Selecting the right BLE module for your project

Bluetooth Low Energy is becoming more and more popular for sensor applications.  It not only needs much less energy than normal Bluetooth interfaces, even the transmission rage is longer. It isn’t design for huge data transfers, but that’s often not needed.

Unfortunately almost none of the popular development platforms (Arduino, ESP8266) comes with BLE onboard. This isn’t a big problem as there are many BLE modules available.

However, make sure you read the documentation of the module before ordering it.


I just received this small and inexpensive HM13 module. I wanted to use it to read data from a BLE plant sensor. Unfortunately when I checked the documentation I noticed that the firmware on this board is designed for serial data transmissions over BLE. It seems you can’t use it as a general purpose BLE interface.

Therefore check the documentation of a module before ordering to make sure the module supports the features you need.


Home Assistant: Logging to a central server

As the Raspberry Pi is relatively cheap, you might think: Why not having multiple Home Assistant installations running in my house? This gives you some advantages:

  • You might monitor temperature and humidity in different rooms.
  • If one instance fails, the other can still do the same job.

However, even with multiple HA instances, it might make sense to have the sensor data logged to a central instance. This makes data analytics much easier.

I use InfluxDB to store the sensor data. With our latest patch that will be included in Home Assistant 0.25, it is now possible to distinguish between the data from the different HA instances.

The logging configuration on the two HA instances would then look like this:

    instance: living_room
    instance: balcony

Grafana: Useful plugins

grafanaGrafana is a cool data visualisation tool. You can even improve it by adding additional panels and plugins. The whole plugin directory can be found here:

I recommend the Histogram panel. Unfortunately you can’t do it directly from the GUI (at least not in the current version 3.0). However, installing on the Raspberry Pi is relatively simple:

cd /usr/share/grafana/public/app/plugins/panel
sudo git clone
sudo service grafana-server restart