Well the next step of my 3d printer is taking quite a while. Luckily I had a different project that I can report on. I am trying to place a set of wireless temperature sensors in my home, without breaking the bank. The goal is to create 4 sensors to connect to my home assistant for less then €50.-. Initially the system may be powered by USB or other power adapters, but in the future I want to look into making them battery powered.

Hardware

I have shopped around for a temperature sensor and a microcontroller with wireless module. I found the following items:

• The E104-BT5040U, a bluetooth/802.15.4 usb dongle.
• The BMP280, a temperature and pressure sensor.

With 5 of these dongles and 4 sensors could make my network.
Total costs, excluding some wire and soldering tin:

Software

For the software I will have to communicate with my home assistant setup in some way. For this I will use RIOT-os, which support the usb-dongle and the sensor.

The structure that is planned is to use 1 of the dongles as a gateway router, to which the rest of them will push their measurement data.
The nodes will communicate with each other and the gateway over 802.15.4 using 6LowPan and Coap.
The gateway is connected to a Raspberry Pi which converts the coap messages to MQTT which is understood by home assistant.
The full setup will look like this:

Next parts

Part2: Nodes explains how the nodes are made and programmed.
Part3: Communication explains how I get the data from the nodes into home assistant.
Part4: Casing shows the casings and mounting of the temperature sensors.