What Is a Photocell for a Light?

Photocells are circuit elements that have many applications. One of the most important application is in lighting industrial such as "dusk-to-dawn" lights. Photocells react to ambient light via a changing electrical resistance.

Photocells are simply resistors that have a light-dependent resistance. Photo-sensitive plates are mounted on the front of the resistor, once it detects the light in the ambient changes,then resistance value of the photocell changes as well.

Application to Lights
Photocells are commonly used in dusk-to-dawn lights. These lights turn on when the surrounding environment is dark and turn off when it becomes bright again. The photocells in the lights tell the circuit when to provide more or less current, thus turning the light on or off as needed.

in CKRA, photocell is a very common option on our DLC listed LED fixtures, such as LED wall pack, LED shoebox light, and so on, with the help of photocell, the fixtures will help our customer for more energy-savings.
Below are the two type of photocells which are used in our current fixture, in the left, it is for small fixture such as wall packs and flood light, in the right, it is for the led shoebox light and large size LED parking lot light.both of them with UL listed.