I have a pair of two-way switches at different floors to control a light bulb. I wish to put an Android-phone-controllable external switch over either switch to flip it up or down. I am familiar with the programming and circuit side, but the problem is I couldn't find any mechanic part to do the external switch's job like mentioned above.

The reason why I'm not going wiring over the original switch is because my mother isn't familiar with smartphones, so I want to implement it without interfering with the basic usage.

  • 2
    $\begingroup$ I'm not sure why you're ruling out a wired-in solution—if you have two switches for the same bulb, you already can't rely on the position of any individual switch to determine whether the bulb is lit. I think Dave's solution is the way to go. $\endgroup$
    – Air
    Dec 28 '16 at 17:40

You don't really want an "external case" to mechanically switch one of the existing switches.

What you really want is a DPDT relay that your Arduino (or whatever) controls, and wire that into the circuit as a third switch. Here's a diagram that shows what I mean:


  • $\begingroup$ or replace one of the 3-ways with a manual DPDT and append a relay with the normally open contact on one traveler and the normally closed on the other. $\endgroup$ Jan 2 '17 at 12:00

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