[fy20]

I'm building a house at the moment and will go the KNX route. It really does seem great, it's just pretty much unknown outside of Germany for residential use.

The way communication works is each device has a number of inputs and outputs that have defined data types (there are one hundred or so in total). When programming devices you just tell them which channel (group address) the inputs and outputs (group objects) should be linked to. Inputs can be linked to any number of channels, but outputs can only be linked to 1. Some devices have basic logic units if you want to do more complicated things. The group address is 16 bits, so there's lots of room for flexibility.

For example, if you have a switch and the on/off output is linked to channel A, when you switch it on, it would send a 'switch on' message on that channel. If you have a light actuator (in simple terms, a programmable relay) that listens on channel A, when it receives that message it would turn the light on. If you want to add another switch at the other end of the hallway, you only need to program that switch to send the on/off output to channel A - the other devices don't need to be reprogrammed.

Devices are certified (which is one reason why they are quite expensive compared to consumer smart home devices), but that means they are guaranteed to work together regardless of the manufacturer. The protocol itself hasn't really changed over time (there are a few minor new features which are not backwards compatible) so if you have a installation from the early 00s, you can buy new hardware today and know it'll work without issues.

[anm89]

What do you get out of it though? What problems are you applying this towards?

[fy20]

The main thing I want is to change the colour temperature and brightness of lights throughout the house based on the time of day. I live in Northern Europe, and find lighting has a noticeable effect on my mood in winter. I'll also have presence and motion sensors throughout the house, so won't need to touch a light switch.

So basically first world problems. And for sure you could try to do something similar with Philips Hue bulbs (I have in the apartment I live in now), and 80% of the time that works, but I'd like to solve the other 20% too.

I'll also have a heat pump for hot water, heating and cooling and solar PV, so I will tie those together to try to optimise my power usage to use as much solar as possible. I'd love to be able to do that with appliances too (e.g. load up the washing machine in the morning, and have it turn on when there is excess solar), but it seems that's a few years away yet. Now I can monitor power usage and know when the washing is done. And if nobody goes in the room for an hour (from motion sensor) I can send a push notification to remind someone to get the washing.