96 ELECTRICALCONTRACTOR | SEP. 14 | WWW.ECMAG.COM
> FOCUS BY CRAIG DILOUIE
A good lighting design requires a good controls design. A
good controls design, in turn, ensures that the lighting system
produces the right amount of light where and when it is needed.
Benefits of a good control design include reduced energy costs
and flexibility, which can support the user’s visual needs and
create a desired mood or ambience. This article provides a brief
introduction to how lighting controls work, resulting control
strategies and how those strategies are applied to projects.
A lighting control device or system operates on an input/
output basis. An input component or device provides information to a lighting controller. Based on its logic circuit, the
lighting controller decides if and how to change output and
subsequently signals the power controller. The power controller then makes any required changes to the output of the
controlled lights. These functions may be integrated within a
single device or enacted as a series of devices that are rated as
compatible. The basic inputs are manual or automatic while
the basic outputs are dimming and switching.
Manual controls require a person to interact with them.
Because the user initiates the control action, it is typically
driven by applications involving output being adjusted based
on a desire to achieve certain visual conditions. A good example
is a meeting space where the lights may be raised to full during
face-to-face discussion but lowered in part of the room for an
With automatic controls, the input is a signal automatically
produced by another component or device, such as a computer,
occupancy sensor or photosensor. These components and
devices generate signals typically based on time, occupancy
or light level. Automatic control is generally driven by energy
management, that is, saving energy by reducing or turning off
the lights in response to conditions such as lack of occupancy
or abundant daylight.
In both cases, the outputs are switching and dimming.
Switching may be enacted as simple on/off, though a degree
of flexibility may be gained through bilevel or multilevel
switching. This allows a choice of two or more output levels
from the luminaire or lighting system (in addition to no output) by assigning alternate lamps, ballasts or luminaires to
different control outputs. For example, a three-lamp fluorescent luminaire may be configured with a ballast that controls
the outboard lamps and another ballast that controls the
inboard lamp, resulting in a choice between outputs of 0 percent (off ), 33 percent (one lamp on), 66 percent (two lamps
on) or 100 percent (all lamps on). Switching is a simple, relatively economical control method well-suited to applications
where a limited range of light-output levels is acceptable and
where abrupt, noticeable changes in light level will not be
irritating or disruptive. A simple example is a device that
automatically turns the lights off (or reduces light output)
when a space is unoccupied.
Dimming may be continuous or step. Continuous dimming
enables light output adjustment across a range, with smooth
transitions between each output level, resulting in a very high
degree of flexibility to satisfy visual need. It is ideally suited to
applications where we need transitions between light levels
that are not irritating or disruptive to users. Daylight harvesting in an open office is a good example of where continuous
dimming is advantageous. As daylight levels rise and fall, elec-
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LIGHTING CONTROLS are devices and systems
that regulate the output of lamps and luminaires. They either turn the
lights on and off using a switch or adjust light output using a dimmer. Growing
demands for energy savings and flexibility to support visual needs have given lighting control
much greater prominence. In particular, commercial building energy codes are driving demand for more
sophisticated, detailed and layered control systems. The digital revolution in lighting control technology
has enabled manufacturer solutions to keep pace with these demands.
Lighting control strategies