LEDs and Lighting Control by CP Electronics
- Published: Monday, 21 May 2012 08:53
The advent of LED lighting has provided a tempting alternative for traditional light sources such as tungsten filament and fluorescent lighting. LED lighting offers many advantages; but because of the hype surrounding the technology, largely due to the immense amounts of money invested in LED technology by the lighting industry, there has been a lot of misunderstanding and indeed misrepresentation of LED lighting.
As we are a lighting control company, and we do not participate in the manufacture of either LED, fluorescent or indeed any other lighting, we can offer an objective viewpoint.
The purpose of this article is to clarify two main questions:
• What are the advantages and disadvantages of LED lighting technology?
• Does it need controlling, and how do you control it?
Advantages and disadvantages of LED lighting technology
The efficiency of an LED light source depends very much on the quality of the LED, and how much it costs. The greater the efficiency, the less electricity is used for a given light output. It is possible to broadly compare them with other light sources. The diagram shows efficiency with the most efficient at the top.
As can be seen there, the most efficient T5 fluorescent tubes as widely used in office and high bay lighting, is either the same or slightly more efficient than an equivalent LED. However there are clear efficiency benefits over incandescent and compact fluorescent (CFL) light sources.
Without a doubt LEDs provide the best lifetime of all common light sources, offering as much as 50,000 hours. This is clearly beneficial where the cost of replacing the fitting is prohibitive e.g. street lighting, hazardous areas etc.
Note that the rating on most LEDs means at the end of life, they will only be giving 70% of rated output. Furthermore, consider the control gear for the LED – it is not much use to have control gear rated for fewer hours than the LEDs.
Unlike fluorescent lights, LEDs start instantly at the rated brightness and can be dimmed using various techniques to give almost any level of brightness. This means that they are far easier to control than their equivalent fluorescent light source, although nowhere near as good as an incandescent light source.
Especially relevant is the use of “light bulb” replacement products. Normal incandescent light bulbs are dimmed using standard low cost triac dimmers. There are a few manufacturers of dimmable CFL replacement bulbs, but these do not work well. Some LED replacement bulbs on the market dim, some do not, and others claim to dim but do a very poor job.
This is the biggest factor restricting the use of LEDs. Across the board, LED light source cost more, from light bulb replacements right through to spotlights and standard office lights. Not only is the cost of the LED element more expensive but the luminaires or the bulbs they are fitted into are more expensive to design and make, because of the optical and heat characteristics of LEDs.
LED lighting control
As discussed above, LED light sources are no more efficient than the most efficient fluorescent light sources widely used in the market.
Taking an average office building, introducing lighting control can save between 20% and 40% of the electricity used. This applies whatever light source is used – therefore it is absolutely necessary to control LED light sources to save energy.
A wide range of occupancy and dimming controls are available from CP Electronics, and the good news is that they can equally well be used for fluorescent light sources as LED light sources.
Commercial lighting can be switched using the relay output of most of our sensors. They can be dimmed as well provided the fitting has a DALI/DSI or 1-10V dimming transformer.
Domestic lighting light bulb replacement can be switched using any sensor with a relay output. If the LED light bulb is rated as “dimmable” then in the majority of cases it can be used with our green-i range of occupancy dimmers.
Where lighting effects such as scene control and colour changing are required, then the control can be achieved using standard protocols such as DALI. Our Rapid and D-mate lighting control systems can achieve this.
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