A light-sensitive switch is commonly called a photo cell. Photo cells are easily installed in your existing outdoor floodlight or other outdoor light fixtures, providing added home security from dusk until dawn. Keep in mind that photo cells keep the light on constantly, unlike a motion detector that turns the light on only when tripped.
Turn the power off to the circuit you will be working on.
Remove the cover of the light you will be working on.
Some exterior light fixtures are designed to accommodate a photo cell. If your fixture has this feature, a plugged hole will be located either in between the two flood lamps or directly below the flood lamps. The plug can be removed by popping it out of the hole or by unscrewing it. If your light fixture does not have an extra hole available, you'll have to replace it with a fixture that does. Remove the plug and install the photo cell, fastening it into place with the provided locknut.
Connect the black (or red) power source wire to the black photo cell wire. Connect the white power source wire to the white light fixture wire and the white photo cell wire. Connect the black light fixture wire to the red photo cell wire. Replace the light cover plate.
Restore power to the circuit. The light will stay on for several minutes when the power is first restored.
Test the switch during the day by placing a piece of black tape over the photo cell window. Do not place a finger over the photo cell window to test the photo cell. Light travelling through the finger may be enough to keep the light off.
Turn the power off to the electrical circuit before you begin working.