How to Wire Motion Sensors

Updated February 21, 2017

Motion sensors attached to exterior lights can improve the security of your home. These sensors use ultrasonic waves to detect motion and activate your light by controlling the flow of current to the light. Motion sensor lights are best placed in areas that provide security to your home, like doorways and patios, or in areas that you'll likely use when coming home after dark, like driveways and walks. While you can purchase lights with integrated motion sensors, it's also possible to retrofit many existing light fixtures to incorporate a motion sensor. No specialised electrical installations skills are required.

Turn off the power to the circuit you'll be working on at your home circuit breaker box.

Unfasten the lighting fixture so you have access to the wires leading to it. Most fixtures will have a locknut or two that can be removed with your fingers. You may find it necessary to have a screwdriver for some fixtures.

Cut the white and black wires leading to the light, leaving about 4 inches of wire on the light end of the wiring.

Drill a hole for the sensor end of the motion sensor on the light fixture. Choose a location for the sensor that will let it point in the direction you want to cover with the sensor.

Place the rubber grommet for the sensor in the hole. Feed the sensor wires into the fixture through the hole from the outside. Insert the sensor into the fixture through the grommet, threaded end first. Secure the sensor from the inside with the locking nut it came with and tighten the nut with your fingers.

Remove 1/2 inch of insulation from the black and white wires you cut earlier. Place the bare ends of the white wire from the motion sensor and the white wires leading from the wall and from the lamp. Place a wire nut on the wires and tighten. Wrap the nut and wires with electrical tape.

Place the bare ends of the black wire from the sensor with the black wire from the wall. Secure them with a wire nut and electrical tape. Place the bare ends of the red wire from the sensor with the black wire from the light. Secure them with a wire nut and electrical tape.

Place the fixture back on the wall and turn on the power to the light circuit.


Never work on a live electrical circuit. Don't be satisfied with flipping the light switch to "off." It's far too easy for someone to flip the switch when you're working on the wiring.

Things You'll Need

  • Screwdriver
  • Wire cutters
  • Drill
  • Wire strippers
  • Wire nuts
  • Electrical tape
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About the Author

Based in Virginia, Nichole Liandi has been a freelance writer since 2005. Her articles have appeared on various print and online publications. Liandi has traveled extensively in Europe and East Asia and incorporates her experiences into her articles. She holds a Bachelor of Arts in history from West Virginia University.