Some manu- number. corresponding to their posi- Media couplers are assigned facturers of KNXnet/IP rout- Examples: tion in the topology. physical addresses corre- ers additionally support the fil- Physical address 1.1.0: line Examples: sponding to their position in tering of telegrams with Indi- coupler coupling the first Individual Address 1.5.0: sys- the system topology. vidual Addresses, to prevent line with the main line in the tem coupler coupling the fifth Physical address 2.3.20: media programming across different first area. PL line with the TP main line coupler with sequential num- lines or areas if desired. During Physical address 2.3.20: bus in the first area. ber 20 in the third line of the operation, KNXnet/IP routers device 20 in the third line of Individual Address 2.3.20: PL second area. communicate with one anoth- the second area. bus device with sequential er and with the other KNX number 20 in the third line of KNX IP devices in the system via Eth- KNX PL the second area. Topology ernet, using routing as a com- Topology munication method. KNX IP can be used in place Most KNXnet/IP routers also The topology in KNX PL is KNX RF of main and area lines. This support tunneling, i.e. they similar to that of KNX TP, and Topology requires the use of KNXnet/ can also be used as an IP pro- is made up of lines and areas. The devices in a KNX RF in- IP routers. On the “top” of gramming interface for ETS. The basic unit of an installa- stallation do not need to be tion is a line containing a max- arranged hierarchically, and imum of 255 devices. An area can be installed virtually an- Ethernet is created by coupling 15 KNX ywhere. Provided that they PL lines using KNX TP; in PL are within range of one an- KNXnet/IP the maximum number of are- other, any sensor can commu- Router as is eight, however. Instead of nicate with any actuator. It is line couplers, in KNX PL sys- not possible to limit the range tem couplers are used. The of RF radio signals geograph- individual KNX PL lines need ically, i.e. KNX RF telegrams Twisted Pair Lines to be separated from one an- can be received by devices in other using band-stop filters. other, nearby KNX RF instal- Figure 23. Coupling of KNX TP lines with KNXnet/IP routers

12 The KNX standard – the basics

Ethernet Internet KNXnet/IP or LAN Router KNXnet/IP KNXnet/IP Router Router

KNX TP Area n

KNX TP Area 3 KNX TP Area 2 KNX Installation KNX Installation KNX TP Area 1

Figure 24. Coupling of KNX TP areas with KNXnet/IP routers Figure 25. Coupling of two KNX systems at separate locations

KNXnet/IP routers can addi- Cable lengths Individual Addresses Mixed topology tionally be used to connect en- Ethernet installations are con- KNXnet/IP routers (routing) All of the topologies for the tire separate systems with one nected using network cables. are given the sequential num- various communication me- another via Ethernet (Fig. 25). Various types of network ca- ber 0 (like area and line cou- dia (TP, PL, RF and IP) can be This can be useful if e.g. two ble are available, each using a plers). KNX IP interfaces (tun- used in combination with one buildings are each equipped different method for shielding neling) can be given any se- another if desired (Fig. 26). with a KNX twisted pair sys- the cable cores. It is general- quential number. tem, and these two installa- ly not permitted for these cations need to be combined bles to be longer than around Examples: into a single system. If there 100 m. For longer installations, Individual Address 1.5.0: is already an Ethernet connec- special network components KNXnet/IP router acting as a tion between the two buildings are needed to join together line coupler, coupling the fifth (which will often be the case individual network segments. line with the main line in the in commercial and institution- In residential buildings cable first area. al buildings), then there is no length is not usually an issue. Individual Address 2.3.20: need to lay a new cable be- As already mentioned, in com- KNX IP programming inter- tween them. KNX IP can also mercial and institutional build- face with sequential number be used to network KNX de- ings the existing network infra- 20 in the third line of the sec- vices, e.g. KNX displays, with structure can be used. ond area. one another. Software is available for communicating with KNX systems via KNXnet/IP.

IP Backbone Ethernet

1.0.0 IP-Router 2.0.0 IP-Router

TP TP Main Line Power Power Supply and Supply and Choke Choke 1.0.1 1.0.62 2.0.1 2.0.63

2.15.0 System Coupler Main Line 2.1.0 Line Coupler 1.1.0 Line Coupler 1.15.0 Line Coupler 2.1.64 Line Repeater PL

Power Power Power Power Supply and Supply and Supply and Supply and Choke Choke Choke Choke 1.1.1 1.15.1 2.1.1 2.1.65 2.15.1

1.1.64 1.15.64 Media Coupler 2.1.63 2.1.128 2.15.255

Figure 26. Example of KNX topology incorporating all media (TP, PL, RF, IP)

13 The KNX standard – the basics

KNX devices

There are two kinds of de- digit of which – y – indicates vices in a KNX system: sys- what medium is used (0 for tem devices and end devic- TP, 1 for PL110, 2 for RF and es. System devices can be 5 for KNXnet/IP). Not all e.g. power supplies, cou- profiles exist on all of these plers or programming inter- media. faces, while end devices are Bus Coupling • The last digit, x, identifies e.g. sensors and actuators. Unit the profile version. Bus Device The following masks serve PEI to notify ETS of what sys- Sensors, actuators tem profile is used: Bus cable and bus coupling units » y01xh: System 1 Components » y02xh: System 2 of bus devices Figure 27. Components of a bus device » y70xh: System 7 » y7Bxh: System B All standard bus devices are » y300h: LTE made up of two parts – the bus » 091xh: TP line/area cou- coupling unit (BCU) and the plers – repeaters application module (Fig. 27). » 190xh: TP-PL110 media If these two components are couplers separable, they are connected » 2010h: RF bidirectional Easy via a standardised, 10 or 12- devices pin physical external interface Transmission » 2110h: RF unidirectional (PEI). If a device was assembled Controller module Easy devices in the factory – as is the case For a long time, System 1 was with built-in devices and most PEI the most common profile. devices designed for DIN-rail However, Systems 2, 7 and mounting – it will not be pos- Bus cable B – a progression on System sible to access the PEI. 1 – are now gradually replac- ing System 1. They offer more Components Figure 28. Components of a bus coupling unit of bus coupling units memory and so allow a larger number of Group Objects For bus coupling units that are and Group Addresses to be permanently integrated into used. All functions required modules for KNX TP (Twist- with the following memories: devices, manufacturers can for e.g. alarm systems have ed Pair) and for KNX PL (Pow- • RAM: the smallest memory. use either a ready-made Bus additionally been revised (e.g. erline). The functions of these Variable parameters gener- Interface Module (BIM), or a data access management via two types of transmission ated during operation of the KNX chipset. In those device password protection). Ap- module are as follows: device are stored here. types where the bus coupling plication software developed • KNX TP: superimposing the • EEPROM or flash memory: unit is a separate device con- for System 1 can be down- data signal onto the DC sup- the data (e.g. parameters, nected with the end device via loaded to devices with a Sys- ply voltage physical addresses and group the PEI, the bus coupling unit tem 2 mask. Many suppliers • KNX PL: superimposing the addresses) input by the user will be visible. A wide variety of KNX devices now no long- data signal onto the 230 V in the application software of different designs are avail- er offer any System 1 devices. mains power. are stored in this memory. able (flush-mounted, DIN-rail Advanced bus devices use Sys- Both types of transmission The contents of this memory mounted, and printed circuit tem 7 or B, which offers con- module also contain a pow- areis downloaded from the boards for integration into cir- siderably more memory than er supply for the bus coupling PC to individual devices, to cuits), but all bus coupling units even System 2. The 10 or 12- unit controller, and generate be programmed, where the are essentially similar in struc- pin connection between the reset and save pulses for the data is then stored. ture, consisting of two func- bus coupling unit and the bus microcontroller. The bus cou- • ROM: the system software tional modules: the bus cou- end device can be used in very pling unit controller is essen- for the bus coupling unit is pling unit controller, and the different ways depending on tially a microcontroller – a chip stored in this memory, dur- transmission module (Fig. 28). the requirements. Depending incorporating a microproces- ing production of the chip. The transmission module de- on the end device used, the sor and various memories and There are already several termines the communication data exchanged via the con- input and output peripherals. different development lev- medium which the bus cou- tacts can take the form of bi- The microprocessor will be a els and versions, known as pling unit will use. The most nary signals, analogue signals, standard e.g. NEC, ATMega or masks. A mask consists of common bus coupling units or a data stream via a serial Texas Instruments controller two bytes of data, the first are those with transmission interface. The way in which

14 The KNX standard – the basics the contacts is used is deter- KNX TP power supplies KNX PL phase couplers KNXnet/IP routers mined on the basis of a resis- KNX power supplies supply In a three-phase network it KNXnet/IP routers support tor in the end device, which KNX TP lines with the nec- should be ensured that KNX the protocols KNX IP rout- is measured by the bus cou- essary bus voltage, and pro- PL signals reach all three phas- ing and KNX IP tunneling, and pling unit. Some end devices vide the power needed for es. If the three phases are rout- can be used for coupling lines have their own “intelligence”, data transmission. ed in parallel in some sections, and areas. KNXnet/IP rout- possibly even in the form of this will often take place auto- ers can also be used as a pro- another microcontroller. In matically. If this is not the case, gramming interface. this case the function of the KNX TP USB interfaces a phase coupler can help by bus coupling unit is often sim- A KNX TP USB interface is providing capacitive coupling KNXnet/IP interfaces ply to manage the group ad- needed in order to program between the three phases of KNXnet/IP interfaces are used dresses and ensure protocol- the KNX system from a com- the 230 V network. for programming KNX sys- compliant data traffic. In rare puter. tems from the Ethernet side. cases it does not even man- KNX PL system couplers age the group addresses, act- KNX TP line couplers/area KNX PL system couplers can ing – like the serial interface couplers be used as repeaters for data – merely as a gateway to the These devices are used for the signals in the 230 V network. KNX bus. coupling of KNX TP lines and They can also be used as line areas. They can also act as line couplers for coupling sever- System devices repeaters. al KNX PL lines, or as media KNX system devices are de- couplers for coupling KNX PL vices that perform primarily KNX PL band-stop filters systems with KNX TP systems. special functions, e.g. KNX PL band-stop filters pre- • Facilitating adherence to the vent powerline telegrams from KNX RF Media Couplers KNX topology leaving the intended propaga- KNX RF media couplers are • Power supply tion range. They are single- used to couple KNX RF in- • Programming phase devices so should be stallations with KNX TP in- fitted to all phases. Here it is stallations. important to adhere to the maximum current capacity of 63 A per device.

15 The KNX standard – the basics

KNX installation requirements

A KNX installation is a Laying the cables RECOMMENDED BUS LINES standard electrical instal- There are special issues to bear Cables typically used in Germany Applicable constraints lation in the 230 V range, in mind wherever bus cables so all requirements appli- could come into contact with YCYM 2 x 2 x 0.8 Suitable for inside buildings cable to standard installa- Test voltage: 4kV mains cables, e.g. (“KNX cable”) tions (VDE 0100, etc.) also • In switch cabinets and dis- apply to KNX. There are tribution boards J-Y(St)Y 2 x 2 x 0.8 Laid like YCYM, but note lower also some KNX-specific as- Test voltage: 2.5kV test voltage in proximity to 230 V • In branch boxes mains pects to consider. Between the bus voltage and JH(St)H 2 x 2 x 0.8 Halogen-free cable, must ho- KNX TP wever be installed at a distance the 230 V network, double in- from the existing 230 V instal- No safety precautions are sulation capable of withstand- lation needed when installing/laying a test voltage of 4 kV is A-2Y(L)2Y or A-2YF(L)2Y Used outdoors (linking separate ing bus lines, because the bus generally required. Minimum buildings) voltage meets the require- spacings apply, depending on ments of safety extra-low volt- the installation system used Table 1. What bus cable is used depends on the place of the installation. age (SELV) and can therefore (Fig. 29). If switch cabinets are be touched. Because the ab- used in which the mains sec- ring topology passing through keep open the option of add- sence of interference during tion is fully separated from all of the rooms, or a combina- ing KNX components at a lat- the transmission of data be- the installation bus (i.e. there tion of the two. An important er stage. There are essential- tween the individual bus de- must be no 230 V actuators aspect to consider before un- ly two ways to proceed here: vices depends on what cable present), then no special re- dertaking a KNX installation is • Lay a bus cable now but add is used, the KNX standard quirements apply. The shield the extent to which a conven- KNX components later includes precise stipulations of bus cables must continue tional installation and a KNX • Use a star topology for the about what bus cables are ac- right up to the terminals, and installation should, or indeed conventional installation ceptable. The cable must be a the use of shield bonding bars can, be combined, e.g. how (e.g. wire each push button shielded twisted pair cable (Ta- is not permissible. Mains and appropriate it is to use KNX individually up to the distri- ble 1), and the shielding on the bus cables should be routed binary inputs in conjunction bution board), to allow the cable must not be contacted or and/or affixed in such a way with conventional push but- system to be retrofitted with connected to earth on any side that they do not touch. Spe- tons rather than KNX push- KNXcentrally in the distri- – it functions purely as a metal cial requirements apply for button sensors. This is particu- bution board. cage. In KNX TP, mains cables junction boxes only if both the larly important if the customer It is therefore important to must not be used as bus lines bus cable and the 230 V ca- has not yet fully decided on a leave enough space in the dis- because of the risk of confu- ble are stripped. For branch- KNX system, but would like to tribution board. sion and their non-compliance ing, either separate boxes or with the applicable communi- a compartmentalised box with cation requirements. two separate chambers should be used. Special requirements 230 V e.g. NYM Second twisted pair apply for “combinations”, i.e. KNX TP The most common bus ca- where a bus component and a bles also include a second, mains component are housed YCYM or J-Y(St) Y (2,5 kV) free twisted pair. The follow- under the same cover, e.g. a Insulated single core 230 V adjacent ing guidelines apply with re- flush-mounted actuator with to the sheath of the bus cable gard to the use of this free pair: a socket outlet controlled via • Only extra-low voltages KNX TP the bus. When the common YCYM or J-Y(St) (SELV/PELV) are permitted cover is removed, the mains Y (2,5 kV) • Max. 2.5 A continuous cur- side must remain covered, as rent, overload protection * is the case in socket outlets 230 V e.g. NYM required protected against direct con- • Cannot be used as a circuit tact. Bus cables should ideally Insulated single core of the bus adjacent to the sheathed mains cable for public telecommunica- be laid together with the mains tions networks and hence in the standard in- • The second twisted pair is stallation zones (for Germany 230 V e.g. NYM used to provide a separate see DIN 18015-3). There are KNX TP * power supply for particular- several different methods for YCYM or J-Y(St) Y (2,5 kV) ly power-intensive KNX de- routing bus cables in individual Exposure of two single cores * > = 4 mm clearance space vices rooms: they can be arranged in or additional insulation a star topology around a central distribution board, or a Figure 29. Minimum distances between bus cables and mains lines

16 The KNX standard – the basics

KNX PL Because KNX Powerline The ETS software sends data along the existing mains network, no special KNX installation requirements apply here. Devices for limiting the transmission A single manufacturer-inde- Functions of ETS ETS program structure range (band-stop filters) and pendent Engineering Tool A KNX installation is typically ETS has been created accord- coupling the phases (phase Software is used to plan, de- configured in S-mode, i.e. using to Windows design rules, coupling) are however need- sign and commission KNX ing a computer with ETS in- so users who already work ed. Circuit breakers or resid- installations with KNX-cer- stalled on it. ETS is used for with Microsoft ® products will ® ual-current devices with rat- tified products: ETS . Sys- processing the application not need long to learn how to ed currents of <10 A are not tem integrators can use this software that manufacturers use it. ETS has a number of permissible in the signal cir- tool for connecting products supply with their products. It windows, each representing cuit of a Powerline system; from different manufactur- can be used to perform e.g. a KNX installation in a differ- fuses must be used instead. ers and from different ap- the following tasks: ent way (Fig. 30): Nor can shielded cables with plication domains to form • Downloading manufactur- • The main window presents an earthed shield or cables a single installation. ers’ application software the installation from the with core cross sections of from the internet (online cat- point of view of the building, more than 25 mm² be used A KNX installation can be pro- alogue) or reading in a man- showing its various rooms for data transmission. All KNX grammed by one of the follow- ufacturer’s database (e.g. as and distribution boards. De- PL devices have a connection ing two configuration modes: offered by the manufactur- vices can be assigned to infor one phase and the neutral • Easy Mode (E-Mode) er via his website) dividual rooms and distribu- line. In actuators the connec- Here the system is config- • Setting the parameters for tion boards, making it easy tions for the load voltage and ured not via a PC, but us- the application software to find a device in ETS on the signal cable are separate, ing a handheld unit, push • Using Group Addresses to the basis of its location in so in installations with a very buttons, or other means. link the Group Objects for the building large amount of interference, This configuration method of the individual Application • The Group Address window it can make sense to separate is suitable for electricians Programs shows the KNX installation the load and signal circuits. with a basic knowledge of • Downloading application from the point of view of the bus technology, but no soft- software into KNX devices KNX RF functions it offers. Here it ware skills. S-Mode devices from ETS is easy to see what devices When planning KNX RF instal- (see below) can still always In addition to design and com- in the building interact with lations, the potential effects of be added to the installation missioning tools, ETS also each other in what way building structures and oth- at a later stage. offers extensive assistance • The topology window shows er physical factors should be • System Mode (S-Mode) with diagnostics and trouble- the structure (Individual Ad- borne in mind. Under favour- To configure S-Mode devic- shooting. dresses) of the KNX instal- able conditions, the transmis- es, a special program – the lation that is being edited. sion range of a battery-pow- Engineering Tool Software ered device is approximate- (ETS) – is needed. ETS can ly 100 m. also be used to connect and commission KNX devices. KNX IP Network cables for KNX IP are subject to the same requirements as cables in IT networks.

Figure 30. Various windows in ETS

17 The KNX standard – the basics

Each window is divided into two halves, with the left-hand side providing a general over- view of the installation in tree form, and the right-hand side presenting in list form individual sections of the tree structure selected in the left-hand part. Along the top edge of the Figure 31. Building layout and devices window are menu bars from which individual functions can be called up. There are also toolbars providing quick, sim- ple access to the program’s most popular functions. The user can customise the appear- ance of the lists in the right- hand part of the window and the symbols in the toolbars, to adapt them to his or her per- sonal working style. Figure 32. Defining the parameters for a bus device Designing a KNX installation To design a KNX installation, it is not enough to merely install ETS on a computer. The product data provided by the manufacturers of the various devices also need to be imported into the program. These data are available free-of-charge from Figure 33. The Group Address window manufacturers of KNX products, either online or directly from the manufacturer. They the actuator behaves, e.g. can also be accessed in the whether it should offer tim- ETS Online KNX Product cat- er functions or, if it is a dim- alogue. Once these data have mer, how quickly the bright- been imported into ETS, the ness should change from the design of the installation can previous to the new setting commence. This involves the • Defining the functions of the following steps: system and the Group Ad- • Creating a project with the dresses (Fig. 33). Example: required data. The project in an office there are two can be later opened and ed- strips of lighting that work ited again at any time via the independently from one an- Figure 34. Programming button for programming the Individual Address attributed project name, other. It should be possible • Depicting the layout of the to turn each light on and off building and the devices in it individually, but it should also Objects in this way, the user Commissioning (Fig. 31); defining the build- be possible to switch both can define which sensors Commissioning is one of the ing structure and bus topol- lights on and off together, control which actuators most important functions of ogy; defining the Individual so the actuator needs to • Specifying the trades to ETS. Each device first needs Addresses of the devices be programmed with three which the KNX devices in to be individually assigned a • Defining the parameters for different functions. Three the installation relate (op- Individual Addresses, which KNX products as required. Group Addresses are there- tional) the ETS user responsible for In the case of a push button, fore needed (strip light 1 on/ • Checking that the installa- commissioning the installation for example, it is necessary off, strip light 2 on/off, and tion has been designed cor- does by pressing the program- to define whether the push strip lights 1 and 2 on/off) rectly, printing documenta- ming button on the device; this button is to be a dimmer • Linking the Group Objects tion, and saving and backing tells the program that the ad- switch, a push-button for of the KNX products via up the project dress next in line to be issued controlling blinds, or a sim- Group Addresses. This is should be assigned to that par- ple push button for switching done by connecting “virtual ticular device (Fig. 34). a light on and off (Fig. 32). In cables” in ETS between the Special care is needed during the case of an actuator, these devices’ virtual inputs and this stage of the commission- parameters determine how outputs. By linking Group ing process, because errors at

18 The KNX standard – the basics

Figure 35. The group monitor this point can lead to malfunc- convenient for e.g. testing indi- • ETS Lite licence: inexpensive ETS Apps tions later on, the correction vidual room controls, for ex- ETS trainee licences offer- Apps are widely available for of which can be very time- ample checking that the heating limited functionality are phones, smartphones and tab- consuming. Once all devices ing switches off when the win- available for school pupils lets – and now for ETS as well. have a Individual Addresses, it dows are open (even though and students ETS Professional offers gener- is time to download the soft- e.g. the relevant window con- ally all that is needed in order Interfaces ware into them. tacts have not yet been fitted). to work with a KNX installa- For use in commissioning and tion. But, like mobile phone us- Diagnostic functions Installation diagnostics, ETS needs to be ers, users of the KNX system and licensing ETS offers a number of diag- connected to the KNX bus. also increasingly want access nostic functions, for example ETS is sold by KNX Associa- There are various ways of to a wide range of addition- for checking devices’ Individual tion in the KNX Online Shop achieving this: the standard al functions. By offering Apps Addresses, or reading the sta- (www.knx.org). After pur- way is via a KNX USB port for its Engineering Tool Soft- tus of a given bus device. This chase it can be download- or KNXnet/IP interface (or ware (ETS), KNX is respond- includes details of the device’s ed directly from the inter- KNXnet/IP router). If the net- ing to growing demand around manufacturer, any error bits in net, and can be installed on work installation has a Wi-Fi the world for specialised so- the bus coupling unit, and the any computer. To work with connection, the bus can also lutions. Compatible Apps can operating status of the device. ETS, users require a licence, of be accessed wirelessly from increase the functions of ETS The operating status indicates which there are several types a laptop. yet further. They allow KNX whether the software is cur- available: experts in particular to enjoy Plug-ins rently running. It is also pos- Software licence for ETS Pro- even greater transparency, sible to see whether there is fessiona. ETS Professional is The configuration and com- and configure KNX installa- an appropriate end device con- the full version of ETS. The missioning of some KNX de- tions more quickly than ever. nected via the PEI to the bus software licence is only valid vices requires additional spe- Thanks to the Apps, ETS can coupling unit, and what Group for one computer cial software. In displays, for be adapted to users’ future Addresses are assigned to the • Dongle licence for ETS Pro- example, the page structure, wishes and to future techni- objects of the device. fessional texts that will be shown on cal developments. All Apps are The bus and group monitor A hardware dongle is also re- the display, and link to events designed by KNX Association (Fig. 35) can be used to mon- quired; this is a portable li- in the bus system are all de- and the KNX members. Val- itor all bus telegrams and cence that can be connected fined by the person responsi- idated by KNX Association, hence observe activity on the to a USB port on any com- ble for designing the installa- they are available to purchase bus. This makes it easy to di- puter. Thanks to the don- tion. For this, a separate soft- from the KNX Online Shop. agnose and locate any errors. gle, ETS can be used on any ware plug-in is typically re- In addition to monitoring tel- computer quired. Plug-ins are automat- egrams, it is also possible to • ETS supplementary licenc- ically called up as soon as the send telegrams from a comes: up to two further licenc- user starts editing the device puter, and in this way to test es can be bought for a small parameters in ETS. actuators and initiate switch- additional charge. This is ing operations in the installa- particularly convenient for tion without the relevant sen- smaller companies sors yet being installed. This is