the pioneering standard that expanded home automation twenty years ago

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Home automation is going through one of its best moments thanks to the wireless communication protocols used by multiple smart devices today. Zigbee, Z-Wave, or HomeKit, among others, have helped smart speakers, thermostats, sensors, and other products to communicate with each other, and with the arrival of Matter, everything indicates that standardization will be even greater. However, there is a protocol that has been with us for more than twenty years and that laid the foundations for IP-based interoperability.

We are talking about KNX.

In the past, home automation was more fragmented, and even today it still is. Although thanks to the WiFi, Bluetooth, and other protocols mentioned above, we can connect devices from different manufacturers and types in a single ecosystem. Having smart devices at home is more common today. KNX sought to be a pioneer in the standardization of home automation, and it succeeded, although it was not within everyone’s reach, and it was intended for the most luxurious homes.

This communication protocol emerged at the end of the 90s as a result of the union of three benchmark standards of that time in the home automation sector in Europe. In this way, EHS (European Home Systems Protocol), EIB (European Installation Bus) and BatiBUS joined forces in 1997 to drive the smart home through KNX, a quite versatile protocol so that home devices could understand each other.

Four different variants for data transfer with KNX

Knx Products All

The ‘KNX Association’ It first released its standard in 2002, a protocol that slowly began to generate interest in a social context where networks and communication were the norm. Since its inception, KNX has been present in many devices. In the most common examples we find the motorization of blinds and awnings, lighting control, or temperature management in the home, among others. all in one way fully integrated on the walls of our home.

Hence, the cost of homes with this protocol skyrocketed.

According to the KNX website, more than 500 manufacturers still adopt this protocol in their products today, including Schneider Electric, Eelectron, Belcom, or Zennio. Most of them are companies that provide electrical solutions. This makes sense, since KNX is usually integrated in most cases through the electricity network that we have at home.

This is how I automated my entire house with artificial intelligence and an open source system

In KNX there are two large groups of devices: transmitters and receivers. The devices that were compatible with KNX could communicate with each other through four main variants; through twisted pair cable (TP), from the electrical network of our house (PL), through radio frequency waves (RF), and through the TCP/IP protocol with Ethernet cables and ports.

KNX-TP (Twisted cable)

Through twisted pair cables, it is possible to transfer data at a speed of 9,600bps (bits per second). Currently it may seem like a ridiculous speed, but the truth is that we must bear in mind that this type of device does not need more to be able to send and receive telegrams with a few ones and zeros, and to lower the blinds of the house, or turn on a light in a certain place.

To power this connection, a voltage of 30V is supplied to devices that support this standard. The receiver evaluates a change in the voltage difference between both conductors, and when this voltage is reduced by about 5V, the receiver considers it as the input of a logic zero. In the telegrams that travel from one device to another, control, address, data and verification bits are housed, being information of vital relevance so that the devices with this standard communicate with each other and do what we have previously programmed.

Telegram Knx Tp

KNX-PL (Powerline)

This variant includes the same concept as the one mentioned above, although this time it makes use of our home’s electrical network to transfer the necessary information. Through the nominal voltage of 230 V in our house, data is transmitted between devices, and these signals are superimposed on the mains voltage. It is a solid option that is usually considered for new installations or to expand an existing one that makes use of KNX.

This standard does not use any specific bus, using only one of the three phases plus the neutral of our network for the transfer of information. Nor does it need any power source, since the devices acquire energy from the house’s own 230 V network. Powerline speed goes up at 1,200 Bit/s. In addition, to represent the logical zeros and ones, this variant used the method known as “transfer frequency keying” (SFSK) coding.

Here a frequency of 105.6 kHz is considered a logic zero, while a frequency of 115.2 kHz generated by the sender corresponds to a logic one.

what is knx

KNX-RF (Radio frequency)

It is the wireless solution of this standard, and it is usually used when it is not possible to transfer the information through a cable, due to the location, or simply because it is more important that it be so. Those sensors that require power to operate can do so through a battery, regardless from the 230 V mains.

Its form of data transfer, as its name suggests, is through radio frequency, modulating a signal wave on a carrier wave. The combination of modifying the amplitude, frequency and phase of the wave makes this modulation possible. Through a slight variation of the carrier wave is how the logical zeros and ones are represented.

This variant is divided into two versions; KNX RF Ready and RF Multi. While the average frequency of a KNX RF Ready is 868.3 MHz and it only has one communication channel, the RF Multi can switch from one channel to another.


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The KNX standard evolved to be compatible also with the TCP/IP protocol via Ethernet, which is an open communication network. Today is essential to enable local networks and for the operation of the Internet, and that KNX was compatible with this standard further expanded the possibilities of home automation.

Devices that are compatible with KNX-IP establish their connection through wired Ethernet networks, communicating by sending data packets from a specific IP address, nothing new in this regard if you are familiar with this protocol. KNX is a standard that also influences the energy efficiency of a house. This is the main claim of this type of installation by its manufacturers. But it is true, since it allows us to program the start-up of the different connected devices so that they work when we want, a basic concept in home automation.

KNX vs. Wireless

Most KNX installations work through cable, and it is usually one of the solutions more reliable when it comes to home automation. This is because the devices have their own modules, interfaces and software to operate, and do not require congested Internet connections that can cause interference due to other devices connected to the home network.

KNX is an open standard, so in the software part we can find multiple ways to connect the devices, and even program our own solution if we are capable of it. Domotising a house with KNX is something like incorporating a central operational core*, where you can remotely manage the control of lights, blinds, temperature, generators and more.

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Its main advantage over a wireless solution that makes use of WiFi, Bluetooth, or standards such as Zigbee or Z-Wave, is the reliability and stability of the connection, where the limit is the price that we want to spend for the installation. This is important to emphasize, since this type of installation is usually expensive and complex start up if you don’t have the right knowledge.

On the other hand, it is understandable why new wireless standards are replacing KNX installations at home. And it is that devices start up Wireless It is tremendously simple and versatile, being ideal if what we want is to control some individual aspects of the house.

The future of KNX and the evolution of home automation

It is evident that home automation tends to wireless standards more and more. Although KNX represents the reliability and total control of a house, the price and complexity of its installation are the grave of this standard compared to current IoT systems that make use of voice assistants, sensors, and other smart devices. It looks like Alexa, Google Home or HomeKit will continue to be the main ecosystems to be chosen by the user to develop a connected home.

In the short term, yes, all sights are set on Matter, a standard that will arrive in a few months to improve the interoperability of these systems.

Home automation is going through one of its best moments thanks to the wireless communication protocols used by multiple smart…

Home automation is going through one of its best moments thanks to the wireless communication protocols used by multiple smart…

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