Centralised Lighting Control Systems

Standalone lighting controls vs centralised lighting control systems

Standalone lighting controls allow ‘standalone’ control of the lighting within a space, typically a single room. Controls may include switches, occupancy sensors, photocells and time clocks (see below), which are typically hard-wired to control fixed groups of lights independently. Adjustment of these needs to be made manually at each device location.

For more information on standalone lighting controls, see Standard Local Controls.

In contrast a centralised lighting control system refers to an intelligent networked system of devices relating to lighting control. The system has user inputs, a processing unit with a programme to process the signals (typically centralised within a building) and a method of controlling the lighting fixtures based on the outputs of the programme. The control programme can usually be changed centrally. The application of local controls such as occupancy sensors can be varied according to time of day, time of year and other input conditions.

User inputs may be made locally by switches, occupancy sensors, photocells, centrally at central processing units via software programmes, or remotely by smartphone / online app. The system may also accept signals from other building systems, such as fire alarms.

Advantages of centralised lighting controls

Centralised lighting controls allow the building manager to have centralised control of all of the circuits in a building from a single user interface or app.

• The ability to control multiple light sources allows the complex ‘scenes’ to be created across the building. An obvious scene is “all off” in which every light in the building is turned off in response to one input. Or the offices on a single floor could be put into “evening mode”, or all lights in the building could be turned on at the start of the working day. Scenes could be operated remotely, or locally using a keypad on the wall (see scenes below).
• It is easy to see how easy and efficient control of all circuits will result in a saving in energy and in building management costs.
• Furthermore the systems allow much more flexibility than standalone controls. For example the mapping of lighting circuits to occupancy sensors and timeclocks can be adjusted without altering the wiring. With DALi control systems, the mapping of individual light fittings or drivers to occupancy sensors can be changed. This is ideal if a space is rearranged, partition walls are inserted or removed, or the general functionality and operation of the space is changed.
• Centralised control systems can cover lighting alone, or they can extend to some combination of lighting, security, windows, blinds, temperature controls, sound systems and other applications, and can also interface with the alarm system. The technology makes the building much easier to manage.

Wired vs wireless

Smart Building technology can run on WiFi, but it is generally better to install a cabled system using low voltage cables to connect devices and circuits to a central processing hub. For commercial buildings, the systems are generally installed in new builds or as part of major building renovation. For domestic properties, the WiFi system may be deemed adequate.

Scenes

A lighting scene is a set of lighting levels for a set of lighting circuits designed for a specific task. For example, a ‘cleaning’ scene might have higher light levels for space illumination, whilst other scenes are set to create a certain ambience or mood.

The scene can be selected with one button, rather than having to set the level of each lighting circuit individually. Note that the controls will need to allow for an ‘off’ scene.

An obvious application of scenes is to turn all lights in a space off at once. A typical conference room might have scenes to allow a discussion, to allow watching of a presentation, or for entertaining in the evening. There will also be a cleaning scene and an ‘all off’ scene:

• meeting;
• presentation;
• entertaining;
• cleaning;
• all off.

The control panel might also allow for the blinds (e.g. North blinds, South blinds) to be opened, closed, raised or lowered. A typical keypad to achieve this would look like this:

Types of lighting control

Lighting control systems typically allow adjustment of the output of a light fitting or combination of light fittings based on:

• local input at a keypad / wall switch / dimmer;
• time clock – time of day or astronomical clock;
• occupancy using occupancy sensors (absence or presence detection);
• daylight availability using photocells (daylight harvesting);
• signals from other systems such as alarms;
• programme logic (“if these things happens, then these circuits should be on at these levels of dimming…”).

For more information on occupancy sensors and daylight harvesting, see Standard Local Controls.

Lighting control protocols

There are various ‘protocols’ underlying control of lights. The most popular protocols in commercial and residential dimming are DALi, 0-10V and phase dimming.