If you are an experienced electronics hacker and you want to do some tests with KNX, you need to invest a bit. However, a minimal KNX setup for initial tests doesn’t have to be very expensive:
- a 29V power supply that supplies at least 300mA
Most bench power supplies will do the job. For a test you don’t have to buy an expensive KNX power supply.
- a KNX choke
You can’t connect KNX devices directly to the power supply. A choke is essential. Without it, no communication on the bus will be possible. Standalone chokes starts at around 35€.
Another option is using a 47-Ohm resistor in between the power supply and your KNX bus line. While it might not work, it is worth a try as it will cost you only a few cent.
- a KNX sensor
If you have some push buttons laying around, a cheap KNX bus coupler from eBay might be the cheapest option. You can get these for less than 30€
- a KNX actuator
Some KNX sensors (like wall-mounted push buttons) have status LEDs that can be controlled from the KNX bus. In this case, you do not need a separate actuator. Otherwise have a look on eBay for old binary outputs. You should be able to find something for less than 30€
- USB or Ethernet interface
USB interfaces are usually a bit cheaper. You might find used USB interfaces in the range of 50-80€. However, I would still recommend to spend a bit more money and buy an Ethernet/KNX interface. You are more flexible with these as multiple devices can access it simultaneously. You might not be able to save a lot of money on a used one, but new Ethernet interfaces are available from 150€
This means, a minimal KNX setup will cost you between 200€ and 300€. This isn’t really cheap, but still less expensive than many people might think. The good thing: The most expensive component is the Ethernet interface. If you decide not to go on with a full KNX installation, you can still sell it for a good price. Otherwise, you can use this in your house installation.
The minimal installation looks like this: