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Developments in customised lighting controllers

Posted: 31 May 2013     Print Version  Bookmark and Share

Keywords:LEDs  lighting controllers  Digital Serial Interface 

As the adoption of LEDs in the lighting market increases, the demand for customised lighting controllers grows as well. These enable customers to adapt brightness and colour to the requirements of their application. In the architectural lighting segment, for example, companies often want to illuminate their buildings both inside and outside to incorporate their corporate design and increase brand recognition. They may want to specify the way a logo is portrayed, add animations and change designs.

Theoretically, any PC can manage the control aspect of this lighting if it is connected to a network, and mobile options are also available with control via smartphones or tablets.

This results in the demand for lighting control that is as flexible and effective as possible. Terms as Konnex (KNX), Digital Serial Interface (DSI), Digital Addressable Lighting Interface (DALI), and Digital Multiplex (DMX) appear

For lighting control, customers may consider a home bus like KNX, an open standard that is supported by over 100 European companies. However, it requires its own bus system, and extending the installation at a later date is usually seen as too time-consuming and too expensive.

Digital Serial Interface (DSI) is a protocol that was originally developed by the company Tridonic. The information is transmitted over a simple 8bit protocol. The disadvantage of this method is that each channel needs to be hardwired to the lights. This has resulted in the emergence of the DALI interface, which is based on DSI.

DALI is one of the most cost-effective control options, as the 1200-baud control signal is transmitted via a 2-wire bus. A simple NYM 5x1.5mmý cable is sufficient to handle both power supply and signal transmission to the ECGs at the same time. It can be combined with KNX or other home buses by means of the appropriate gateways. However, DALI is limited to simple on/off and dimming functions. In addition, it only supports a maximum of 64 individual devices (i.e. addresses), 16 groups (group addresses) and 16 ambiences (ambient light values).

In order to get round these limitations, DMX is available. Originally developed for theatrical lighting, it is an open standard that has been established for several years. DMX-512 enables simultaneous control of brightness (dimming), colour changes and movement, such as for moving heads. At 250kbit/s, the baud rate is high enough to control a large number of lamps. DMX-512 can address 512 channels, known as a DMX universe.

RS-485 is the electrical standard for DMX-512. A Universal Asynchronous Receiver Transmitter (UART) protocol is used to transmit data. This is another case where adding wiring at a later date can be very time-consuming, because a maximum of 32 receivers can be connected to one DMX-512 bus. A repeater and splitters are also required. Due to the high data transfer rate, the installation required an appropriately shielded cable with 110 Ω impedance. As a result of these requirements, a pure DMX-512 system has limited suitability for architectural lighting.

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