There are several systems for building automation that also serve as the basis for a smart home. KNX KNXWired bus system for building automation (since 1990). Professional standard using twisted pair cabling. Home Assistant has had an official KNX integration since 2023 , Loxone and Homematic are probably the best known in Germany. We decided on LCN LCNLCN (Local Control Network) – German bus system for building automation by Issendorff. Uses existing 230V wiring as bus line. Can be integrated into Home Assistant via LCN-VISU or custom integration Issendorff in 2016. LCN is a system that, although it has been on the market for over 25 years, is still relatively unknown. This may also be related to the fact that it was more likely to be found in the commercial sector. There are large office complexes, theaters, congress halls and hotels that are equipped with it.
⚠ [affiliate] Keine Produkte mit Cache für home-assistant.
Bitte affiliate-sync --lang en ausführen.
We decided on it because there are many interesting modules and solutions as well as attractive control elements from a single source and I also liked the setup better than, for example, with KNX. For the basic functions of a house, it was also important to me that there is no central control, but that the modules - as with KNX - can work autonomously. This means you don’t have a SPOF (Single Point of Failure), but a certain redundancy.
How does LCN work?
The basis of LCN are the “intelligent” bus modules, which have their own data processing. Instead of relying on additional cabling with CAT cables, etc., the modules are connected to each other via a bus made of simple installation cables. You therefore only need one additional wire in the installation cable over which the data flows. This saves additional laying work for a new installation. The bus can be laid in line, star and tree topology.
An LCN installation can be divided into segments. 250 intelligent modules can be planned per segment. A total of 120 segments are possible, which corresponds to 30,000 modules - that should be enough for a single-family home ;-)
The modules are available for flush-mounted (UP) installation directly in a flush-mounted box, but also for central installation in the control cabinet as DIN rail modules. For example, there is the LCN-UPP module, which has two switchable or dimmable outputs, both for UP installation and for the control cabinet. You can thus decide whether you want a central installation, where the “intelligence” sits in the control cabinet, or a decentralized variant, with modules in the areas where they are supposed to have an effect. The latter is particularly interesting for retrofitting or renovation, as only new cables may need to be pulled into empty conduits that have an additional wire for the LCN bus.
Inputs and additional outputs such as relays can be connected to the intelligent modules. For example, you can connect 8 simple (existing) buttons via an LCN-T8 adapter to an LCN-UPP. This connection is made via the T input (button), which is found on all intelligent modules and can be used once per module.
LCN also offers its own buttons, which are usually equipped with sensor functions, such as the LCN-GT8. These glass buttons have bar graph displays to output, for example, the room temperature and LEDs that can provide information about various statuses. In addition, they provide orientation in the dark with the corona light ring. With the built-in temperature sensors, they simultaneously measure the room temperature. In the glass buttons with display (LCN-GT4 and GT10), a 24-channel time switch with 96 switching points is also available, which can be freely programmed and used.
These buttons are connected with the I connection (intelligent connection). In contrast to the T connection, several components can be connected to the I connection. The adapter LCN-IV or LCN-IVH (DIN rail) is required for this.
The 6-fold relay block LCN-R6H, on the other hand, is connected to a DIN rail module and thus offers 6 switchable outputs that are potential-free. This means that a contact for a garage door can also be controlled from LCN.
Other sensors are, for example, the LCN-PMI presence and motion detector or LCN-GUS for temperature, illuminance, humidity and motion. But there are also fingerprint sensors, RFID readers or contactless, capacitive switches that can also be laid under tiles.
A multi-stage acknowledgment system in the LCN bus ensures that commands are actually executed.
Dimming LED lamps is still often problematic today, as each model behaves differently. With LCN, however, you can store prefabricated, but also individual dimming curves that lead to the best possible result with LEDs and a uniform increase in illuminance.
Setting up LCN with the LCN-Pro software
For setup - also called parameterization in technical jargon - you need the LCN-Pro software. In the LCN installation, an access point, called an LCN coupler, is also necessary for this. With the LCN-PKU, there is a USB coupler that enables the connection from a PC to the LCN bus.
The new LCN-PKE coupler is therefore much more practical, as it has its own LAN interface and can thus be connected directly to the existing network. This is also practical in that the LCN-PKE comes with two licenses of the LCN-PCHK software, which you need for the permanent connection of a smart home software such as Home Assistant, Symcon, OpenHAB. With the two licenses, you can operate the smart home software simultaneously with the LCN-Pro software, which you constantly need.
The LCN-Pro software is quite clear and logically structured. When connecting to the LCN installation for the first time, the modules are automatically recognized and read out. If the modules have already been parameterized once, these settings can be completely read out again, even if no project file for LCN-Pro is available.
The programming itself is done via a graphical user interface, which lists all connected and accessible modules and extensions connected to them such as buttons, inputs, etc. The LCN-Pro software is only needed for setup and programming of the modules. It does not take on any active control tasks and can be closed again after programming.
Modules can be integrated into up to 99 groups. This allows commands to be sent to a group, to which all modules contained in it react. One application is, for example, a central-off function that switches off all lights and unnecessary consumers. Each module that is supposed to react to this must be included in the corresponding group, e.g. group 99 “Central Off”.
Light scenes enable the simple configuration of different lighting moods. All outputs of a module can be addressed in a light scene and stored in 10 registers with 10 scenes each. Via the group function, this also works across modules. This allows settings of different outputs including dimming settings such as “Watching TV” or “Cooking” and thus several lights to be switched simultaneously.
LCN provides logic functions that generate commands from different states or controllers and threshold values for the evaluation of analog inputs and counters. Simpler mathematical functions can also be implemented directly in the module. With some creativity, you can use these functions to, for example, call up several light scenes in succession with a single button, using a counter and threshold values. On the first button press, the counter is increased by 10. If the threshold value is 10, this function calls up the first light scene. On another button press, it is increased by 10 again and the corresponding threshold value calls up the next light scene. When the counter reaches 90, the threshold value for this resets the counter to 0.
This is also simultaneously one of the challenges with LCN: There are many ways to implement certain functions and the combination of different functions enables very complex switching and control behavior. “Delayed buttons”, “locked buttons” or the button tables must first be explored and understood.
However, with the LCN-Pro software and the status overview and its command functions, you can in principle also test all functions completely via it, without having to run through the house to press a button or to see whether the light is actually off again. The bus monitor also displays all status messages and you can filter specifically by modules, events or errors. These outputs can also be logged in a text file to track down errors and unusual behavior.
LCN planning and preliminary considerations
When planning, you should fundamentally first consider which functions you want to implement. Which lighting circuits are there? Should these be dimmable? Do I want to work with many switches or buttons or rather with presence detectors (which we do)? Where do I still need switches and buttons? Where do LCN-GT buttons with display offer me added value? Last but not least, the budget also decides the realizable possibilities. However, if you fundamentally have a 5-wire cable laid, even if 3-wire would suffice, you can later, thanks to the flush-mounted modules, also retrofit functions and turn a “dumb” switch into an “intelligent” LCN button.
Which special functions do I need such as garage door control, switchable outdoor sockets or motion detectors outdoors. By the way, you can use completely normal motion detectors here that have a relay and integrate these into LCN via an LCN-BT4H (H = DIN rail) or LCN-BT4R (UP version) 4-fold input.
Do I want to control blinds and have them automatically go up in a storm? Do I want to control a ventilation system via humidity sensors or control the room temperature with the built-in temperature sensors in the LCN-GT buttons?
These questions require quite a bit of thought and advance planning and as a layperson, you should definitely get professional help on board here. Incorrect planning is not only expensive and can only be improved later with great effort, it will also always annoy you.
If you should have forgotten a switch somewhere, however, this is not too big a deal with LCN, because with the LCN-EGR you can integrate EnOcean buttons , which work without batteries and can be stuck to the wall at (almost) any location. I too - in retrospect - didn’t do everything right and perhaps overdid it a bit with the lighting circuits and switched sockets. Ultimately, however, none of this caused any problems. It was just sometimes a bit too much …
And then there is also …
LCN and smart home software
I’ve often written here that a smart home is only really “smart” when a wide variety of devices and protocols can communicate with each other and functions are automatically executed depending on the time of day, presence, etc. Simple operation via a smartphone is far from being a smart home - that’s just a switch in a different place.
LCN offers its own hub with the LCN-GVS and with LCN-GVShome even a complete computer on which everything is pre-installed and ready to go. Some comfort functions can be realized with this. LCN-GVS can visualize your system, i.e. show in the floor plan where which lights are on or off, which temperatures prevail in which rooms, simple programming of switching times, access control, etc. Access to your LCN building control via smartphone is also possible with it, as well as notification functions via email. However, it is a solution that is limited to LCN functions and products. To integrate external devices, a solution such as Symcon, OpenHAB or - as I use: Home Assistant is needed.
I initially had Symcon in use, a commercial product from Germany that is very often used in connection with LCN. This is also fundamentally a good solution with which you can implement a lot and has a helpful German-speaking community and manufacturer support. Simpler automations can be configured quite quickly with it. If you want more extensive functions, you have to resort to PHP scripts.
This was not a problem for me, as I programmed PHP professionally for many years. Before that, I had done a test with OpenHAB and LCN. However, LCN is treated very neglectfully in the OpenHAB project and also has some quirks. OpenHAB is also somewhat “cerebral” and JAVA knowledge is absolutely necessary.
Some time ago, I then came across Home Assistant, one of the largest open source projects on the code platform GitHub. Over 5000 developers work on it and the pace of releasing new versions and functions is incredible. There is practically nothing that cannot be integrated or that someone hasn’t already implemented. In addition, the configuration is initially unusual, but very elegant and easy to maintain.
You can read the whole story of why I switched from Symcon to Home Assistant (although I of course had to set up all functions again) in this post: Is Home Assistant the best smart home software?
Let me say this much in advance: It was more than worth it! You can find a project in which I explain the basic functions of Home Assistant HERE .
Great thanks go to André, who implemented the LCN integration of Home Assistant. This works flawlessly and you practically have access to all native LCN functions with it. With LCN and Home Assistant, you get a system with endless possibilities, Google and Alexa voice control, Node-Red connection , built-in visualization, which runs very stably and has a large support community behind it. The only show-stopper for some could be that you should be able to speak English to get the most benefit from the helpful community.
To be able to implement all of this, you have to be willing to deal deeply with the subject matter and also have understood the LCN concept. Whether LCN, Home Assistant or other systems: none of them can simply be realized on the side with great functions.
Here it must be said that this is also the limit of what specialist companies can and want to offer. Hardly any electrical company gets so deeply involved in the subject matter and connection of third-party systems or can oversee them. In addition, this would be unaffordable for the customer. Here you have to get hands-on yourself and work as a pioneer, but you will also be rewarded with a modern smart home and a lot of comfort.
Conclusion
LCN Issendorff offers a very good solution for realizing building automation and thus the foundation of an intelligent smart home. In my opinion, the parameterization is easier than, for example, with KNX and compared to Loxone, it has the advantage that all modules work autonomously and are not dependent on a central server. The elimination of additional cabling via CAT cable as with Loxone or KNX also speaks for LCN. If you take the total installation, the different systems don’t differ much in price. If you would like an info display in one place or another, you can get this directly from LCN in the form of the LCN-GT4 and GT10 glass buttons.
The fact that LCN has so far been more at home in large projects means that it hasn’t yet caught on as much with private builders. On the other hand, these very large projects show that LCN technology is mature and reliable. Together with a smart home hub like Home Assistant, other solutions such as ZigBee devices , Z-Wave, Tasmota TasmotaOpen source firmware for ESP8266/ESP32-based smart home devices (sockets, lights, relays). Replaces manufacturer firmware for local control without cloud , Homematic and much more can then also work together with LCN.
More info: https://www.lcn.eu/
Hi! I'm Markus – the Fricklr. ⚡ Electrical engineer, 🎵 musician (bass, guitar, keys) and professionally 'something with the internet' 🌐 for over 30 years – nowadays with AI too 🤖 – a 55-year-old generalist from Bavaria, Germany.
Your feedback helps me write even more interesting posts. After "Yes" there's also a small option to support my work.
What do you think? Leave a comment!
Share your thoughts, questions or experiences with the community.