8/6/2003 - Modern building automation requires flexibility down to the last data point. PC and Ethernet-based automation enables complex control concepts to be realised at the medium and company-wide building management level. The new DALI standard now offers a further alternative for the lower automation level. The DALI Bus Terminal can be used to couple electronic devices, e.g. fluorescent lamps, to the modular Beckhoff I/O system in order to enable communication with the higher-level systems.
Fluorescent lamps have been a standard component of lighting systems for decades. The entry of electronics into this sector, in particular the development of electronic starters, led to noticeable improvements for the application. The electronic ballast controls the complete energy flow electronically. The lamp can be started quickly and gently. How does the user convey the desired brightness value to the electronic ballast? The electronic ballast requires a digital interface that should be as cost-effective as possible and simple to handle. Ideally, all lamps should be operated in parallel from the 230 V AC mains supply and via a 2-wire bus. This would minimise the installation effort and the cost of materials. With DALI, several manufacturers of lamps and electronic ballasts have defined a standard that meets all requirements and opens up new options.
DALI master in standard Bus Terminal
Beckhoff facilitates access to DALI networks: A KL6811 Bus Terminal with an overall width of only 12 mm contains a DALI master and a DALI power supply unit for the operation of up to 64 DALI devices (slaves). As a DALI controller, the KL6811 searches the addresses during start-up and supports the user during commissioning of his system. Due to its design as a master terminal, the unit is independent of the Bus Coupler used. The DALI Bus Terminal can therefore be integrated as a subsystem in all common bus systems such as Ethernet, Profibus or CANopen.
Simple installation of the digital "lighting interface"
DALI is not a building management bus system, but a signal for the digital control of lighting devices. To this end it links lighting, sensor, switch and contact elements. These DALI connections can be changed without problem. DALI enables flexible lighting control for changing conditions, e.g. changes in room layout, in which case lamps and operation elements are reassigned.
The Installation of the DALI system is extremely simple and can be implemented via the mains voltage and a standard 5-wire line (NYM ribbon conductor or non-metallic sheathed cable). Since the DALI signal does not have any polarity, the possibility of a wrong connection is eliminated from the outset. Further protection is offered by the DALI Bus Terminal, which is not damaged if 230 V are connected accidentally, but switches off.
Groups of lights are simply allocated via mouse click
The Beckhoff configuration software KS2000 enables simple configuration or commissioning of the DALI master terminals and the connected DALI devices. For each DALI device, the basic setting, variable changes and the group or scene allocation can be set. Direct or indirect lighting control according to the DALI specification can be implemented via the device settings.
An ideal combination: Ethernet and DALI
The significance of Ethernet for building automation will continue to grow. EtherCAT opens up further options in terms of cost reductions and performance. The DALI standard is the ideal complement to Ethernet: low costs for actuator control, simple installation, low design effort.
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