In our previous post ”Lighting regulation and control systems“, three of the most common control systems were analyzed. These systems offer a lighting that adapts to the needs of each facility, creating suitable environments for all times and providing both a high degree of comfort and a high energy savings. Let´s remember the three systems we spoke about:
- Leading & trailing edge dimming
- 1-10V regulation
- Regulation by means of Touch Control pushbutton
DALI is the regulation that we will analyze in the present post.
A. DALI Regulation
As revealed by the meaning of this acronym, Digital Addresable Lighting Interface, DALI is a digital and addressable communication interface for lighting systems.
This is an international standard system in accordance with IEC 62386, which ensures compatibility and interchangeability between different manufacturers’ equipment marked with the following logo:
Logo of DALI regulation
It is a bi-directional regulation interface with a master-slave structure where the information flows from a controller, which operates as the master, to the control gears that only operate as slaves, with the latter carrying out the orders or responding to the information requests received.
Digital signals are transmitted over a bus or two-wire control wire. These control wires can be negatively and positively polarised, though the majority control gears are designed polarity free to make connection indifferent.
No especially shielded cables are needed. It is possible to wire the power line and DALI bus together with a standard five-wire cable.
DALI regulation graphic
Unlike other regulation systems, there is no need to create wiring groups, thus all the pieces of equipment are connected in parallel to the bus, without bearing in mind the grouping of these, simply avoiding a closed ring or loop topology.
Mechanical relays are not required to switch the lighting on or off, given that this is done by means of orders sent along the control line. Neither are bus termination resistors required.
Consequently, the DALI interfaces offers wiring simplicity in addition to great flexibility when it comes to designing the lighting installation.
DALI operating device
The maximum voltage drop along the control line must not exceed 2V with the maximum bus current of 250mA. Therefore, the maximum wiring distance allowed depends on the cable cross section, but it must never exceed 300m in any case.
After wiring, software is used to configure the DALI lighting system. Up to 16 different scenarios can be created, addressing the equipment individually up to a maximum of 64 addresses, by groups up to a maximum of 16, or simultaneously by means of a “broadcast” order. The configuration can be changed at any time without any need for re-wiring.
The DALI system has a logarithmic regulation curve adjusted to human eye sensitivity, defined in the international standard, IEC 62386. The possible regulation range is set at from 0.1% to 100%. The minimum is determined by the equipment manufacturer.
Graphic of luminous flux
The time needed to go from one light level to another, known as the ‘fade time’ and the speed of the change, the ‘fade rate’ can be set by the software.
The DALI system lies in the fringe between the complex and costly but powerful ones; control systems for buildings that offer total functionality and the most simple and economic regulation systems, such as, for example, the 1-10V one.
Graphic of DALI functions
This interface can be used in simple applications, independently, to control a luminaire or a small room and in high level applications such as being integrated by means of gateways into building smart control systems.
B. Control system components for DALI:
Apart from the light source to be controlled, lighting management systems are made up of other additional components. Among these you have control gears, switches and command wire equipments, sensors, controllers, adaptors, repeaters, converters, gateways and configuration and monitoring tools.
Control gears:
Lighting control gears, drivers for LED modules, ballasts for fluorescent and discharge lamps, transformers for halogen lamps are the components commissioned with making the light sources work properly. They must be adjustable by the control method chosen to enable their integration into a lighting management system.
Switches or control elements:
These are components by means of which the user interacts with the lighting management system, making it possible to switch the light on and off and regulate it directly by hand. This group consists of pushbuttons, knobs and control panels.
Sensors and detectors:
These are devices capable of detecting physical and chemical magnitudes and transforming them into signals that can be processed. In lighting management systems, presence detectors and photocells are particularly important as they serve to switch on and off and regulate the lighting automatically, depending on the presence of persons and the natural level of light in the space to be illuminated.
Control units and controllers:
These components serve to receive all the information from the rest of the system’s components, process it and generate the control orders to be distributed intelligently.
Repeaters:
These are components that amplify the level or power of weak signals, thus, in lighting management systems, they must be used when longer wiring distances are required, or a greater number of equipment needs to be connected than is allowed in principle.
Adapters, converters and gateways:
These components are needed when you have to connect components that do not use the same communication protocol. They serve to convert a signal into another in order to enable communication between the different devices. They range from simple adapters that convert an electrical signal to communicate between a few components to gateways that enable communication between systems with different protocols and architectures at all levels of communication.
Configuration and monitoring tools:
More advanced lighting management systems need software tools to enable their addressing, programming, parameterising and monitoring.
A solution for every application:
Lighting management systems can be more or less complex depending on the solution chosen for each one; the control method chosen, the number and type of components, the interconnection between them and their integration with buildings’ control systems.
There are a wide range of possibilities ranging from the simplest solutions consisting of individual luminaires fitted with adjustable equipment and photocells connected directly between them, which regulate the light separately from the rest of the lighting, to more advanced lighting management systems, integrated into the smart control of buildings, which can control luminaires in different rooms and on different floors with multiple uses, to the extent of being able to create different atmospheres adapted to each situation and to report information on their status at all times.
Jesús Gallego, engineer I+D+i
