Advantages of Dimmers
We have dealt with simple knob operated in wall dimmers but the more sophisticated
types are programmable. These dimmers often known as scene dimmers have many
advantages over manual ones, including convenience, increased design flexibility,
energy savings, repeatability, reduced lamp replacement costs and security.
Convenience & Ambience
Intelligent lighting forms part of home automation where the circuit levels are
pre-programmed according to use and according to other factors such as time of
day. Light fittings can be controlled individually or grouped together in circuits.
Each circuit or fitting can be set to be at a different level of brightness.
These levels are then stored as a "scene" which can best be though of as being
a complete look of a room. Some systems have 10 or more programmable scenes.
Once set up scenes can be easily recalled manually from touch screen, switch
panels, infra-red or wireless remote controls. They can be recalled automatically
by time clock, or according to occupancy. Once a new scene is selected the
lighting will fade to the new set of levels at a pre-determined fade rate.
Energy Saving
When dimming a lamp the energy saved is as high as 98% of the proportion of
unused energy. Because the human eye perceives light non-linearly, it is possible
to reduce light levels by over 10% before the reduction in brightness is noticed.
This would lead to a near 10% saving in energy consumption. A 50% reduction
in dimming levels would save around 40% of the energy.
Intelligent dimmers ramp or fade a lamp to a preset level. This is particularly
important when the lamp is first turned on. Incandescent lamps tend to fail
at this point due to thermal shock of the cold lamp filament. By fading the
lamp to the set level, also know as "soft start", a lamps life is extended
considerably. At 10% dimming, a lamp will last twice as long and at 50% dimming
it will last 20 times as long. Voltage stabilisation, available on more expensive
systems, protects lamps against spikes and peaks in mains voltage.
Not all lamps are dimmable, some like compact fluorescent lamps, can only
be switched on or off. However, energy can still be saved even if they are
turned off automatically when not required. For example, during a bright day
the lamps near a window can be turned off where normally they would be left
on. A sensor that measures daylight provides an input value to the controller
that will measure the value over time and use that information to switch or
dim circuits to per-determined levels.
Energy savings can be derived through occupancy detection. Sensors are mounted
in rooms, which detect if there is movement within the room or area. They feed
that information back to the controller, which counts a period of time that
no movement has been detected for. Each time movement is detected the count
will be reset. Once movement has not been detected for a preset period of time
the lighting in that room or area can be either switched off or turned down
to a low energy saving level. After a further period of no movement they can
be turned off altogether. In warm climates and in the summer months when air-conditioning
is used, lowering the thermal load of the lighting can also save energy.
Security
Lighting can play an important part in security, deterring intruders whether
the property is occupied or not. Low levels of illumination can be programmed
to operate at night in certain rooms or hallways. When the house is vacated
lighting levels can be selected that copy normal usage. This can be by time
clock or by selecting a vacation mode. Dimmed or selectively switched levels
of illumination will save energy and is more effective than leaving lighting
on or using simple plug in timers.
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