You have seen them advertised as a feature of a security light, outdoor and indoor lights, and even for sprinklers and security cameras. But you are not quite sure what a photocell is, and how it figures into these different applications.

A photocell is a simple concept that has been applied to all these differences to help improve security, reduce expense, save energy, and save time and energy.

A photocell is …

Photocell is short for photoelectric cell, or photoelectric sensor. Simply put, a photocell is a light sensor. And when it senses light, or the absence of light, it can be programmed to trigger a light to turn on or off.

They have been in streetlights for years. Perhaps you have a streetlight near you that turns on and off all night. A common culprit is a sensitive photocell. It turns the light on at dusk, but then its own light causes it to turn the light off. Then it realizes (again) that it is dark, and the cycle repeats.

How a photocell works with lights

As in the example above, a common application of a photocell is to turn lights on or off.

A most common use is for lights that are remote or that a property manager or homeowner does not want to have turn on manually all the time. Think of a security light outside a barn or garage, or at a large business. Setting the outdoor security lights to come one at dusk and turn off at dawn helps keep the property secure and saves money compared with leaving the light on all the time.

Another usage is for nightlights in a home bathroom or hallway. When it is too dark, the light illuminates, making sure your nighttime trip to the bathroom does not lead to a trip down the stairs.

Places to use them

The places to use a photoelectric light sensor are really only limited by your imagination and needs.

Obviously, they work well for remote areas where a light helps keep buildings and people secure. They also work in applications where there are too many lights to turn on or off manually.

Additionally they are being used in LEED construction in combination with skylights. During the day when there is enough light coming through the skylights, the electric lights turn off, reducing the need for electricity and saving money. Then when the day is cloudy, the sensor turns the lights back on so the area remains well lit and ready for business.

Where might you use photocells in your home?

Photo by Burak The Weekender: https://www.pexels.com/photo/hanging-light-bulb-132340/