What is a Photocell and How Does It Work?

When an LED light is equipped with a photocell, the light will turn on and off automatically based on the available ambient light. Their unique functionality makes them ideal for outdoor area lighting specifically.

Photocells are variable resistors that change the resistance in an electrical circuit depending on the amount of light present where they are mounted. Because of this, they must be mounted in exposed areas where they receive adequate light to function. Photocells, or photocontrols, come in a variety of shapes and sizes and can be integrated into a luminaire or be an added accessory depending on the light.

Can a Photocell Be Bypassed?

Some lights allow for a photocell to be bypassed as needed. When the photocell is bypassed, it allows for the luminaire to remain on constantly or be controlled by an existing switch or timer. Depending on the type of photocell and how it is installed in the fixture, it may be bypassable using a shorting cap, a slide or DIP switch, or by unplugging the photocell. Consult the user’s manual of the light to confirm which option(s) may be applicable and how to implement them safely. Always use caution and turn off supply power before working on wiring of any type.

Shorting Cap

Photocells on many commercial applications like parking lot and area lighting applications are mounted externally with a twist-lock socket or adapter. Swapping this for a shorting cap simply closes the circuit on your LED light fixture, which keeps your light in an always-on state. This allows it to be controlled externally as well if a central photocell or switch system is being utilized.

DIP Switch or Slide Switch

While DIP switches and standard slide switches function differently in most cases, when integrated into the photocontrol system of a light they perform the same function. Switches like these are common on canopy and dusk-to-dawn barn lights. These types of switches allow you to toggle the photocell sensor on or off to fit your needs without any rewiring or replacing parts.

Disconnect the Wiring

Some photocell designs, such as those commonly found in wall packs, allow the operator to simply unplug the photocell to allow the light to work in an always-on state or be controlled by an external switch.