FEATURE OPTOELECTRONICS LIGHTENING THE LOAD


dimmer switch, or with the use of a DALI or 1-10V controller. There are two main dimming protocols


which typically use a Phase control dimmer switch - TRIAC and trailing edge. TRIAC is the cheapest and most common method of dimming but generates an undesirable amount of Electro-Magnetic Interference (EMI). Trailing edge dimming is more expensive but produces much less EMI. DALI is widely recognised as the leading


Russell Fletcher, Sales and Marketing Director at Harvard Engineering explains how LED lighting, combined with new LED driver technology, improves performance and cuts energy bills


T


he light-emitting diode (LED) is one of today’s most energy efficient and


rapidly developing technologies. Quality LED light bulbs last longer, are more durable, and offer comparable or better light quality than other types of lighting. In addition, when combined with leading edge control technologies, they can offer up to 80 percent savings on a building’s electricity bills. The new generation of LEDs illuminate


rapidly and can be easily dimmed either by pulse-width modulation or by lowering the forward current. They have an average lifespan of 50,000 hours - five times longer than any other light source - and emit more light per watt than traditional light bulbs. Unlike fluorescent light bulbs or tubes,


their efficiency is not affected by shape and size and they emit light in a specific direction, making them up to eight times more efficient. While conventional light bulbs lose most of their energy as heat, LEDs remain cool, saving on air conditioning. Switching to LEDs evidently has huge benefits but, to gain optimum energy efficiency, reliability and durability, they need the support of dedicated control gear - LED drivers. The main task of LED drivers is to


regulate power output, providing a steady supply despite possible power variations. They offer various power supply options to achieve maximum energy efficiency along with a variety of configuration options and adjustable soft


Figure 1:


When combined with leading edge control technologies, LEDs can offer up to 80 percent savings on a building’s electricity bills


start or emergency light functions. LEDs are ideal for applications using occupancy sensors, time-based switching or switched daylight harvesting, but it is the LED driver that determines the quality of control performance. Each lighting solution requires its own driver design, considering the type and quality of LEDs being installed, whether they will be placed individually or in series strings, size limitations and with reference to the overall lighting design goal. Two main types of driver are available -


“DALI is widely recognised as the leading intelligent


dimming protocol for LEDs. DALI drivers allow users to


constant current and constant voltage – in a number of variations. Constant current drivers are generally used when one driver is required per light fitting; the current will remain the same, however many LEDs are in the fixture. Constant voltage drivers are best for applications where flexibility is needed with the number of luminaires connected to one power supply. As lamps are added, the current will increase to the maximum limit. Dimming


send control information to each light using digital signals...."


functions offer further energy savings and open up


opportunities for creative lighting


designs. They are controlled either by a / ELECTRONICS


intelligent dimming protocol for LEDs. These drivers allow users to send control information to each light using digital signals. Analogue 1-10V drivers offer a less costly and more basic dimming solution. They are programmed with a simple passive controller or a fixed or variable resistor and use voltage input to manage the intensity of the light. Computer software giant Microsoft


installed LED lighting, supported by drivers from Harvard Engineering’s market leading CoolLED range, in their award-winning Stockholm office refurbishment. The company replaced its 600 desks, which were not regularly used, with alternative types of working spaces ranging from sofas to small clusters of tables, and the lighting needed to suit this new environment. A flexible lighting solution with good


glare control, providing a discreet profile for the building’s low ceilings and energy efficiency, was installed. This compromised of LED fittings driven by 30W CoolLED DALI drivers from Harvard. These constant current drivers provide a high performance solution for powering high brightness LEDs from a mains supply. Researched, developed and manufactured in the UK they aim to offer an intelligent, programmable digital dimming, energy efficient lighting solution. The installation will provide Microsoft


with energy savings of up to 85 percent and the LEDs’ long life expectancy will help to keep maintenance costs low. Escalating energy prices may be the


wake up call that other businesses need to realise the benefits of controlled LED lighting. Global penetration is expected to reach 60 percent by 2020, according to the US Department of Energy and hopefully it is only a matter of time before everyone sees the light.


Harvard Engineering  www.harvardeng.com  (0)113 383 1000


Enter 203 ELECTRONICS | MARCH 2014 15


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36