LED: what the end-user should know

September 4th, 2014, Published in Articles: EE Publishers, Articles: Vector, Featured: EE Publishers

 

It is expected that LED lighting will account for more than half the global lighting market by 2017, making it essential for the end-user to better understand this technology.

Although the cost of LED products is currently higher than regular lighting systems, the demand for LED technology is growing exponentially, which will inevitably result in reduced production and selling costs. In addition, the life-expectancy of LED products is considerably longer than those of traditional technologies, which could mean a substantial reduction in running costs. Furthermore, with the phasing out of the incandescent light bulb, end-users may be forced to consider alternative lighting sources.

Know what you’re buying

With so many LED manufactures offering products with different wattages, colours and sizes and with all of these manufacturers promising huge savings, it can be challenging to select the right product. With incandescent light bulbs, the end-user can select the wattage according to the desired brightness, but with LEDs, the choice is far more complex and does not follow the traditional line of thought. Consider these five factors before purchasing a LED product:

Brightness

Wattage does not determine the light output of an LED lamp – instead, it is a measurement of how much energy the lamp draws from the power source. Lumen (lm) is the real measurement of brightness. This is the number for which end-users must look when considering brightness, and when replacing existing incandescent light bulbs with LED ones.

Fig. 1: LED lighting is expected to account for over half of the lighting market by 2017.

A traditional 100 W bulb produces about 1200 lm. The end-user must try to find an LED lamp which best matches this number when selecting brightness levels. Efficacy, expressed in lumens per watt (lm/W), is a good way to determine just how efficient a LED light bulb is. For example, a 100 W incandescent bulb produces 1200 lm (1200 divided by 100 = 12 lm/W). A 9,5 W LED Voltex produces 806 lm (806 divided by 9,5 = 85 lm/W). Simply put, the higher the efficacy, the more light is produced using less wattage. This, therefore, conserves energy.

Colour

Colour is an important factor when choosing the right light source. Colour is measured in “colour temperature” and is expressed in degrees Kelvin (K). Between 2700 and 3000ºK match that of the incandescent light bulb. For clear, white light, consider colour temperatures ranging between 4000 and 5000ºK. Therefore, when comparing the wattages of LEDs, end-users must ensure that the colour temperature is the same. For example, an LED producing between 2700 and 3000ºK will generally have a lumen output of less than that of an LED producing between 4000 and 5000ºK. This is due to a phosphor coating on the LED chip which produces the different colours. Once the colour temperature has been determined, the next step is to look at the colour rendering index (CRI). Always look for a CRI greater than 80 because the colour produced from a CRI of 80 upwards will emit more natural than artificial light. The range of measurement is from 1 to 100 with 100 being sunlight – therefore, the closer the CRI is to 100, the more natural the light will appear.

Not all LED bulbs are dimmable

Dimming should also be considered. Unlike incandescent light bulbs, not all LED bulbs are dimmable. Dimmable LEDs cost considerably more than non-dimmable ones. Furthermore, not all traditional dimming switches are compatible with LEDs. Therefore, it is necessary to know whether the current system will work with a dimmable LED.

Beam angles

EDs are available in a variety of beam angles. Their packaging includes their beam angle rating, which shows the degree of width that light is emitted from a light source. A wide beam angle “floods” the area with light and is called a flood light, whereas a narrow beam angle is a concentrated “spot” of light – a spotlight. It is recommended to use LED spotlight with a beam angle of between 25 and 35º for highlighting pictures or sculptures. For general lighting, use an LED with a beam angle of 60º or more.

Power factor

Finally, the power factor of LEDs is represented by a figure which indicates the efficiency of the source. The higher the figure, the more efficient the source. It is recommended to use an LED product with a power factor of over 0,85.

Professional market

LED technology is advancing rapidly, with new developments frequently announced. Not only are chip manufactures able to create LEDs with high efficacy, but there has also been a shift towards controlling the light and reducing glare more effectively.

In addition, new, highly-reflective materials and high translucent optics are being developed especially for LEDs. This allows designers to be more creative when designing new luminaries.

A trend for “indirect” lighting is starting to become popular in luminaire design. Indirect lighting is the process of shining light at a surface and manipulating it to reflect in a different direction. This trend will allow for a more subtle lighting effect without having the LED source shining directly in the eye.

Contact Allan Loxpon, Voltex, Tel 011 402-0251, info@voltex.co.za

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