Add a motion detector to existing porch lights

[Metspitzer]

I replaced my flood lights, so I bought new ones with built in motion detectors. They are "smart" enough to work with only a hot and neutral. They work because you leave the switch on all the time. The controller board then will turn the lights on when it detects motion, but it will also allow you to manually turn the lights on by switching on/off the switch.

I would like to add the same type motion detector to my garage lights. I assume the best way will be to remove the switch leg from the existing light and move it to a new cut in box where I can mount the sensor, and then go from the sensor back to the existing light.

Anyone here retro fit their existing lights? My existing lights are expensive and I would like to keep the existing ones. The lamp cover mounts over the entire fixture so adding a motion detector to the existing fixture's base is out.

Anyone opted for a wireless method?

[RBM]

What you want to do is cut in a box in the vicinity of the fixture you want to control, preferably above it if not too obtrusive. Run a three wire cable from the existing fixture box to the new box. Mount a motion sensor onto a single half inch KO cover in the new box. Connect the hot wire from the fixture box to the black of the sensor, all the neutrals together, and the red returns from the sensor to the fixture. Now it'll work just like the other one

[Dean Hoffman]

Wouldn't he also need an equipment ground?

[gfretwell]

Only if there is metal in the system (metal box or cover)

Most retro replacement heads are all plastic and do not have a green wire. I have a bunch of them around my house.

[RBM]

Sorry for the omission, the ground would be integral to the cable and connected at each end to any equipment ground connections

[DT]

switching

Yep, I installed a Heath Zenith wireless motion sensor on my string of three porch lights. The sensor is battery powered and goes wherever you want, and the wall switch is replaced with a receiver. It also has a switch and dimmer built into the new wall switch.