How to access a list of historic state values for an item?

[franks (Frank Seidinger)]

Hi there,

is there a way in openhab scripts/rules to get a list of historic items between a given time interval? I would like to get all data of an item for a given interval and do some calculation.

I tried the PersistenceExtension. But this API let you only get a specific value or a predefined aggrate function.

Kind regards,

Frank

[rlkoshak (Rich Koshak)]

The short answer is no, there is no easy way. You can use the REST API perhaps but there is nothing built in to get anything but the functions provided by the PersistenceExtension.

[rossko57]

@franks

and do some calculation.

Maybe if we knew more about this. You can, for example, request data for each minute (or hour or whatever) across a period from a loop in a rule.

[franks (Frank Seidinger)]

@rlkoshak

The short answer is no, there is no easy way. You can use the REST API perhaps but there is nothing built in to get anything but the functions provided by the PersistenceExtension.

I already thought so, that there is no easy way to do this. The REST API might be suitable but it feels strange to use the REST API from a script inside OpenHAB.

The only possible alternative I can think of is using the PersistenceServie or to be more precise the QueryablePersistenceService, though I currently do not know how to get a reference on a persistence service from within a script.

[franks (Frank Seidinger)]

@rossko57

Maybe if we knew more about this. You can, for example, request data for each minute (or hour or whatever) across a period from a loop in a rule.

I bought one of these guys: Rain Gauge Model RG-11. I configured it to simulate a tipping bucket and feed the signal to my KNX binary inputs.

I would like to implement the following functionalities with it:

1. Count the tipping bucket impulses and sum them to get the total tipping bucket count.
2. Scale the tipping button count with a factor to calculate the total amount of rain fallen since the counter was last started/reset. In my case the factor is 0.001 mm rain per tick.
3. Calculate the amount of rain fallen for at least the last hour, the last day and the last month as derived values.

The functionality 1. I’ve already solved by feeding the tipping bucket pulses to my KNX binary sensor configured as a counter. So summing the pulses since last device start/reset is already available. I’ve gone this way because the pulses are coming fastest with 50 ms pulse width and I thought that this will maybe to fast for feeding them directly to a contact switch on OpenHAB.

The functionality 2. and 3. would be easy when the counter never gets reset. Then you only have to take the minimum and maximum value of a given time interval and calculate the delta.

But here lies the rub. If the counter gets reset at least once in the given interval, the simple calculation does not lead to the correct result. You have to find the resets and calculate the individual intervals for that.

To give a better understanding I made the following example. For simplicity I only took the counter part and I want to have the total count at 01:00:00 o’clock for the last hour. If using the minimum and maximum difference, I get 12 - 0 = 12 as the total count.

But taking into account that the counter was reset at approximately 00:34, I get the two intervals with 0 to 10 and 0 to 12. This will lead to the total counter value of 22 in the last hour. And this would be the correct value.

Greetings

Frank

[rossko57]

@franks

because the pulses are coming fastest with 50 ms pulse width and I thought that this will maybe to fast for feeding them directly to a contact switch on OpenHAB.

It probably is. That’s a shame, because if you had a persisted series of ‘pulse’ much else becomes easier, just sum over time.

Any value in a divide-by-ten or similar, send an event to openHAB every tenth pulse?

[franks (Frank Seidinger)]

@rossko57

It probably is. That’s a shame, because if you had a persisted series of ‘pulse’ much else becomes easier, just sum over time.

Any value in a divide-by-ten or similar, send an event to openHAB every tenth pulse?

I went another way for this project now and described it in a new DIY topic under Optical rain gauge sensor connected to openHAB with rain fall calculation for 1h, 24h and 30 days.