Modbus,KNX trying to understand?

Hi i got a Q from my brother who is building a new Home…
what is the best standard for Home auto…
leaving aside the hab and all the connected devices, say i want to build a good infrastructure
with hard wires and not wireless (zwave,zigbee, wifi,)

when searching the net i see KNX ,Modbus, and allot more
i see the two above as the main standards?

but i am still trying to understand what can they do?
can i put cameras, lights, and all IOT devices on this protocols?

Nope. knx is an industrial standard. There are hundreds of manufaturers which build devices like wall rockers and all sorts of actuators and sensors for this bus system. knx is one of the older standards, started in the late 80s, it’s often used in large buildings, hotels, or in luxury houses :wink: It’s very stable and very expensive…
Modbus is another industry standard, I can’t say much about it, as I don’t use it.
Most common products for home automation enthusiasts are zwave, zigbee or sonoff (and other ESP8266 devices) as they are much cheaper and wireless.

Yes Udo i know the world of the enthusiasts (i am there with you)
wanted to know about real life …

and not me that can debug my issues all day and not feel sick :slight_smile:

one day i want to build a house, OH can be the controller, but i think i should have hard wires where ever i can
don’t you agree?

do you recommend any other approach?
i think to spend a little more on KNX(or anything that is the best)
is something to think about ,when doing a new home in lets say in 2020 :slight_smile:

Ah, if building a house from scratch, wiring is definitely the best approach - I did it this way with knx :wink:

As I did the complete electrical installation myself, I saved a lot of money and spent it in knx, and gues what, I never regretted this decision.

Cool if you did that i canbe calm :slight_smile:

is there anything that KNX cannot cover?
lets say NVR/DVR is it too complex or expnsive? or maybe better soultions outside of KNX

knx is only to control. The bus speed is 9600 bit per second, 2 wires (for power AND bidirectional communication), so no video, no audio, you have to use ethernet or something similar for this. knx is to control heating, cooling, lights, shutters, ventilation, … window and door contacts, presence detection… there is special hardware to give equalized light (i.e. if it becomes darker outside, the light will dimmed brighter to compensate this)

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Hello dear,

Related to this question: is it practical acceptable to merge between KNX and Modbus to reduce the cost. So Findings will be KNX and actuators will be Modbus (Wago or Beckhoff). And system like openHAB to do the integration?

Also, about Modbus: as I don’t know about it; by using it with openHAB. Does it mean the Modbus slaves will be just digital and analogue devices with addresses; and programming them can be done by openHAB without getting in PLC programming?

You can have both KNX and Modbus driven by the same OH host. They must use separate wiring buses, so that might require planning in advance to get cables to the right places.

I have Modbus working with simple slaves - relays, sensors. Others have openHAB interacting with PLCs okay. But you can’t use OH to program PLCs.

Unlike KNX, there aren’t that many Modbus devices well suited for home lighting use more complicated than on/off. Although many HVAC units have Modbus built in.
Using both technologies with openHAB allows you to choose the devices you want from either range.

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I don’t mean to program PLC using openHAB. I meant if I use for example Beckhoff equipment (controller with I/O modules such as KL2751 ); then to program the dimmer module based on button pressed, can I do that from openHAB only (as it is item) or I have to make it from twiCAT (the software of Beckhoff) using Ladder, ST language ?

I don’t know what means.

If the PLC has a slave Modbus interface, openHAB can act as master to send/fetch data to the PLC, and the PLC can do what it likes with that data according to it’s programming. That might include controlling slave devices on a separate modbus where the PLC acts as the master.

If you have a slave device, a dimmer, then openHAB can control it directly by acting as the master on a modbus with no PLC.