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Theme: lighting

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To some it may seem like a subject shrouded in technical mystery, to others it is just downright dull. But choosing the right lighting control method for a project is essential, and straightforward once designers understand the key jargon involved

As well as looking good (or looking invisible if possible), lights need to perform quite specific tasks. It is important to think about when and why they are on or off, or at a given level of brightness. We all take for granted the fact that if we want to make our home more cosy in the evening, we might switch off the main light and switch on some table lights, and this is the point: you need the right light for the right situation.

With thoughtful lighting control we can, for example, maximise the amount of daylight within a space, increasing user comfort and saving energy.

The simplest form of lighting control is the ubiquitous light switch. We all feel comfortable with its simplicity and ease of use, though its range of functionality is limited. The next level of sophistication, with which most of us would be reasonably happy, is a time switch, or time clock switch.

At its most basic level this is what individuals might use in conjunction with a table light to pretend someone is at home while they are on holiday.

At a commercial level, they can be useful for areas where the patterns of use are completely predictable, ensuring that lights are always on when required and that they are not left on unnecessarily. This could be ideal for stairwells, underground car parks, or utility areas. If a time clock also has an 'astronomic' function, then switching on or off, or calling up a scene, can link to sunset and sunrise times (or any specific time period before or after). They also take account of clocks going back and forward.

Keep it natural Many great pieces of architecture from the ancient civilisations show a mastery and understanding of the uses of daylight that makes you wonder if we are doing anything quite so considered now. We don't always make the best use of natural light, and what's more it is free! A relatively simple control method is to use a light sensor to bring lights on at a given light level. This is how many street lights work and is the kind of functionality we now expect from domestic garden lights.

With not a great deal more technology, this basic method can be used to achieve what is often referred to as daylight linking or daylight compensation. This involves monitoring ambient light levels and bringing lights on as required inside buildings, making full use of natural light and using less energy into the bargain. This can be by individual luminaire, a room of luminaires, or an entire office block. The potential problems of lights going on and off all the time have been thought about. Some kind of dimming for any area where people have to work or concentrate would normally be included, and a variety of features means that the problems associated with earlier uses of this type of technology are a thing of the past.

Who's there?

The way light comes on in a room helps form our perception of the space, along with whatever else we see, hear and smell. Simply, lights can be switched on and off by a sensor that, by infra red or movement for example, determines that someone has entered the space. This may be appropriate for WCs, certain corridors, utility cupboards and exterior or security lighting. If this method is to be used in areas that remain occupied for periods of time (for example, if a person sits still for a while), then designers should consider occupancy sensing, which generally involves sensors that have several different ways of detecting within one unit.

Beyond this, levels of activity within a space can be used to trigger changes to lighting.

Lighting designers with more adventurous clients have used this control to deliver some interesting schemes. It can be particularly effective in public spaces such as shopping centres or town squares. A word of caution though: ensure plenty of flexibility in what the system can do, and test a part of the scheme to ensure it works as you imagine, especially if a delicate and subtle interaction is sought.

Nice but dim While some of the control methods discussed above can be used with switching, in practice it is usually preferable to dim.

Dimming can be done in several ways. The simplest method is to control the amount of power going to a circuit of lights. This is how domestic dimmers work and how all mainsvoltage and low-voltage light sources are dimmed, even commercially.

Likewise, there are many ways to dim fluorescent (linear tubes or compact fluorescent lamps) systems. Analogue dimming is simple and works by supplying the power down one cable and a 0-10V signal down another, which controls the amount of light the fittings produce. The fittings are switched on and off through the power cable. With digital dimming, the power supply can come from any cable, and a separate signal cable sends commands to an 'intelligent' ballast within each of the fittings, telling it what to do and when, including switching on and off. Each fitting can act independently, making it ideal for daylight linking. It can also be useful for retrofitting dimming capability into a space that has existing power distribution set up, as the control is independent of the power supply.

DALI Protocol is a term that suppliers will almost certainly quote if you ask about digital dimming. It is a standard protocol developed by a coalition of companies trying to establish a common system for digital control so that various systems and components are compatible with each other. While good in theory, the practice is a bit less awe inspiring as there are some compatibility issues with different manufacturers' interpretation of DALI. If specifying this kind of kit, designers should get all the suppliers involved to discuss compatibility and confirm in writing (preferably after testing) that all compatibility issues relating to the project have been resolved.

Some lighting manufacturers can supply light fittings that include their own integral controls. This is generally restricted to either presence detection or light-level detection, and sometimes a combination of both. This can be a simple and effective way to control lighting and save energy in spaces where overall control is not a priority. However, it is important to consider user override otherwise designers may be faced with frustrated people who feel they have no control over their immediate environment.

Setting the mood Scene setting involves marshalling some or all the lights in an installation to follow a pre-ordained setting or 'mood', which has been agreed upon by the designers and users of the space, at the touch of a button.

Most spaces usually require no more than four presets, although multifunction spaces, including conference facilities, open-plan living areas, restaurants, bars, and hotels, may benefit from a few more. The key is to keep the installation user-friendly. Schemes for restaurants and bars where the scenes are called up automatically by the astronomic clock ensure that staff do not have to be bothered with choosing scenes at all.

The time taken to change from one preset scene or mood to another - known as 'fade' time - is important. Most systems allow for fade times from 0 seconds, and up to hours in some cases.

Choices, choices There are a number of suppliers available to provide the types of control outlined so far, all with products at varying levels of sophistication.

Lutron is probably the largest supplier of architectural lighting-control systems, and has an extremely comprehensive and wellestablished range of elegant products. At entry level, its Grafik Eye 3000 series offers simple and intuitive self-contained control units which are very cost effective. They can be used together and, with various accessories, can deal with surprisingly complex installations. In particular, the Integrale unit is unique in offering the ability to control 0-10V fluorescent and/or mains or low-voltage loads on any of its four circuits, straight from the box. These products are so straightforward that, in the US, they are sold through the equivalent of B&Q for DIY installation.

Lutron's range also includes systems that can accommodate the largest of projects, such as its 5000 series and Conditional Logic system.

However, the consistent feature of the company's systems is that they are all relatively simple to operate and programme. The user interface, both in terms of programming and everyday use, is well considered. Lutron has perhaps been a little slow to develop a DALI compatible system, but it assures that this is now under way and will be available imminently.

Also supplying systems more specifically aimed at commercial environments is Luxmate. It has what is probably the most comprehensive DALI system available. Again, there are products that will control a single room or an entire building, and ranging from a simple daylight compensation system to a centrally controlled scene-setting and lighting-management system. The larger systems offer building managers information about lamps or fittings that have failed, and how many hours in total a given circuit or light has been burning since relamping.

ILight's products will cater for most scenarios and also have a stand-alone unit that competes with the Lutron Grafik Eye 3000 units. Though not quite as fully featured, they have their own unique elements and are worth a look as an alternative.

For homespun products, consider Mode Electronics, which has a range of systems that are well made and reliable. The programming interface is not as user friendly as some systems but the company is constantly developing innovative products.

All the main lighting manufacturers offer their own lighting control systems. Of these Erco's is probably the most useful and the user interfaces are reasonably good. However, its system can be expensive. Philips and Thorn both offer various control systems including DALI-based systems which can cope with large installations, though they are a little limited in their higher-end scenesetting features.

Tridonic, which mainly manufactures ballasts and other components for light fittings, also offers a very simple control system based around its Eco ballasts. It has been very active in developing DALI compatible components and, in particular, a range of One4All ballasts that can be controlled via 0-10V analogue, digital, and DALI systems. These units can be controlled with almost any system. Tridonic also makes a DALI-compatible transformer for low-voltage lighting.

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