Well, to avoid laying a 3-core cable (L, N, PE) to every consumer, you can use 5- or 7-core cables. These then have 2 or 5 phases (L) and "share" the N and PE conductors.
With a 7-core cable, 5 consumers (light, socket) can be supplied and switched separately. For shading (direction-dependent), however, you need 2 phases.
The KNX bus has 30V DC. Some sensors need the power supply, some get enough power via the bus. Black and red are the bus, and yellow and gray are the power supply (illogical to me, but whatever). That’s why the typical KNX cable is 4-core.
Wow, 16 buttons.
Just use standard light barriers. Preferably with a 30V operating voltage so you can power them with the second pair of wires from the bus cable. The switching output goes to a binary input. The logic you can figure out yourself.
For example, this is what my mailbox looks like. Of course, two magnetic contacts would work as well, but I found the light barriers more accurate because it only reports mail when something is actually inside.
Just use a bit of imagination. Temperatures are reported to the bus and logic switches the appropriate lighting effects accordingly. You can also monitor times. With KNX, this is done in no time. It’s really very special, but some people need it. I know someone else who has push notifications sent with the measured values from the meat. Everyone has their own quirks and sometimes gets creative.
Yes, that’s how you should do it. Lay the bus cable everywhere possible. I always write that, and opinions always come in saying that it’s unnecessary. But that’s not the case. Because later on, you will need the cable, as RomeoZwo proves with his awning.
Well, as just said, if the bus cable had been laid everywhere, the awning would have been connected in no time. (Rollotube X-Line)
As a bus cable, you should use the freely available J-Y(St)Y 2x2x0.8. At that price, you can’t complain, and it’s approved for all bus applications. Sure, one could repurpose CAT or DMX cables, etc., but why should one do that? If no other option is available, I’d consider it, but in new builds, just lay the green cable everywhere and that’s it. Then you consume 3-4-5 rolls, so what? The ~35€ per roll is hardly noticeable. The NYM cables must be laid anyway, and the green cable next to it does not interfere at all.
Where you really plan only sensors (PM, buttons, etc.), of course, the green cable alone is sufficient, as RomeoZwo already said.
Many thanks for the explanations
And many thanks for the explanations on the topic "cables".
One more question: assuming we don’t lay bus cable everywhere, do I still have options later on to make an otherwise completely normal socket switchable?
I also have a question about push-buttons. The goal is, of course, to install as few as possible, but you probably can’t do without them completely if you assume that at the beginning not everything is perfectly parameterized and you still operate one or another function manually by button until the project is gradually extended with scenes.
Now there are thousands of possibilities. Assuming for simplicity’s sake here, let’s limit ourselves to the MDT range. Unfortunately, I’m not allowed to link, so I have to try to describe as precisely as possible.
Let’s take the “Glastaster II Smart” and the “Glasbedienzentrale Smart” for example. I still don’t fully understand what I use how. Do I understand correctly that the Glastaster is primarily a push-button for lighting, shading, scenes, etc., and the Bedienzentrale is basically a control device for the house? Even if that is correct, I still haven’t quite understood what I can do with one and not with the other and vice versa. And, if I had both, would I use them independently or in combination?