How to Add a Motion Sensor to an Existing Light

Updated: 02/14/2022
man add motion sensor to light

Motion sensor lights are great for adding automation and security to your house and significantly reducing electricity waste. Many homeowners are sensitive to their home security and leave the outdoor lights on all night for illumination and detecting burglars, causing light pollution and huge electricity waste at night.

With a motion sensor light, you don’t have to compromise your safety by leaving the lights off all the time. The motion sensor light will be only on when it detects people around, combining security, illumination and energy saving in one light fixture.

Adding a motion sensor to your existing light can be easy and it has benefits over replacing your light with a motion sensor light.

One notable advantage of wiring a motion sensor to the light is that you can locate the motion sensor standalone everywhere you like to detect movement from the sensitive area, where a motion sensor light is only limited to detecting motion from the light’s position. And it will be a total waste to replace your existing light when the light is working just fine, and adding a motion sensor is definitely cheaper than replacing the entire light.

In this post, you’ll learn the following:

Motion Sensor Light Wiring Diagram

The wiring diagram of adding a motion sensor to a light is relatively easy and the wiring is usually identical between different brands and models.

motion sensor wiring
The universal wiring of adding a motion sensor to a light

Most motion sensors use 3 wires:

  • A black(or brown) wire connects to the hot wire
  • A red wire connects to your light
  • A white wire connects to the neutral wire.

What we need to do is to connect these 3 wires like above and the combination of the motion sensor and the light will work without an issue.

Another wiring diagram example of how to add a motion sensor that controls multiple lights at the same time.

motion sensor wires to multiple lights
A motion sensor controls multiple lights

We can see the wiring is nearly identical, except the red color load wire from the motion sensor connects to both lights instead of one.

Adding a Motion Sensor to an Existing Light

  1. Prepare tools: a non-contact voltage tester, a wire stripper and a screwdriver.
  2. Shut off the circuit breaker to turn off power to the light and use the voltage tester to confirm.
  3. Place and install the motion sensor: Depending on which type of motion sensor you buy, you can decide where to place it. Some motion sensors can be directly attached to the light and some motion sensors can be placed at the position where you want the sensor to spot and detect motion. Make sure the motion sensor is placed between the power source from your house to the light so the motion sensor can control the light’s power supply. And insert the motion sensor to the light or the pre-installed junction box for the motion sensor.
  4. Connect the wires: Connect the hot wire from your house to the hot wire on the motion sensor. Connect the load wire to your light to the load wire on the motion sensor. Tie and connect all neutral wires together. If you don’t know which wire is hot and load wire, turn on the power and use the non-contact voltage tester to confirm. The hot wire has power while the load wire does not. Remember to turn off the power before wiring. 
  5. Adjust the motion sensor setting to where it suits your needs, such as motion detection mode, sensitivity, time delay, and ambient light. 
  6. Adjust the motion sensor to face the detection area, screw tight and complete the installation. Turn on the power and test your motion sensor to see if it needs adjustment.

Other Solutions for Using a Motion Sensor Light

Adding a motion sensor to your existing light requires some work and electricity skills which are not friendly for some DIYers. Here are some common ways to enjoy using a motion sensor light with less handwork.

The most common way is to use a motion sensor light directly, and the installation is relatively easy and similar to installing a regular light. There are various outdoor motion sensor lights with different styles such as security floodlight, spotlight or solar light. You can definitely find one that suits your needs and they are getting more and more cost-friendly.

Another work-a-round for having less installation work is to use a motion sensor socket or motion sensor light bulb. These two products have a motion sensor built-in so they can work out of the box. What you need is to replace your light bulb with a motion sensor socket or motion sensor light bulb and that’s it. 

When you need to add the motion detection function to indoor lights, it’s way better to directly install a motion sensor switch to control the light. Replacing your manual wall switch with a motion sensor light switch can be fast and easy too.

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