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North American Wiring:

Let's say I have an outdoor lamp that turns on and off via a switch from the inside (something like pic below).

enter image description here

I want to add a motion (long-distance) sensor floodlight to this situation. Such that I still have an outdoor lamp that turns on and off via a switch from the inside, and additionally I have some kind of floodlight that turns on if it detects motion (up to about 70 feet), and only runs dusk-to-dawn.

The wiring for the floodlights will have to come from this existing lamp fixture.

I have never done electrical work. But I know how to turn off the mains and splice wires together.

If you've done something like this, please share how you did it. If you haven't, but have suggestions on fixtures / bulbs etc. please share (they're even making motion-sensitive bulbs these days).

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  • Where do you want the flood light? Usually a flood light would be installed in a higher location. If you put it here next to or instead of this light, it will shine in people's eyes. If you put it elsewhere, you have a more challenging, not-for-first-time-beginners project.
    – jay613
    Sep 21, 2021 at 12:03

1 Answer 1

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Note: this answer assumes North American wiring. You don't give a location but that photo looks like an American fixture to me.

There are two ways the existing fixture may be wired. The first way is by "switch loop": enter image description here Here, power enters at the fixture and a separate cable (switch loop) carries hot to the switch and switched hot back to the fixture. If this is what you have, your new wiring is easy: connect your new cable to the back, white and ground cables coming from the breaker panel (the wirenuts shown in the center of the diagram). This provides hot, neutral and ground for your new, unswitched floodlight.

However, you may instead have it wired that power comes to the switch first: enter image description here This would be a problem because there isn't an always-on hot wire at the fixture. If you connect your floodlight to the fixture wires, it will only operate when the switch is on.

Assuming you don't want to change the existing wiring, the only answer I can see is to leave the switch always on and replace the existing fixture with a smart light that can be controlled through another means.

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    Interesting that this diagram of the switch loop is new enough to show the unused neutral in the /3 going to the switch itself. I'd bet 99% of existing switch loops use a /2 from the fixture to the switch with the white "neutral" remarked with black tape as the switched hot.
    – FreeMan
    Sep 21, 2021 at 11:46
  • @freeman These are just diagrams I found on the internet. I considered commenting on that but the question really didn’t ask about the switch.
    – DoxyLover
    Sep 21, 2021 at 17:03
  • Fair enough! Thought it would be important for the OP to know if he opens his switch that he may not find a neutral there.
    – FreeMan
    Sep 21, 2021 at 17:05

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