White Paper
KNX and EnOcean
New avenues in KNX building automation by integrating self-powered
wireless sensors
Interaction between self-powered EnOcean sensors and a KNX solution unites
the enhanced flexibility of wireless with the high performance of a bus. The
result is a single consistent system of wireless, twisted pair and – if desired –IP (Ethernet) too. Expansion with KNXnet/IP means that the data of wirelesssensors can also be used in very large-scale installations, and will present
them on the Internet too.
Thomas Weinzierl, Dr.-Ing. (Weinzierl Engineering GmbH) and Armin Anders,Dipl.-Ing. (EnOcean GmbH)
EnOcean technology was developed to detect sensor data without the need forbatteries or an external supply of current, and to transmit them wirelessly.
The wireless range is up to 30 meters in buildings, and up to 300 meters in
the open. Minimal amounts of energy from the environment – some 50
microjoules per action – suffice to send a wireless telegram. Similar to thedynamo principle of generating energy for a bicycle light, a tinyelectrodynamic transducer produces an electric voltage from finger pressure.
The wireless telegram accompanying this is transmitted by the EnOcean
wireless switch when the button is pressed or released. A KNX gateway
receives the wireless signal and generates the appropriate KNX telegrams on
the bus to switch something on and off, to dim or to adjust blinds.
Sensors intended to monitor their surroundings in cycles can be powered by aminiature solar cell. A small energy storage mechanism (Goldcap 0.1 F)
charged during the day (minimum approx. 50 lx) serves to maintainfunctionality in the nighttime.
In a typical scenario the sensor is waked every 10 seconds for about 5
milliseconds to meter something. Any change in the metered value istransmitted. A socalled presence signal is sent after maximally 15 minutes.
For 99.95 percent of the time a sensor is in a sleep state – with minimum
current drain of its ultra-low-power timer, whose typical requirement of 100
nA dominates the energy balance.
But EnOcean also uses other energy sources from our surroundings –difference in heat for example – to generate voltage. Two degrees are
sufficient for a thermal converter, currently being developed, to send a signal.
That is less than the temperature difference between the air in a room and thesurface of warm radiators or machine parts.

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Secure wireless transmission – even in systems with hundreds ofsensors
The principle of ultra-low-power wireless technology is simple: Energy is theproduct of power multiplied by time. The transmitting power (about 10 mW)
determines the wireless range, so the technology must be extremely fast.
EnOcean wireless telegrams are only about one thousandth of a second long(energy = 10 mW x 1 ms = approx. 10 microjoules), and are sent at a datatransmission rate of 125 kilobits per second. The microprocessor and the RFtransmitter of the wireless sensor are cut in for only a few milliseconds foreach action, so they can be operated on the tiny amounts of ambient energy.
The processor data come from connected sensor elements. The transmitted
amount of data can be varied to match the requirement. A typical datatransmission is 4 bytes. These data are given a 32-bit identification number
and a checksum, and are sent by the RF transmitter as a digital datatelegram. The EnOcean wireless signal is transmitted in the 868 MHz or 315
MHz frequency band, meaning it fits into solutions worldwide.
Little risk of collision through extremely short wireless telegrams
When a number of transmitters are operated on the same frequency there is,basically, a risk of two data telegrams being sent at the same time and theirinformation thus colliding. The probability of EnOcean wireless telegrams
colliding is nevertheless very slight because the signals are so short. Plus, thetelegrams are transmitted consecutively three times with a random time offset
in a matter of a few milliseconds. In this way a receiver can detect the signal
intended for it even if there are hundreds of wireless sensors simultaneously
working in its receiving radius. For further security each sensor sends its
personal identification number as a 32-bit address. That makes it possible todifferentiate more than 4,000,000,000 transmitters.
Ecological – no battery disposal
conventional light switches

andlessradiationloadthanIn addition to the ecological aspect of constant battery consumption, thepossible radiation load of a wireless system is often the focus of attention. The
reputed ECOLOG Institute in Hannover examined low-power wireless lightswitches incorporating EnOcean technology. The results showed that theradiation produced by an EnOcean wireless switch is one hundred times lessthan that of a conventional wired switch. The reason is that with aconventional switch, during the actual switching, a broadband pulse isproduced directly on the switch. This pulse virtually breaks down after a shortgap, but nearly always strikes the person touching the switch.
In the case of a low-power wireless switch on the other hand, there is nospark chopping at the moment of switching, but instead a wireless signal ofminimal energy is sent to a receiver for a thousandth of a second. The current
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is switched on the relay, which is usually a few meters away from the person
however, so the electric smog is absorbed in the air.
EnOcean sensor profiles
For reasons of energy, EnOcean wireless telegrams need to be kept as short
as possible. So the sensor only informs its receiver during the single teach-inphase of its properties and data decoding. For this purpose there is thesocalled EnOcean Equipment Profile (EEP), a telegram profile number thatpoints to an interpretation table in the receiver. To ensure interoperability
between devices from different manufacturers, a standard was defined for theteach-in procedure, data exchange and the EEP profile. To date thespecification was restricted to unidirectional sensor communication (about 50EEPs), but is currently being expanded to bidirectional sensor communication
and bidirectional communication of a gateway with EnOcean wirelessactuators.
Byte#Description

SYNC_BYTE 0

Synchronization Byte (0xA5)

SYNC_BYTE 0

Synchronization Byte (0x5A)

TYPE

Telegram info, e.g. length, Rx/Tx

ORG

Telegram info, e.g. PTM/STM

DB_3

Data byte 3

DB_2

Data byte 2

DB_1

Data byte 1

DB_0

Data byte 0

ID_3

Byte 3 of transmitter ID

ID_2

Byte 2 of transmitter ID

ID_1

Byte 1 of transmitter ID

ID_0

Byte 0 of transmitter ID

STATUS

Status info, e.g. repeater level

CHKChecksum (LSB)

Fig. 1: Serial data protocol of EnOcean wireless transmitter at receiver output

1. Press LRN
pushbutton
Sensor
2. LRN telegram will be sent
ORGID

8 Bit
ORG
Value

32 BitSensor
ID

FunctionType

EnOcean Equipment Profile (EEP)

Fig. 2: Serial data protocol during teach-in phase (EEP profile)
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The KNX standard
KNX has become the major communication system in building system
automation, and was recognized as a worldwide standard for building
management systems (ISO/IEC 14543-3-x). KNX is suitable, among otherthings, for controlling lighting, blinds or room climate.
The technical basis of the system is formed of the different communication
media, guaranteed interworking with defined data types, plus scalable
configuration methods for different applications and markets.
KNX media
KNX twisted pair is currently the most important medium for KNX products.
This combines high quality of data transmission with the possibility of a
voltage supply to the connected devices.
KNX power line (PL) uses the power network that is generally already installedin buildings for its data transmission, making it popular in particular in oldbuildings.
KNX RF is a bidirectional wireless solution enabling KNX features to be usedwirelessly. KNX RF works with frequency shift keying (FSK) for data
modulation on a center frequency of 868.30 MHz.
Internet protocol KNXnet/IP is specified as a separate medium in KNX, andshows
thewaytotop-level
communication
inbuildings,e.g.
telecommunication or multimedia. The Internet protocol also allows accessfrom the exterior to the KNX installation.
KNX configuration modes
The KNX standard includes powerful methods for network management thatare termed configuration modes. Complex installations generally use what iscalled the system mode. Like all other modes this is non-proprietary andbased on the ETS™ (Engineering Tool Software) PC program. For ETS eachmanufacturer creates a product database in which the properties of theirdevices are described. There is also a socalled easy mode allowing, as thename implies, configuration without a PC.
KNX interworking
A major asset of KNX technology is the strictly defined interworking, whichguarantees the compatibility of products of different manufacturers andWhite Paper – KNX and EnOcean

4/ 9different application domains. For this purpose there is a complete set of datatypes standardized in KNX for wide-ranging functionality.
KNX/EnOcean gateway from Weinzierl
The KNX/ENO 622 serves as a gateway between EnOcean wireless sensors
and the KNX installation bus. It comes with 32 channels, each of which can be
assigned one of the following functions:
••

•
•
•
•
•

Button sensor of a switching module◦ Switch (on/off/changeover/value entry)◦ Switch and dim◦ Blind up/down
Temperature sensor with selection of◦ Presence sensor/switch◦ Setpoint sensor◦ Stepping switch◦ Humidity sensor
Window contact
Window handle
Binary input
Light sensor
Motion detector

The wireless telegrams from EnOcean sensors are interpreted, and the data
mapped on KNX group objects – allowing for the KNX data point types.

Fig. 3: KNX/EnOcean gateway KNX/ENO 622 from Weinzierl
The function of each channel is set by parameters in the ETS software.
Depending on the set function the EnOcean telegrams are mapped on up tosix communication objects per channel. After programming of the device byETS it is possible to teach in the wireless sensors. For this purpose the device
has two buttons and a display to show channel numbers and their assignment.
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Button sensors allow configuration for single button operation or as a rocker.
As many as four buttons/rockers can be teached in on one channel. For thewindow contact function it is also possible to connect up to four sensors to asingle channel. "Window open" is signaled on KNX if at least one window isopened, "Windows shut" only if all windows are closed. Only one sensor perchannel can be teached in for the temperature, humidity and brightness
functions.

Fig. 4: How KNX/ENO 622 appears in ETS
The KNX/ENO 622 additionally offers six controller channels. Each of thesechannels can be assigned one of the following functions:••••Temperature controller, continuous
Temperature controller, 2-level
Light controller, continuous
Light controller, 2-level

These controller channels use the data received from EnOcean sensors as their
input to then control actuators on the KNX bus.
Application example – heating control
Fig. 5 illustrates heating control as an example. Both the actual temperatureand the setpoint temperature are sent from a room control. From this thecontroller in the gateway calculates a manipulated variable and sends it on theKNX bus to the heating valve. If a presence detector or a window contact is
integrated in the system, the controller can include their input to achieve
optimal energy efficiency.

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EnOcean
Raumbediengerät
KNX EnOcean
Gateway
KNX ENO 622
KNX Stellventil
für Heizkörper

EnOceanFenstersensor

Fig. 5: Application example – heating control
Application example – lights control
Another means of energy saving is lights control with the KNX/ENO 622 as
illustrated in Fig. 6. The device can be parameterized to implement an energy
saving function where the user turns on the light when it is needed. The
controller turns off the light when it is obviously no longer needed.
Disturbance to the user by the automatic function is reduced to a minimum,
and the occupant of a house or office can always decide for themselves when
they want to turn the light on or off. It is also possible to parameterizeautomatic turning on of the light.
EnOceanPräsenzmelder
mit Lichtsensor
KNX EnOcean
Gateway
KNX ENO 622
LeuchteKNX
Schaltaktor
EnOceanTasterFig. 6: Application example – lights control

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Current KNX/EnOcean references
In the meantime there are numerous installations throughout Europe in which
a KNX/EnOcean solution was implemented, for example the SAP corporatebuilding in Walldorf. This building, with some 25,000 square meters floor
space, uses 2000 self-powered lights and blinds switches in its automation.
In 2008 a 249-meter high-rise building in Madrid was completed, fitted
entirely with wireless, the Torre Cristal. Light, shade and climate in the 52
storeys are controlled by a KNX automation system from Siemens. About 4000
self-powered wireless nodes are connected to the KNX system throughgateways from Weinzierl.

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8/ 9About Weinzierl Engineering GmbHWeinzierl Engineering GmbH develops software and hardware components forbuilding systems engineering. The emphasis is communications technology
based on the KNX standard. The strong focus on components and tools for
KNX development means that all of KNX technology is covered, for example
stack implementations for the various media and profiles of the KNX
specification. Based on this, Weinzierl develops solutions for a variety ofapplications. A key product is the KNX/ENO 622, a gateway between EnOcean
wireless and KNX twisted pair. Weinzierl Engineering GmbH is a member ofthe KNX Association and active in a number of its technical working groups.
For more information visit: www.weinzierl.de
About the KNX Association
The KNX Association is formed of a number of manufacturers, and emerged in
1999 from the following associations:
EIBA (European Installation Bus Association)
EHSA (European Home Systems Association)
BCI (BatiBUS Club International)
The association is the owner of the KNX standard, and also of the KNX
trademark logo worldwide. The KNX Association is a profit-orientedorganization coverned by Belgian law (cvba).
The aims of the KNX Association are the further development and promotionof KNX as a worldwide standard for home and building systems engineering.
For more information visit: www.knx.org
About the EnOcean Alliance
Leading companies worldwide from the building sector collected to form theEnOcean Alliance and establish innovative automation solutions forsustainable building projects – and so to make buildings more energyefficient, more flexible and lower in cost. The core technology of the Allianceis self-powered wireless technology from EnOcean for flexibly positioned andservice-free sensor solutions. The EnOcean Alliance aims to standardise andinternationalise EnOcean wireless technology, and is dedicated to creatinginteroperability between the products of OEM partners. More than 120
companies currently belong to the EnOcean Alliance. The headquarters of thenon-profit organisation is located in San Ramon, California.
EnOcean®, alliance logo, alliance member logo and ingredient logo are
registered trademarks of EnOcean GmbH and EnOcean Alliance Inc.
For more information visit: www.enocean-alliance.org

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