Choosing the Best
Security Lighting System
There are two types of sensors for security lights and
similar purposes: active and passive. Active sensors send out a signal, like a
beam of light across the path of a door or walkway, and then trigger a light or
other action when the beam is interrupted.
Some devices send out a radar signal and trigger a light or other action
when the returning radar signal is changed by the presence of a person.
Most security lighting systems do not work this way,
however. The preferred method for detection of human intruders is the use of
passive infrared (PIR) sensors. A Passive Infrared (PIR) sensor detects motion by sensing any thermal
contrast between a moving object or person and a stationary background; such
sensors are very sensitive. They can be set to avoid “false positives” from
is also important about PIR motion detector lights is that they are relatively
inexpensive and, in most cases, can replace existing light fixtures. Motion sensing
security lights vary in cost from $25 to $100.
Motion sensors for security lighting have capabilities that
are expressed in degrees (arc of detection) and distance. An arc between 900
- 2700 can be found in different sensors and the distance of effectiveness
can range from 30’ to 100.’ Since these amounts of coverage may leave a great
deal of area unprotected, a security plan needs to be thought through carefully.
If the property to be guarded is a house or office, then all
doors and windows may need to be covered by a group of sensors. The house or
office could be drawn on a piece of paper with a grid, with walls and yard
shown proportionately. Window and door
placements would need to be identified, as well as tall bushes that might
become shields for an intruder. Then the placement of planned security lights
can be drawn with the arc and distance of coverage marked for each. This will allow you to determine how many
fixtures are needed and where they are needed.
If the area covered is much larger, such as a large yard or
a warehouse, then a similar plan is still needed to cover all of the entrances
and windows. A grid could be used on a piece of paper in much the same way.
An example can be seen in the graphic below:
A sensor with a range of up to 2700 can be placed
on a corner, while a sensor with a range of 1800 can be placed along a wall. Coverage for a
door and windows along a wall may only need a sensor range of 900. By drawing out the areas of possible entry by
an intruder on a grid, it makes it easier to determine the number, placement,
and sensitivity of security lights.