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EETE SEP 2014

ENERGY HARVESTING Control from the light perspective By Matthias Kassner Few aplications have been transformed as radically in recent years as lighting. Well-established products such as incandescent or fluorescent lamps are increasingly being replaced by LED-based solutions, which consume significantly less power and offer the option of tuning their lighting colour. This shift in fundamental light source technology requires more advanced driver circuitry, which in turn results in an increased amount of electronics being integrated into lamps and luminaires. It is only natural to extend the basic electronic functionality required for driving the lamp with additional communication technology to enable remote lighting control. LED lighting control can implement three fundamental functions, which are switching the light on and off, modifying the light intensity and changing the colour of the light. The first two functions are long established with basic switches and more advanced phase control dimmers having been available for many decades. Recent trends focus on automating dimming and switching based on external factors such as ambient lighting or the presence of persons. Focus on the user’s needs Energy-efficient buildings today need to dynamically adjust their lighting based on actual needs, meaning that lights have to be switched off automatically if no person is present. According to the Lighting Industry Association, the combination of presence detection and daylight-linked dimming can save up to 75 percent on fluorescent lighting. In doing so, however, they need to avoid situations where only a limited area in a bigger area is illuminated (so-called “island lighting”) as this might create a perception of insecurity or poor concentration. The second function – modifying the colour of an individual light – is a more recent addition, which has already seen significant growth, driven primarily by multi-colour LED lamps. Such lamps can output a variable colour light which either spans the traditional white range somewhere from 2.700K (warm white) to 6.500K (cold white) or even output coloured light. Key factor lighting control Lighting control is a key factor in many applications. Modern lighting control must not only enable interaction between lights, switches and sensors but it must also provide communication between the individual lights themselves to synchronise their status. Wired control, in the form of switches and, more recently, dimmers which work by modifying the power supply to the lamp, has been the standard control method since the invention of electric lighting. This approach enables direct control of lights but requires adequate cabling and equipment for dealing with mains voltage levels. Low-cost wired control The more recent approach in wired control systems is to separate the power delivery from the control signals, allowing lower cost electronic control solutions dealing only with low voltages. Such solutions should enable simple, low-cost wiring and control of individual lights or group of lights. In addition, they should offer feedback channel from the light to the controller and support additional device types, such as sensors, in the network. A variety of different standards has emerged for wired lighting control that meets some or all of these criteria. Two representative examples are 0–10V/1–10V Dimming & Control and DALI (Digital Addressable Lighting Interface). 0–10V/1–10V Dimming & Control is probably the simplest form of lighting control. It is based on an analogue control signal ranging from 0V indicating 0 percent brightness (equivalent to OFF state) to 10V, which indicates 100 percent brightness (equivalent to ON state) with linear scaling in between. Fig. 1: Different Bus Topologies for 0–10V Control Several light sources (especially dimmable fluorescent lamps) are limited in the dimming range and do not allow smooth dimming all the way to 0 percent. For these devices, a slightly modified scheme called 1–10V is used. This provides control voltages between 1V (equivalent to minimum dimming level) and 10V (maximum dimming level) similar to 0–10V. In addition, the 0V output state is used to trigger the shut-off of the light source, for instance via a relay. 0–10V control is still commonly used due to its simplicity, which allows easy integration into simple user interfaces such as dimming Matthias Kassner is Product Marketing Director at EnOcean – sliders. www.enocean.com – He can be reached at info@enocean.com 22 Electronic Engineering Times Europe September 2014 www.electronics-eetimes.com


EETE SEP 2014
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