This is the power supply board (including relays) for the touch switch plates that I made for Livolo.

The project complements the previous touch switch plates that I made a long time ago providing a full solution for creating a custom in wall RF switch which works with no neutral line.

NRF52832 Touch Switch 1ch

NRF52832 Touch Switch 2ch

The project is based on the DER-622 design from Power Integrations which is free to download and study in order to understand how it works (schematic is available also). There's also another one called DER-832 which is more recent and a little bit improved.

Although there is a possibility to use loads that draw several amps I don't advise you to do so because it wasn't quite designed for it.

Saying this because of the heat dissipation and pcb traces.

Max current that can be drawn should be limited to 1.5 - 2 amps.

The touch sensing board including radio/mcu must not draw more than 8-10mA on average.

This can be achieved theoretically via the built-in dc-dc converter of the NRF52xxx IC.

The output capacitor (C3) of the 3.3V LDO must be increased to 220uF (case B tantalum - yes, it can be soldered over the 0805 footprint) if instability is observed. Also a 0.22 - 0.47uF AC rated capacitor (275Vac) must be placed in parallel on one of the light bulbs (can be avoided only if the front board draws 1-2mA max - this can be achieved only if used with a Bluetooth LE project - I'm sorry but these are the laws of physics).