Installing a Remote Motion Detector for Lighting

Updated: Jan. 05, 2024

Wire a remote sensor to operate light fixtures anywhere around the house.

outdoor motion sensor flood lightFamily Handyman
A remote sensor automatically lights up dark sidewalks and yards. And it'll operate any light fixture. In this story, we'll show you how to install a remote motion detector to your outside lights.

You might also like: TBD

A full day

Step 1: Getting started

A gangly-looking motion detector floodlight is fine for scaring off a backyard intruder, but it doesn’t look good on your house. A remote-style motion detector is a better choice. You can connect it to any type of decorative fixture—even existing ones—and mount it discreetly off to the side.

This article will show you how to install and connect a remote sensor to new or existing lights. The wiring is a little more complicated than it is for most electrical projects, but even a novice can handle it by following the wiring diagrams we provide. We won’t detail the most basic aspects of electrical work, so you may need to do some further reading.

Apply for an electrical permit at the local inspections department so an inspector can check your work. The toughest part of this project may be running the wires that connect the sensor to the light fixtures.

In some situations, you can “fish” wires through finished walls. But in many cases, this project is only practical where you have open studs, as in an unfinished garage (as we show), or during a major remodeling project. If new wiring isn’t an option for you, consider sensors that give you similar results but with little or no rewiring.

remote sensor replacement for outdoor motion activated light

Choosing a sensor

Home centers and hardware stores carry motion sensors ($20) that look like the ones you see mounted on floodlights. They’re usually labeled as “replacement” sensors for floodlight fixtures, but you can attach one to a mounting plate and use it as a remote sensor.

Before you buy a replacement sensor, add up the wattage ratings on the fixtures it will control. The wattage rating of the sensor must be at least as high as the total watts of the fixtures. For example, if you have two fixtures, each rated to hold a 100-watt bulb, the sensor must be rated to handle at least 200 watts.

Step 2: Install junction boxes

Photo 1: Cut junction box holes

Cut holes for junction boxes. On stucco, drill a series of holes around the perimeter, break out the stucco with a chisel and then cut the sheathing with a jigsaw.

Photo 2: Fasten the junction boxes in place

Install junction boxes so they’re flush with the exterior surface of the wall. Have a helper outside position the box while you fasten it.

The sensor and each light fixture require electrical boxes set into the wall (Figure A).You can rewire boxes at existing fixtures as well. Choosing a location for your motion sensor isn’t complicated: Check the manufacturer’s directions for viewing range and place it where it can “see” visitors or intruders as they approach your house. Typically, the sensor will detect motion best if you place it 6 to 10 ft. above ground level.

The sensor we used can be mounted on a round or rectangular box. If the interior walls are unfinished, buy boxes mounted on an adjustable bar (Photo 2). This design lets you position the box anywhere between studs. If the wall is enclosed, use “remodeling” boxes, which clamp to the siding and wall sheathing and fish in the cable.

Hold the box against the wall and trace around it with a pencil. Avoid placing the box directly on a stud or other framing. With brick or stucco, use a 1/4-in. masonry bit to drill a series of holes all around the circle. Then break out the middle with a chisel (Photo 1). On stucco, you’ll have to cut the exposed metal mesh with snips. Cut out the sheathing behind stucco with a jigsaw.

If you have wide lap siding made from wood, cement board or hardboard, cut your hole near the center of a board so you can mount the fixture on the flat surface. If you have vinyl siding or siding courses that are too narrow to provide a flat mounting surface, you’ll need a mounting block that fits over lapped edges. Plastic blocks are available at home centers. To cut a hole in any type of siding, drill a 3/8-in. starter hole through the wall and then cut out the circle with a jigsaw.

Editor’s Tip: Here’s how to install a motion sensor light that offers peace of mind and safety when it lights up a dark driveway, sidewalk, or yard along with tips to prevent it from coming on when you don’t want it to.

Figure A: New Junction Boxes and Cable

The sensor and each light fixture require electrical boxes installed in the wall.

Step 3: Wiring options

Before you run electrical cable to the junction boxes, you have to determine how you’ll wire your system. We show the simplest method here: drawing power from a switch box and running cables to the sensor and then light fixtures (Figure B). You can also run the cable to a fixture and then to the sensor (Figure C). But cable and connection details will vary a bit.

Simply choose the method that will make running cable easier. If your sensor will be placed close to the switch, the method shown in Figure B is probably best for you. If a light fixture is closer to the switch, the method shown in Figure C is probably best. Both illustrations include additional light fixtures. If you have a single light, just eliminate the wiring that feeds the second fixture. Your system must have a switch that can turn off the power to the sensor and light fixtures. We used an existing switch in an existing junction box; you may need to add a box and switch.

With either method, you can add as many fixtures as you like as long as you don’t exceed the wattage rating of the sensor. Boxes have to be a certain minimum size to contain the wires. A 16-cu.-in. box is adequate for all the wiring configurations we show here.

Figure B: Sensor Between Switch and Lights

Running cables from an existing switch to the sensor and then to the light fixtures is the simplest way to wire your system.

Figure C: Sensor Between Lights

Running the cable to a fixture and then to a sensor is the best choice if a light fixture is close to the switch.

Step 4: Run cable to the boxes

Photo 3: Run cable to junction boxes

Drill 5/8-in. holes in the center of the wall framing to create a path for cable. Then run the cable between the junction boxes. Fasten the cable to framing with plastic cable staples.

Photo 4: Insert wires into the boxes

Strip off 12 in. of the cable’s sheath and feed wires into the box. If two or three cables enter a box, label wires with masking tape and a marker to avoid confusion.

Once you’ve determined how you’ll wire the system, run the electrical cable between the junction boxes (Photos 3 and 4). First, look at the existing cable you’ll use to power the sensor and lights. On the cable’s plastic sheathing you’ll find one of these numbers: 14/2, 14/3, 12/2 or 12/3. The first number (12 or 14) indicates the gauge of the wire.

The second lists the number of wires in the cable (plus the bare ground wire). Be sure to buy cable that’s the same gauge as the existing cable. If you plan to follow Figure C, you’ll need some cable that contains two wires and some that contains three wires.

Stand back and take a few minutes to plan the paths of the cables. The shortest route isn’t always the best. Avoid a path that will force you to drill holes in tight spots or through heavy framing members. In an unfinished garage, run wire high in the walls or along rafters where it’s less likely to be damaged.

If you only have a few holes to drill, an inexpensive 5/8-in. spade bit works fine. But if you have lots of drilling to do, buy an auger bit. The screw at the tip of the bit makes for faster drilling with much less strain. When you’ve created a path for the cable, run the cable from box to box and then fasten the cable to framing with plastic staples. Place the staples within 8 in. of each box and no more than 4 ft. 6 in. apart.

Step 5: Connect the sensor and the lights

Photo 5: Wire the sensor and fixtures

Connect the sensor and the fixtures as shown in the wiring diagrams. Hang fixtures on a leftover piece of wire while you make connections.

Photo 6: Adjust the sensor settings

Adjust the sensitivity and “on-time” of the sensor according to the manufacturer’s instructions.

When all the cable is in place, you can connect the sensor and the fixtures (Photo 5). It’s tempting to rush through this part of the project so you can see the results of your work. But take your time. With one wrong connection, your system won’t work. And finding where you went wrong is a hassle.

If you’re connecting to existing wires, cut off the old bare ends and strip off insulation to expose fresh wire for your new connections. With all the connections complete, turn on the power and set the sensor to “test” mode so you can make sure the system works correctly. Then aim and adjust the sensor (Photo 6).

Caution: Turn off power at the main breaker panel before removing the cover of the electrical box you intend to use as a power source. Then check the wires inside with a voltage detector to verify that the power is off.

Energy-Saving Bulbs and Sensors

Power-saving compact fluorescent (CF) light bulbs designed for outdoor use are becoming more popular and economical. Unfortunately, most motion sensors aren’t designed to handle CFs. Some sensors tell you right on the packaging whether they work with CFs. With other sensors, you have to check the wattage rating in the specifications. If the wattage rating specifies “incandescent” lighting but doesn’t mention “fluorescent,” assume it won’t handle CFs. The Tuff Dome sensor shown here is CF-compatible.

Sensors That Don’t Require New Wiring

Built-in sensors
Some outdoor fixtures have a built-in sensor. These decorative lamps operate like floodlight motion detectors but are more stylish. Like any other light fixture, they take just a few minutes to install. They’re not designed to control other light fixtures and are available in a limited range of styles.

Wireless motion sensor lights
A wireless sensor works like the remote control for a garage door opener. It sends a radio signal to a receiver that switches on a light. No wiring is necessary to control existing lights. Just screw the receiver into a light socket and mount the sensor anywhere you like. There are some limitations to this system, though. The sensor requires batteries, which you’ll have to change every few months. In rare situations, the radio signal can’t reach the receiver because of interference or blockage. Finally, the shade or globe on your light fixture has to be large enough to hold the receiver along with a light bulb.

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • 4-in-1 screwdriver
  • Corded drill
  • Drill bit set
  • Extension cord
  • Jigsaw
  • Non-contact voltage tester
  • Safety glasses
  • Stepladder
  • Utility knife
  • Wire stripper/cutter
You’ll also need a hammer and chisel if installing junction boxes in brick or stucco siding.

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.

  • 14-2 cable
  • Junction boxes
  • Motion sensor
You may also need 14-3 cable, depending on how you wire your system.