Anything you want to know about dimmers














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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