Sum (and chart) all switched on lights

[Cyril Jaquier]

Hi all,

I'm experimenting a bit more with openHAB and would like to chart the number of switched on lights over time. I tried different things like:

Group:Switch:SUM(ON,OFF)    Lumiere_Chart    "Lumières"
or
Group:Number:SUM    Lumiere_Chart    "Lumières"

but "Lumiere_Chart" does not change its state. The persistence part is currently not a problem. I should see my "Lumiere_Chart" item getting updated. Here is the relevant part of my items:

Switch Lumiere_SS_Garage_Plafond    "Plafond"                (Garage, Lumiere_SS, Lumiere_Chart)
Switch Lumiere_SS_Garage_Etabli        "Etabli"                (Garage, Lumiere_SS, Lumiere_Chart)

So how do you do this? Thank you.

Regards,
Cyril

[Kai Kreuzer]

Hi Cyril,

Here is what you can do (based on the demo setup):

Add an item

Number NoOfLights

and make sure you persist it with rrd4j. Then create a rule like:

rule "Set number of lights"

when

Item Lights received update

then

NoOfLights.postUpdate(Lights.getStateAs(NoOfLights.acceptedDataTypes.get(0)))

end

The part "NoOfLights.acceptedDataTypes.get(0)" is only a workaround for "DecimalType" - out of some reason, putting "DecimalType" is not accepted here…

Now you can simply add a chart in your sitemap:

Chart item=NoOfLights period=D

That's it! Please note that as we use a number item, rrd4j does treat the values as floating point and not discrete numbers. That means that if you have 1 light on for 30 seconds and two lights for the next 30 seconds, you will see the line at 1.5 in the graph for this minute (which is the minimal resolution). But I think this should be fine for your use case.

Best regards,

Kai

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[Cyril Jaquier]

Thank you Kai. I will try your solution. This is actually just a test so the 1.5 is fine.

However, I would have expected to be able to do this without any rules. Could you tell me if this is possible? Or said differently, could you explain or point me to some documentation about the expected behavior of Group:Number:SUM, Group:Switch:SUM, etc?

A detailed documentation about the items and sitemap file syntax would be of great help ;-)

Regards,
Cyril

[Kai Kreuzer]

Hi Cyril,

However, I would have expected to be able to do this without any rules. Could you tell me if this is possible?

Not in the past, but now it is - I have just pushed a change that makes this possible: https://code.google.com/p/openhab/source/detail?r=5f026f2f38e156c3df8678f9bd94f38f7cb2c476

Using a Group:Number:SUM should give the result you are asking for!

Best regards,

Kai

[Cyril Jaquier]

Hi Kai,

That's good news :-) Thank you. I will give it a try.

Regards,
Cyril