Window sensors
There are a lot of advanced wireless sensors on the market that will tell you whether a window is open or closed. But since I had the option of running new wires, I decided to save costs and go with a fairly low-tech solution.
- I installed cheap wired magnetic sensors into the frame of each window.
- Each window sensor is connected to a KNX input push button interface which exposes the state of each sensor to the KNX bus.
- The KXN part is not necessary, those sensors can be connected directly to Home Assistant for example via ESPHome. In my case, the KNX wiring was already going to be installed in every room, so it made sense to plug into that.
Motorized curtains
The use case of motorically closing curtains has also many expensive solutions on the market. And then there are some fairly cheap ones. I didn’t find many practical differences, so I opted for one of the cheap ones, specifically Dooya.
- Dooya offers models supporting various wireless technologies for controlling motors.
- In my case, having the option to go wired, I went with DT82TN.
- Documentation is sparse. TLDR; it has an RJ11 connector that uses 3 pins: common ground, open and close. To open a curtain, connect the open pin to the common ground. Similarly, for closing, connect the close pin to the common ground.
The motor provides movement, but the curtain also needs a track to move over. There are plenty of Dooya (Aqara) compatible tracks online.
To control the motors, I’m using KNX relay actuators.
Yes, but: Relays are overkill as they are meant to connect 230V and all I’m doing is closing a low-powered control circuit. The relays are also fairly noisy and you do hear clicking sounds when they connect. There are better ways to do this, but I found used relay actuators on eBay and they turned out to be the most affordable option.
Ideas for automation
- Send an alert when it starts raining and a window is open (see next chapter for rain detection).
- Open/close curtains automatically when the door is opened/closed in the morning/evening.
Future projects
- Stop AC or send an alert when AC is running and a window is open. Ideally, an opened door should also trigger this. However, I don’t have door sensors installed right now.
- I’d love to explore motorized windows. Although when I briefly looked into this, it sounded like a rather large investment that may make sense only for new constructions.