KNX connection to Mini server

[Alan]

Hi

I've been trying to find some information on how KNX switches connect to the miniserver? Are they daisy chained to each other first? or do they all go back to a central point? I thought it was a Bus topology, but just curious about the physical connections required so I can understand what needs to be allocated.  

Thanks

Alan

[Duncan]

the knx is a slow speed bus that uses 2 core wire to carry power and signal combined, and can be connected linearly, star, or a combination of both as needed

the 2 cores from a knx power supply go to the 2 pins on the miniserver, then 2 cores again to each knx device, pretty much whatever wiring pattern you need

since most loxone installs would have light switch locations star wired back to the miniserver using cat5/6/7 to connect to digital inputs, the easiest thing to do is wire all locations like this, then simply swap out some normal switches for knx and reconnect the cat5/6/7 for that switch at the miniserver end to its knx inputs (and install the knx power supply adjacent to the miniserver)

there is a knx standard wire, but lots of people use cat 6/7 for knx loxone install, which enables the same cable to be used for conventional loxone 24v switches as well, or the extra cores to link to other sensors such as 1-wire sensors (although some knx switches such as mdt glass ones include knx temperature sensors anyway)

there is lots of argument about whether cat6/7 is sufficient for knx, and it certainly is from a signal/frequency spec, but the thicker cat7 fits the connectors easier and ive not personally experienced any problems doing this. i guess on a massive office-size knx install you should probably use the correct cable, but i dont think its necessary for a domestic loxone/knx combination

knx a very elegant way of adding high quality visually appealing switches and controllers to a loxone install, and some devices have feedback leds, displays for text and outputs etc so saving a lot of loxone inputs and outputs.

[Alan]

So presumably all the connections going back to the Miniserver from each individual KNX switch are somehow bridged together (perhaps with those layered connecting blocks) along with those from the KNX power supply and then 2 cores get connected directly to the miniserver through the specific KNX terminals? 

Apologies for the vagueness, I've yet to purchase my loxone and i'm still trying to identify whats required for a fairly basic installation (lights, LED's, dimming perhaps the odd window blind)....need to sell it to the other half ;)  

Thanks again for all the useful information, its a very informative forum. 

Alan 

[Duncan]

exactly - im using the layered connection blocks that loxone supply and bring all the connections together there from kxn power supply, miniserver and all the switches

i used cat5 wiring because i wired before changing to knx for some switch locations (the 'public' rooms such as entrance, kitchen, lounge etc, and havnt had any connection problems or knx programming problems and its a large install - i used around 10km of bulk cat5/6/7 cables in my house/garden

each knx device comes with its little black/red 2 pole connecting block (including the miniserver) that the single solid core wire just pushes in to. all the other cable ends for each device then go back to the multi-layer connector which has a similar push-fit

[Alan]

10km! thats some install you've got there...I don't think i'd be hesitating at all if i were building a place from new or completely renovating, However its only a partial renovation and I can see us moving on in a few years, so there's also a bit of concern about the 'selling-on' element if i start to make it complicated(....as i really want it of course!).

Ok, i think i'm getting the idea with the connections presumably those blocks are the interconnected ones,  which i assume have coincident layers so that there's continuity between similar layers.  I think i'd be tempted to go with the cat5/6 I think. 

Thanks for the info

Alan

[Rob_in]

There's a topic about connection blocks here: Terminal block for cat cables

KNX connectors are just Wago 243 series blocks. They come in up to 8 way and you can get little plastic carriers (Wago 243-112) to hold them on your DIN rails if you don't want them just floating around in the cabinet. I bought mine from Conrad where they are less than 50c each (EUR).

On this subject, Conrad (http://www.conrad-electronic.co.uk) and TME (http://www.tme.eu/gb/) are both awesome suppliers for little things like this. Ie. the blocks I'm talking about on the UK site are:

http://www.conrad-electronic.co.uk/ce/en/product/526251/Screw-terminal-flexible-06-rigid-08-mm-Number-of-pins-8-WAGO-1-pcs-Red

http://www.conrad-electronic.co.uk/ce/en/product/526264/Screw-terminal-flexible-06-rigid-08-mm-Number-of-pins-8-WAGO-1-pcs-Dark-grey

http://www.conrad-electronic.co.uk/ce/en/product/526292/Mounting-adapter-WAGO-243-112-Orange-1-pcs

(I bought the dark grey blocks instead of black because for some reason they didn't sell black ones individually).

Both these suppliers have multi-lingual sites and ship all over europe. I'm particularly impressed with TME. Stuff like cable ties, wire, etc. are dirt cheap there. I got my Meanwell LED PSUs from TME, some wall boxes for my temperature/humidity sensors, few metres of hook up wire for 24v power, etc.

FWIW, RS & Farnell are also good (I bought some ELDOLed LIN180D2 from RS) but TME is my go-to choice for small parts now... erm... now I've finished ;)

HTH,

Robin

[Alan]

Thanks Robin, that really useful info and alot cheaper than the alternatives. Those are terminal blocks, so i'm guessing you could also bridge them too in order to cross link the knx cable if necessary? I think the easiest way for my install would be a star network back to a single point at which point I could bridge to a KNX power supply and onto the miniserver (hopefully thats correct.. ;) ).

Thanks for the info..

Alan