How to Add a Photocell to an Outdoor Light

If you have an outdoor light that doesn’t turn on automatically at dusk, or if it turns on too early in the morning, you can add a photocell to it to fix the problem.


A photocell is an inexpensive device that senses the amount of daylight and activates or deactivates a device accordingly.

Adding a photocell to outdoor light is a great way to save on energy costs and keep your home well-lit. A photocell will automatically turn the light off during the day and on at night.

This blog post will show you how to add a photocell to an outdoor light. We will also provide some tips on how to get the most out of your photocell. So let’s get started!

What is a Photocell?

A photocell is a device that uses light as a trigger. It can be used to determine whether or not there is enough light present for a device to work or activate.

In this case, the photocell will be used to control when an outdoor light comes on and off during daylight hours.

What are Photocells Used For?

Photocells are used in many outdoor lighting fixtures. For example, if you have an outside light that automatically turns on at night, then the photocell is what controls this function.

At dusk, the photocell will see there is not enough light around to turn on the outdoor light, so it sends a signal to the outdoor light and turns it off.


When there is enough light around, the photocell will signal to turn on the outside light again. Photocells are used for many other outdoor lighting functions as well.

Some of these functions include; controlling the light sensitivity, turning on lights that are too far away or too near to be turned on with a regular wall switch, and turning lights on during daylight hours when it is raining.

These devices use photocells, so they will only turn on when enough light is present. If something else is triggering the photocell, then this may result in the outdoor light turning on during the day or at night when you don’t want it to.

How Does a Photocell Work?

Photocells work with light waves and electricity just like our eyes do. A photocell has a small strip of special materials and metals.

When light hits these materials and metals, it causes a resistance between them and generates electricity.

This electrical current sends the signal to turn on an outside light when there is not enough daylight present.

It works in reverse, so when there is too much daylight, the photocell will signal to turn off the outside light. Photocells are very sensitive to light and will activate when even a small amount of it is present.


If your photocell turns on when there is still enough daylight, this could be because the photocell isn’t covered or shaded enough. This problem can easily be fixed by covering the device with shade or covering.

If your photocell activates when it is raining, cover the device with something waterproof like a plastic bag. As you can see, adding a photocell to outdoor light is simple and easy.

If you plan on adding one to your outdoor lights, there are some tips we recommend for getting the most out of your outdoor lights.

8 Advantages of Using Photocell to an Outdoor Light

1. Save electricity and be environmentally friendly.

2. Save on installing an outdoor light: No wires to run and no electrician needed.

3. Save on the cost of bulb replacement.

4. Easy to install and no maintenance or rewiring required.

5. The photocell turns off the light at night to conserve energy, but it is on when you are outside enjoying your yard during the day.

6. It’s easy to install with just a screwdriver or drill that you already have at home.

7. Place the photocell on a fence post or wall that faces where you want it to turn off and on, then replace the bulb with a CFL or LED light bulb that uses very little energy.

8. It’s excellent for people on vacation, have outdoor pets, have security concerns, or get up at night to use the bathroom.

Step by Step Guide: How to Add a Photocell to an Outdoor Light

Step 1: Power off the Circuit Breaker

Power off the circuit breaker. It is usually located in a nearby weatherproof “box” that is on the exterior of your house and is also marked with an address on the door.

If you are not sure how to power it off, don’t hesitate to call an electrician.

Step 2: Remove the Existing Outdoor Light Fixture

Disconnect the existing light fixture by unscrewing any screws holding the unit together. Once free of screws, pull apart by hand but be careful not to damage.


Use a screwdriver to remove the existing outdoor light. Place it in a safe place to not lose any of the pieces.

Step 3: Identify your Option for Installation

There are two options when installing an exterior light with a photocell: one uses a conduit, and the other uses junction boxes, both of which can be found at a home improvement store.

This task should be much easier if you already have a conduit or junction box installed because all the parts you need will be included in the installation kit.

To install your light with either method, you must purchase an exterior light fixture and photocell from a local home improvement store and any other tools that might be needed to complete this task.

Step 4: Use Pliers to Cut off the Insulation on the Cable

Cut off about 4 inches of insulation from the cable with a pair of pliers. Be sure not to cut into the interior wires inside.

If snipped correctly, you will have exposed one black wire and one white wire in addition to two insulated cables still intact.

Step 5: Strip the Cable

Strip about an inch of insulation on each wire using wire strippers. You will be left with five wires one black, one white, and three bare copper colors (green/yellow/red).

Remember to keep the wires separate, so you don’t confuse them for another step.

Step 6: Twist-On Connectors

Twist each exposed end to its corresponding color on the back of the junction box or conduit.


It may be difficult to make all the connections by hand, so we recommend using a set of pliers or duct tape to hold them in place while you twist.

All the colors must be connected to their correct counterparts. If they are not, your light fixture will not work and could be dangerous.

Step 7: Mount the Junction Box or Conduit to Existing Wall

Place one large wire nut on the black wire and then insert it into the junction box or conduit. If you use a junction box, just push the wires to the back and screw closed with pliers.

Using a conduit, use the Duct Tape to hold everything in place while you “fish” it through. Once pulled through, a twist on the large wire nut.

Step 8: Insert the Photocell to Junction Box or Conduit

Insert one end of the photocell into the empty side of either device. Once inserted, twist on a small wire nut to hold it in place.

Make sure that each end is connected tightly and securely. You may also need to adjust (by bending) the photocell’s small wires so that they are not sticking out too far.

Step 9: Connect the Other End of the Photocell to Existing Cable

Take one of the white wires on your external cable and strip about an inch off with wire strippers.

Next, twist on a twist-on connector to connect the external cable and the photocell. Remember that all white wires are connected, so it is okay if you accidentally end up with two white wires at this step.

Step 10: Cover All the Connections

Cover all the twisted connections with electrical tape to secure them in place. If you use a junction box, just close it and tighten it with pliers.

Using a conduit, use the Duct Tape to hold everything in place while you “fish” it through. Once pulled through, a twist on the wire nut over all of the connections.

Step 11: Mount the Fixture to the Existing Junction Box

Using the brackets that came with your light, mount the fixture onto the conduit or junction box. Ensure all parts are secure and tighten them down with pliers if necessary.


Step 12: Test Your Installation

Once mounted, test out your new light by turning on your exterior light switch. If the photocell is working, your new light should go on and off automatically depending on how much sunlight is available there.

Five Common Problems With Photocells That You Need to Be Aware of

1. Photocells have a bad habit of being fooled by light reflecting off nearby surfaces, which causes them to turn on or stay on when they should be off.

This is often hard to avoid in the photocell’s defense without putting it in a deep-set box. The solution is to keep the photocell out of bright light.

2. Photocells are not very accurate when turned to face straight up because they can’t tell whether what they’re seeing is sunlight or moonlight.

This means that an outdoor light will stay on for a long time after the sun sets, instead of just until there’s no more ambient light anymore. The solution is to turn the photocell, facing away from the moon or using a very bright light.

3. Photocells can’t tell between dim sunlight and no sunlight at all, so they don’t trigger when it gets cloudy.

The solution is to coat them with petroleum jelly (Vaseline) on the reverse side, which faces the sun, reflecting more sunlight than the surrounding air.

4. Photocells can’t tell between dim light and darkness, so they won’t turn on an outdoor lighting system until it’s already entirely dark outside.

The solution is to use a lighting system that comes on only when motion is detected or to up your ambient light.

5. Photocells are more likely to activate when they’re on their “off” setting than when on their “on” setting.

This is usually because the manufacturer wants them to last a certain amount of time before failing, but it means that an outdoor light will turn off less often than it should.


Adding a photocell to outdoor light is a great way to save energy and money. When it gets dark, the photocell will turn the lights off. This process happens automatically, so you don’t have to worry about forgetting to turn your lights off or on. 

Installing a photocell is a simple process that can be done in minutes. However, you will need some basic tools and supplies. There are several different types of photocells available on the market today.

We recommend using a PIR (passive infrared) sensor for outdoor lighting applications, as they are specifically designed for outdoor use. We hope this blog post guided you on how to add a photocell to an outdoor light. It is very affordable and easy to do yourself in just minutes!

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