9

I have a set of lights that are controlled by two different switches. Flipping either switch at any time always changes the state of the lights (on to off or off to on).

I have OCD and so I want both switches to be in the down position when the lights are off. Right now the lights are off whenever the switches are pointed in different directions, and the lights are on whenever both switches are in the same direction.

I remember playing a "game" as a kid with three-way switches (that controlled the stairway lights) where by running up and down the stairs I could change the order for which the lights would turn on. Is there an "algorithm" for the order with which to flip the switches in order to get to my desired state (both switches down = off), or do I need to physically go and remove the wall plate to rotate one of the switches? If so, which one?

Currently:

Switch A Switch B Lights
DOWN UP OFF
UP UP ON
UP DOWN OFF
DOWN DOWN ON

Desired:

Switch A Switch B Lights
DOWN DOWN OFF
UP DOWN ON
UP UP OFF
DOWN UP ON

If this is a better question for StackOverflow, please let me know.

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  • 2
    You can't get the state you want without changing the wires. Or as one of the answers says, turning the switch upside down - but don't do that.
    – Glen Yates
    Apr 1, 2022 at 18:10
  • 2
    Why not turn it over @GlenYates ?
    – jay613
    Apr 1, 2022 at 18:13
  • 1
    I would be worried that it would involve to much twisting of the wires, better to undo a couple and connect them right. Also, all your switches should be installed consistently, "professional and workman like manner" as the code says.
    – Glen Yates
    Apr 1, 2022 at 18:18
  • 2
    @A.I.Breveleri another option is to go for some of the "smart" switches that can communicate with each other one, and change state if another is toggled. These probably lack a tactile flip-switch, though I recall old electromechanical ones that could clonk-out the opposite switch(es) if any one was toggled.
    – Criggie
    Apr 3, 2022 at 8:25
  • 3
    At least here (Bulgaria, EU) the code mandates that all switches down absolutely should turn all lights off.
    – fraxinus
    Apr 3, 2022 at 19:03

6 Answers 6

16

Don't make it harder than it is lol.

Pick either switch. Flip it over.

3-way switches are symmetrical. They do not have an "on" and "off" legend.

So no wiring is needed. Remove the cover plate, remove the 2 screws attaching it, feel to see which direction it will flip the easiest given the wires attached, flip and screw it back on. Be careful that the ground wire doesn't hit the side screws.

Only flip one switch.

I have OCD and so I want both switches to be in the down position when the lights are off.

Me too.

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  • 3
    I performed a switch-flip first thing when I moved in. Well, 2nd thing, after I'd found and opened the appropriate circuit breaker (or fuse YMMV). Must de-energize!
    – waltinator
    Apr 2, 2022 at 18:29
15

Swap the travelers at one end

Pick one of the two switches involved, and with the power off, swap the two traveler wires so they land on the other traveler terminal on the switch compared to when you started. This will fix your "cross-ways" three-way switch. (Just don't mess with the wire connected to the differently colored hot screw on the switch, as that's a common wire, not a traveler.)

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  • Alternatively, if it happens to be a four-way (DPDT) switch (I've seen four way switches used this way; a four-way switch with just three connections is basically a three-way switch), you can just move the single wire to the other connector.
    – SQB
    Apr 4, 2022 at 7:54
7

Two approaches:

  1. On the switches you SHOULD have two terminals in one color and one terminal in another color. Not all switches are built this way. But if you do, just on one switch swap the two wires connected to the same-colored terminals. (Ignoring the ground terminal, that might be green or brass, and will have a green or bare copper wire attached or no wire attached. IE, besides that one, there should be three more and two of them might be the same color.)

  2. Physically turn one switch upside down. Hopefully you can do it without disconnecting any wires, but if any are too short or too awkward to twist around the rest, disconnect only what you must to be able to turn the switch upside down, then reconnect them to the same place they were. In case your switches are marked with a "Top" and you wonder if that matters, this Question might help (but not very much).

7

To explicitly answer your question here:

Is there an "algorithm" for the order with which to flip the switches in order to get to my desired state (both switches down = off)

No. Here's why:

Let's call down D and up U. We can represent each state of the combined two-switch system as a node in a graph:

  • DD (on)
  • UD (off)
  • UU (on)
  • DU (off)

From any state, either switch can be flipped to cause a state transition (eg. DD–>DU or DD–>UD). Likewise, after flipping either switch, one can flip that same switch again to transition back to the original state (eg. DD–>DU–>DD). This makes the graph a symmetric directed graph. So, if the nodes as listed above are arranged clockwise on the corners of a square, then the graph's edges trace the edges of that square.

Your problem asks to starts at a state in {DD, UU} and perform an even number of transitions to reach a state in {DU, UD}, so that the original on/off state will be preserved by the end of the sequence. Note that both {DD, UU} and {DU, UD} are states at opposite corners of that square. I'll skip a formal proof, but this should make it obvious that any sequence of such transitions will take an odd number of steps, and thus the on/off state cannot be preserved without changing some wiring.

3

Each switch is known as a "single pole, double throw" or SPDT. This means that the centre common terminal can be switched between the other two, known as L1 and L2. Wikipedia has a good diagram: SPST switch
As earlier answers have said reversing the connections to L1 and L2 on one switch will result in your light being off when both switches are down. However it will also be off when both are up and the light will only illuminate when the switches are positioned differently. The annoying positioning is unavoidable if you want two way switching without "something" remotely moving the distant switch.

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    Exactly that. With the regular SPDT switches, having the light off only when both are down, is an unachievable goal. It will be off if both switches are in the same position, or, if he turns one around as advised by others, if they are in different positions. I don't see either of those methods make his OCD any easier.
    – WooShell
    Apr 2, 2022 at 13:45
  • @WooShell See other answer re "switch flip".
    – waltinator
    Apr 2, 2022 at 18:32
  • It is achievable with the wiring in a typical 3-way circuit @WooShell... it would just not provide a very good UX. Apr 2, 2022 at 18:34
0

I solved this by using impulse switches and a impulse relay at the lamp.

This can also be a tremendous simplification of wiring, as there is only a single 'switched' line common for all switches.

I don't know if it's legal or otherwise acceptable in NA though.

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