I work from home in a house with roommates and I would like to set up a light system to let them know if it's OK to disturb me during my work. I was thinking a stoplight system of Red: Do not disturb unless it's an emergency; Yellow: you can come in to get something, or if you need something quick / important; Green: consider the door open, feel free to come in and chat or whatever.

I'd like to have these lights place outside the door, and a 4 position switch on my desk that would have: Red, Yellow, Green, Off on it.

  • Can I wire the neutral of all the lights together so I only have 4 cables running from the switch to the lights, or should they each have a neutral running back to the switch?
  • Do I just hook the power to a specific terminal of the switch, and then have 3 different power lines (each from positions 3-1) out with one neutral running back and position 0 empty?
  • Do I need any sort of adapters if I'm going to run 25w incandescent bulbs?
  • Am I missing anything else?

I've been looking around for switches and think I found what I wanted in this switch, although I'm certainly open to suggestion. It's important to me that the switch be large enough that the space between positions is enough for them to be labeled and for it to be obvious to an observer which position the switch is in. I think what I'm looking for is a 3 throw knife switch, but I don't think one exists. Perhaps I could just do a 2 throw, and have a Red / Green / Off? Or maybe use a 2 throw for the RYG, and then a separate kill switch that turns it all off?

Theorized image: Crazy circuit from a guy who doesn't know how to draw them

  • If you want to go super cheap just buy 3 switches and only turn one on at a time.
    – Craig
    May 15 '14 at 16:18
  • Yeah, I thought of this, but I like the visual effect of the knife switch.
    – Koibu
    May 15 '14 at 20:15

your drawing is exactly right, except that there should be no breaks in the grounded (neutral) conductor, and that you'll likely have to have a grounding conductor throughout the circuit as well. You should also be able to find a rotary switch with 3 positions plus off, though it might be a bit pricey.

So your wiring could look something like this

enter image description here


I would do it with battery power and LED's... maybe even an Arduino. I wouldn't run wires with some kind of switch to my desk using full building voltage. That would be expensive and difficult to make safe and convenient.

  • Expensive and dangerous? Could you elaborate please? I was hoping not to have to change out batteries so I thought plugging it into a wall would be easiest.
    – Koibu
    May 15 '14 at 20:14
  • There're a lot of different kinds of batteries, charging circuits and plug in power supplies, but I'd keep it under 30 volts for indicator lights.
    – Rand
    May 15 '14 at 23:58

I'm assuming you will be working on a computer during this time, and if that is true might as well use an usb port for a easy power source and have your lights be LED's instead of incandescent. This way you can use a cheap low volt 4 conductor cable, 3 position knife switch, some LEDs and an old USB cable. There will be no safety issues and minimal cost. If you have a radio shack (US electronic hobby store) near by you should be able to find all the parts there for under 10 dollars (instead of 50 for 120 volt AC)

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