Why a bridge is not a brain

A hub or app that connects to your KNX gives you a phone screen and voice control. That is useful. It makes the house easier to command. It does not stop the house doing the wrong thing at the wrong time, because the rules behind it work the same way as before. Whether that matters depends on what you want from the house.

What a bridge is

Your installer may offer a hub, a home server, a voice assistant or a screen that speaks KNX on one side and something newer on the other. Homey, Josh.ai and a Control4 processor with a KNX driver are examples of the kind of product we mean.

The usual pitch is fair. Your KNX is reliable but older. Add this, and you get an app, voice control, and a way to connect devices your KNX cannot reach. These are real products that solve a real problem.

One question to ask

After this is installed, how many decisions a day will my household still make about the house?

Not how easily. How many.

A bridge makes each command easier. You can dim the lounge by voice instead of walking to a keypad. But it rarely reduces the number of commands. It often adds interfaces: the phone, the panel, the keypad and the voice assistant now overlap.

If the honest answer is “about the same, but easier”, you are buying convenience. That may be exactly right for you. Just know which one you are buying.

What is inside a bridge

Most bridges have three parts.

A translator. It speaks KNX and other systems such as Zigbee, Z-Wave or Matter. This is the valuable part.

A list of what is on right now. It knows this light is at 40% and that room is 21.5 degrees. It only knows now. It does not keep a story of what happened.

Rules. If this happens, do that. Many have a friendly editor.

Where rules run out

If-this-then-that handles a lot. It struggles with three things.

Anything that needs history. “Warm the towel rail before the bathroom is usually used” needs to know when it is usually used. A rule only sees the trigger and the current state. You can write a timetable by hand. But then you learned the pattern, not the house, and you must keep it up to date forever.

Anything about a room as a whole. “Turn off lights in empty rooms” cannot be written once. It is written per room, per light, per sensor. Thirty rules instead of one, and thirty to check when the study becomes a nursery.

Anything where two goals clash. Many rule systems let each rule act on its own. Some have priorities and conditions, and a good programmer can make them work. But the system as a whole does not stop to look at both wishes and choose. So the vacancy rule can switch off the lights while someone reads quietly in the next room.

Owners of heavily automated houses all have a story like this. It is usually not a setting someone got wrong. It is how the rules are built.

A better chat does not fix this

A voice assistant is a better way to give a command. It is real progress on one front. But the house still waits to be told. You can make the command effortless. You cannot make it unnecessary.

The same goes for a chat assistant put in front of the rules. What matters is what sits behind the chat. If the same rules sit behind it, the house is no more aware. It is just more polite.

What would have to be different

Three things. None of them is a screen.

• Rooms, not just a list of devices. Describe what a type of room should do once, and use it wherever it fits.
• Clashes settled by the room. When two requests clash, the room’s own behaviour is checked first, and the log says why.
• A log you can read. When the house does something odd, you can see which rule ran and why.

That is what Casient adds. Casient does not replace your app or your hub. It adds room behaviours and a log. A room’s own behaviour is checked first, and a child’s bedroom doesn’t light by itself at night. A request made through Casient is checked and logged before anything is sent. Casient is early: one real home so far, with pilots under way.

How to choose

A bridge is a good fit if your main wish is to use your phone, add voice, or connect devices your KNX cannot reach. It is usually quick to install, and it does what it says.

A bridge alone will not help if your complaint is that the house keeps doing the wrong thing at the wrong time, or that you are tired of telling it things. For that, ask your installer how the system decides between two requests, and whether you can read why it did something.

To see where products sit on the way from “manual” to “self-running”, read what “AI in the home” actually means. For the reasons behind the three limits, read KNX in plain English. Installers can find fix-it notes at KNX notes.

Send this to your installer, or ask them:

• How does the system decide between two requests?
• Can you run a free Readback on our project?

For installers

Installers: run a free Readback