In the last 20 years electronics and computers have profoundly influenced the development of most areas of peoples lives. Buildings are no exception, on the contrary not only are they the accommodation of this technology they are also a user of it. As society has changed, buildings have evolved in their design to provide a more comfortable, secure and energy conscious environment. While some of these changes are in design and materials, one of the biggest changes has been in the introduction of intelligent microprocessor based controls.

One of the most significant developments within this technology, is the use of intelligent lighting controls. These controls provide greater flexibility, leading to better management of light. They make it possible to create an aesthetically pleasing environment, while at the same time saving energy.

Intelligent Lighting Controls

The concept behind these controls is to operate lighting automatically according to the function of an area, the time of day, ambient light levels, or occupancy. The single most important aspect is programmability, that is the ability to remember lighting levels as a series of settings. These settings, also known as scenes, can be recalled automatically by the dimmer system or by a central building control system. Domestically this can take the form of an integrated central controller, which may have a touch screen interface. In effect this takes the place of a full building management system (BMS) which would be used in a commercial situation.

Lighting controls can be either stand alone, room dependant types, or larger networked systems, where the dimmer units are fitted in an electrical cupboard and operated by a network of external devices like sensors and control panels. The networked systems have the advantage of allowing control of different rooms or areas from many points. In a domestic setting this could be a wall mounted switch panel near the main entrance that acts as a master to several rooms.

Network systems also have standard serial ports, which makes integrating to central controllers much easier. These interfaces are usually bi-directional so a central controller can request a level change and then confirm the action. The information from the lighting system can also be used to determining energy consumption or for mimicking occupancy patterns while the house is unoccupied. Standalone dimmers can be interface too, via Infra-red remote control though this only provides for one way operation without the ability of determining if a request has taken place.

Advantages of lighting controls

Intelligent lighting controls have many advantages over manual ones, including convenience, creating ambience, increased design flexibility, energy savings, reduced lamp replacement costs and security.

Convenience & Ambience

With intelligent lighting the circuit levels are pre-programmed according to use and according to other factors such as daylight level entering the building. 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" to a room or area. A common number of scenes are eight, though some systems can have many more.

Once set up scenes can be easily recalled manually from wall mounted switch panels or by remote control. They can be recalled automatically by timer, by daylight sensor or according to occupancy. Once a new scene is selected the lighting will fade to the new set of levels at a pre-determined 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 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.

In warm climates and in the summer months when air-conditioning is used lowering the thermal load of the lighting can also save energy. Solid state dimmers, unlike their rheostat predecessors, do not dim lighting by loosing the excess energy in the form of heat through a resistive load. Instead they switch the load on and off 100 times a second with a time delay proportional to the amount being dimmed. * see how a dimmer works.

Not all lamps are dimmable, some like compact fluorescent lamps, can only be switched on or off. However, energy can still be saved 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.

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 building is unoccupied 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.

Light Sources

Tungsten

The most popular light source is the common household lamp, the incandescent lamp. Though they are the most common, they are also the most inefficient source of light available and have the shortest life. The lamp consists of a resistive tungsten filament that heats up and glows. Tungsten evaporates, gradually weakening the filament, and leaving a blackened inner surface on the bulb.

Tungsten halogen

An improvement in this lamp type is the tungsten halogen lamp. The halogen gas helps redeposit the evaporated tungsten onto the filament leading to a 2-3 times longer life span. The color of light is better, it is whiter at full brightness and when dimmed passes through shades of yellow and orange. Both of the above types operate at mains voltage and can be dimmed.

Low Voltage Tungsten Halogen

Low voltage lamps are used domestically for spotlights, down lighters and modern table lamps. They are available in different sizes, beam angles and wattage's from 5w to 50w. They are all categorized by requiring a 12v supply that is derived by using a transformer of the correct wattage for the lamp.

The input to the transformer is the mains supply (or channel output from a dimmer) the output of the transformer is a (dimmed) 12v supply to the lamp. These lamps give a more complete crisper light with better color rendering. They are more efficient and last up to 5 times longer than tungsten lamps.

Fluorescent

Comes in a variety of sizes, but most common is the tube and compact fluorescent types. The latter is used domestically in the form of a low energy replacement for a normal lamp.

They operate by creating a UV arc that excites a phosphor coating which fluoresces creating the light and hence the name. Interrupting the supply to a choke also known as ballast starts the UV arc. Fluorescents are much more efficient than incandescent lamps and are available in different colour temperatures. Domestic compact fluorescents are not dimmable but instead can be switched as part of a scene or program. However, tube fluorescents can be dimmed with a high frequency dimmable ballast. These have a live supply and a control supply commonly 1-10v. Most Intelligent lighting controllers have an interface card which provide a control signal for telling the ballast what level to dim to. Typically fluorescents can be dimmed down to 5 to 10% depending on the ballast manufacturer. Energy saving through dimming is proportional to the dimmed level on a 1.1 ratio.

Neon - Cold Cathode

Used most often in signage and to light ceiling recesses in buildings. They are usually custom made, with different gases and tube coatings for different colors. A high voltage transformer that operates at-3 - 6KV at a low current powers them. These transformers can be dimmed on the mains supply side by some controllers. The minimum dimming level, typically, is 10% dependent on the lamp and transformer characteristics. Energy is saved when dimming though lamp life is not extended.

How do light dimmers work

The principle of lighting controls is to either dim or switch the lighting according to requirements. Mains power is comprised of an alternating current that flows in one direction and then in the other along the cable at the rate of 50 or 60 cycles per second, measured as frequency in Hertz. The value 50 or 60Hz is dependent on the countries power system.

If we were to look at this waveform it would appear as stretched S shape on its side. Draw a line through the middle and this is what is called the zero crossing point. Dimming is achieved by turning a solid state switch, or triac off and then on again a period of time after this point has elapsed. The longer this time, the less energy will pass through the triac and into the lamp and the more it will be dimmed. This turning on and off of the triac occurs every time the mains crossing point is reached (half phase), 100 times per second. Some controllers use a microprocessor control with the above timing function being handled by an analogue circuit. More sophisticated systems, called digital dimmers, operate the switching direct from microprocessor. This has the advantage of greater reliability, quieter operation, lower cost and smaller controls.

Summary

Intelligent lighting controls have the capacity to improve the quality and function of our environment. They provide cost savings as well as convenience.

With improvements through R & D and a lowering in the cost of manufacture, lighting controls are destined to become an invaluable part of many of our everyday lives.

Further information on lighting and lighting dimmers can be obtained by visiting the Futronix web site at: www.futronix.com. Futronix is one of the world's leading manufacturers of lighting control systems manufacturing and a wide range of, all-digital consumer and dimmers - commercial.