I have an application to control some fluorescent lights in my kitchen. I can’t easily access the light fixtures to add a Sonoff Basic to them so I need to do it at the switch. However I live in a house that is over 40 years old so there are no neutral wires run to light switches. This makes using a wifi switch difficult. Nearby (within 30cm) I have a GPO but one can’t mix lighting and power circuits.
So I took a Sonoff Dual and isolated the relay contacts from the incoming Sonoff mains supply. It’s a fairly simple mod. The Sonoff itself will now be powered from the mains at the GPO and the isolated relay contacts will simply replace the rocker light switches. To add a manual on/off I have put two pushbutton momentary switches on the wall plate instead. These connect to the external button connections on the Sonoff board. The blue LED rings on the pushbuttons connect back to the wifi LED.
The Sonoff is to be placed in the wall panel behind the switchplate where there is a large cavity and wires placed in trunking inside. I will also likely duplicate the pushbutton for pairing just under the switch wall plate top cover so it can’t be seen and accidentally pressed.