A motion sensor activates the light when it detects something moving within its field of view. Photocells work with a resistor that changes its conductivity based on how many photons are hitting it.

A gangly-looking motion detector floodlight is fine for scaring off a backyard intruder, but it doesn't look good on your ...

Amazon Echo’s built-in ultrasonic motion sensing can let you easily automate lights and fans with Alexa routines, without buying anything else.

A motion sensor in your hallway or entryway is the simplest and most efficient way to dip your toes into smart home automation.