Starting Openhab mit KNX - Beginner question

Hi everybody,

im just startet installing Openhab on my Raspberry Pi3 and want to start some different automation tasks.
I have a general question concerning KNX for example.

KNX is quite expensive for me. You have to buy software and a server for my understanding. The software is not necessary if i use Openhab for it, right?

So if i just want to turn some light groups on and of, depending on some PIR-sensors and maybe depending on time, am I right, that I just need a KNX IP Gateway, KNX I/O actor and Openhab itself?
No “KNX server”, no additional programming software?

Thank you very much for your help.
best regards

Correct, you do not need any additional knx hardware, besides an IP interface.
Your ‘server’ will be your Raspberry PI and OpenHAB will be the software that will run the automatisation taks.

Thank you so much. Now I will buy some hardware and give it a try :slight_smile:

I thought ETS was required to configure the KNX IP router/interface after installing it… is it not?

Yes, of course you need ETS, but not for the automatisation or visualisation as such. That’s what I was referring to…
Once the system is setup with ETS, you don’t need it anymore for the automatisation as such.

So to be clear - thanks for pointing out Martin - you indeed need ETS to setup your knx system (and adapt it later if needed).

So i have to buy the software anyway?

…or you can have a technician install the IP router/interface for you and configure it with his copy of ETS.

So it is not as easy as i thought…

first, I think you have to understand, how KNX works. Do you understand german? Then I can recommend you a good book on this.

  1. KNX doesn’t need a server in any way - it’s not meant for central intelligence or logic but Independent actuators which communicate with sensors and do something.
  1. You can add more sophisticated logic and/or some input (or output) from (to) non-KNX devices via openHAB
  2. for setting up KNX devices, you need a Software called “ETS”, which allows you to programm actuators sensors and the KNX bus. As this will usually only be necessary for Setup, this will be done by your electrician. He should then give you a detailled house plan, including all adresses and actions. After this you can adress these with openHAB. - to connect openHAB with KNX you need a KNX IP gateway/router.

I personally think, that for just “turning some light Groups on and of”, you won’t need KNX, which is a full blown home automation concept. You could do that with less effort and money with other concepts.
If you would like to start with some small tasks and extend it later - then this would be a good start, indeed.

If you only have vew KNX-Devices, it can work with the ETS free version. I don´t know the exact value, but you can manage small projects for free.

Maybe you can split your KNX Installation into some few parts and this will work, too - i don´t know. I have a full ETS version. KNX is not cheap and so you can calculate the price of the ETS to the installation costs. I have installed and programmed the KNX system all by my own, so i have saved a lot of money and with this saved money i could buy many ETS licences… That is my point of view.

I often make changes to my smarthome, so it wouldn´t be a good advice to always call the electrician to program my KNX bus - you have to pay him and you have to look at this later costs also.

Hex binderth,

yes, I actually am German :wink: .
I do have some further tasks like reading some energymeters and our photovoltaic earnings. That is why i came to openHAB. I originally came to Loxone which looked easy to set up for me.
I will use it in our company primary and asked our electric wholesaler for his opinion. He told me to consider KNX because of it’s great scalability.
The light issue is currently on top of my list, that is why i try to start with it. I think it is easier than connceting all our energymeters, so i have a successfull start in openHAB.
If there is an other solution for light, please feel free to let me know. I do will have 5 groups of light which are separated in 2 levels each. So i just have to control 10 relays. I want to switch them on and off via PIR sensors and switches for 2-3 different “light-scenes”.

Here you can get the free ETS version. It is working up to 5 devices.

So if you only have:
1 x KNX IP Interface / USB-Interface
1 x actuator with 10 channels
2 x PIR detectors
1 x binary actor with many channels for wall switches

it is working with the free version.

I would prefer knx, because you are not a slave of one company, you can buy knx devices from many companys. If you will go the loxone way, you only can buy from loxone directly. There is no other producer.

KNX is working with base functions without an additional server. So if your Openhab Server is down, lightswitches and PIR detectors do still work.

And the biggest advantage in my eyes: KNX is made for industrial use, so it is very good designed and has a very good stability. There are many other systems out, which are only designed for home use. You can make your own thought on this…

The licensing model of ETS is a pitty for private users.
But I think in general they are aiming for professional users like electricians, who are using ETS for many customer projects.

Maybe you can work together with an electrician in your area if the solution will be bigger than 5 devices.

I am lucky to work for a company that owns a license.
I just need a house now, where I can build in knx. :smile:

I think once if i start to work with KNX, many things will come together and 5 devices will not be enough very long…

If you stay below 20 devices in your project the 200€ license will be enough.
But if you use switches and binary inputs you may will come over that amount too.

I would seriously not recommend you to implement a knx system without mastering ETS yourself. A technician will setup a basic configuration, but once you get going you will want to add stuff or change things. You really don’t want to have to call a technician, each time you want to change or add a knx group address.

Once you know how ETS works, you can do everything yourself: change functions of switches, add new functionalities, etc…
Note: It doesn’t mean you have to do all the cabling and wiring yourself (although it’s not that difficult). You could also have an electrician do the hardware part and then do the ETS configuration yourself. There are plenty of youtube video’s that explain how ETS works. The learning curve is steep, but once you understand the methodology it goes very fast.

I found the visualisation in knx relatively expensive (especially if you go for a homeserver). There are some cheaper options, but it’ll always cost you a few 100 bucks at least. Openhab is free and a RPI only costs you a few 10 bucks. So the combination of KNX with visualization from OpenHAB is really powerful and cheap.

Note: I do think it is possible to setup a home system yourself using ETS for free by splitting it up in projects of each max 5 devices. Not really very user friendly, but certainly doable.

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Agreed. To keep project costs low the contractor will only set up the really necessary things to deliver what has been requested by customer. E.g. if it was not specified to put the lux value from a motion detector onto the bus it won´t be accessible by a group address. If you want to use it later e.g. for a roller shutter logic you are at a dead end.

When starting with home automation together with knx the ETS software is a mandatory thing.
At least spend the 200 Euros on the “light” version, this allows you to implement some more complex installations is you split them up into functional projects.
The free version is the very basic thing - for resolving situations where you want to reconfigure single devices or, like above, want to put additional object data onto the bus.
In case you are technically interested ETS gives you fully control over your installation.
I bougth the full version when reconstruction wiring of my house was done, allowing me to check and have influence on the way things were being configured. In my opinion the cost for ETS compared to the overall cost of a complete house or a rewiring project only can nearly be ignored. You may even save more money with ETS than without.
Thinking about having changes being implemented by an electrician every time you want to change a small thing after he finished his project you will be paying much more than e.g. the 200 Euros or even the 1000Euros for the full version. If everything was set up logic changes can be a cash cow for the constructor…

On the other hand: if you have zero clue on how bus systems work or how the overall knx stuff (devices, topology) is being configured plus you do not have programming skills, it may make no sense.
In that case I´d recommend software like Domovea from Hager (I have that running but am not associated with the company). This will give you UI, Logic and stability without the hassle openHab sometimes causes, but limits you to knx.
Nevertheless openHAB and similar solutions provide much more flexibility at the price of very complex software to be handled.
If you want to go for openHAB you should have at least some version of ETS available, the complete group address documentation of your installation, an IP Interface (Prebuild knx component is easy to handle, but a ninterface based on a Raspberry Pi is much cheaper) plus basic Linux and programming skills.
I love the combination of ETS/Domovea and openHAB for having a) control, b) UI with high WAF and c) integration across technological borders.

Overall knx is not a cheap, but an extremely stable technology for home automation, targeting (as said before) professional users. If something need to be extended in a knx environment the price is quite high for beginners/novice users, but can be low (time and money) in case you know how and where to adjust things.

I’m running the ETS Inside in a Windows 10 VM. Its working very well an its not necessary that the vm is running all the time.

Maybe it is more interesting than ets free, lite or pro.

I guess ETS Inside be sufficient for most single house KNX installations? I see there is lack of support for plug-ins, and “gateways with complex functionality”… what is plug-ins and gateways with complex functionality anyway?

ETS Inside does not support line couplers, so you can’t build an outer line and an inner line.
This is: If you want an outdoor motion sensor coupled to knx you would make your inner bus available - e.g. someone could short-out the bus, this would prevent any communication to the whole knx system.
Of course this short-out could be avoided by using a line repeater, but one could simply use the bus to grab communication (the only thing needed is a bus coupler with serial or USB interface) and he will be able to control everything.
If using a line coupler, this would filter all telegrams on the bus, one would not see any telegram on the outer bus and no telegrams other than the configured ones for the motion sensor would pass the line coupler.