Mastering the possibilities of DALI

Digital Addressable Lighting Interface (DALI) is a protocol set out in the technical standard IEC 62386 for network-based systems that control lighting in buildings.

DALI multi-master permits field devices other than ballasts controlling lamps to be added to the DALI system for increased functionality.

As this new standard is adopted by the industry around the world, Daniel Walker, Philips Dynalite Product Manager, discusses a simple yet powerful system solution that blends the benefits of the original DALI AG system with the unlimited scale and flexibility of a fully functional networked solution. Such a solution enables building owners to achieve even greater energy savings and operational efficiency. In addition, the comfort and productivity of occupants is improved, ensuring that the result from the whole system is better than the sum of its parts.

The DALI data protocol and transport mechanism was developed by the DALI AG (activity group) in the early years of this century. When it was launched onto the commercial lighting scene it heralded the possibility of a new era in lighting control and soon emerged as an IEC and industry standard. The ability for each device on a segment of data cable to be separately addressed - allowing up to 64 devices to be installed on a single DALI system (universe) - has dramatically simplified control infrastructure and wiring, as well as enabled advanced individual lamp reporting tools.

The latest evolution of DALI - referred to as DALI multi-master - takes wiring simplification and flexibility one step further by permitting field devices other than ballasts controlling lamps to be added to the DALI system for increased functionality. This permits DALI-enabled devices such as sensors and user interface panels to communicate directly with the DALI ballasts and eliminates the need for parallel data networks.

However, the application of DALI comes with functional restrictions, in both the original and multi-master formats. The main drawback is that the number of luminaires in a DALI universe is limited to 64 and the number of addressable lighting groups, as well as lighting ‘scenes’ that can be recalled, is limited to 16. Furthermore, it is not possible for devices (such as sensors and user interface panels) in one DALI universe to communicate with devices in a separate universe. The implication of this is that many applications for medium and large offices are limited, thereby preventing building owners and occupants from maximising the potential comfort and productivity gains, and savings on the total cost of operation.

These restrictions have been successfully overcome through the innovative use of networked lighting control systems in conjunction with DALI, and now also with DALI multi-master. This creatively engineered solution leverages the best of both standards. DyNet protocol - a more feature-rich control network - can handle as many groups and scenes as are required by a project. Approximately 65,000 groups and scenes can be controlled or recalled allowing for a huge range in scalability - well beyond the 16 groups and scenes in a DALI universe. The solution also supports advanced reporting and control functionality, communicating via a gateway to the DALI field network.

DALI meets DyNet

To optimise a smart and scalable DALI multi-master solution, key devices such as ballast controllers, sensors and dry contact interfaces need to be DALI enabled. A DyNet-based solution allows up to 10 DALI sensors or dry contact interfaces to be connected to the DALI fieldbus on top of the maximum allowed number of 64 DALI lamp drivers without compromising any of the DALI advantages such as polarity insensitivity and free topology network cabling.

The adaptations to the DALI ballast controller device permit it to receive signals from DALI-enabled field devices such as sensors and user panels, and act as a network gateway or bridge to translate these messages into the DyNet protocol. The DyNet connectivity then allows it to communicate with other controllers associated with different DALI universes, which is not possible with standard DALI systems. For example, a building might have one universe that contains the lights in all the meeting rooms, with the lights in an individual room, controlled by an occupancy sensor, forming one group. Lights in the associated corridors and other common areas might be part of a separate DALI universe controlled by a timer program which dims or switches off the lights according to the time of day. If the sensor in a room indicates that the space is occupied late at night, it can communicate with the controller for the corridor lights and override the programming to ensure that corridor lights remain illuminated and provide a safe environment for occupants when they leave the reference area.

DALI multi-master controllers are fitted with an integrated power relay to ensure that the luminaire standby current can be removed if all lamps are dimmed to 0% - a key energy-saving feature over DALI systems that still consume energy when the lights are off. All ancillary DALI components - including power supplies for the device, the DALI driver and the DALI transmitter - are integrated within the controller. These components are usually supplied and installed separately in a standard DALI system. The new ‘smart’ device therefore further reduces initial and total cost of ownership by eliminating multiple terminations and minimising the number of additional individual components to be installed.

Some manufacturers use rotary-pot components in their devices to manually select which of the possible 16 DALI lighting address groups a specific sensor has been assigned to. This requirement for on-site physical adjustment of each sensor not only accepts the arbitrary limitation of 16 lighting addresses, but also greatly increases commissioning time and project delivery risk. There are also additional labour costs when changes to the system are required.

The smarter and scalable solution is to digitally address the sensors using the DALI network. To this end, project-proven universal sensors - that combine occupancy detection (PIR) and ambient light level detection - have been adapted to accept the DALI protocol. On networked solutions, DALI-enabled sensors are configured using the same head-end software so that it can transmit messages to the ballast, as well as communicate with the DyNet network via the controller gateway. Power for the DALI sensor is supplied via the IT network, obviating the need for a mains power or DyNet connection.

To permit the application of a wide range of other devices, in particular user interfaces such as keypads, button panels and touch screens, a DALI-enabled dry contact interface has been developed. Featuring programmable input functions, this allows mechanical switches and relays to be interfaced to the DALI network. Its small size makes it perfect for installation within a wide range of devices to enable them to sit as a device on the DALI network. Moreover, the dry contact interface can support the integration of ancillary building systems, such as BMS, lifts and controlled access, with the lighting control network, providing for the possibility of energy savings beyond just lighting.

Across the universe

The emergence of DALI multi-master compatible devices onto the market is being met with great enthusiasm by the lighting industry, largely owing to the huge reduction in wiring costs. Key lighting equipment specifiers have become aware that for larger-scale installations - where more than one DALI universe is required - not all systems or market offers will be appropriate, or even capable of meeting their needs.

An unlimited number of logical addresses can be formed within each DALI universe on the Philips Dynalite DALI multi-master system. This means that the system can be tailored to project requirements without the need for an additional universe. If more than one universe is required by the specifier the system will communicate seamlessly between them via the DyNet network.

The key to the simplicity of the solution is systems integration that delivers the ideal combination of smart control and wiring minimisation. The fully functional network is used for addressing and configuration of all devices, with information stored in either the DALI drivers or centralised head-end software. Systems integration can be further streamlined - and project delivery risk is significantly reduced - by having all devices of the system designed and manufactured by one company. In addition to this, all aspects of commissioning, device configuration, system and group overviews (using a graphic-style display), system override and event scheduling are carried out using a single software package.