ESP32 nodeMCU connects to WiFi and MQTT broker, syncs time and sends DHT22 temperature and humidity sensor data in JSON format via MQTT.

My setup:

The data is send to my Mosquitto broker which runs on Ubuntu 18.04.02 LTS. For visualisation and smart home hub I use Grafana and Openhab2.

In Openhab2 I defined items for the temperature, humidity and battery voltage data. Each time the values are published in MQTT the server reads them and displays them on my sitemap.

To get a history of the measurements, the data will be saved to an Influx database in a defined interval.

This database is connected to Grafana. This allows me to create a dashboard to display the sensor data, create alerts and compare values with historical data.

In order to be able to interpret the data at a glance, the sensor data are displayed for the respective room. As soon as a threshold value for the air humidity is reached, an alert is sent via telegram with the hint to open the window in the respective room.