Blog Post

Surprising and Versatile - the KNX A3-B2 Control Module for Door Drives

Published on 14 Nov 2021 help


Having a son-in-law that is an electrician is mostly helpful, sometimes too helpful. Recently, we purchased a new house and as we were away when the sale went through, the family decided to go take a look. The remote control was a bit iffy and we managed to set off the alarm, and of course, no one knew the code to turn it off. 

How would any self-respecting electrician fix that?  - of course, you say - he would break in, unplug the battery and disconnect the power supply. So there was no more alarm noise, no more alarm, and no more garage door opener! 

Hmmmmm - of course, I could factory reset and reprogram the alarm but where would be the fun in that, besides the Elsner A3-B2 KNX has been sitting on my desk calling me for a month now. Why not connect it to my KNX system and through that to my Basalte Home Server, then I can control it from my phone and write heaps of logic functions so it can do all sorts of things automatically. My wife says she just wants it to go up and down via the motor and she is a little miffed at having to wait 12 months for me to get around to doing it but I think the result is spectacular.


The Elsner KNX door module is a real surprise packet! 

The Elsner door module has three outputs that can be set as "Defined Open/Stop/Close", "Pulse Mode" or "Deadman Mode" and two inputs that can be set as "Switch, Changeover Switch, Shutter, Blind, Awning, Window, 8-bit Encoder, Temp Encoder, Brightness Encoder, or Scenes". For the status of the door, I used one of the inputs on my door module to connect a small reed switch about 200mm in front of the door motor with the magnet glued to the chain drive.

The module itself sits in the ceiling behind the GPO with a small discrete piece of 4 core security cable coming down to the motor support. One pair connects to an output set to pulse to open/close the door and the other pair to the reed switch. It's all very discrete. I know you can do this with a security system but if you are like me and don't have a security system and you see the value of having as many of your field devices as possible living in the one reliable and robust KNX ecosystem then this is a really cool device. I can input information to the bus in multiple formats and configure the outputs in multiple formats. Sometimes it is just the right device and sometimes it is a great get out of jail card.  

I am going to show my age here, many years ago I had to write code into a minder system to control a car turntable that was in an awkward position. If the client didn't get the car in the right spot and the turntable rotated it would crush the very expensive car against a sandstone wall. No pressure on me at this point. In the end, I did it by making the remote function in "dead man mode" with a couple of sensor inputs. Where were KNX and the Elsner A3-B2 KNX door module when you needed them?

In my current situation, I am only using it for a couple of things. It checks the status and ensures the garage is closed at night. It checks in with the movement sensor and the weather station and closes the door if no one is in there and it starts raining. If we are both out and the door is left open it will shut and most importantly I can use it to open the door when the wine delivery arrives - yes I do live on acreage in the Hunter Valley. When I get my gates up and running I will use one for that as well as my machinery shed when I get to it. Everything is robust and together on one bus.