Motion sensor lights are security devices typically positioned around the outside perimeter of a home or office. They usually have a photocell that reacts to changes in the surrounding lighting caused by movement. The system then turns the light on to deter intruders or vandals. Sometimes the lights can be too sensitive and activate when a small animal runs by, or they may not be sensitive enough and not activate at all. Resetting motion sensor lights can usually be done very quickly.
Flip the light switch off and on several times if your light is connected to a switch. Turn it off for about 30 seconds before flipping it back on again to make sure it resets completely.
Remove the battery from batter-operated sensors. This serves the same purpose as cutting the power in that it resets the device back to its default settings.
Find a small switch or button on the lighting device around where the photo sensor is located. Hitting it resets the system automatically.
If your light is not functioning properly, clean off the photo sensor to make sure dust or dirt are not affecting its sensitivity.