POPP Z-Rain (700168) immediate notification on rain?

I have a Popp Z-Rain device and several questions:

  • The measurements are updated every approx. 4 minutes if there is a change. This is as described in the manual.
    I would like to get an immediate notification/update when it starts to rain (open windows…) and not have to wait up to 4 minutes. This seems to be possible via association groups, but I don’t know how to use them. Should I add the main controller to the association group 2? How can I get an item updated from there so I can use the immediate update in a rule?

  • What are the 3 measurements sensor_general, sensor_rainrate, meter_water_cubic_meters meaning exactly?
    What unit (mm, mm/m^3,…)?
    sensor_general seems to upcount by 0.5 per seesaw dip and not resetting to 0.
    sensor_rainrate is upcounting by 7 per seesaw dip and resetting to 0 if there is no further dip after 4 minutes.
    meter_water_cubic_meters is upcounting and not resetting to 0. It is the same value as sensor_general, but with a scale of 1000 (when using default config meter multiplier of 1). So f.e. sensor_general shows 167.5, meter_water_cubic_meters shows 0.1675.

How are the measurements related to the configuration parameter “Rain counter” that is at 1305 fix (default config) here? Shouldn’t the Rain counter count up?

  • Is there an items/sitemap example that someone would like to share?

Maybe not enough moisture?

I don’t think so - until now, I have only tested it by moving the see-saw by hand.
It’s clear that it needs some rain until the see-saw moves and a notification could be sent.
So there is a first delay that can’t be changed and that’s okay.
But I would like to get the notification directly after the move, not up to 4 minutes after it, adding an additional delay.

If that is in the manual and a technical spec you can’t change it.
When I remember correctly that device is driven by solar power? That limits the available power a lot and therefore the device can only sent out data every couple of minutes.

The device is battery powered (the wind sensor is solar powered), but you are right, there is no config that could be changed.
In another thread, I saw that someone mentioned the association group 2 which could be used to notify immediately on the first dip. So maybe my question is more related to association groups.
As I understand it, they are normally used for alarm notifications between devices without main controller interaction.
But can they be used for setting variables/items so I can trigger a rule?

Association groups are used to send notifications directly to other zwave devices without the interaction of the controller (and therefore openHAB).

I did not try this, but do you by any chance have an unused channel from a zwave relay or some other double equipped, unused device?
You could try setting the association to that device channel and then trigger on those received events.

Good idea, I will have a look for that.

For measurements and scaling, I have contacted POPP directly. I will report if there is something new…

I have one of this devices.

A question which I had to chris was, how to catch messages send to association group 2 by a item: This was not possible. I have a workaround and use a rule to device if heavy rain or normal rain.

But you are still limited to the 4 min interval, right?
Or (how) do you use the association group 2 message?

yes, it need a amount of rain for the seesaw. Then the item is triggered with the current rain mm/h.

I use a rule and if the item reaches 45 heavy rain is detected and I do addition things.

I use an proxy item in additional to store raining information there. Because if it is raining not so much, the seesaw will not detect this in the next interval and will send 0 mm/h. So I wait for 2 additional intervalls and if all three are no rain, it is really no rain :wink:

Okay, so I will have to test if the speed (max. 4 min) and the resolution of this rain sensor is okay for my purpose (rule and notification to close windows on the roof).

I also have that sensor in my environment and had some questions about the rain measurement. So I contacted POPP support because I always saw a rain rate in multiples of 7 measured.

That seems to be by design, I will citate POPP support here where they explained the rain rate measurement. The conversation was in German, hope that’s no problem:

die angebenen Werte von 0,7mm/h sind korrekt und lassen sich berechnen.

Eine Wippe hat ein Volumen von 0,5 mm
Der Timer senden aller 256sec ~4.26 Min ein Signal dies entspricht ~ 14,08 mal pro Stunde

Rechnet mal jetzt 0,5 mm * 14,08  ergibt das 0,7 mm/h

Um den Regenmengenwert zu erfassen können Sie auch den Generic wert verwenden.

So the device is not really precise. It’s nearly impossible to get the real beginning of rain because the first message to OH2 arrives after the first move of the seesaw. And even if it continously rains I often get a value of 0 in between because the next triggering of the seesaw was not within 4 minutes.

So visualized in Grafana you get values like this:


I can guarantee that between 2pm and 3pm it was continously raining, so the measured values are “wrong”.

Regarding your question resetting the total amount of rain: that counter can only be reset by setting the value manually via zwave configuration.

Thanks a lot for this info - it helps understanding the sensor.
But I think the actual value is in 7 mm/h (as you show in the graph), not 0.7mm/h as mentioned by Popp, right?

So I will have to write a rule that sets “no rain anymore” only delayed, not if the actual value changes from >=7 to 0 once.
Even then another sensor might be more appropriate (if there would be one)…

I also got an answer from Popp:

Der Generic Wert liefert den Wert der Regenmenge ohne Einheit.
Der aktuelle gemessene Wert, welcher in 7 schritten angezeigt wird, trägt die Einheit mm/h. Der
Gesamtwert wird dagegen in m³ Angezeigt.

Der Rain Counter Wert zählt mit hoch, aber dieser Parameter muss  Manuel abgerufen Werden und
ist zum Zurücksetzen der Gesamtregenmenge gedacht.

Grundsätzlich ist die Funktion:
Ca 4 Minuten nach Regenbegin wird die erste Regenmenge (wenn die Regenmenge ausreichend ist
um die Wippe zu betätigen) gesendet. In dem Moment wird auch Regen beginn gemeldet.
Danach erfolgt die Meldung aller 4 Minuten mit der aktuelle Regenmenge. Wenn nach 4 Minuten
kein Regen mehr ist wird der Wert wieder auf 0 gesetzt.

Yes, it’s 7 mm/h.
But I think it’s difficult to write an appropriate rule for detecting the start or end of rain with that kind of sensor. With slight rain it’s nearly not possible to detect the begin of rain and you will have values of 7 every few hours.
Here’s another example of last night where it continously drizzled the whole night.


So I’m also thinking about using a different sensor because the Z-RAIN is not precise enough to visualize the real situation. My intention was to measure rain rates for statistical examination over all four seasons.
But for that purpose the sensor is not sensitive enough.
Another fact is that it is not really cheap for what it delivers…

Oh, one event every ~2 hours during continuous rain/drizzle - that’s bad…
With this resolution, this sensor is really only suited for detecting floods…

Do you know another sensor that works out of the box?
I have seen many sensors without controller+radio protocol, so you would have to build the complete device by hand.

Since I live in a dike area, flood detection might be of my interest in the future :grinning:

When it’s only important for you to detect start and end of rain, you should have a look at this approach:

But that’s a homegrown solution and doesn’t have the possibilities to track the rain rate.

Hi there, there is also a good rain sensor available in US - Hydreon Optical Rain Sensor. Seems to be quite clever device with fast response and able to track rain rate, not so accurately as Popp though. All you need is just some binary input. Unfortunately it’s not really available in Europe, so I decided to go with Eltako, as mentioned in above link.
Eltako uses very primitive resistance measurement principle, so it’s not able to detect rain, but triggers immediately as any drop shorts the traces on the PCB. What I also find good is that it heats the PCB continuously - it’s really warm - so the drops evaporate quickly and there is no problem with snow. Off-course it can’t work without mains for this reason.

My Popp does not give any values.

Number Rain_Sensor 			"Regn Sensor"				<rain>	(Outdoor, gPCR)  { channel="zwave:device:512:node23:sensor_general"}
Number Rain_Sensor_Rate 	"Regn Sensor Rate"			<rain>	(Outdoor, gPCR)  { channel="zwave:device:512:node23:sensor_rainrate"}
Number Rain_Sensor_Meter 	"Regn Sensor Meter"			<rain>	(Outdoor, gPCR)  { channel="zwave:device:512:node23:meter_water_cubic_meters"}

It is online.