The (Un)Official LED Photocell Dictionary

What is a photocell and what is it used for? An LED photocell, or daylight harvesting sensor, is a device that detects light levels and turns LED fixtures on and off according to whether it is dark or light outside. Photocells are beneficial to many outdoor lighting projects because they conserve energy by extending the life of a light fixture and take the work out of turning lights on and off.

That being said, there are many different types of LED photocells and terms surrounding the use of photocells that you might want to know before you begin your next outdoor lighting project.

LED Photocell Glossary

The following terms are associated with the use and installation of LED photocells.

3-Pin Receptacle: A 3-pin receptacle is a standard receptacle on a fixture that accepts 3-pin shorting caps and 3-pin twist-lock photocells.

7-Pin Receptacle: Like a 3-pin receptacle, this receptacle accepts shorting caps and twist lock photocells, but these must have 7 pins. 7-pin receptacles are also newer and better suited to future wireless control.

Button Photocell: A button photocell is  a square or rectangular object that is mounted inside a light fixture such as a wall pack and visible to the outside world through a knockout hole. There is a button photocell inside the wall pack fixture in the image to the right.

Pencil Photocell: This type of photocell functions in the same way as a button photocell, except this photocell mounts outside the light fixture. Pencil photocells are usually longer and cylindrical and can be tilted or moved in order to catch the light in a certain way.

Shorting Cap: A shorting cap is a plastic device that plugs into a 3-pin or 7-pin receptacle on a light fixture. If a photocell is not going to be used, a shorting cap acts as a conduit that completes the circuit and allows the light to turn on and off manually. These are sometimes called photocell bypass caps.

Twist-Lock Photocell:  A twist-lock photocell plugs into either a 3-pin or a 7-pin receptacle on top of a fixture such as a sports lighter or an area light. These photocells are more rugged and durable than button and pencil photocells, and some operate via remote control. Larger outdoor fixtures usually have this type of photocell.

A Note on Voltage

It is important to note that all photocells must be compatible with the voltage of the fixture it is attached to. For example, a photocell for 120-277v would not work with a 247-480v fixture. Photocells are available from Access Fixtures as well as from many other online retailers.

Call 1-800-468-9925 for more information about photocells. Wondering if your fixture is compatible with a photocell? Give us a call or send an email to [email protected].