@aproxx said:

Hi all,

After spending a few months on this forum and a few prototypes later, I decided I wanted to build a small but cheap PCB which could be placed in either the wall behind the light switch, or above the lamp.

Besides the boards I've seen on this forum, I wanted these boards to contain a module to go from 230v AC to 5/3.3v DC in order to power an Arduino nano and the NRF module. I eventually ended up with a PCB which is about 4 by 4.5cm. So with all components attached I'm hoping to get in stuffed in a 5x5x3cm plastic printed case.

Modules which I've used to power the board:
[http://www.aliexpress.com/item/5-pcs-HLK-PM01-AC-DC-220V-to-5V-Step-Down-Power-Supply-Module-Intelligent-Household/32319202093.html?spm=2114.32010308.4.19.8oKfZg

UPDATE: 2015/09/18
As promised, I've got an update for this project. The board has been tested in the past week, and everything is working as expected. Compared to the previous board I've posted, I have updated the following:
• Solder pads of LE33CZ have been placed a little wider apart to avoid short circuit while soldering.
• Solder pads of the resettable fuse (Fuse2) has been placed closer together to better fit the fuses of the BOM.
• Moved the NRF24L01 connector a bit away from the solid state relay. Should make it easier to solder.
• Moved Fuse2 to another location on the board, away from the 230v circuit.

Some 3D pictures (Top and bottom):

Anyone who is interested can order the PCB HERE

Some documentation, complete list of required components and all gerber / DipTrace files (in case you would like to make some modifications) can be found here: MySensors board v3.2.3.zip.