Controlling multiple Homematic Dimmer as a group via a slider or Alexa

Setup, Configuration and Use Beginners
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1

I have three Homematic-IP dimmer (HmIP-BDT and HmIP-PDT) in openHAB 3.01 (openHABian 1.6.3, Raspi 2) working perfectly well individually and in an “Alexa-Group” with Alexa. However, grouping them in an “openHAB-group” and controlling this one group does not work at all.

Here’s what I tried and what doesn’t work for multiple reasons:

value: oh-slider-card
config:
unit: “%”
min: 0
scaleSteps: 10
max: 100
footer: Test
scale: true
step: 10
label: true
title: Licht Gruppe
scaleSubSteps: 5

Three problems with that:

  • Controlling the three dimmer via the Slider in WebUI works, BUT:
  • Although I can set the brightness to anything above 0% in WebUI, I cannot switch them off again by setting the slider back to 0%.
  • Whenever accessing the status of the group in WebUI, the slider is always at 0% (even though the lights are on)
  • Controlling this group with Alexa only controls the first dimmer in the group (see screenshot above), but not all three of them.

Reading in this forum I read multiple threads on the same problem (e.g. Lights - Dimmers and Groups - #4 by rlkoshak , Adding a Dimmer switch ( group? ) in a sub item in a sitemap - #7 by samverner777 , [SOLVED] Dimmer item behaviour with Group items - #3 by Nico111 , Trying to control multiple dimmers with one slider - #21 by Gufti or Hue group dimmer slider always set to zero - #2 by rlkoshak). However, since I’m fairly new with OH (and some of the solutions appear to relate to OH2) I have problems applying them to my particular situation.

Edit: The “0%-problem” appears to be covered here ([SOLVED]Struggle with Rollershutter HMIP-BROLL) as well for the rollershutter, but I’m still having problems applying this to my setting.

2

What is the type and the aggregation function for the group?

3

Dear @rlkoshak, thanks a lot for your response.

Your question guided me in finding the answer / solving the problem myself: Turned out the Type appeared to be correct already (“Group”), but it was the Members Base Type which i forgot to set (now “Dimmer”, which also sounds logical, so I could’ve found this out myself in the first place ;).

Screenshot from 2021-03-01 12-05-14
Screenshot from 2021-03-01 12-05-14774×462 17.6 KB

What I also found out: The aggregation function can lead to some pretty funny behavior with three dimmer, when set to “AVG” (–> leading to an endless loop of the lights powering up and down ;).

Thanks again for your help.

4

The UI widget is the badly-behaved part here, not your approach using Group with AVG

5

You could also use group feature from alexa if you don’t need them in OH. This won’t solve the grouping issues you’ve seen but it may be a solution for someone who don’t need them in OH.

Add all lights which should be controlle in that room to one group.

Group name: “living room”
“Alexa, turn of the living room lights”
“Alexa, set living room lights to 30 percent”
“Alexa, living room lights 30 percent”

You can still say something like:
“Alexa, turn off the couch light”
“Alexa, couch light 30 percent”

6

Thanks. I had it work that way before, and it worked perfectly well. Though I try to build things in a way to have the least amount of “logic” in Alexa, since I’m considering switching to another voice-controlled system in the near future.