I like home automation a lot. For automation purposes data must be collected. I also like open software. But mostly I do like my own data not being on any strange servers outside my home.

So my goal is to design a sensor node to gather mostly useful data, that can be used to automate everything in my home (like lights, heating, blinds, media etc). They should speak MQTT, so I can easily integrate them in my home automation server (I use home assistant).

For my first tries I used NRF24l01-modules, they are cheap and have low power consumption, but you need an extra controller and a gateway to the host system. In the last years the ESP8266s showed up. Cheap, with Wifi, own microcontroller and a growing software environment and community. Great! But they are power hungry and bad for battery applications. But there are ways to deal with it - more of that later ;)

Let’s summarize my objectives for this project.

• Battery powered (battery life better than 6 months)
• PIR sensor
• Ambient light sensor
• Temperature and humidity
• Not that expensive
• Small form factor