Although it seems futuristic, motion-activated lighting is already in widespread usage. As its name suggests these lighting systems are activated by the detection of nearby movement. Since they operate only when needed, instead of on a continuous basis, they enhance security while at the same time save homeowners money.
Many contend that these lighting systems increase security over simpler and more familiar dusk-to-dawn lighting that stays on all night, implying that the occupants may not be home. In addition, since they operate only as needed, they do not contribute little to visual glare "pollution."
Components of Motion Sensor Outdoor Lighting
The key to motion-activated lighting is the motion sensors which trigger activation of the light source. An electronic control unit reads the signal from the sensor in order to determine if the sensor's input falls within the parameters of the system's settings.
In other words, it decides if there is a change in the system's surroundings. If the input falls outside of those settings the control unit interprets the signal as a change and triggers a relay switch that operates the lighting system. The consumer should note that the relay must be able to operate the voltage and current of the system. Finally, the system must be connected to a power supply to be operable.
The power supply also should contain a transformer to supply the correct amount of power to operate the system but not overload it. It is possible to connect a solar collector to the control unit as a power source. The system may utilize any sort of light source, including fluorescent, incandescent, low or high-pressure sodium, mercury vapor, or metal halide lights.
The sensor should be set up to sense the approach of people in locations where security is a concern, such as doors and windows. It is important to note that the infrared radiation cannot penetrate glass, therefore placing the sensors inside windows does not allow detection of motion outside.
A well-built, durable system should have a life span covering up to fifteen years; however, control units tend to falter more quickly, between six and ten years due to breakdowns in the transformer or relay. High humidity and very cold or hot temperatures have also been shown to affect systems' life spans negatively.
Operation of Lighting with a Motion Sensor
Operation of some lighting systems rely on sensors attuned to temperature changes. With their body heat, human beings radiate infrared energy, a wavelength that is found outside of the visible spectrum and contains very little energy. The energy pattern changes when human beings begin to move.
Infrared Motion Lights
Passive infrared (pyroelectric) sensors detect changes in this energy radiating between 8 and 12 micrometers, based on the heat radiated by human skin temperature. When the infrared light comes in contact with the sensor's substrate the sensor activates the system, sending out an amplified signal that turns on the light. Most systems remain lit for about ten to fifteen minutes.
Of course, human beings radiate heat whether standing still or in motion. The systems are able to discern between motionless objects and those in motion because a person entering the sensor's field of detection radically changes the amount of infrared energy within the detection field. In technical terms, the sensor employs a multi-faceted lens (one with many different surfaces) to employ many conically shaped views to detect radiation changes.
When objects cross the cones, the sensor sends the signal to the control unit. Gaps between the cones widen with distance from the camera, allowing the greatest sensitivity proximate to the camera. Other systems rely on a field of ultrasound waves which are emitted from the system and bounced back to it. There are no gaps in the sound field. Therefore, when a disruption occurs anywhere in the field it triggers the control unit and then the relay to operate the lighting system.
Ultra Sound Motion Sensor Lights
In comparison, ultrasound sensors are more sensitive and are able to spread a wider detection field. Therefore, they are generally more expensive. However, because there are no gaps in the detection field, objects crossing anywhere through the field trigger the system's operation and generate many more false alarms.
For both types of technology, consumers are able to select from a range of different field extent and survey angles. A hybrid of the two types of technology are now available. These use both ultrasound and infrared radiation detection. They, thus represent a near-optimal level of detection strength and avoidance of false alarms.
Microwave Motion Sensor Lighting
Some motion detection systems utilize a field of microwave radiation that detects a disruption in the microwave field when a person enters it. This type of detection system is more commonly utilized in commercial establishments to operate automatic doors. Its usage for home security is not common. Other types of motion detection such as audible noise and disruption of light beams have, thus far, not proven to be reliable.