Using KNX wall switch without Gateway

[Jasper298]

Hello,

Sorry for writing in English, but my German is not that good....

I am new here, my name is Jasper and live in the Netherlands. Currently I am a FPGA developer at Bosch.

Since a few weeks, I am using the Philips Hue lights. Very nice, but I always have to control them with the app on my phone. Not a big deal for me, but my girlfriend cannot get used to it. So I bought a Particle.io Photon development board (Arduino like programming) and wrote a piece of code to switch on/off the lights using the API. It is quite easy.

I really would like to integrate this in my wall switch, but my standard wall switches (JUNG) do only have an ON/OFF option. Jung also sells the KNX variant of the wall switches and then, I have multiple options. I would like to use such a switch without the gateway and use my arduino-like board as gateway. I already found some projects that an Arduino became an actor, but not the other way arround. I want to receive the Uart telegrams and interpret them according my own specification to switch on/off, set theme or dim the lights.

Anybody know if this is possible. I have tried to search this forum, but allmost everything is in German

Thanks in advance....

Jasper

[tuxedo]

Isn't it a kind of overkill to use knx to just trigger a signal on your arduino like dev-board?
What not use a jung push-button instead of a jung switch or a knx replacement? Would be the cheapest and easiest solution?!

[Jasper298]

Well, maybe an overkill. But when I use just Jung push-buttons, I don't have 8 options like in the Jung F50 in 1 switch. So this might be the only option to use many switches to replace my current one. And when This is working, I can extend the system with other switches and create my own KNX network which is cheaper then using the KNX gateway.

[tuxedo]

Ok, if you want more than one option on the switch, then go for KNX ;-)

But for using an KNX device (no matter what device), you need an KNX power-supply (starts at ~85EUR --> https://www.google.de/search?q=STV-0...60.01&tbm=shop). Then you can use an TPUART (like http://www.opternus.com/en/siemens/k...eneration.html or http://www.opternus.com/en/siemens/d...-btm2-pcb.html, also available from siemens (exactly this type...) http://www.voltus.de/hausautomation/...festigung.html) to interface the bus with your arduino like dev-board.

So, your KNX switch on the wall sends a knx telegram over the green bus-cable (powered by an KNX power supply), which can be received by the TPUART which can be read from your arduino like dev-board. Of course you can send also telegrams the other way around.

[Jasper298]

Yes, That is actually what I would like to do. 85 euros is a bit expensive for just a 230AC to 30DC converter. maybe I build one by myself because I also need a 5v/3v3 psu for my development board.
Are there some examples for Arduino to act as a KNX gateway? Normally you assign an address to the switch with the SW on the PC, right? Now I have to do this in the Arduino and don't know (yet) how that works.

[tuxedo]

Yes, That is actually what I would like to do. 85 euros is a bit expensive for just a 230AC to 30DC converter. maybe I build one by myself because I also need a 5v/3v3 psu for my development board.

It's not a plain stupid power supply. Data and power comes over the same lines. There are schematics for a power supply out there (search for freebus), but it is more or less experimental and might work (or not) on very small installations. The DIY supply does not fulfill the specs at all.

Are there some examples for Arduino to act as a KNX gateway?

What do you mean by "gateway". Gateway from KNX to what?
Search github for "knx" and "arduino" and you will find at least two projects that interfaces with an TPUART over UART. The rest is up to you.

Normally you assign an address to the switch with the SW on the PC, right? Now I have to do this in the Arduino and don't know (yet) how that works.

The Jung KNX Switch needs to be programmed with KNX ETS. This software costs ~1000EUR. There is no real alternative to programm knx devices. So 85EUR for power-supply and 1000EUR for ETS.

With ETS you give the options on your knx switch "group addresses". Once you push the button on the switch, one or more telegramms are sent to one or more group-addresses.

Your arduino will see those telegrams and can read them to do something.

All in all: Do you now get my initial comment "Isn't it a kind of overkill to use knx to just trigger a signal on your arduino like dev-board?" ;-)

If I where you, I would go for dual-push-button switches. And maybe install two of them (to get 4 push-buttons).

[basti76nie]

You can use the Hue Tab for about 60€. There are 4buttons for individual use

[Jasper298]

Thank you for your input. And yes, I understand you comment. I do this not to save money, but because I can... I'd like to program my own stuff.
The ETS program is not a problem. A friend of mine has this program and can program this for me.
But what can the ETS program do, what an AVR or Cortex can't do? It is just a "protocol" to program the switch right? So I think that it should be possible to program a switch with a microcontroller.
I will program a switch first with ETS and check with a scope to see what is send from ETS

[ElectronMass]

Or if you have switches from the Jung CD or LS series you can use the 531-41U (or 532-4 U) 2-gang multi switch which gives you 4 Pushbuttons to do what you want. Going the knx way is an absolute overkill (but as long as you only use 3 knx devices you get a free ETS licence from knx.org as far as I know).

[tuxedo]

It's very clear what it sends. See ETS Busmonitor-Output. Problem is: This is a lot of work noone yet finished..
In the end, it's easier to just use ETS.
But I would also be happy of there would be an ETS like tool which can run under linux and is as comfortable as ETS (or even more).

[basti76nie]

You can use the hue Tab also with Standard 55mm Frames and the hue tab doesn't need power because it's EnOcean selfpowering. c't shows a video

[Jasper298]

That was my other option. But can't find the standard 55mm frames for Jung without the Enocean module. I only can buy a complete switch including Enocean.

[l0wside]

Why don´t you opt for EnOcean? It does not require a central infrastructure, and the TCM300 (EnOcean to serial) is not overly expensive (about 20 EUR plus tax). If you connect the TCM300 to your µC, you can do whatever you like.

Max

[Jasper298]

I will use this module: https://www.particle.io/prototype
It is directly connected to my WiFi, so I don't need the TCM300. This module is $19 and I can connect many switches to one module.