I needed a cheap, small reliable presence sensor that incorporated temperature and luminance to trigger lights and was fed up of the time out on normal motion sensors which would leave the light on after leaving the room for a set amount of time.

Electricity costs are high in the UK.

Wemos D1 mini, small and reliable board.

LD2410c is a cheap reliable and responsive sensor.

BH1750 is fairly accurate and can be calibrated easily in ESP Home. (needs a 4.7Kohm resistor on most EPS8266 D1 mini boards).

DS18B20 is a very cheap and also accurate and can be calibrated easily in ESP Home.

The temperature sensor was incorporated to control ceiling fans that are controlled by an RF remote signal.

ESP Home was used as it is easy to program and easily used in HomeAssistant.

I 3D printed a small case with a corner bracket to attach to it.

Can be powered by USB or JST (or any other 5V connector) depending on your case design.

Is expandable as GPIO pins are accessible via the optional second set of headers.