Lighting control systems: DALI, KNX and detection serving your installation

A DALI or KNX lighting control system turns a static installation into a set of communicating luminaires, able to adapt in real time to the occupancy of the premises and to daylight. For a company, a local authority or a design office, the right choice of protocol determines visual comfort, maintenance and the level of energy savings. This article reviews the technologies available and their practical benefits in a B2B context. Municipal sports facilities · gymnasiums and multi-sports halls occupied by time slots · are among the contexts where control and presence detection pay off the most.

Why control your lighting?

In a modern LED installation, the luminaire represents only part of the overall performance. Control adds a layer of intelligence that makes it possible to light the right area, at the right level, at the right time. In practice, a lighting management system meets three objectives:

• Reduce consumption by switching off or lowering the illuminance of unoccupied areas and making use of daylight.
• Improve visual comfort through gradual dimming, scenes suited to each activity and the maintenance of stable illuminance (in lux).
• Make operation easier through supervision, feedback of information and preventive maintenance.

These benefits rely on standardised communication protocols. The two references of the commercial and industrial market are DALI and KNX, often combined.

The DALI protocol: the lighting industry standard

DALI (Digital Addressable Lighting Interface) is an international, non-proprietary protocol dedicated exclusively to lighting control. It is based on a two-wire digital bus, non-polarised and not very sensitive to electrical interference. Its major feature is individual addressing: each luminaire driver receives its own address and can be dimmed alone or in a group.

A DALI bus manages up to 64 addresses (luminaires or sensors), which can be organised into 16 groups and 16 scenes. Three levels of addressing coexist: general broadcast, group, and individual address. Communication is bidirectional: the system knows at all times the actual state of each light point and its dimming level, which opens the way to preventive maintenance (reporting a faulty luminaire, for example).

DALI-2: reinforced interoperability

The second version, DALI-2, extends standardisation to control devices: presence detectors, light sensors, push buttons. Whereas the first generation mainly standardised the drivers, DALI-2 guarantees interoperability between equipment from different manufacturers, including for sensors. A DALI-2 presence detector thus controls the illuminance of a space according to its actual occupancy, in a reliable and standardised way.

KNX: the protocol of building management

KNX is a much broader home automation and building management system (BMS) protocol: it controls lighting, but also heating, ventilation, blinds, access control or energy metering. Whereas DALI is a specialised "industry" protocol, KNX acts as the central nervous system of the building.

In practice, the two worlds complement each other. A KNX/DALI-2 gateway interfaces the communicating lighting network (DALI-2) with the KNX bus. The lighting retains the fine dimming and status feedback specific to DALI, while being integrated into the overall supervision of the building. This is the preferred architecture for large commercial projects, where lighting must communicate with the other technical packages (HVAC, BACnet, TCP/IP).

Presence detection and daylight management

Control only takes on its full value when combined with sensors. Two families are essential:

• Presence (or absence) detection: the luminaire switches on when an occupant arrives and switches off (or dims) after a time delay when the area is empty. Particularly effective in circulation areas, toilets, car parks and warehouses with intermittent occupancy.
• Daylight management (daylight harvesting): a sensor measures natural illuminance and modulates the artificial lighting to maintain a stable setpoint in lux. Near windows, the artificial share is reduced or even cancelled during the brightest hours.

These two strategies, combined with dimming, form the core of the energy savings of a controlled installation. We detail the orders of magnitude in our dedicated article: how much is saved with intelligent lighting control.

Scenes, dimming and supervision

Beyond sensor automation, a control system makes it possible to programme scenes: reduced illuminance outside working hours, meeting atmosphere, cleaning mode, lowered night profile in a car park. Gradual dimming avoids abrupt variations and preserves comfort. Finally, supervision centralises the status of the installation, measures consumption and gives an alert in the event of a fault.

At luminaire level, control requires dimmable drivers and, ideally, integrated sensors. The SKY-S-S 80 desk lamp with intelligent sensors illustrates this logic at workstation level: detection and automatic adjustment of direct/indirect illuminance. At floor level, our whole commercial range is designed to be integrated into DALI management.

Benefits for B2B

For a decision-maker, the value of a control system comes down to a few tangible points: significant energy savings, preserved LED lifetime (a dimmed luminaire runs cooler and lasts longer, which helps L70/L80), maintenance made easier by status feedback, and great flexibility of use. The extra investment cost is justified by the return on investment (ROI) over the operating period, a subject we cover in detail in the article on the savings from intelligent control.

FAQ

DALI or KNX: which to choose for my building?

DALI is the standard dedicated to lighting, ideal for finely dimming and addressing each luminaire. KNX manages all the technical packages of the building. For a purely lighting project, DALI-2 is often enough; for a BMS including HVAC, blinds and energy, KNX and DALI-2 are combined via a gateway.

How many luminaires can a DALI bus manage?

A DALI bus manages up to 64 individual addresses, divided into a maximum of 16 groups and 16 scenes. Beyond that, the number of buses is increased and they are federated via gateways and a supervisor.

Are specific luminaires needed for control?

Yes, the luminaire must have a dimmable driver compatible with the chosen protocol (DALI, 1-10 V…). Before any purchase, a study makes it possible to check the compatibility of the drivers and the sizing of the buses and sensors.

Is presence detection suitable for all rooms?

It is very effective in areas with intermittent occupancy (circulation areas, car parks, warehouses, toilets). In spaces with continuous occupancy, daylight management and dimming are preferred rather than switching off.

Need a photometric study? Sizing your installation and its control system is the work of a lighting design office: we recommend the expertise of the Luminance Consulting agency, the lighting design office that contributes to developing our ranges of luminaires based on an in-depth analysis of the needs of the most demanding customers. Rexylum then supplies you with the prescribed luminaires and control solutions: contact us.