I want to retrofit motion sensing onto my floodlights.

I want to be able to easily override the motion sensing lights-on function to turn on the lights whenever I want.

I have three double-bulb floodlight fixtures on the house. Controlling those floodlights are three separate wall switches (presumably a couple of 3-ways and a 4-way).

Is there an easy way to retrofit one or more motion sensors to control all the lights in unison? I willingly would give up two of the three wall switches to accomplish my goal (leaving just one wall switch to control the manual lights-on function).

If there is an easy way, can you sketch a diagram and suggest the parts list? Many thanks.

  • I take it these are outdoor floodlights? Commented Nov 9, 2017 at 2:53
  • just use smart bulbs; cheaper, more flexible, and doesn't need re-wiring.
    – dandavis
    Commented Nov 9, 2017 at 5:38
  • Can you add pictures of the wiring at the switch boxes and the lights? If the lights are too high to get to, perhaps a look at the switch box wiring would be enough to go on. I'd like to know where the power is coming in to explain which options you have for doing what you are asking. Commented Apr 6, 2018 at 16:14
  • First are these all on the same breaker? They should be and if not they must be on the same leg or things will go boom.
    – Ed Beal
    Commented Sep 22, 2018 at 16:10

2 Answers 2


Yes. Wire the circuit with /3 cable and assign values as follows:

  • Black: always-hot
  • Red: switched-hot
  • White: neutral

Connect each lamp between switched-hot and neutral.

The switch goes between black and red. Keep in mind a 3 and 4 way switch complex basically equates to a single switch, provided it is a spur.

Everywhere you site a motion sensor, it connects to all always-hot, neutral and switched-hot.

Do not allow power to be severed from the motion sensors. They need power 24x7 to retain their memory of day-night light changes.

If you're trying to do this with combo sensor-lamps, they're not made to do that. You'll need to "hack" them to do that, and that's electronics.se's bailiwick. Also it violates Code, which makes it off-topic here, and we see nothink. Keep in mind many combo sensor-lamps create 12V internally to power sensor and lamp(s), as 12V sensors are much cheaper than 120V sensors.


An over-ride can be accomplished, but the steps will vary depending on where the power supply is located on the existing circuit. It may come into the light box first, or it may come in at the switch box location.

If the power is supplied at one of the switches:. enter image description here

Preliminary: Turn the power off to the branch circuit supplying the light.

  1. Mount motion detectors at appropriate places (follow manufacturer’s instructions carefully as these usually are very particular about heights and proximity to trees, etc.), and wire them together in parallel with ##/3-wire cable (Black,White,Red).
    1. Run ##/3-wire cable from last motion detector down to one of the 3-way switch locations. I’ve shown it in my diagram coming into the same box as the power supply.
    2. Remove the 4-way and final 3-way switch, wiring the colors together as shown. You won’t need the red wire, just cap or tape it at each end.
    3. At the first 3-way remove the Black Constant Hot from the common screw and splice it together with the black that comes from the motion detector AND a pigtail that attaches to one of the brass screws on the 3-way switch.
    4. Connect the red wire from the motion detectors to the other brass screw.
    5. Now connect the black wire from the other ##/3-wire cable (coming from the old 4-way) to the black common screw.
    6. Splice the neutral of the supply with the white from the old 4-way and the white from the motion detector.
    7. Cover and test with power back on.
    8. Suggestion, permanent labels on the switch cover: "Automatic"(where toggle points to the automatic position; "Override"(where toggle points to the override position).

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