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I have some motion lights in the back of my house, I want to also be able to use them to illuminate the back when I'm out there. I drew up the following schematic, the idea is to have the motion lights "on" when the switch is in one position, "constantly" on when the switch is in another position, and off completely when the switch is in the middle.

Is there anything wrong with my schematic? Is it ok to override the motion sensor this way? Do i have to worry about back-feeding it with power?

enter image description here

Side note: I come from the electronics world as a hobby and the only switch I could think of is called an SPDT, is there an equivalent version for home switches? I don't think its a 3-way switch as that is used when you have more than 1 switch (although I could be mistaken).

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  • Most floodlight motion sensors have override mode built in. Usually to activate you flip the switch off and back on quickly. To restore motion mode turn off for 30 seconds then back to on.
    – Tyson
    Commented Feb 27, 2018 at 0:16
  • thanks tyson, i'm aware of that, i just don't particularly like that functionality
    – Alex
    Commented Feb 27, 2018 at 0:21
  • The SPDT is called a 3-way switch, or 2-way in UK. Severing power to the sensor may cause problems. Sensors have memories and if you bypass them, they may do silly things like take awhile to recalibrate when they come on again, or forget to disregard the nearby street light when calculating night or day, something it takes 24-48h to learn. Also, don't count on this method working on LED+motion sensor all-in-ones. Have you done a teardown on your unit to confirm it does work as you are anticipating?
    – Harper - Reinstate Monica
    Commented Feb 27, 2018 at 0:52
  • Good luck getting rid of the built-in functionality. What you’re suggesting should be no problem with some/many/most models. Some come with illustrations in the instructions showing how to make the same effective backfeed connection, except in the printed versions it’s how to interconnect multiple motion sensors. If one detects motion, the lights of all energize. Effectively the lights come on when the first motion trips, and go off when the last times out.
    – Tyson
    Commented Feb 27, 2018 at 1:05
  • i have a motion detector fixture that can be toggled on by flipping the switch off and back on quickly; and it's nothing fancy, just a regular unit from a box-store. That seems a lot simpler than rewiring everything...
    – dandavis
    Commented Feb 27, 2018 at 20:34

3 Answers 3

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The problem with a regular "3-way" switch it that it doesn't have an 'off' position where neither of the sides is connected. For that you'd need a 'center-off' switch like this Leviton 5685-2W.

Then, as others have commented, it may not be a good idea to cut power to the sensor as it could take some time to get itself restarted and operational.

So, how about this instead:

schematic

This way, the sensor is always powered, but you're switching the light between the sensor's output and the always-hot line (with the off position in the middle).
The down-side is that you'll need an extra wire in the cable so that you can bring the sensor output back to the switch.

Another option which uses more easily available switches is to use 2 of them.
One switch is a "Three-Way" switch which selects between Manual Control and Sensor Control, and the other is a simple On/Off switch

schematic

As with the 1st option, the sensor is always powered.

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    Thank you. I was worried about connecting a switched hot wire to the Out side of the sensor, but your solution avoids that situation entirely. This is just what I needed. I think it's called an "SPDT (single-pole, double-throw) toggle switch with center off."
    – Michael H
    Commented May 5, 2020 at 17:06
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The switch you show in your question will work as you want. Everything is fed from the same hot line so there would not be an issue. I would on off on or 3 position so the light could be turned off if needed, but a 2 position switch would also work.

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Just to elaborate on Brhans' answer, wiring the SPDT, which worked for me was:

  • The hot end of your light fixture goes to the SPDT Common terminal (L1).
  • Sensor Out (usually Red) goes to either SPDT Travellers (A1) or (B1).
  • Line Hot (Sensor L) goes to the remaining SPDT Traveller.

enter image description here

Huge thanks to Brhans, btw!

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