Hello,
I am running a kind of this device https://www.stall.biz/project/robuster-sonnensensor-ganz-einfach and it worked like a charm for month. Main difference is: my two temp sensors are DS18B20 on a Wemos D1 mini.
Since some days I am receiving something like this:
Normally the green values were updated similar to the red values see here:
Any idea where I should search for a solution? I am thinking it might be not an openhab issue but maybe you can forward me to a fitting forum …
So… your Wemos D1 is sending to your MQTT Broker the messages, you are subscribing to the topics using OH2 Items and you persist their states using rrd4j ? These charts are from an OH2 sitemap element?
If yes: I would start looking at the comms between the D1 and the Broker. Maybe the messages are not being delivered reliably (loss of WiFi signal etc). Check the logs of the Broker for the time period where the OH2 items are not getting state updates.
Yes and Yes.
I will try to look for the mosquitto logs. Thanks so far
Are these two DS18B20 connected to the same Wemos?
Maybe a faulty sensor?
note: the logs won’t show you the temp values (the mqtt message payload). they will only show you connection info. You may want to increase the log level on the mosquitto broker to catch more info about the connection and publishing attempts.
set
connection_messages true
log_type debug
in your mosquitto.conf
maybe with debug log level you will be able to see the payload also… I don’t remember
Yes I am receiving connection lost messages …
Have to search for the reason
Maybe I was too fast. I am receiving (as expected) connected and disconnected messages, because of the deep sleep. But what I recognized now is that one sensor is not regularly sending its values. Sometimes it does sometimes not.
Do you think the DS18B20 is faulty if it is sending not all the time? Still searching …
update:
Just to have it complete here the setup:
Wemos D1 mini
connected a BMP280
and a DS18B20
all is powered with 2x 18650 Li Ion batteries charges by 2 solar panels. This setup was running for 3-4 month without issues
The wemos is in deep sleep mode and is sendig each 10 minutes the values to my mqtt server
I logged today my mqtt traffic and it was quite curious.
in the time I logged it was 108 times status message of the wemos itself (connected,disconnected, connection lost)
but only 29 times /each the values of BMP280 and
only 15 times the DS18B20 temperature.
Maybe you have an idea how or where to look for the issue even if it is ahint for a different forum 
The wemos is loosing wifi connection. Could be a number of issues.
I would try swapping the wemos with a new one. There are reports of ESP8266 loosing wifi after a while when the signal is weak
I will change it this week end. And lets cross fingers.