Why DALI in addition to KNX?

Hi,

I am planning new house. I plan to design and implement most of automation myself, so I am investigating the available technologies and other people’s projects.

My current plan is to use KNX for most sensors and actuators. I would program KNX components with basic logic (i.e. this switch turns on/off that light, this switch moves this window shutter) and then add higher level logic (scenes, automation, remote control) on top of it using OpenHAB.

I have seen that many projects use DALI for controlling lights, connected to KNX with some bridge. However, I have never seen explanation why they made that choice. It looks like additional complexity to add another distinct component to the system, another kind of wires, etc.

Why would one use DALI instead of switching/dimming lights directly with appropriate KNX actuators?

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Because KNX is way too expensive ? Because of the lack of actuators+control capabilities for color lighting ? Because it requires the bus to be where the light is, i.e. it’s immobile ?

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Because KNX is way too expensive?

Ok, pricing is good argument. I still need to get proper overview about pricing. Unfortunatelly many vendors don’t publish prices and just have “ask us” option.

Because of the lack of actuators+control capabilities for color lighting?

I don’t see principal reason why could KNX not control colors. I have seen KNX actors that can control RGB lights. From quick search for example this one:
https://www.eibmarkt.com/en/products/MDT-New-KNX-EIB-RGB-LED-Controller-for-LED-Stripes-AKD-0324V-01.html?userLocale=DE&CountryID=41&Currency=EUR

Is there some catch?

Because it requires the bus to be where the light is, i.e. it’s immobile?

Can you please extend this answer? I don’t see how is KNX and DALI different in this point.

Dunno. But for sure there’s less KNX color options than in DALI which was specifically built for this purpose.
That also applies to controlling software.

There’s wireless DALI controllers available.

Then again, I probably wouldn’t use neither KNX nor DALI but rather ZigBee (Hue, Tadfri, …), ZWave or WiFi controllers for the purpose of color lighting. All of them are cheaper than KNX, and they’re all mobile (in principle) because they’re wireless technologies.

Ok, thank you for the answers. I’ll compare the pricing and the advanced features. However, I don’t think I need that much features in the dimmers themselves, since I plan to implement any advanced things in level above them (probably using OpenHAB).

I want to have my base lights on wire. I may add some secondary/mood lights later using some wireless technology. So maybe I don’t need any color stuff in the base system at all.

You don’t have to go KNX for that either. ZWave and WiFi actuators and a number of proprietary systems such as LCN, HomeMatic, … allow you to attach light AND switch, so to turn on the light works manually even when your server is down.

Ok, but then there is still wireless communication between the switch and the server and/or it uses proprietary protocol on the wire.

I want to stay away from wireless as much as possible (and practical) and to not depend on single company. So I don’t have to worry about replacing components in future. So far KNX seems like the right choice, even though it’s old and expensive.

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I’m at a similar design stage than you so I’ve gone through the same. Just some thoughts, that are very similar to yours. I too want the system to work without outside “influence” if say OpenHAB would happen to crash. Likewise I’m going for a wired solution.
As far as Dali/KNX is conserved it’s my understanding that KNX was/is designed as a “jack of all trades”, whereas Dali is specifically for lights and as such might offer greater control. As far as I’m concerned, KNX has enough lighting features to be enough for me (including RGBW). As for wired/wireless and lights, you always have to run power to the lights anyway, a KNX bus wire pair is not too much to add.p, or you could use a top rail mounted KNX controller (e.g. the one from MDT) and the just run the power wires.
Yes KNX is old, but it’s maintained and updated p, so I’d call is robust rather than outdated. And if you choose wisely, it doesn’t have to be hugely expensive. Sure 200€ is a lot for a light switch, but was if the switch actually has 16 switching functions + a luminance sensor and can act as a room thermostat while also including a logics module. I’d say you get quite good value for the money there.

Mikael

Hey there,
just wanted to through in my experience to the mix as well since we recently built a house as well including both, knx and dali components.
To the already stated claims i want to add that especially if you want to go the led route that there are a lot of dali led drivers out there, which are usually not that much more expensive.
Wiring is also a topic to be taken into consideration. With dali you simply run one cable with five phases (three for your power and two for dali) to all your lights in series where as with knx you always have to run one cable to your actor (wich can sum up to a view :wink:
Also if you want to add/change lights in the future, dali is a bit more flexible in that regard since the controller is always included and all you need is only the one cable where as with knx you have to have the right actor and getting a new cable to your breaker board after everything is built is quite a challenge. ^^
If you have any further questions let me know, I can also write you a brief summarization of my installation.
Anton

Thank you for the reply. As far as I can tell, you could do exactly the same wiring with KNX. People seem to usually place all KNX actors together in a switch box, but they could be placed near the lights just like with DALI.

I’m in the same position - designing whole home lighting from scratch.

  • I’ve still not got my head around the difference between DALI and KNX and why I’d do either, hence I find this discussion interesting. I don’t think you’ve got a conclusive answer yet

  • Same, it’s hard to get pricing for these components, also I’d add that, unless you are very familiar with the systems, it’s really hard to know what equipment you’d need to make a system. I have looked through so many DALI and KNX products and to be honest I’m confused by it

  • The above, as well as pricing, has led me towards DMX. I know it’s a very old standard, and mainly used in theatres etc, but from what I can tell it’s excellent in the home. You can control anything, the idea of RGB can be extended to RGBW, and then even to RGBCCWW, etc. You can pick up 12 channel actuators and run them from a central location for very low cost second hand, because of the very active market in commercial / stage DMX. For example I purchased a high quality 12 channel, 4A per channel dimming unit for £120. That’s £10 per channel, including nicely designed triacs and low EMF noise. You can’t beat it.

Also I have made an MQTT to DMX interface from a £5 Arduino. In my experience the Arduino is as reliable as its power supply (my test rig has been running constantly for years) but at this price you could buy 5 and keep them as backups.

The only sticking point for me is running LOTS of thick mains cable back to central location. I’d be much happier running thinner data cable back, and wiring the mains using ring circuits.

Like you said, why can’t you do this with KNX directly?

The flip side to this is that, at least I can easily access the dimmers when they overheat / break / need changing etc. I don’t like the idea of drivers in the ceiling voids or behind walls, because I just KNOW when you have 50 in the house, they will break often and need to take ceiling down. My parents house is littered with old transformers that never got replaced from the 1980s, and lights that just don’t work OR make a loud humming noise in the ceiling! So maybe running lots of thick cable back is not too bad.

Thoughts anyone?

To be honest, DMX (and DALI either) do only Lighting, and mostly with dimming, although there are ways to really switch circuits (and of course you could add a fog machine to DMX :wink: ). knx on the other side is for “the whole stuff” and therefor there are gateways to control DALI or DMX with knx.

Please I’m in same option.

What did you do ?

Can I contact you by email

I went through this same assessment a couple of years ago and settled on DALI for lighting with KNX for window blinds and heating control. KNX is the ‘supervisor’ and an MDT KNX-to-DALI gateway makes all the DALI devices look like KNX devices, so I control them (using openHAB) as if everything was KNX.

For me, the main factors were:

  • I found there was much more choice of DALI dimmers than KNX dimmers, covering:
    • LED down-lights (need a Constant Current driver)
    • LED strip-lights (need a Constant Voltage driver)
    • LED RGB strip-lights (need a three-channel Constant Voltage driver)
    • Mains-voltage dimmable lights (e.g. LED table lamps)
  • I found the DALI dimmers were cheaper than comparable KNX dimmers
  • I only have about 10 KNX devices so only need the ETS Lite license (max 20 devices) - if every light dimmer was KNX I would have needed an ETS Professional license (much more expensive)

I agree with others who have said that DALI is just for lighting - which is true - but it is very good for lighting.

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What downlights are you using with the Constant Current drivers? All the downlights I find are mains voltage (and those marked as dimmable appear to expect phase dimming).

For closure, this is what I ended up with: First I decided to use KNX actors for all lights, in order to have everything wired into the main distribution box, so I can upgrade or replace any part easily.

But then we got together with a seller of the actual light fixtures and it turned out that many of the nicer ones already have DALI built into them, so that is the ideal way of controlling them. So now I have a mix - some basic lights switched thru KNX actors and some better lights thru DALI over KNX/DALI gate.

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A lot of LED downlights are aimed at the retro-fit market, where they try to make it as easy as possible to replace halogen equivalents. My advice is to ignore those (i.e. ignore anything that says it takes a GU10 or similar) and look at the alternatives which take advantage of the characteristics of LED technology:

  • You get most flexibility by using fittings where the LED Bulb (the bit that takes a DC input and actually emits the light) is separate from the Driver (the electronics that take an AC input and give a DC output).
  • Since decent LED Bulbs last for decades (it tends to be the Driver rather than the Bulb which fails first) there’s no need to have a fitting where the bulb is replaceable. My advice is to use one where there’s an obvious heatsink to help keep the LED Bulb cool and further prolong its life.
  • LED Bulbs are always dimmable; it’s the Driver that determines whether / how you get to control the dimming setting.
  • If you have a group of downlights, you’ll want to wire the Bulbs in series and use a single Driver to push the same Constant Current through them all (subject to the capacity of the Driver).
    • If you need to use multiple Drivers for a group of lights just because of capacity, DALI lets you “group” the Drivers together so they all work together.

In many ways, the best option is to buy Fittings which have built-in Bulbs but no Drivers then buy suitable Drivers separately - which is what I did.

All my downlights came from Spanish company BPM Lighting who were recommended by some lighting experts I spoke to. They’re mostly used by the trade though so you might have difficulty buying them retail.

See e.g. https://www.ledkia.com/uk/buy-led-downlights/3416-white-round-12w-cob-led-downlight.html where the photos make it clear there’s a heatsink on the Bulb and the Driver is separate. (If you can’t find fittings without Drivers buy ones where the Driver is separate, take it off and use your own.)

I used DALI drivers from TCI - see e.g. this product page from Mr Resistor which has a lot of good supporting info on series wiring etc.

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Thanks for giving update. This is likely the approach I’ll go with too.

I’m retrofitting my house so I won’t be wiring back to the main electrical box, so the KNX actuators I’ll use will be flush mounted.

Thanks for all the detail - really helpful.

I definitely agree with the retro-fit statement - this dominates so it’s hard to find ‘raw’ led downlights.

I did find some here, however they’re not fire rated, which I’ll need in some rooms.

For the time being I’ve taken your advice and found some basic downlights that have a separate driver. I’ve bought one for testing and an Osram OTi DALI driver. Will see how that goes.

When I started renovating a old house in December 2018 I had to rewire the whole house. First I planed to go with KNX and Dali as well, but I switched to KNX and DMX since this ended up a lot cheaper.

All lights have there own cables powered by 24V connected to a DMX 24-Port Dimmer. The Dimmer is connecte to an DMX Art Net Bridge that receives commands from openHAB.

The only downside at the moment, that I did not buy a KNX2DMX Bridge. So If openHAB is down, the switches will not turn on the lights. But since openHAB is verry stable for me that has not been a problem so far.

So if I calculate 100 € for the dmx dimmer with 24 channels I do end up with approx. 4€ per channel. That was the best I could find on the market for my use cases.

You can connect any 24V LED to the Dimmer.