Most of the data is captured by two cheap RTL-SDRs (software-defined radios) that are set to listen to 433 MHz and 915 MHz radio frequencies. I use the open-source project [rtl_433](https://github.com/merbanan/rtl_433) to automatically decode the signals and forward them to an MQTT broker, which is a messaging server that services can publish and subscribe to. Other sensors run an MQTT client directly or expose their data through other means like a web interface that I poll.
The data gets collected by a central Python script that process and stores it in an InfluxDB database for "efficient" storage. The script also runs a web server that queries the database and exposes the data over an API to the dashboard at various dates and ranges. The dashboard is written in JavaScript / React using a simple chart library.
My biggest regret was using InfluxDB. It's a stupid database and I wouldn't recommend it to anyone. The documentation is confusing and I ran into timezone issues with `group by time()`. It also assumes the column data type is an integer if your sensor happens to send it a whole number at first and it won't let you change that. Their docs are bad. They dropped the SQL-like InfluxQL syntax for querying with a pipeline-like syntax called Flux in version 2.0. Debian's repos seem to be staying with version 1.x though.
