This Arduino lights dimmer project is based on Doug Hitchcock’s comment: “I need to have a lamp dimmer that can “cascade” from one lamp to the next (up to 4 lamps). Basically, when you close a switch, ...

Replacing it gives you three routes: Use a two-gang dimmer to keep separate control and dim both circuits. Fit a one-gang dimmer and cap off the unused switched live, leaving the second circuit ...