Bus systems - wiring, planning, etc.?

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Really high data rates in wireless on a consumer level work at most at a distance of 1-2m.

As an example, measurements from the day before yesterday:
FritzBox 7530 behind Vodafone cable router to phone Note 10+

Connection 500/50 MBit/s
Measurement distance approx. 1m: 440 MBit/s
Measurement distance approx. 15m: 45 MBit/s
(From the utility room to the terrace, no wall or window in between or open (shell construction)

And: Flexible cables are usually used from the LAN socket to the end device. Always!

Sockets can be easily extended and you can operate "endlessly" many devices. In the bus system, it is a star-shaped structure. Therefore, only one end device per connection.


Those are bad values. But still no problem because a real 45 MBit/s would easily be enough for pretty much any household device/control.

But a different question: The bus system also contains the power supply, right? Could you then connect every socket through a bus cable and do without the "normal" power cable? In other words, is there a kind of wall socket that can work uncontrolled but later allow connecting an end device?

Also the question: what happens in a short circuit? In a normal power grid, usually nothing. In the worst case, a fuse blows. But the control unit of a bus system is probably more expensive than a 10€ fuse. Or is the same protection connected upfront so nothing can ever happen to the system? What about lightning strikes?

With the bus system, it is a star-shaped structure.

Now you’re making me curious

In the bus system, it is a star-shaped structure. Thus, only one device per connection.

No, that is not entirely correct. You can connect as many devices as the cable, actuator, circuit breaker allow, and of course, these can be quickly and easily rewired on the bus at any time as needed.

There are many different variants of bus topologies. Depending on the type of bus, it can be a star, tree, ring, open ring, and of course various combinations of all these variants.

The bus system also includes the power supply, right? Could you then connect every socket via a bus cable and forgo the "normal" power cable?

No, because a bus usually uses SELV voltage. That means some kind of low-voltage variant. Naturally, you cannot operate a TV or toaster with that. But wiring bus cables to the sockets is not wrong, because that way you always have the option later to make every socket switchable/monitorable, etc. Or you remove the socket at a certain spot and instead install a sensor/detector/probe.

Of course, there are now more or less exotic systems like Digitalstrom, which use the 230V cables for communication, so no bus cable is necessary. However, with this approach, there are other significant disadvantages.

So, is there a kind of wall socket that can work uncontrolled but to which you can connect a device later?

In a well-thought-out bus cabling, this is the norm. Each socket can usually be supplied with constant power or made switchable with just a few easy steps.

Another question: what happens in a short circuit? Usually, nothing in a normal power grid. In the worst case, a fuse is blown. But the control unit of a bus system is presumably more expensive than a 10€ fuse.

Bus components are generally short-circuit proof. That means nothing happens. The short circuit is eliminated, and the system works again as usual.

Of course, not all faults can be predicted, and defects do occur. However, a short circuit in today’s networks is still a scary story whereby the savvy consultant often guides the gullible builders to buy expensive additional devices for protection against it.

Or is the same protection installed in front so that nothing can ever happen to the system?

Depends on the system, but yes, basically, little can happen there.

What about lightning strikes?

Here it is naturally a bit more serious. Depending on how the system is protected, it ranges from everything dead to: "What happened???"

So you can also connect a long cable to your network sockets and/or extend it. Apparently, you don't care if you then have a line running through the room. It just doesn't fit with the statement regarding final positions.... You have already read the same opinion several times, partly from people who do this professionally. Bus systems are not star-shaped. I also don't know why you are so "resistant." Wireless is possible but more expensive. In new buildings, cables are laid there more stably and also significantly faster regarding the network. The costs for the cable are negligible. I would like to learn more about your construction project. Are you similarly "keen" and "innovative" in other areas of construction? No one here has written "that's how it’s done because it has always been done that way" but has explained to you why it should be done that way.

Hi, no, I'm also not a fan of cables running through the room. But I would prefer a single power cable rather than possibly additional bus cables. But if the bus system doesn't have to be star-shaped, then my statement is of course wrong. Because then you can lay the cable to a new location just as quickly as with power. If it were star-shaped, then you would have to lay a new cable through the whole house. I had understood that only one actuator may hang per branch and therefore a star-shaped setup is necessary. And I found that extremely complex. So, sorry. If KNX doesn't have to be star-shaped, then of course it becomes much easier. Would it then be enough to lay one bus cable per room and then run it within the room from socket to socket? And you could then tap off the bus cable at each socket and still have multiple actuators on just that one branch? By the way, my confusion came from web search and MyCraft's statement (no blame! Definitely my mistake): No, exactly the opposite is the case. They try to sell simpler solutions. It hardly gets easier than KNX. Star wiring and bus line and then everything is switchable, remote controllable, etc., possibly also by radio if you install an interface.