Breadcrumb
What is a Dusk-to-Dawn Photocell?
Dusk to Dawn Feature
Many times we are asked about the meaning of the "Dusk to Dawn" feature of motion lights. This is a very nice feature that you will find on most motion sensor lights, so understanding this will help you make the best choice when choosing the light that is right for you. In short, the dusk-to-dawn feature of a light will cause your motion light to only activate when it is dark. In daylight hours when existing and ambient light is present, the light will not activiate when motion is detected. This feature uses a small photocell like the one pictured above to detect the presence of available and existing light. If light is detected, the motion light will not trigger. If light is not detected, then the light will turn on when motion is detected.
How Motion Detector Lights Work
Motion detectors sense moving objects by picking up the heat that radiates from the object. The motion light will automatically turn on when the motion detector senses an object moving within its detection range -- the sensor will work especially well when warm objects move within the detection area, such as animals, people and cars.
Once motion is detected and the light turns on, the light will remain on for a set period of time. Most outdoor motion lights will allow you to set the amount of time that the light will remain on, typically anywhere from 1 minute to 25 minutes. Then, if the detector no longer senses movement after the set time, the light will automatically turn off. In addition, most outdoor motion lights include a photocell that will deactivate the light during daylight. As a result, the light will only turn on when motion is detected during darkness.
Understanding the Dual Brite Feature on Motion Lights
You will see many motion detector lights with a feature called "Dual Brite" or "Dual Brite Timer". What is the Dual Brite feature? It is a very convenient and valuable feature that adds a new level of function to a motion light. Below, I'll describe how the Dual Brite feature works.
The Dual Brite feature adds another set of light control settings to a motion light. When the Dual Brite setting is on, the light will automatically turn on in a half-bright mode for a set period of time after dusk. So when it gets dark, the light automatically switches on in dim mode, providing you with convenient lighting during times when it gets dark early in the evening, and the security of automatic dusk lighting. The Dual Brite setting does not interfere with normal motion light settings--if the motion detector picks up motion, the light will switch on in full power mode, even if the light is already on in dim mode from the Dual Brite setting.
Setting the Motion Detector Sensors on a Motion Light
Once you have installed a motion detector light, your next step will be to make sure the motion sensors are covering the correct area of your yard. In following articles, I will go into more detail about the actual installation instructions for an outdoor motion detector light.
In order to set the motion detector, aim the head of the detector unit toward the area where you would like to detect motion. Then, walk across the detection zone at the farthest point you wish to cover with the sensor. Note that this is easier to do with a helper involved--preferably a child if you want to make sure the sensors will pick up movement from a smaller child at that range.
Adjust the sensor as necessary, and repeat the steps in the above paragraph until your light comes on from movement in the desired detection zone. You're done!
Always consult the specific manufacturers instructions for proper installation (and safety) steps when working with your light or any electrical connection.
Key Tips For Adjusting Motion Detector Sensitivity
Have an overactive motion detector? The sensitivity level on today's motion detector lights may cause the sensor to trigger too frequently, causing the light to stay on longer than desired, or causing the light to turn on too frequently due to motion detected from an unwanted area. Here are some tips to fix this problem:

















