Appliances & Equipment

Energy-efficient Lighting Control

  • Automatic dimming control of fluorescent lamp using analogue technology and electronic ballast has long been used in commercial lighting
  • It was not popular because of high equipment cost (separate sensors, controllers & lighting control modules) & wiring cost (dc control cables)
  • New development in digital control technology has greatly reduced equipment & wiring cost
  • Intelligent digital lighting control with integrated sensors to detect daylight and occupancy is also available to enhance energy saving in T5 lighting system

  • Analogue Dimming

    • Phase control was the earliest form of dimming fluorescent lamps by reducing input/output power of ballasts (magnetic type)
    • With the evolution of HF electronic ballasts, analogue dimming was the first attempt to dim lamps more accurately by using an independent bus line
    • A 1-10V DC signal sent along a ELV bus to ballast changed its output frequency to lamp for dimming
    • Potentiometer could also be placed into the circuit & vary output signal generated by ballast
    • Analogue dimming became popular during late 80' and early 90', but was limited in accuracy & applications

  • Analogue Dimming: 1-10V System

    • Imprecise 0.1V = 1% (Minimum level normally 10%)
    • Voltage drop over long distance makes inaccuracies
    • Proportional scale not reflecting true sensitivity of human eye human

  • Digital Dimming

    • Micro-processors nowadays evolved into computers to perform many function at tremendous speed
    • The increase use of network languages such as LON, EIB, C-bus etc., all made use of the power of processors
    • Analogue technology in lighting control is to send a signal to switch or a voltage to regulate lighting level
    • Digital works on numbers, send the data bit for the level required more accurately & ON/OFF commend if necessary

  • To achieve smooth dimming, a logarithmic scale (127log(%)+1) is used in digital dimming to reflect true sensitivity of human eye

  • Digital Dimming

    • Data is biased towards the lower end of the scale to improve perceived dimming quality
    • Digital signal simply gives the lighting level (1 to 255) required & it is up to the controllable ballast to interpret the signal which is able to do
    • Control of ballasts is by a 2 wire bus
    • Multi-point control anywhere along the bus
    • Bus voltage is 12V & universal polarity

  • Digital Dimmable Ballast

    • Precise commands
    • Switching via digital signal
    • Disturbance free signal
    • Polarity free installation
    • All ballasts receive the same signal

Typical equipment for intelligent digital control using Digital Serial Interface (DSI)

  • DALI (Digital Addressable Lighting Interface) is a new industrial standard to lighting control system
  • DALI protocol (amendment to IEC929) has been adopted as new standard by major ballast manufacturers (Helvar, Philips, Osram, Tridonic, Trilux, VS etc.)
  • As dedicated communication interface for control of lighting system, DALI enables sophisticated control with increased flexibility and reduced installation costs
  • DALI digital control signal used to control electronic ballasts, relays & sensors belonging to the system
  • Each system components has its own device-specific address for individual device control

A typical DALI Lighting Control System

  • Main differences between DALI & building automation buses:

    • DALI system has a limited system size (64 addresses)
    • DALI is meant only for communication in lighting systems and BMS includes other functional control as well (HVAC, security, fire services, etc.)
    • BMS normally has unlimited expansion possibilities, which DALI does not have
    • DALI system is not competing against BMS, it is only complementing them through an interface