FAQ

LEDs are notable for being extremely long-lasting products. Many LEDs have a rated life of up to 50,000 hours. This is approximately 50 times longer than a typical incandescent, 20-25 times longer than a typical halogen, and 8-10 times longer than a typical CFL. Used 12 hours a day, a 50,000 bulb will last more than 11 years. Used 8 hours a day, it will last 17 years!

They can be used almost anywhere. LED replacements are already available for bulb types such as A-shape, PAR reflectors, MR reflectors, decorative, under cabinet, and more. When used on dimmers, particularly dimming systems that support many bulbs.

Enclosed fixtures are defined as not only air tight, but also are fixtures that are enclosed on the side, rear and open in the front, such as many track heads. LEDs that are used in fixtures where there’s less than 1/2″ around the circumference of the lamp when installed in the fixture are also considered an enclosed application. If you plan to use LEDs in these types of applications you should use an LED that’s rated for enclosed fixtures. Using an LED lamp not rated for enclosed fixtures in this type of application may cause the LED lamp to flicker and will dramatically reduce the life of the lamp.
LEDs not rated for enclosed fixtures should only be used in fixtures open in the front, where the lamp’s lens is open on the sides and the rear, and should have at least 1/2″ space around the circumference of the lamp.

The advantages of switching to LED are numerous. LEDs use much less electricity than other bulbs, have extremely long rated lives, produce very little heat, do not emit UV or infrared, contain no mercury, are resistant to shock and vibration, and can operate effectively in extremely cold environments.

LED is a new technology, and the expense of producing quality product is still high. However, pricing has come down dramatically from just a few years ago and prices are expected to continue to drop. In terms of whether LEDs are worth the extra cost, it’s helpful to look at the cost to operate a bulb in addition to the up-front cost. The energy savings realized in a switch to LED means that the extra up-front cost is often paid back rather quickly, and you’ll wind up saving money over the life of the bulb. Here is an example: for a residential customer who may have the light on for just 10 hours per week ñ the payback is over 10 years. On the other hand, a retail or restaurant client who is burning lights for 90-100 hours per week will calculate their payback on a $70 LED PAR to be less than 18 months. Taking a look at your payback estimate should definitely be a consideration when deciding if LED is right for you.

Light emitting diodes produce light by the movement of electrons between the two terminals of diode, which occur by a process called electroluminescence. When a light emitting diode is electrically connected, electrons start moving at the junction of the N-type and P-type semiconductors within the diode. When there is a jump over of electrons at the p-n junction, the electron loses a portion of its energy. In regular diodes this energy loss is in the form of heat. However, in LEDs the specific type of N and P conductors produce photons (light) instead of heat. The amount of energy lost defines the color of light produced.

LEDs produce light by direct conversion of electrical energy to light energy.
On the other hand incandescent light sources produce light by heating a filament until it grows red hot. Linear and compact fluorescent lamps use a UV discharge plus phosphor to produce the light. HID lamps use the ionization of gases in a discharge tube which in turn produce photons.

No. LEDs directly convert electrical energy to photons. It is a one step process of electroluminescence that does not require time to reach maximum output. Other sources such as fluorescents or HID, work on discharge technology. This requires an arc to warm up and may take a few minutes to reach full output.

LEDs are more efficient than most other light sources, so they usually consume less energy for a given task or at a specific light output. Also, they do not contain hazardous materials such as toxic mercury. Moreover, LEDs have a longer lifespan and hence reduce the frequency of disposal of lamps.

Color temperature defines the color appearance of a white LED. CCT is defined in degrees Kelvin; a warm light is around 2700K, moving to neutral white at around 4000K, and to cool white, at 5000K or more. Note that CCT does not tell you anything about the color rendering ability of the LED.

This is an elliptical region on the CIE chromaticity diagram that contains all the colors that are indistinguishable to the average human eye, from the color at the center of the ellipse. Adjacent ellipses are “just distinguishable” in terms of color. This system is used to refine the binning process of LED colors. Slight color differences in the appearance of LED light are measured in MacAdam ellipses or steps.

The white LEDs are made of phosphor coated blue LED chip. The degradation of the phosphor layer over time causes the bluish tone of the light emitted. This degradation is most likely to be caused by the chip running too hot. Remote phosphor technology overcomes this issue.

RGB LED means red, blue and green LEDs. RGB LED products combine these three colors to produce over 16 million hues of light. Note that not all colors are possible. Some colors are “outside” the triangle formed by the RGB LEDs. Also, pigment colors such as brown or pink are difficult, or impossible, to achieve.

SMD means surface mounted diode. This is a better technology than the first generation DIP LEDs. The SMD type LEDs are mounted on an aluminum substrate and enveloped in an epoxy resin.

LED modules may be available in the following forms:

• Prefabricated chip on board which can be used for specific applications by luminaire manufacturers who design the heat sink and mounting conditions.
• Chip on board with an optical lens or diffuser as a prefabricated piece with or without integrated heatsink. That can be used by luminaire manufacturers to integrate into luminaire.
• Retrofit lamps to replace older (halogen) technology. This comes with an integrated heat sink and standard lamp base that can fitted directly into existing luminaires with a standard lamp holder.
• Prefabricated luminaires with an integrated LED light source and heat sink complete with luminaire housing that is available as a sealed piece. The driver may be integral in the housing or may be remote.

The basic types of chip LEDs are:

• SMD (Surface mounted diode) is a standalone chip on a ceramic base that can be integrated into various packages for linear LED strips or downlights.
• COB (chip on board) LED, which comes as a high powered chip in direct contact with a printed circuit board optimal thermal management.
• MCOB (multiple chips on board) LEDs, which are multiple COB LEDs integrated to form a single chip. This technology is used in LED bulbs and tubes.
• MCCOB (multiple chips and cups on board) packages, which are used for high bay fixtures and floodlights.

Yes. LEDs are very similar to consumer electronics and quality really matters. In order for an LED to function properly and provide an acceptable light output, all of the components must be built to last. It’s always a good idea to buy from a manufacturer and retailer that you’re confident will stand behind the product.

For most applications, yes. Off-the-shelf LED products are now reliably replacing incandescent equivalents of up to 100 watts, and specialty products are available to replace even higher wattages. If you’d like to learn more about LED light output.

If you buy quality product, the light quality is excellent. Color Rendering Index (CRI) is generally used to measure light quality on a scale from 1-100. Most LEDs have a CRI rating of at least 80, and many are rated 90 and above.

LEDs are very green. For starters, they use much less electricity than many other lighting products. This means that less electricity has to be produced to operate them, and resulting in lower emissions from power plants, especially in areas where coal-fired plants are common. Unlike CFLs, they contain no mercury. Because of their long life, they also reduce solid waste: If you replace an incandescent bulb with an LED, you will prevent fifty 1,000 hour incandescent bulbs from being thrown away. Additionally, they produce very little heat and can reduce energy usage related to HVAC.

Usually, yes. Many LEDs are specifically listed as being dimmable. Some dimming systems work with LEDs better than others, so it’s best to test one or two before completely re-lamping a space.

The term solid state lighting is used because the electronics produce light directly from solid materials in which the electrons are embedded. This is unlike other technologies, for example fluorescent technology, which requires a gaseous discharge medium to initiate production of light.

LED chips are mass produced in millions and there are inevitably slight differences in color appearance and light output. Binning is way of sorting the chips so that all the LEDs from one particular bin look the same and have similar light output.

A light engine is the LED equivalent of a conventional lamp. It normally consists of a LED chip mounted on a circuit board that has electrical and mechanical fixings, meaning it is ready to be fixed in the luminaire. Note that the light engine may not consist of only one chip; it may be an array of 9 or 16, sometimes with a phosphor coating.

LEDs have no gases, filaments and no moving parts to fatigue. They provide light through a one-step process that takes place within the diode. There is no glass to break or screwed contacts to loosen

Although the initial cost of conventional light sources is less than LEDs, the operational and maintenance costs of LED are significantly lower. LEDs, having a longer life, reduce maintenance and lamp replacement cost. . Because LEDs need to be replaced less frequently, the owner spends less on new lamps and the labor needed to change them. LEDs also consume less energy; thus the overall cost of a LED system can be significantly lower than that of conventional lighting systems. Most applications with LEDs offer a payback period as low as three to four years.

Some of the strategies for reducing the cost of LEDs in the future are:

• Reduction in the production process.
• Simplification and reduction in the number of components.
• Introduction of new materials.

Here are some of the aspects that need to be taken into consideration: when

• Luminaire spacing and layout.
• Ways to prevent a view of the light source and minimize glare.
• Ventilation/cooling of LEDs
• Wiring access
• Access to LEDs in case of maintenance or replacement.
• Location of driver, if not integrated in luminaire.
• Switching / dimming capabilities, or control type and location.

Most insects are primarily attracted to Ultra-violet rays, which help them forage, navigate and select mates. For example, Indian moths are attracted to UV-365nm and green light-500nm. LEDs do not have UV content and hence do not attract many insects compared to conventional light sources.

In retail and display environments where the range of products change by the season, the colors can be changed to match the type of product on display. For example, electronic goods may require a cool white light while a warmer tone may be required for fabrics. When a fashion season has red as a theme, the store can utilize a color of light with more red in its spectrum to enhance and bring out the vibrancy of the display.

• The lamp base / holder screw fixing position.
• The physical dimension of the LED lamp and how it fits into the existing housing.
• The electrical characteristics of LEDs compared to the existing system. (Main voltage, low voltage, control methods).
• The location and size of the light emitting surface in relation to the luminaire reflector and in comparison to the original light source.
• The light distribution, lumen output and other photometric properties like color temperature in comparison to the original light source.
• The heat generated by the LED during operation and the maximum operating temperature.

LEDs do not emit ultra-violet light and do not carry heat in the beam, unlike their conventional counterparts. This helps keep food fresher in refrigerators and cold stores.

In General, every light fitting must have a CE label. This tells you that the seller claims that the fitting conforms to all the relevant European safety standards. The most important of these is EN 60598 which covers electrical, thermal and mechanical safety.

LEDs are low voltage devices. Therefore, they require a device / Power supply unit / driver, or integrated electronics that convert line voltage to low voltage in order to run the LEDs. Sometimes, the driver has electronics that can interpret control signals to dim LEDs.

LEDs are driven by constant current (350mA, 700mA or 1A) drivers or constant voltage (10V, 12V or 24V) drivers.
Constant current drivers fix the current of the system and vary the voltage depending on the load of the LED.
Constant voltage drivers require a fixed voltage, and the LED loads are added in parallel across the output of the driver until maximum output currents are reached.

Constant current drivers are typically used in downlights where one, or a series, of luminaires is used per driver. These are connected in series.

The LED rating of a product is usually noted in milliamps, mA or volts, V. Products rated in mA can be used with a constant current driver, while those rated in volts can be run with a constant voltage driver. LEDs designed for constant current drivers cannot run with constant voltage drivers without damaging them.

LEDs are inherently low voltage devices and require drivers. However, many LED products in the market come with built-in drivers and hence can be directly connected to the mains voltage.

LED drivers need to be mounted in a ventilated space. Access to the driver needs to be provided for general maintenance purposes. The IP (ingress protection) rating of the driver needs to be considered before finalizing the mounting location of the driver (only those drivers designed for outdoor environments can be located outdoors). The distance between the driver and the light source needs to be taken into consideration in order to prevent voltage drop, which results in reduced output of the LEDs.

LEDs are dimmed either by Pulse Width Modulation PWM, or by Constant Current Reduction CCR. PWM dimming involves switching current at a high frequency from zero to the rated output current. CCR dimming: The lighting level required is proportional to the current flowing through the LED. Current flows through the LED continuously and is reduced or increased based on whether the LED is to be dimmed further or made brighter.

Dimming LEDs offer the following advantages:
Saves energy, because less energy is used for reduced output levels.
Extends life; the electronic components run cooler. This not only extends the life of LEDs but also increases the life of the phosphor coating that is used to produce white light.
Helps designers create ambient lighting presets to create mood settings.
Increases flexibility in usage of space. A brightly lit space for reading or an office space can turn into a presentation/conference area by dimming.
Increases productivity by enabling individual control of lights in order to reduce eye strain and fatigue, or to improve concentration.

This is usually due to incompatibility between the driver and the control system. When purchasing an LED product, it is important to use the correct driver type as specified by the manufacturer and verify the ripping ratio. It is also important to check that the LED is dimmable. Some retrofits are not.

Heat management is critical for the performance of LEDs. Increasing heat in LEDs has the following effects in performance characters:

• Reduction in luminous flux
• Color shift (change in color appearance)
• Reduction in life of the LED

LEDs are cooled either by passive cooling or active cooling. Passive cooling involves a finned heat exchange system made of cast or extruded metal or a plastic coated metal heat sink that offers a totally silent, robust, heat transfer. Passive cooling is reliant on the surface area of the heat sink material and is orientation dependent. Active cooling may include conventional fans or diaphragm- based forced air cooling. Active cooling using a fan, although more efficient, is noisy, not so reliable, and requires electricity to run. Active cooling places emphasis on forced air flow rate and is not orientation dependent.

Junction temperature is the LED’s active region; the point at which the diode connects to the base. This is where the electrons jump between the two semiconductors to produce photons. A low junction temperature helps LEDs to produce more light also reduces lumen depreciation. Junction temperature is affected by the driver current, the thermal path, and the ambient temperature.

Here are few of the ways in which glare can be reduced from LEDs:

• Use of micro prismatic technology to develop special diffusers that disperses light from individual LEDs. This system gives out homogeneous light with optimum levels of contrast avoiding any direct or reflected glare.
• Design of secondary reflectors systems; where the primary reflector, which will hide the view of the LED and direct the light into the secondary reflector that will distribute the light in the intended way.
• Use of a combination of TIR (total internal reflection) lenses / collimator lens, which that produce a parallel beam of light, and a facetted lens. This combination will distribute the light beam as intended.

Here are few of the ways in which glare can be reduced from LEDs:

• Heat buildup occurs as the luminaire is turned on, and as it cools down when it is switched off.
• Pressure changes caused by a change in altitude and environmental conditions during transportation in cargo holds or in planes.
• Thermal shock due to rain, snow or washing cycles.

No. It is true that there is no heat, IR, in the beam. However, the LED fixture itself, does produce heat. However it may become warm, or hot, to the touch.

The LED chip, or light engine produces heat. This needs to be dissipated as quickly as possible. This is normally done by with a heat sink, which often has fins. Cool LEDs are more efficient than hot ones. They also have a longer life. Of course, higher power LEDs generally run hotter than low power ones because of the extra heat to remove.

50,000 hours would imply 5.7 years if the light is operated for 24 hours in a day, 7.6 years if the lights are on 18 hours per day and 11.4 years for 12 hours a day.

Unlike conventional light sources that reduce in output and eventually fail, LED products do not normally suddenly fail. Instead, the light output reduces over time. The normal convention is to measure the life from when the output has reduced by 30%, i.e. when there is 70% light output remaining. This is often quoted as the L70 life and is measured in hours.

The thermal management of the LEDs. If LEDs come on a standalone chip, appropriate heat sinks have to be designed to prevent premature failure of LEDs. The electrical stress: Running LEDs at currents higher than specified make the LED run hot. This can happen with wrongly matched drivers. For example, if the driver produces 700mA but the LED needs 350mA, this will put stress on LED and reduce its lifespan. Higher ambient temperatures than the ones that the LED is rated for will reduce its expected life.

Sometimes simply comparing the lumen output of LEDs and conventional light sources may not be adequate. The amount of light falling on a specific task area (the lux) gives a more realistic comparison. You should also consider the amount illumination visible on the walls. This helps identify applications where LEDs offer better solutions than other light sources.

Unlike discharge lamps, LEDs are semiconductors and their life span is not affected by the number of times they are turned on and off.

This may occur if you are using the same product from the same brand, with the same optics and hardware. However, in general, the nature of the components (like the optical system, the heat sink, the LED chip, and the driver) affects the output more than the wattage does. A 3watt LED luminaire from one manufacturer will have a different output to a 3watt LED luminaire from another manufacturer, even if the same LED chip is used. Hence, using a high quality chip alone does not guarantee better performance. Note that as the wattage increases, the efficiency drops slightly. An LED driven at 3W will emit slightly less than three times the output of one driven at 1W.