How to Install Motion Sensor Lights
Automatic night lighting, when and where you need it.
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IntroductionA motion sensor light offers peace of mind and safety when it lights up a dark driveway, sidewalk or yard. Here's how to install one, along with tips to prevent it from coming on when you don't want it to.
- 4-in-1 screwdriver
- Voltage tester
- Wire stripper/cutter
Our step-by-step photos and tips from our experts provide a general guide of how to install motion sensor lights around your home. In most cases, you’ll simply replace an existing light fixture with the new one. Make sure to turn off the power to the fixture at the main panel before removing it.
However, if you have to run a new electrical line and install a switch, the job can get much more complex. Outdoor electrical lines must be encased in approved conduit and weatherproof electrical boxes. If you’re not familiar with conduit or the rules for running new electrical circuits, call in a licensed electrician.
Get an electrical permit from your local department of inspections. Check for special local rules and have your work inspected when finished.
CAUTION: Don’t let your ladder or your body touch lethal overhead power lines while you’re working.
CAUTION: Aluminum wiring requires special handling. If you have aluminum wiring, call in a licensed pro who’s certified to work with it. This wiring is dull gray, not the dull orange that’s characteristic of copper.
Motion detector lights are easy to install, but each brand has a few different details, so read the instructions. You’ll find the basic information printed on the outside of the box. Read the box before you buy the unit so you know what you’re getting. You’ll find more detailed instructions inside the box.
How Do Motion Detectors Work?
Motion detectors are small electronic eyes that detect infrared waves, i.e. heat waves that radiate from moving objects. When the detector senses an object moving across its field of view — especially warmer objects such as people, animals and cars — it electronically turns on the lights.
An outdoor motion sensor light will react to the movement of your dog, an approaching person, a passing car or sometimes even wind-blown leaves. Nuisance “trips” occur when things like that fool the detector and activate the motion sensing lights.
These can be annoying to you and your neighbors, and some homeowners won’t install motion detector lights for this reason. However, you can solve most unwanted switching-on by adjusting the distance-range setting and carefully aiming the sensor to limit its field of view.
- Pro tip: You can narrow the field of view even more by applying tape to the sensor.
Where to Put Motion Lights
Ideally, it’s best to mount motion sensing lights six to 10 feet above the ground and positioned so that most movement will occur across the sensitivity zone, rather than directly toward the detector. This project walks you through the installation for hard-wired lights, so you’ll have to take into account access to electrical outlets or wires. There are wireless options available too. One key advantage of hard-wired lights is that you’ll have a steady, reliable source of power and won’t have to worry about changing batteries or having ample sunlight to charge solar-powered lights.
How Many Security Lights Do You Need?
There’s no magic number. The best way to figure out how many security lights you need is to determine which areas around your house you want to light. For maximum effectiveness, position a motion sensor light to cover the walks leading to your front and back doors and the driveway. That way the lights will come on when you come home at night. You can also use them to light up decks, patios and potentially hazardous locations such as around stairways and swimming pools.
If improved security is a priority, position the motion sensor lights to cover all the approaches to your house, including fence gates, the patio door, the darker areas of your yard, and around trees and bushes. Good lighting can’t guarantee security, of course, but it’s one of the best low-cost ways to discourage intruders.
Project step-by-step (8)
Shut Off the Electricity
- Turn off the power to the fixture at the main panel, then test the wires to make sure the current is off.
- Rub one lead of a voltage tester against the ground wire and rub the other lead first against the hot wire (black), then the neutral wire (white).
- If the tester lights up in either case, the power is still on. Shut off the correct circuit at the main panel.
Install a Larger Box
If your existing electrical box is too small, you’ll have to install a replacement electrical box. Plastic boxes have the size in cubic inches stamped on them.
Wire the New Fixture
- Mount the motion sensors according to the manufacturer’s instructions.
- Run the wires through the rubber gasket.
- Then connect the neutral wires (white), hot wires (black) and ground wires (green or bare copper) with wire connectors.
Mount the Fixture
- Screw the fixture into place.
- Make sure the rubber gasket seals the edges of the box so moisture can’t get in.
- Pro tip: Apply a bead of clear silicone caulk around the edges if necessary.
Aim the Security Light Sensor
- Aim the motion detector sensor and the motion detector light bulb at the field of view you want covered. (Later, you can aim the detector lower to reduce the field of view if nuisance trips are a problem.)
- Point the light bulbs to the area you want lit. Keep the bulbs as far away from the detector as possible.
Set the Controls
- Set the detector’s distance range as desired. You can also reduce this later, if necessary, to eliminate nuisance trips.
- Also, set the timer shutoff control. On most units you can choose automatic shutoff after either one, five or 20 minutes.
Limit the Field of View
- Cover a portion of the security light sensor lens with plastic tape if it becomes necessary to narrow its side-to-side field of view more than the adjustments will allow.
Additional Installation Tips
- The cover of an outdoor electrical box must be waterproof. Seal the rubber gasket carefully. If you are placing it against a rough surface, caulk it as well.
- Moisture can seep into the detector and light sockets and ruin them. To prevent this, either locate the fixture under an eave or other protected area, or buy one with bulb seals and angle the bulbs downward so water can’t run into the socket.
- Heat from the light bulb itself can confuse the detector. Keep the bulb and detector as far apart as possible.
- Adjust the field-of-view angle and set the distance range of your motion detector to avoid nuisance trips from normal passing traffic, animals, pools of water, air conditioners, heating vents and wind-blown trees and shrubs.