Topologie: Stern

[adonchevski]

Hallo,
Ich versuche die Sterntopologie zu verstehen. Ich habe eine Datei mit zwei Diagrammen angehängt.

1. Im ersten Diagramm befindet sich ein Backbone-KNX-Buskabel im Verteilerkasten, bei dem mehrere Einzelkabel zu den Sensoren vorhanden sind.
2. Am zweiten Digaram für jeden Sensor gibt es ein KNX-Kabel vom Verteilerkasten zum Sensor und ein KNX-Kabel vom Sensor zum Verteilerkasten.

Es scheint, dass Option 2 auf jeden Fall funktionieren sollte.
Ich bin interessiert, ob Option 1 auch funktioniert und wenn ja, warum? Wie werden die separaten Kabel an die Backbone-Leitung angeschlossen? Gibt es im Internet eine wirkliche Verschränkung?

Ich schreibe auch auf Englisch, da Deutsch nicht meine Muttersprache ist.

///

Hi,
I am trying to understand the Star topology. I attached a file with two diagrams.

1. On the first diagram there is one backbone KNX bus cable in the Verteilerkasten where there are multiple single cables to the sensors.
2. On the second digaram for every sensor there is one KNX cable out from the Verteilerkasten to the sensor and one KNX cable from the sensor to the Verteilerkasten.

It seems option 2 should work for sure?
I am interested if option 1 works also, and if yes, why? How the separate cables are connected to the backbone line? Is there any real imlementation on internet?

I am writing in English also since, German is not my native.

[Gast1961]

Yes, both physical routing topologies are fully functional. KNX communication is "slow" and does not require matched terminations. The physical wiring is almost arbitrary, so even a complex tree structure is perfectly fine.

[Beleuchtfix]

Both will work well, figure 1 my be a backbone, from the English terminology, but it it not a backbone from the meaning in the KNX usage. There you woul connect the strings via a line cuppler with the backbone cable.

Regards Florian

[gbglace]

You have to think about 2 different aspects in planing your KNX-Bus regarding the topology.

1) physical topology >> how all the green KNX-cables are connected
2) KNX-logical topology >> Connection of different bus-segments to assure correct telegramm data traffic

1) all connection types excepted for closed rings are allowed, daisy chain, tree, star, or any mix of it. Then there only are some limitations in total length of knx-cable, but this should not be a problem in a normal one familiy house. clic here for excample

2) therefor you can find a lot of information material at KNX.org or google KNX network topology.


Your fig 1 would work, fig 2 cost a lot of cable which is not necessary, because that is not a star thats a daisy-chain topology.


The green knx cable will be connected with WAGO Micro clamps (Wago 243 Series), you can find them at each KNX-device. So you can connect from one deivice to the next, you don't have to go back to your "Verteilerschrank".

Inside "Verteilerschrank" the KNX-Clamps phoenix pttbs 1,5/s-knx are recommended.

A good compromise between star and daisy chain is to take one cable to each floor and there you connect one KNX-device with the next nearest one and next and next, from the last one you go back to the "Verteilerschrank". But the end dont have to be connected (open end, ring is not allowed). If there is a break in line you can use the open end to repair the bus. Youn can realise this on floor level, or for each room, its all possible only different amounts of cable are used.

[adonchevski]

There you woul connect the strings via a line cuppler with the backbone cable.

Then the pure star topology seem a non-sense to me if I have a line coupler for every sensor!?

I am attaching again a file. Fig 3 is the way I initially planned. I am attaching also the typologies as per the book Heimautomation, which I have.

1) all connection types excepted for closed rings are allowed, daisy chain, tree, star, or any mix of it. Then there only are some limitations in total length of knx-cable, but this should not be a problem in a normal one familiy house. clic here for excample

I am aware of that. I have ETS and a lot of devices already bought. I am interested only about the physical aspect of the wiring currently.

The green knx cable will be connected with WAGO Micro clamps (Wago 243 Series), you can find them at each KNX-device. So you can connect from one deivice to the next, you don't have to go back to your "Verteilerschrank".

This is also my plan as noted above, but I want to understand the other options.
If as answered above, star means line-couplers:sensors 1:1, why someone would want to implement such topology (its pure variant without a mixture of star ans something else)?

A good compromise between star and daisy chain is to take one cable to each floor and there you connect one KNX-device with the next nearest one and next and next, from the last one you go back to the "Verteilerschrank". But the end dont have to be connected (open end, ring is not allowed). If there is a break in line you can use the open end to repair the bus. Youn can realise this on floor level, or for each room, its all possible only different amounts of cable are used.

This is exactly what I planned. It is about a big 3 floor house with alto of automation - lights, heating, curtains, windows rolls etc. I planned 1 line (line coupler) for every of the floors (+ 1 separate line for the outdoor) and on every floor a daisy chain line from Verteilerschrank to Verteilerschrank without making a loop at the end.

Everything about line topology and daisy chain is clear. I just want to understand whether star means line-couplers:sensors 1:1 and what is the difference between the others defined in the book - Bus and Baum.

[gbglace]

The pictures you can use, the text is for limitations in 1-wire Bus thats not KNX. I'm not an expert for bus systems and electronic. KNX as a bus is very stable so a star or a bus or a line or a mixture of it is possible. DMX Bus for excample only daisy chain is allowed.

You can make a mix of topology, take the picture of "Baum" and put one endpoint as the "M" in "Stern" and one endpoint of this connect a new "Baum". If you have your green cable connected from the Verteilerschrank into the ceiling and presence sensor, than you could connect from their directly to the ligth switch nearby the door and direcly to the windows for connecting the reed contacts in the windows. Thats a little star and its a sollution. Feel free to mix "Baum" with "Stern" with "Bus" with "Linie".

You don't have to by a linie coupler for each floor, it makes only sence if you have more than 80-90-100 devices in the house or you plan to have one floor as a separate appartment for rent. An extra line outside makes sence.

[adonchevski]

The pictures you can use, the text is for limitations in 1-wire Bus thats not KNX. I'm not an expert for bus systems and electronic. KNX as a bus is very stable so a star or a bus or a line or a mixture of it is possible. DMX Bus for excample only daisy chain is allowed.

I added the correct picture for KNX.

If you have your green cable connected from the Verteilerschrank into the ceiling and presence sensor, than you could connect from their directly to the ligth switch nearby the door and direcly to the windows for connecting the reed contacts in the windows.

Isn't this a "line"? A daisy chain forming a line.
Again I still do not have an answer of the question: What is a "star" in its "pure" (no mixture) variant? Is every line star formed with a line coupler - line-couplers:sensors 1:1?

[gbglace]

Sorry I don't understand your Question, when you have one KNX-power supply and a number of x KNX devices with exactly x green parts of green cable connected directly to the one power suply, than you have a star all other are a mix of star and the other ones, why a mix should be a star?
If your KNX device is a sensor or an actuator or a special device like line coupler is not relevant this are all KNX-devices, powered by the power supply in this one bus segment called logical line.

So as I said the one is thinking about physical topology in cable and the otherone is the logical in areas / main lines / lines and Segments, which are connected by linie couplers and each part needs his own power supply. The KNX-power supply defines the starting point of the KNX-bus not a coupler.

An other meanig of the word coupler is the bcu.
The bus coupler unit is in modern devices an integrated part so normaly we only speek about line couplers as a special KNX device. So every actuator or sensor normaly have their own bcu (only old designs of devices have two peaces of hardware). And there you can't connect different sensors on one bcu.

[adonchevski]

Again I am talking only about "Die physikalische Topologie von KNX TP" - only about green KNX wires. The pictures above are for that.

KNX-power supply and a number of x KNX devices with exactly x green parts of green cable connected directly to the one power suply, than you have a star all other are a mix of star and the other ones, why a mix should be a star?

Could you point me to a KNX power supply device where I can connect directly 60 devices with 60 cables? It seems this is the missing part for me. I attached a picture. Please tell me if you mean the wiring from the picture. I thought a device like a switch (LAN) is needed there and not just bridged KNX-Clamps.

What I thought was that the power supply is the starting point, but to it only a single device can be connected. Then a second device could be connected to the first device and so on - like Fig 3.

Most probably the misunderstanding comes from Florian's answer above - "There you woul connect the strings via a line cuppler with the backbone cable."

[mumpf]

Hi,

Could you point me to a KNX power supply device where I can connect directly 60 devices with 60 cables?

in principle you can do this with any device (I just would not suggest this): Take 60 knx cables, solder the red wires all together, do the same with the black ones, and solder them somehow to the power supply. Here you have your "star". But nobody would do it that way!

Each device has these nice black-red clamps, where you can directly connect up to 4 KNX wires. Use them and you are happy. If you connect just 1 wire, your device is an endpoint. If you connect 2 wires, your device is a part of a line, if you connect 3 or 4 wires, your device is a node of a tree or the center of a star.

But all these things don't matter, just connect them and it works, that's important.

What I thought was that the power supply is the starting point, ...

No, the power supply has to be connected to the line - SOMEWHERE!

... but to it only a single device can be connected.

As stated above, many devices might be connected, it is a mechanical problem to connect more than 4.



Regards,
Waldemar

[adonchevski]

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Take 60 knx cables, solder the red wires all together, do the same with the black ones, and solder them somehow to the power supply.

Ohh, that was the answer that I was searching for. Thank you! This would mean that the picture attached in my previous reply is what you explained?

[mumpf]

Yes, you picture represents a star.

But - to be very clear: I would not recommend a star for the KNX wiring. It is not necessary and costs you a lot of KNX-cable and a lot of place in the "Verteilung".

Regards,
Waldemar

[adonchevski]

It is not necessary and costs you a lot of KNX-cable and a lot of place in the "Verteilung".

Yes, I am aware of that. Thanks!