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I am installing a rectangle of 3 x 4 recessed can lights in the ceiling and would like to have 4 separate circuits where each individual row of lights can be illuminated by its own switch.

This means that the lamp in each corner would be lit if either or both of the switches for those rows are closed. Four of the possible combinations are shown here:

enter image description here

I looked at relays and multi-way switches but could not find an example of how the corner lights can be wired and still only use four switches.

If anybody could point me in the right direction, that would be great. Thanks.

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    Your last figure should be 1 & 3.
    – Scivitri
    Commented Sep 24, 2014 at 0:12
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    Sometimes you need to ask yourself why you want to do something and think about the why. Once you understand the why, you might see a better approach to meet your why.
    – diceless
    Commented Sep 24, 2014 at 3:08
  • Is it me or is this getting to the point where each light should just have its own switch? Lutron also makes a ton of lighting systems with wireless remotes or app ability... these are costly though.
    – DMoore
    Commented Sep 24, 2014 at 6:46
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    God help the person after you who tries to replace a light fixture or switch...
    – Grant
    Commented Sep 25, 2014 at 1:55

6 Answers 6

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The problem is, whenever you turn one set of lights on, power can go through that shared light into the other circuit. So each switch controls all lights. While it -might- be possible to make 2 light groups (1 common light) work the way you want with two 4-way switches back-wired through each other, you're asking for something even more complicated. Each switch interacts with 2 others, which means you'd need at least triple-circuit switches (likely paired 4-ways). I don't think they make those. Certainly not in home light switch form-factors.

This will be much easier if you start with home-automation tools. Most vendors make an in-wall module for a slave device; then you just need to install and configure smart switches to manage them. Or you could go for all wifi bulbs, and have the option of other light patterns if you wanted. And maybe even programmable color.

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There are a couple ways to do this, either with 3-pole single-throw relays or switches, or with 2-pole double-throw relays or switches.

Here I show the 3-pole single-throw method. I have drawn relays because I can't imagine finding approved 3-pole home wiring switches.

enter image description here

This is the 2-pole double-throw method. I'm sure you can buy approved DPDT home wiring switches.

enter image description here

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  • I don't know what it's like where the OP lives, but other than massive "supply changeover" switches i've never seen a DPDT switch intended for home wiring here in the UK. Commented Oct 7, 2022 at 16:42
  • @Peter Green: Legrand, Leviton, and Bryant all show in their catalogs DPDT switches suitable for home wiring. I think the Legrand is cheapest at $22 ea. Plus, OP will need a junction box that has 9 knockouts and the cubes for 14 wire-nuts or Wagos. Commented Oct 7, 2022 at 17:48
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Should be doable with relay logic.

  1. Switch one powers the center top light and the coils of two relays that do the top left and right corners.
  2. Switch 2 powers the left-center 2 lights and the coils of two DIFFERENT relays that power the top and bottom left corners.
  3. Switch 3 (once you correct your diagram per comments) powers the bottom center light and the coils of two relays that power the bottom left and right corners.
  4. Switch 4 powers the right-center 2 lights and the coils of two DIFFERENT relays that power the top and bottom right corners.

Each corner light has power supplied, independently, by two relays. The relay that is OFF will not feed power back to the light of the other relay on its circuit. If both relays are on, not a problem, the light is on with one, the other, or both on.

You will need eight (8) relays in total. Or just 4 relays with double, independent contacts (DPST), as I think about it further (one per switch, each pole powering one corner light.)

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  • Actually, I think four DPDT switches would suffice if one could find them in a suitable form factor. Tie the centers of each switch to one corner lamp, one NC contact to the edge clockwise from it, one NO contact to the edge counter-clockwise from it, and the other NO contact to AC Hot. Depending upon how a 4-way switch is constructed, it might be possible to modify it for the required operation, though such a thing wouldn't be suitable for permanent installation.
    – supercat
    Commented Oct 18, 2014 at 23:31
  • @supercat -- DPDT lighting/electrical switches do exist -- the Leviton 1282 is an example of such. Commented Apr 3, 2015 at 16:44
  • @ThreePhaseEel: Do you think my logic would work with four DPDT switches (and no relays)?
    – supercat
    Commented Apr 3, 2015 at 16:53
  • @supercat -- I'll have to write up an answer for that :) Commented Apr 3, 2015 at 17:17
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    @ThreePhaseEel: Unless I'm missing something, jpfreire's answer doesn't work without relays.
    – supercat
    Commented Apr 3, 2015 at 20:41
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You have not used switch n. 3

A better approach would be use it and simplify circuit logic:

Using 3rd switch

enter image description here

Not using 3rd switch

If you must not use 3rd switch, use Boolean logic (more switches will be necessary).

Boolean logic... can be achieved using Protoboard

boolean logic

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    Without relays to isolate the corners, this does not work. If a corner is connected to a side and an end, then turning on the side or the end will turn on all the lights connected to the corners - only one or two lights (the center of the end or side opposite the end or side you intend to be on) will ever be off.
    – Ecnerwal
    Commented Apr 3, 2015 at 18:29
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    If it was DC, you could use diodes and this answer would work. But the question is about AC overhead lighting which you're not going to wire on protoboard.
    – bobpaul
    Commented Sep 9, 2017 at 1:48
  • The requirement begins with being able to turn on each row independently. This comprises sixteen states for the lights. Using binary switches, you cannot signal sixteen states with less than four switches. Commented Oct 6, 2022 at 19:39
  • Once any of the corner lights comes on, all lights will be powered, because the corners are connected to each of the sides. Each corner will pass power to each of the edges that it's connected to, and power will cascade all the way around the room.
    – FreeMan
    Commented Oct 7, 2022 at 13:55
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What you're describing is called "scene lighting" and is customarily achieved using automation modules either at the switches or fixtures. Each of the four configurations you have shown would be its own scene, and you would program each automation module to respond as either on or off when each scene is selected.

I have use Insteon automation modules for a very similar purpose to what you describe. They're not cheap, but they are readily available and have the required regulatory markings so there's hope that you won't be excluding your house from insurance coverage if you use them.

You'll need to figure out exactly how your switches and lights are wired and then work out the most efficient combination of automation modules you need to achieve the scene lighting you are looking for.

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If you use low-voltage DC lighting (e.g. halogen), you can use the switch to switch DC power and use suitably rated diodes to provide power to the corner bulbs. You'd have to check the wiring in the walls can carry the required currents and take great care to isolate the DC side from AC.

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