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Bluetooth mesh network and DALI

Dec. 08, 2020

Bluetooth mesh network and DALI


In May of this year, the Bluetooth SIG and DiiA (Digital Lighting Interface Alliance) announced that they are cooperating. The goal is to specify a standard interface that can configure, monitor, and control D4i smart lamps on the Bluetooth mesh lighting control network.

The two organizations will lead the lighting industry to create a future IoT lighting system that is fully interoperable and can be upgraded in the field by harmonizing standards.



Bluetooth mesh network


The Bluetooth Technology Alliance released a set of mesh network specifications in 2017, including mesh network configuration files, mesh network models, and mesh network device attributes. The mesh network configuration file specifies how the general mesh network operates. Although the idea of using Bluetooth technology to build low-power wireless networks has existed for many years, the release of mesh network models and mesh network device attributes has greatly exceeded the expectations of the industry, especially in view of their coverage.


The mesh network model specification includes a complete set of functions required to build a powerful lighting control network with high scalability. It is not entirely appropriate to just classify them into lighting control because an important part of the mesh network model specification involves sensors and data. Nowadays, sensors have obviously become a basic part of lighting control systems, and a more obvious trend is that the control part of the lighting system begins to be affected by data from non-lighting environment sensors (such as temperature, air quality, noise, carbon dioxide concentration, etc.) Covered. The Bluetooth mesh network model specification supports all these trends from the beginning.


In addition to sensors, some people also predict that the industry will be more and more eager to collect more data from field devices, which also gives mesh network device properties a "useful". In 2017, the mesh network device properties formulated hundreds of data point definitions that can be exchanged between Bluetooth mesh network devices. This exceptionally rich collection of data definitions brings about a data-rich lighting network.





DALI is a brand under the Digital Illumination Interface Alliance DiiA (Digital Illumination Interface Alliance). It is the abbreviation of "Digital Addressable Lighting Interface" and its official name is IEC62386. It is a very complete and extensive lighting standard and is well known for its components. Recently, people are paying special attention to DALI 25x (especially the 251, 252, and 253 standards), which are collectively referred to as D4i (Internet of Things DALI) or the data part of lamps and lanterns.


The three together provide data report items for nearly one hundred lamps. Considering that there may be thousands of lamps in a Bluetooth mesh network, the lamp business can be said to be a big data service. You may be surprised by this. But these data can indeed be used for many purposes, such as managing lighting systems, optimizing energy consumption and predictive maintenance, etc., and all these data are now available.



Benefits from cooperation


Because it can read data from the digital drive, the sensor controller suddenly has a new role: it can forward the data about the drive and light source to the cloud system through the mesh network, where it can be converted and analyzed before being sent to Various applications.


The space utilization application can visualize the collected building usage data. The lighting maintenance application can monitor the working condition of each lamp, observe abnormal conditions, and trigger repair measures before the problematic lamp fails. Energy reporting applications can send data to utilities to help improve the energy balance. These applications bring endless possibilities.



New specifications


The Digital Lighting Interface Alliance DiiA is responsible for the definition of the DALI bus, the functions in the digital driver, and the data report format. Bluetooth technology is responsible for realizing the wireless mesh network between lamps (mesh network profile specification) and providing lighting control and sensing functions (mesh network model specification) and compatible data format (mesh network device attributes).


Although the control function and data type mapping between Bluetooth technology and DALI are very intuitive, it is necessary to develop Bluetooth-DALI specifications to upgrade it to a globally unified interoperability level. Since the two institutions have signed a cooperation agreement, this work is in progress. The specification will also lead to a joint certification program to ensure that intermediate devices (such as sensor controllers) between the Bluetooth mesh network (wireless network between lamps) and DALI (bus in lamps) are tested for interoperability and functionality



A match made in heaven


As you can see, this system can be described as a match made in heaven, not only can accurately map control functions, but also accurately and clearly map data, and the Bluetooth distributed control architecture is perfectly integrated with the DALI application controller concept. This kind of independent architecture with such a high degree of matching and scalability is rare. Such win-win cooperation makes us very much looking forward to the bright future development prospects of the pair.


With technical matching and the close cooperation between the Bluetooth Technology Alliance and DiiA, more interoperable smart lighting components will appear on the market, further accelerating the adoption of IoT smart lighting systems in modified environments and new environments, and finally To achieve the goals of saving energy, improving comfort and user experience at a moderate cost.



Connection method

In order to explain the connection between the Bluetooth mesh network and the DALI brand under the Digital Lighting Interface Alliance DiiA, let's start with the lamps, such as the light troughs on the office ceiling and the elongated hanging lamps. Despite the different dimensions, the interiors of the lamps are very similar, including a light source (LED) and a driver (to provide power to the LED). Under normal circumstances, the luminaire also has space usage and brightness sensors. The sensor controls the driver through an analog line (0-10V line). When the voltage is 0V, the driver is turned off; when the voltage is 10V, the driver reaches the maximum power, and any voltage in between is converted to (approximate) lamp brightness. For example, when the voltage is 4V, the driver reduces the brightness of the lamp to about 40%. This is the analog lamp of the past. With the arrival of the Bluetooth mesh network, sensors are added to the lamps through the mesh network. The previous sensor devices generally include space usage and ambient light brightness sensors, and now they have also added microprocessors and Bluetooth radios (usually in the form of integrated system chips). Unlike blindly controlling drivers, sensors can exchange information through mesh networks, publish their own data, and subscribe to other sensors. Strictly speaking, in a Bluetooth mesh network, one sensor cannot subscribe to another sensor because it cannot process the received data.


This makes the most powerful "weapon" in the Bluetooth mesh model library-the lighting controller (LC) useful. LC is a kind of software running on the internal microprocessor (or chip-level system SoC) of the sensor, which can convert the dumb sensor into a lighting controller equipped with a smart sensor.


The miniaturized design makes the device still look like a sensor, but it is more powerful and can drive a complete set of lighting control strategies, such as manned, unmanned, or daylight modes. And it behaves like a cell in an intelligent creature, which can achieve complete synchronization of actions by coordinating actions with nearby lights. All of this does not need to be equipped with the central controller that was common in the previous generation of networked lighting systems. The traditional control box is gone, and the distributed controller embedded in the lamp sensor turns the lighting network into a collective intelligent lighting system. Since each lamp is fully autonomous, there is no single point of failure in the system, but each lamp can still be fully synchronized.


In today's digital lighting world realized by DALI, the 0-10V control line between the sensor controller and the driver has been replaced by a digital bus. The structure of the bus is very simple-only two ordinary lines. First, this two-wire bus can provide communication and power at the same time, so the sensor does not need to be connected to any external power source but is powered by the DALI bus. Second, the communication through the DALI bus is digital communication, so there is no room for approximation, which means that the approximate value of "about 40%" will no longer appear, but it can be adjusted to exactly 40% (or any required Other brightness), which is like simulating the precision difference between vinyl records and optical discs. Third, DALI not only supports control commands, but also supports queries that can feed back part of the data, which is impossible to achieve in analog lamps. Strictly speaking, according to DALI terminology, a Bluetooth mesh device with all networking, sensing and control functions has become an application controller in a lamp.


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