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I'm have this 3-way switch in my house, and there's an annoying "problem" that I'm sure anyone who's had 3-way switches knows about... I think it's best summarized by this definition of three-way switches below -- When you switch one switch, the other one doesn't change position.

Three-Way Switch: Three-way switches are always utilized in pairs. They allow the control of a light or receptacle from two different locations in the room, such as at two different entranceways. These switches necessarily do not include on/off markings, as the positions will change as the switches are used.

https://promiseelectric.com/3-types-residential-electrical-switches/

It's particularly annoying since "down" is usually off, and every night without fail I try and turn off all the lights and 50% of the time I'm wrong. I'm thinking there's got to be some electrical + mechanical solution to this. Has this issue been solved?

Here's what I have for the electrical diagram of a 3-way switch is:

3 way switch diagram

I'm asking if there's anything on the market that solves this issue, if there's a switch that's able to change its mechanical position based on an electrical input. The closest I could find online is this Stack Overflow post about a non-residential solution.

My electrical engineering with capacitors is seriously awful, but assuming a switch exists that allows you to toggle it with electrical pulse (such as a electromagnet or something to pull a switch in a specific position) how would I start about implementing this? I'm thinking that when one switch triggers, it sends a pulse to the other switch to tell it to trigger. Coming from the software engineering, I think this could be done with a microcontroller for sure, but I'm wondering if there's a purely hardware solution.

A solution would be given:

  • Switch A with position ON and OFF
  • Swtich B with position ON and OFF

Then:

  • If you flip Switch A to ON, then Switch B moves to the ON position
  • If you flip Switch A to OFF, then Switch B moves to the OFF position
  • If you flip Switch B to ON, then Switch A moves to the ON position
  • If you flip Switch B to OFF, then Switch A moves to the OFF position
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    \$\begingroup\$ A few points/thoughts: There are automation systems that use momentary buttons instead of switches (Control4, Legrand Vantage, etc.) to provide control of loads from multiple places. Is the problem you are trying to solve the up/down position of toggle switches relative to the load? Is it even a problem? "Down" is generally "on" in some countries such as the UK. Finally, adding some sort of mechanics to switches to enable positional state changes, while entirely possible (like motorized linear potentiometers (faders)), adds complexity and reduces reliability. \$\endgroup\$
    – JYelton
    Commented Sep 13, 2023 at 20:25
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    \$\begingroup\$ Possible duplicate/related: electronics.stackexchange.com/q/102808/2028 \$\endgroup\$
    – JYelton
    Commented Sep 13, 2023 at 20:27
  • \$\begingroup\$ Are your switches positioned such that you can't see the lights they're controlling? \$\endgroup\$
    – brhans
    Commented Sep 13, 2023 at 20:29

2 Answers 2

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What you need is an 'impulse' or 'ratchet' relay that changes state with a pulse input to its coil and reverts on the subsequent pulse.

In other words, it changes state on consecutive pulse inputs to its coil.

The application schematic is as follows:

enter image description here

The lamp is switched on with one push of either button and switched off on the subsequent push.

Here's an animation, courtesy Homofaciens.de, that gives an idea of how an impulse relay works.

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This should only be a problem if you can’t see if the lights are on or off from where the switches are.

You can buy three way switches with indicator lamps that will tell you if the circuit is on or off. If you go to turn off the lights and the lamp on the switch is not lit you know they are already off.

The downside to these is that you will probably need to get a qualified electrician to install them and rewire the circuit. You can do some research, search on ‘three way switches with pilot lights’ and see if they look like they’d solve your problem.

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