Controlling an Outdoor Security Light

Exterior of residential garage at dusk
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One of the best things about an outdoor security light is that you can set it to be on only when you want it to be. With some controls, you can even set it to be on dimly when it's dark out and to switch to bright light when someone steps in front of it.

If your light came with built-in controls, then you will work with those. A lot of times, though, you can make your own outdoor security light by combining one or two lamp holders with a separate control unit. Those usually offer more controls and more choices within each control. For example, the control unit senses light and motion and has selectors that you can set for when and how it will be on, how long it will be on -- or stay bright -- after it's triggered, and its sensitivity to motion triggering.

Separate controllers are wired, or connected, to power coming from a switch, and then the light bulbs - the lamp holders they're in - are connected to the controller. That way the controller always has the power it needs to operate, and the lamps only have power when the controller sends it to them.

The Automatic Controls

Almost every outdoor security light has a control that will keep it from being on when it's light outside. Some have timers, and some have photocells. Some have both.

The photocell is the small eye in the lower right corner of the bottom plate. It's a normally-closed switch that opens when the light is present. That means the other controls will have power anytime it's dark. It also means that if the photocell fails, the light will stay on all the time. For security, of course, that's the way we'd prefer it to fail!

The large lens across the front of the unit is the motion detector. A motion detector uses an infrared view to sense when a warm body has entered its field of vision. This control is a normally-open switch. It won't close, and send power on to the lights, until and unless it sees something.

The Controls You Set

There are two slide buttons and a dial with a pointer on the bottom plate of some controllers. The slide switch next to the eye for the photocell sets the hours of operation. One particular controller is a DualBrite model, which also has a setting for OFF. That can be selected to disable the low-power setting, so that the lights stay off until the system is triggered, rather than being dim. The other three settings are Dusk to Dawn, 3 hours after dark, and 6 hours after dark.

The other slide switch selects how long the light will stay on, or stay bright after it's triggered -- one minute, five minutes or twenty minutes. This slide switch also has a TEST setting. That's a handy feature that allows you to turn the lights on at any time -- even in the middle of the day -- to see if they're both working. It can be particularly useful when the fixture is being installed, telling you whether everything is connected the way it should be.

The dial with the pointer is the Sensitivity control. This controls how far away or close in a person must be before the motion detector will react, and close the circuit.

Choose the Right Light Bulb

This may not seem important for controlling your outdoor security light, but it is. The reason is that not all light bulbs can be smoothly controlled with photocells, and that's part of these controls. To have your security lighting come on when you need it to, you can install any outdoor-rated incandescent, halogen, or LED light bulb. But you shouldn't install a CFL light bulb.

Why is that? Because CFL light bulbs, like all fluorescent light bulbs, require full power at startup. Most photocells don't provide that. What a typical photocell does is provide just as little power as night falls or the sky becomes cloudy. It won't go to full power until it's fully dark outside. And the ballast in most CFL light bulbs can't deal with that. In fact, trying to control an ordinary CFL light bulb with a photocell can cause the bulb to fail. The exceptions to this are the dimmable CFL bulbs. If you have one of those that are outdoor rated, you can try it.