Controlling Air Vent via KNX an

Hi community,
i want to control an LTM Air Vents which is connected throgh a KNX Analog output (0-10V).
Therefor i have created the following sitemap and item definition.
Group item=gLueftung label=“Lüftungsanlage” icon=“fan”
Frame label= “Lüftungsanlage”
Selection item=Lueftungsstufe mappings=[41=“Thermo 1”, 30=“Thermo 2”, 26=“Thermo 3”, 57=“Entlüftung 1”, 70=“Entlüftung 3”, 86=“Entlüftung 5”]

Dimmer Lueftungsstufe “Lüfter Modus” (gLueftung) { knx = “5.001:4/4/20”}

The different numbers in the mappings on the sitemap equals to the percentage i want to sent to the analog KNX Aktor, meaning f.e. 86 = 86% = 8,6V. if i choose a mode in the selection, the event file seems quit good,and also changes if i try diffrent modes but nothing seems to happen on the KNX bus. Other KNX Switches/Dimmers etc. work a desired. As i am a absolutly NEWBIE to openhab, i appreciate any help !
2017-12-21 19:50:29.969 [ome.event.ItemCommandEvent] - Item ‘Lueftungsstufe’ received command 86
2017-12-21 19:50:29.999 [vent.ItemStateChangedEvent] - Lueftungsstufe changed from 70 to 86

firstly, please use Code fences for your Code (``` start and beginning - or just click the neat icons on the right).


  1. is your KNX setup already and working the way you describe? (meaning working with your touch sensors, or whatever pure KNX-tech?)
  2. do you have the KNX binding running and working for other actuators?

from the first looks it seems, your item gets updated within openHAB, but won’t update the KNX bus? so could you:

  1. post your knx.cfg
  2. are there anything knx-relevant entries in openhab.log?

Hi, Knx is working within openhab, light switches, dimmer, charts, so the binding for knx is good. I use Knx for years now, only openhab is new to me. There are no errors in the opehab.log if i start a selection for the air vent control…

I meant, is your LTM Air Vent working outside openHAB with those KNX telegrams? do you have a running ETS and can you record the KNX Bus while trying to change your vent?

Yes, the Ltm Air Vents working properly with the KNX. I use Siemens Contouch KnX Displays to sent Values for every vent Mode, which works perfect. The Value the Sensors sents out is 8 Bit unsigned (percentage) - EIS6. The analog actuator works 0-10V -> 0-100% .every Vent Mode got his own Voltage spectrum f.e. 5,7V is one mode. Between the different modes are 0.7/1V

in openHAB, to be precise! :wink:

Actually i do not know how to record knx bus in openhab, but i will figure out :slight_smile: (hints welcome) Seamless in ETS Budmonitor and openhab is not possible as i do not have an router, only a simple ip interface to the knx bus. Will try to monitor knx bus tomorrow if u figure out on how to…

hmm… If you can’t start ETS Busmonitor and openHAB in parallel, it’s getting a bit more complicated, but we’ll manage.

  1. I guess, you’re just using the KNX binding?
  2. if so, you can install “knxd” on your machine (next guess, it’s a Pi?)
  3. after having installed knxd, you can monitor the bus via knxtools and vbusmonitor:
$ knxtool vbusmonitor1 ip:
$ LPDU: BC 11 17 00 19 E1 00 81 3C :L_Data low from 1.1.23 to 0/0/25 hops: 06 T_DATA_XXX_REQ A_GroupValue_Write (small) 01 
$ LPDU: BC 11 17 00 19 E1 00 80 3D :L_Data low from 1.1.23 to 0/0/25 hops: 06 T_DATA_XXX_REQ A_GroupValue_Write (small) 00 
$ ^C  <- from user to stop it

you should be able to see, what goes on on your bus, especially what openHAB sends.
You can then compare openHABs Messages with the ones from your SIEMENS displays.

shame on me, but while i was playing around in the ETS to revalidate the percentages of the fan modes i recognized that i had a transposed numbers in the middle of the group adress of my analog actuars group . Actually as i fixed that in the items file my air vent controll works just perfect, took me 4 hours to figure that out, but wihtout your hint with the busmonitor i would not have obened ETS so far, so thanks anyhow for your help Thomas

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No prob! Great to hear it works now