Ask A Lighting Specialist: LED Photocell Q & A

Q: I am planning on purchasing 18 bollard lights to illuminate a pathway soon. I want them to automatically come on at night. Will I need to buy 18 photocells as well?

A pencil control photocell used with many bollard lights.

A: No. You only need one photocell.

A photocell is a device that works like an electric switch. When the photocell detects ambient light, the photocell switches off the luminaires controlled by the photocell. When the photocell doesn’t detect ambient light, it turns those same luminaires on. One photocell can control multiple luminaires assuming they are on the same line, just like a manual switch can turn on and off multiple luminaires. 

Photocells were developed to prevent the need for someone to go outside and manually turn on outdoor lights every time it becomes dark. They are also more efficient than timers, which turn lights on and off based on a certain time of day. Timers do not address the changing light levels associated with seasonal changes and Daylight Savings Time, but photocells do. 

So why would buying 18 photocells not make sense? Because, only one photocell is needed to control a group of light fixtures connected to a single power source. Here is how. 

• • Ample power is provided from a line to a switch which turns the power on and off 
  • The power line continues to an electrical box that is mounted in a location that can detect natural light but not illumination from luminaires
  • The power is run to a photocell mounted on the electrical box. 
  • The photocell acts as a second switch. If the power is on at the first switch, the photocell will control the power out of the electrical box.
  • The power line then goes continues to each of the 18 bollard lights to power the bollard lights 
  • When the first switch is on, the photocell will determine when it gets dark and will turn on all the bollard lights 
  • Using a photocell guarantees that all of the LED fixtures will turn on and off at the same time. 

Photocells are a highly efficient option for allowing outdoor lights to turn on and off. Certain types of photocells work better with some products over others, which is usually left to an electrician’s discretion. The photocell shown in the image above is a typical photocell that works well for many applications. Photocells may be purchased from Access Fixtures when you purchase bollard lights. If you have any other questions, please contact an Access Fixtures lighting specialist for assistance.