LED stands for light emitting diode and is the latest technology in lighting industry. It is still very fast developing and as a technology, it is such that continuous development/ improvement is always going on. Moreover, there is no standard product, lamp or type of fixture. Thus, customer awareness is a key while making the purchase decision.There are so many nuances in the product that any layman may take a wrong purchase decision if he/she is misguided.

1.  Types of LED and their application

There are many types of LED Chips that are produced ideally for different type of applications and have different advantages/features.

1.1 Low power SMD LED:  These LEDs are up to 5 watt each chip and they generally need a special PCB (printed circuit board) to be mounted on and to provide them power to.

These LEDs being low power are generally used in clusters and are thus good for diffused spread lighting. That is, it is good for areas where we need ambient and general lighting.

They have the advantage of better heat management and better lumen efficiency. That is, we need to invest less in the housing or the body of the light fitting with these LED and thus they are more cost effective. They, being a lower wattage Led chip and the easy heat management with them, helps achieve a high lumen per watt output and high lumen per rupee spend output. In simple words for each rupee spent and each wattage of energy we can get higher light output from these LEDs that is when the product designer wants. Meaning technology-wise the SMD LEDs have this advantage but if the product is ill designed, then these advantages can be compromised to any extent. Thus, be mindful of the product design too, which I will mention later in the book. These LEDs are used in tube lights, LED bulbs, LED panels etc.

 

1.2 High power COB LEDs: These are chips on board LED and as the name suggests they have a cluster of many small LED chips mounted on a single board. They don’t require a PCB to power them, due to dense concentration of LED chips, they have in a small area. We required better heat management with these chips. They are used for directional lighting as the small single light emitting areas makes easy to give direction with the use of right optics.

 

Their main applications are in places like retail showrooms for product lighting and accent lighting in homes.

Hence, while purchasing and for planning light scheme, we can select the suitable fixture and suitable type of above LED to create a better optimum balance between cost and utility.

SMD LED lights for focus lighting will not give the right light effect and thus will be less effective in achieving the objective of the lighting scheme, while using COB LED light fixture for ambient lighting can be costly and can create glare.

2.  LED Driver and Purchasing Decisions

LED runs on constant low voltage DC current. Thus we need Ac-Dc converters to get the desired current required to run an LED. If an LED chip is the heart of a product, A ballast or converter is the mind of an LED product. The life and quality of the LED product depends very much on the quality of the driver. So before buying an LED product, check the following features in a driver.

2.1 Isolated or non-isolated: Isolated drivers have a protection against high input voltage. Thus, they give a protection against LED damage due to high voltage, while non-isolated drivers are cost effective but can damage the LED. Wherever possible use an isolated driver which comes with many more other benefits too over non- isolated drivers.

2.2 Input voltage range: Indian voltage conditions are very rough and advisable voltage range of 100-300 volts is good for Indian conditions.  Having an over input voltage protection is also advisable for extra protection. This means 100-300 is a range in which driver would keep running while over 300 if a driver has over voltage protection, it would go into protection mode and shut the driver off to safeguard the driver from damage. For outdoor this protection can go up to 440 volts also.

2.3 Surge protection: Surge is a voltage fluctuation that occur in millisecond and can damage the driver. This is how lights and other electronics items get damaged when generators are switched on as the generator produces huge amount of continuous surge. For indoor a surge protection of 2kv and above is advisable and for outdoor a minimum of 4kv surge protection is required.

2.4 Power factor: This is a ratio between the energy consumption and the current that a product withdraws from the grid. This means if the power factor of any product is less than 90, it means that it withdraws more current from the grid it should do ideally. The electricity distribution companies measure this and will put a multiplier on your electricity bill for this. Thus, if your LED lights have low power factor, then you will get a higher electricity bill. A power factor of above 0.9 is considered good.

2.5 Efficiency: This  means  how  much  energy  is  used up  by  the  LED ballast to drive the LED. That is if the LED is of 10 w and the total power consumption by the ballast is 12 w, this means 10 divided by 12 the efficiency of the ballast is 83 percent.  Thus, higher is the efficiency, better it is, as less electricity is consumed. An efficiency of above 85 percent is considered good.

2.6 Total harmonic distortion: The sum of total harmonic distortions created by the ballast is termed as total harmonic distortion or commonly known as THD. These  interferences  disturb  other  electronics  devices like  mobiles,  computers  televisions.  Generally,  a  THD (total harmonic distortion) level less than 15 percent is considered good.

3.  LED chips

A LED chip is the heart of any  LED lights, as they are the ones that give the actual light. The most innovation happens in LED chips only. Manufacturing a good quality LED chip involves huge R&D, years of experience and huge manufacturing set up, thus selecting the right LED  is hugely critical for the success of a lighting setup. We need to consider the following factors for selecting the right LED.

3.1 Brand of the LED: There are many premium huge brands of LED manufacturers  that  have  a  reputation in  the  market for their quality due to their experience and brilliant manufacturing facilities and superb quality standards they maintain. Let me mention some popular brands in LED chips which are a good combination of price and quality in the market. And also, different companies are specialist in different types of LED, thus we need to look out for that. It is highly advisable to use such LEDs that are popular and already being widely used in the market. Below mentioned is a selection guide for the brands according to LED type. COB LED – Cree, Lumileds (which is a Phillips company).Bridgelux, Samsung, Citizen, SMD LED – Everlight, Bridgelux, Osram, Edison

3.2 Lumen output : Lumen is the unit of light output and in LED light industry there is no standard of lumen per watt. That is every LED chip manufacturer have their own specifications of how much lumen per watt they are going to provide. Then each brand has many ranges of LED with different lumen per watt options. They have economical range with low lumen efficacy that is per watt lumen and premium ranges with high efficacy also. Thus, it is the final product manufacturer whose role is most crucial here. It is simply because it is he who decides as to which LED should be selected in his products.

Hence, always ask manufacturers to mention lumen level in the product and brand of led chip used in their product. It also depends on the design of the product how much total final lumen output the product is going to emit, thus do ask the manufacture to specify that number too.

 

3.3 CRI: In simple terms, this is the quality of the light output of an LED which will bring out the accuracy of colour’s shade and contrast in the item displayed in that light. Thus, if the CRI is low the item will look less appealing and beautiful while higher CRI LED will bring out the true beauty in the interior or products lit by it. This has a huge application in retail, home and hospitality. Your purchasing decision should include considering this factor. A CRI of above 80 in warm white/neutral white and above 70 in cool white is the minimum industry standard below which you should not accept. But for better results and specially in some special applications like retail a CRI of over 90 is preferred.

3.4 Driving current of the LED: All the LED chips have a range of wattage in which it can be run. So, if the LED will be operated at the minimum specified wattage, it will provide higher lumen efficacy, lower colour shift and will have a longer running life. Similarly, it is vice versa if LED is operated at the maximum wattage. Hence, it is always advisable for customers to ask the manufacturer the LED model used in the final product and ask what is the operating wattage of each LED. The user should prefer that LED to be run at the minimum power only.

3.5 Colour of LED: LED   light   technology   does   not   have any   standard colour of light as it was in other previous technologies of lights. Though the most prevalent ones are cool white (6000k), warm white(3000k) and neutral white(4000k) , in LED chips, there are numerous shades available from the range of 2200k to 7500k; that is orange to bluish white. So now designers have an option to choose many different colours in their lighting layout. They can choose 2700 k for warmer look in hospitality applications or use a 7500k to enhance the look of diamond jewelry in retail showrooms.

This brings  another  challenge for the manufacturer and consumer to maintain the colour consistency in the product. Thus, this is a major factor, while purchasing which needs to be considered.

3.6 Material of LED Chips: LED chips are made with different materials which define the quality of the chip. A SMD LED package can be made of plastic, ceramic or any other material. Some materials like plastic are not specified for outdoor use, thus be wary of that fact as due to market price competition pressures, such misuse is prevalent in the market.

4.  Housing of LED lights

This is the case or the body used to manufacture a LED light. It is a very important factor and has to be considered before purchase of light.

4.1 Material of the body: This is the material  of which housing of a LED light is made of. LED has a special requirement as mentioned earlier to manage the heat produced as a by- product.  Thus, most  widely  used product  is  aluminum that is a good mix between price and heat conductivity. Nowadays  other  cheaper  materials like  plastic  is  also prevalent due to competition in the market. Thus, being a customer be wary of the materials of the body of the LED light product. Cheaper mass scale standard products like tube lights and bulbs can be in plastic. Other products like spotlight and downlight panel should be in metal aluminum housing only. SMD low power LED up to 0.2w when operated at a lower than minimum wattage can be used with plastic body. This is also only if we are using a metal core PCB. And in most conditions, the life of plastic LED light products will be shorter than the ones made of aluminum. Hence, while purchasing lights make sure to check what is the material of the product.

Many manufacturers also mention a working ambient temperature that is often quite low as a form of disclaimer.

5.  Optics and diffuser

Any diffuser, reflectors, lenses or any other kind of optics has an impact on the efficacy of the complete fixture that is the amount of light coming out of the LED chips and the amount of actually usable light may be different due to wastage of lights because of all the optics mentioned above. Thus, the quality of these materials matters a lot.

5.1 Reflectors and lenses: Optics like Reflectors and lenses are used in focused lighting with COB LED chips generally.  They come in various beam angles. The amount of light that will spread or be focused will depend on the degree of the beam angle.The higher is the beam angle of the reflector, more the light will spread. Thus, it is critical to select the right beam angle suitable to your lighting layout.

Moreover, better the quality of the reflector and lens, better the light output and a more even distribution of light. In the common practice, there are two types of reflector/ lens, branded and unbranded. Branded reflector/lens have higher efficiency, and are of good quality and obviously more expensive vice versa for the non-branded reflector/ lens., Hence, if you need a good quality product, go for branded reflector/lens and if a lower price is the preference, you can select local reflector/lens for your products.

 

 

5.2 Diffusers: When we use SMD lights in indoor application, reducing glare and  improvingand improving aesthetics  are  important. Thus, diffusers are used for dispersing the light so that multiple LEDs are not visible. Again, higher the efficiency of diffuser better is the  light efficacy that is more usable light coming out of the fitting. So, consumers need to be aware of this fact and select a product with branded diffusers only.

 

6.  PCB

As mentioned above, many low power SMD and highpower LED need an electrical board to power the LED. This has electrical circuits that wire the LED in correct series and parallel combination. Thus, the LED can be run at the desired current of the available ballast. Generally, a metal core PCB is used for LED but due to current price competitions and pressures in the market other materials like FR-4 (composite material composed of woven fiberglass cloth with an epoxy resin binder that is flame resistant) or not metal non heat conducting materials are also used. These are not advisable and unless LED is run at a lower wattage than their specified minimum wattage, these are not good for the LED chips. In metal core PCB also, there are many qualities available. So higher the wattage of the product, better quality of PCB should be used.