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I have a ceiling light fixture with 2 bulb sockets. Right now it's controlled by a single 2-way switch (on/off).

My idea was to install a 3-way (or possible 4 but not necessary) switch that can control each bulb independently. The point to that would be in being able to individually control two contrasting bulbs, ie: 1 5000k and 1 2700k to set different 'scenes' if you will.

States:

  1. position 1, bulb 1 on, bulb 2 off
  2. position 2, bulb 1 off, bulb 2 on
  3. position 3, bulb 1 off, bulb 2 off

Ideally I'd like to be able to do this without pulling the wiring or adding an additional wire and to instead mod either either access point (light switch or light fixture).

Logically speaking, one can get 4 states with 2 wires (00,01,10,11) so it stands to reason that it is possible but would be a matter of what components to use and if there are off-the-shelf solutions.

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This blog post might be helpful. –  Tester101 Feb 5 '13 at 19:44
    
That definitely has a lot of good info but I'm looking for somewhat of an unorthodox configuration. –  Enigma Feb 5 '13 at 20:06
    
What I was trying to point out, is that you won't be able to do what you want using a stock 3-way switch. Your best bet might be to create some form of wireless control mechanism (or find one commercially available), and use that to turn the lights on and off. –  Tester101 Feb 5 '13 at 20:14
    
I did think of that but could I configure it along the same lines as how an H-Bridge works? ie, taking the direction of the current into account, I could use that as a single wire switching system... maybe –  Enigma Feb 5 '13 at 20:16
    
mhm.. overlooked that - isolated phase-shifting? that might be kind of ridiculous though making wireless seem like the best option. other possibility would be to rectify the ac into a + and - dc perhaps –  Enigma Feb 5 '13 at 20:21
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1 Answer

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Your Plan

Your analysis about two wires makes an assumption that is forbidden in residential electrical work. One of the wires in a standard fixture is the neutral whose state cannot change. It must always be connected to the other neutrals in the system, connected to the main electrical panel and ultimately to ground. If 1 reresents connected, the white wire is always in the 1 state.

The black, or hot wire can be connected or not. Similarly, in a three wire system, the red wire, as well as the balck, can also be used as a hot wire and can be connected or not, depending on the state of switches. In a three wire system, the white still stays connected all the time.

How to do it

If you want separate controls, you need a separate wire to power (carry the hot current) to each bulb. A single neutral (white) can be used.

Hot wire originating at switch

If the power is presently comming into the switch box from the electrical panel, and then being routed to the fixture, the standard way to wire this would be to run a three wire cable (white/black/red) from the switch to the fixture and to use a double switch, such as this type.

double spst

The white wire coming from the panel is connected to the white wire going to the fixture. The black wire coming from the panel is connected to the incomming sides of both sections of the switch. The black wire to the fixture is connected to one of the outgoing terminals and the red wire from the fixture is connected to the other outgoing terminal (outgoing because the power is coming through the switch and going out to the fixture).

Hot wire originating at fixture

If the power comes directly to the fixture, and there is just a two wire cable going to the switch, you need to run a three wire cable to the switch. The white wire will actually be used as a black/hot wire to carry power to the switch. It needs to be marked with black tape a both ends to show this. At the fixture this pseudo black wire is connected to the black hot from the main panel. The real black is connected to one bulb and the red to another bulb.

At the switch, the white (now marked black) is the incoming line to both switches and the red and black are attached separately to the outgoing terminal on each switch.

In either setup, the switches are independent. You can turn on either, both or neither.

There are double throw switches that would allow you to have one or the other or neither, but not both. You still need the three wire cable at the switch site.

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Does a wireless state (3 states) replication switch exist? ie, if I click state 1 on the switch, it will wirelessly transmit that state change to a receiver switch in the light fixture? –  Enigma Feb 5 '13 at 21:04
    
@Enigma There are numerous wireless systems that involve placing receivers in the fixture and a wireless remote, either handheld or wall mounted. See these examples. –  bib Feb 5 '13 at 21:18
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