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I am trying to operate two AC current light bulbs with one switch so that while the switch is in the OFF position, bulb B1 is OFF and bulb B2 is ON, and while the switch is in the ON position, bulb B1 is ON and bulb B2 is OFF. Only one bulb needs to be turned ON at any given time and the other bulb is OFF.

Let me know how can I make this possible.

I would appreciate if you can provide any diagram.

  • 7
    Is there ever going to be a time when you will want both lights off? Or are you going to have eternal light? – A. I. Breveleri Jul 25 '16 at 19:58
  • I second A. I. Brevleri; this is not a good idea for the stated reason. – Joshua Jul 25 '16 at 20:18
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    In that case, a switch upstream of the 3-way would turn both off. – isherwood Jul 25 '16 at 20:19
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    I've done this for a reptile tank: daylight in daytime, heatlamp at night. Don't automatically assume he's talking about chandleliers. //IIn fact, I wired a timer switch to a DPDT 120VAC relay so it was automatic! – Carl Witthoft Jul 26 '16 at 17:46
38

A single-pole, double-throw switch would do the job. A common 3-way switch is exactly that.

You'd simply connect power to the common screw, and run power out from each of the traveler screws. All the neutrals tie together. Here's a nice animation showing the idea.

enter image description here

More on switch terminology

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Use a single pole double throw switch, called three-way in the U.S. (as isherwood suggests). Wire it like this and the circuit will do what you say you want.

strange request .1

Of course with this, there is no way to ever switch everything off, so the circuit will consume power as long as the building stands. We strongly advise you not to do this.

Instead, (again, as isherwood suggests) you should include a master switch to control power to the three-way switch. Here I've placed both switches in the same junction box.

[strange request .2

You may want a different layout.

Most people would look at this and say, if you're going to have two switches anyway, why not just wire each one to one light?

strange request .3

But if you have a reason to never allow both lights on at the same time, the second circuit is better.

This is probably the best advice you're going to get unless you want to explain more about your overall project goals.

EDIT: See curious_cat's answer for a switch that allows you to use the first circuit. This looks like the simplest and best solution.

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    Another option is to go for a Single Pole Triple Throw switch, right? Are those available commercially? – curious_cat Jul 26 '16 at 3:30
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    Yes, well, strictly speaking, a double throw with a center-off. A triple throw would work, but would have another contact screw, which OP would not use. - I have never seen a center-off switch designed for residential wiring use. – A. I. Breveleri Jul 26 '16 at 4:12
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    Alternatively this one: Leviton 1257-GY 20 Amp, 120/277 Volt, Toggle, Double Throw, Center Off, Momentary Contact, Single-Pole AC amazon.com/Leviton-1257-GY-Momentary-Single-Pole-Industrial/dp/… – curious_cat Jul 26 '16 at 4:48
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    Loved the bit about the urchin. :) Whatever works, eh? ;) – curious_cat Jul 26 '16 at 15:36
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    Diagrams drawn using MS Paint and a library of .bmp images. – A. I. Breveleri Jul 26 '16 at 21:24
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How about something like this product (Thanks to A I Breveleri for pointing me in the right direction):

http://www.leviton.com/OA_HTML/ProductDetail.jsp?partnumber=5685-2E&section=47084&minisite=10251

15 Amp, 120/277 Volt, Decora Plus Rocker Double-Throw Ctr-OFF Maintained Contact Single-Pole AC Quiet Switch, Commercial Spec Grade, Self Grounding, Back & Side Wired, - Black

enter image description here

enter image description here

enter image description here

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    Good find! +1. - That is a strange-looking device. I wonder what you press to select the center-off position? – A. I. Breveleri Jul 26 '16 at 16:29
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    @A.I.Breveleri To me it looks like a very flat switch with three positions: Top pressed in ; bottom pressed in; flat. You press towards the middle from either ON position to return it to its neutral state. I vaguely remember coming across switches like this in Germany. I could be wrong. – curious_cat Jul 26 '16 at 16:42
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    I have used one like these before. It should work. The largest annoyance is that selecting off is a bit weird. Sometimes, when your not paying attention you switch instead of "off". Other times you off instead of switch. – coteyr Jul 26 '16 at 23:37
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    In other words for lights that you can see and respond to, probably not an issue, for lights that you can't see or other things (plugs, and appliances that you may not notice running) this is probably a really bad idea. – coteyr Jul 26 '16 at 23:39
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    Similar switches are often used for auto, off, manual setups. For example if you have a motion or light activated porch light, this could be used to turn the light on (manual), off or provide power to the sensors (auto). The two things I learned with these is that they always surprise you the first time you hit one (off in the middle is not expected) and labels are your friend (Make thim big and easy to read). – hildred Jul 27 '16 at 0:27

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