The sensor in a motion sensor light fixture is a type of switch that turns on the light when it detects motion. It's all there in the name. When the bulb burns out and you need to change it, all you need to know is that the procedure is no different from changing a bulb in a regular light fixture. However, you may want to take some extra time to readjust the sensor while you're doing the job.
How Does a Motion Sensor Work?
A motion sensor light fixture typically has a semicircular attachment mounted just below the light, and that's where the sensor is located. Depending on the type, it may detect motion by detecting changes in infrared radiation in the vicinity of the fixture, it may respond to changes in light intensity, or it may use both methods to detect motion.
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The sensor is a switch, so for the fixture to work, the power must always be on. It's important to remember this when changing a bulb because you need to turn the power off to do the job safely. The fixture may be connected to a wall switch in the house that you can turn off, but many aren't. If there's no wall switch, you have to find the circuit breaker in the panel that controls the light circuit and turn that off.
Removing and Replacing the Bulb
To access the bulb, you may have to remove a cover from the fixture, and the procedure for doing this varies from model to model. Some models have finger-grip screws that are easy to remove by hand, others have actual screws for which you'll need a screwdriver, and still others just snap off. If the cover is made of glass and is breakable and if you're working from a ladder, it's a good idea to come down from the ladder and put the cover in a safe place before you change the bulb.
If the bulb or spotlight just went out, it's likely to be hot, especially if it's incandescent. To avoid burning your hands, get a soft cloth and use it to unscrew the old bulb. It doesn't happen often, but if the bulb should break, cut a potato in half and use one of the halves to grip the socket so you can turn it. After removing the old bulb, screw in a new one (incandescent, CFL, and LED bulbs all work) and replace the cover.
Adjusting the Motion Sensor
If you're happy with the response of the motion sensor, no adjustments are necessary, but if you want to increase or decrease the sensitivity, you can use the control dial located on the fixture just underneath the sensor. You need to turn the power back on to do this.
Increase the sensitivity by turning the dial in the direction indicated by the arrows (usually clockwise) and decrease it by turning the dial in the opposite direction. If the sensor is light sensitive (most are), you may have to wait until it gets dark to make this adjustment. There may also be a control to adjust the peripheral range of the sensor. Widen the range if you want the sensor to detect motion to the right and left and narrow it if you prefer the sensor to only detect motion directly in front of it.