What are Led?
Led are light emitting diodes. These are electronic components that produce light by conversion of electrical energy directly to light by the movement of electrons within the material of the diode. They are important because due to their efficiency and low energy, they are beginning to replace most conventional light sources.
What is meaning Future-proofing of LED products?
Led technology is constantly changing. Rapid innovation continues to improve the performance on a almost daily basis. Future-proofing of Ledmodules allows luminaire manufacturers to switch from one generation to the next improved generation without major retooling or changes in luminaire design, offering backward compatibility with drivers.
What makes Led more robust than other light sources?
Led have no gases, filaments or any 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.
Why do Led have a higher initial cost than conventional light sources?
Led are made of electronic components which need to be packaged together to offer long lasting efficient light sources to the end user. Apart from the Led chip itself which has sapphire and gallium in the semiconductor, the process of packaging with materials like ceramic, rare earth phosphors, silicone, solder and gold wire add to the overall cost. White Ledrequire further tests for calibration and standardisation.
What are the economic advantages of using Led over conventional light sources?
Although the initial cost of conventional light sources is less than Led, they do not take into account the operational and maintenance cost of the lighting system. Led, having a longer life , reduce maintenance and lamp replacement cost. This reduces cost of labour to replace lamps and the cost of new lamps at the end of lamp life cycleLed, also consume less energy. Thus the overall cost of a LED system can thus be significantly lower than conventional lighting systems. Most applications with Led offer a payback period as low as 3-4 years.
What aspects need to be taken in consideration when replacing a light source with Led in a retrofit scenario?
- The lamp base / holder screw fixing position.
- The physical dimension of theLed lamp and how it fits into the existing housing.
- The electrical characteristics ofLed compared to the existing system. (mains 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,lumenoutput and other photometric properties like color temperature in comparison to the original light source.
- The heat generated by theLed during operation and the maximum operating temperature.
Is it true that LED lights do not attract insects?
- Most insects are primarily attracted to Ultra-violet rays to help them forage, navigate and select mates. For example Indian moths are attracted to UV-365nm and green light-500nm.Led do not have UV content and hence do not attract so many insects compared to conventional light sources.
What are the benefits of using Led in mining areas specifically?
Using Led in mining areas have the following benefits:
- Better focus on work area
- Safer due to lowglare and being cool to touch
- No start-up time
- Being solid state it is easier to make it explosion and vibration proof
- Can be powered with AC or DC and has longer battery backup with option of charging battery with solar panels
- Led lights can be installed with satellite connection and can have integrated motion sensors and GPS which offers remote access to live information about usage, location, condition and offer further security as well.
How does the wide temperature tolerance expand their application?
LED work more efficiently in cold temperature and their life is extended since the cold air offers a passive heat absorption mechanism. This gives LED an advantage in various applications like ice-skating rings / tracks, refrigeration applications, public places in colder countries.
How do I know a light fitting is safe?
In Europe, 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.
Why do Led require power supply / drivers?
LED are low voltage devices. Hence they require a device / power supply unit / driver or integrated electronics that convert line voltage to low voltage to run the LED. Sometimes the driver has electronics that can interpret control signals to dim LED.
What are there different types of LED power supplies / drivers?
LED 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.
Typically, what sort of applications are constant current drivers used for?
Constant current drivers are typically used in down lights where one, or a series, of luminaries used per driver. These are connected in series.
Typically in what sort of applications are constant voltage drivers are used for?
Constant voltage drivers are used in applications where the load is not known and the Led loads are connected in parallel; such as in coves and signage applications. These drivers are sometimes similar to the low voltage electronic and magnetic transformers used for halogen light fixtures (MR16 lamps). The type of Led driver suitable to run a Led product is stated by the LED’s manufacturer in the product specification.
How do I know what type of driver is required by an LED product?
The LED’s 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 a constant voltage driver. LED’s designed for constant current drivers cannot run with constant voltage drivers without damaging it.
What are the advantages of 24V Led over12V Led?
LEDs driven by 24V drivers have longer permissible distances between light source and driver compared to 12V DC LED’s. 12V LED’s are usually suitable for applications where low light outputs are required. 24V LED offer products with higher outputs than 12V products.
What precautions are to be taken when mounting LED drivers?
LEDs 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 to prevent voltage drop that results in reduced output of the LED’s.
What are the advantages of dimming Led?
Dimming LEDs offer the following advantages:
- Saving energy, because less energy is used for reduced output levels.
- Extended life; the electronic components run cooler. This not only extends the life of LED’s 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.
- 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 individual control to reduce eye strain and fatigue or to improve concentration.
What is the difference between analogue and digital dimming?
Analogue dimming is usually referred to as 1 – 10v dimming. In this case, a dc voltage is sent to the driver which dims the LED’s in response to the voltage. With digital dimming, the driver receives a digital signal which tells it how to respond. The advantage of digital dimming is that fixtures are addressable. You can also have many more different levels of light output.
Why do some Led flicker when dimmed or turned off?
This is usually due to incompatibility between the driver and the control system. When purchasing an LED’s product, it is important to use the driver type as specified by the manufacturer. Also it is important to check that the LED’s is dimmable. Some retrofits are not.
Why is the heat sink design critical for the performance of an LED fitting?
Heat management is critical for the performance of LED’s. Increasing heat in LED has the following effects in performance characters:
- Reduction in luminous flux
- Color shift (change in color appearance)
- Reduction in life of the LED’s
What are the heat transfer techniques used to cool Led?
LED sare cooled either by passive cooling or active cooling. Passive cooling involves a finned heat exchange system made of cast or extruded metal or plastic coated metal heat sink that offers a totally silent, robust, heat transfer. Passive cooling is reliant on the surface area of heat sink material and is orientation dependant. 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 needs electricity to run. Active cooling lays emphasis on forced air flow rate and is not orientation dependant.
What is junction temperature?
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 Led’s to produce more light and also reduce the lumen depreciation. Junction temperature is affected by the driver current, the thermal path and the ambient temperature.
Why are lenses preferred over reflectors for many LED luminaires?
Led are directional sources of light rather than omni-directional from traditional sources of light. For Led with reflectors, much of the light at the centre of the beam passes out of the system without even touching the reflector. This reduces the scope of modulating the beam of light and is a very visible source of glare. Lenses help guide virtually every ray of light emitted by the Led.
What are the different ways in which luminaire design can help reduce glare from Led?
Here are few of the ways in which glare can be reduced from Led:
- Use of micro prismatic technology to develop special diffusers that disperses light from individualLed to give out homogeneous light with optimum levels of contrast avoiding any direct or reflected glare.
- Design of secondary reflectors systems; where the primary reflector will hide the view of theLed 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 that produce a parallel beam of light and a facetted lens to distribute the light beam as intended.
What does a life of 50,000 hours mean in the case of – Led?
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.
What are the factors that affect the lifespan of the Led?
- The thermal management of theLed. If Led come on a standalone chip, appropriate heat sinks have to be designed to prevent premature failure of Led.
- The electrical stress: RunningLed at currents higher than specified make the Led run hot. This can happen with wrongly matched drivers. E.g. the driver produces 700mA whereas the Led needs 350mA stresses the Led and reduces its lifespan.
- Higher ambient temperatures than that for which the product is rated reduces the life of theLed.
Is lifespan reduced if the Led are frequently turned on and off?
Unlike discharge lamps, Led are semiconductors and their life span is not affected by the number of times they are turned on and off.
What is the best way to compare the output of Led with other light sources?
Sometimes simply comparing the lumen output of Led and conventional light sources may not be adequate. The amount of light falling on specific task area (the lux) gives a more realistic comparison. You should also consider the illumination on the walls. This helps identify applications where Led offer better solutions than other light sources.
Why are Led considered more efficient than conventional light sources?
In many cases when comparing the lumen output between Led and conventional light sources, Led may have lower lumen value However Led are directional light sources. All the lumens emitted from an Led are directed towards the task area; while conventional sources emit light in all directions which are then modulated in a given direction with optical systems like reflectors and lenses. The proportion of lumens that falls in the task area from an Led light source is greater than that of a conventional light source.
Why are Led considered green technology?
Led are more efficient than most other light sources, so they usually consume less energy for a given task or light output. Also, they do not contain hazardous materials such as toxic mercury. Moreover, Led have a longer lifespan and hence reduce the frequency of disposal of lamps.
How can LED lighting help reduce CO2 emission?
Led normally use less power for a given application compared to traditional halogen and fluorescent sources. As such, the overall kW/hr consumption per year is less, so this helps reduce the overall CO2 emissions.
What could be a possible hazard when retrofitting lamps in existing installations?
Overheating of Led lamps in retrofit scenarios could be a potential fire hazard. Overheating can not only cause damage to lamp sockets, circuitry and lamps but can, in extreme circumstances, melt fixtures and floor coverings.
Can linear Led be used as a substitute for T8 or T5 fluorescent lamps?
Most Led tubes, although they have the same size, lamp base and possibly a lumen output close to that of linear fluorescent; do not have the same omni directional light distribution of linear fluorescent. Many luminaries, especially troffers with reflectors that offer batwing (wide-spread) light distribution with fluorescent; emit 20%-30% less light output with narrower beam spreads with Led. This needs to be taken into account when considering the overall 30-50% less power usage by Led with increased system efficiencies.
It is likely that the luminaire will need some rewiring and this should be done in conformance with the local electrical installation standards.
How is light produced in an LED?
Light emitting diodes produce light by the movement of electrons between the two terminals of diode 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 in 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 Led the specific type of N and P conductors produce photons (light) instead of heat. The amount of energy lost defines the colour of light produced
How are Led different from other light sources in the way they produce light?
Led 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 a phosphor to produce the light. HID lamps use the ionisation of gases in a discharge tube which in turn produce photons.
Do Led require time to reach maximum brightness?
No. Led 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 fluorescent or HID work on discharge technology. This requires an arc to warm up and may take a few minutes to reach full output.
What are O-Led?
O-led are organic light emitting diodes. They are made of carbon based films sandwiched between two electrodes; one metallic cathode and one transparent anode; which is usually transparent glass.
What are the characteristics of O-Led that make it different from other light sources?
O-led are thin, flat, two dimensional surfaces offering a soft glare – free luminous surface. Some versions of o-led are flexible. They can be transparent, mirrored or diffused when not electrically connected.
How is white light produced by Led?
Led do not directly produce white light. There are two ways in which white light is produced from Led as below:
Using a blue LED with a phosphor coating to convert blue light to white light by a process called fluorescence.
Combining red blue and green Led to produce white light. White light is produced by varying the intensities of the individual red, blue and green chips.
How is coloured light produced from Led?
The color of light produced is dependent on the inorganic material used in the P-type and N-type semiconductor (organic material in the case of (O-LED). Different inorganic materials in the semiconductor release different amounts of energy when the LED is connected to a power supply. This amount of energy released defines the color of light produced. For example, red is a low energy light and blue is a high energy light.
Why do Led produce more vibrant and saturated colours than conventional lamps?
Led emit a very narrow spectrum of light. The type of material used in the semiconductor permits only a specific wavelength of light (one color) to be emitted when electrons cross the junction.
What does RGB LED mean?
RGB LED means red, blue and green Led. 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 Led. Also, pigment colors such as brown or pink are difficult, or impossible, to achieve.
What does correlated colour temperature, CCT, mean?
Color Temperature defines the color appearance of a white LED. CCT is defined in degrees Kelvin where a Warm light is around 2700K moving to Neutral White at around 4000K to Cool white, 5000K or more. Note that CCT does not tell you anything about the Color Rendering ability of the LED.
What defines the colour temperature of a white LED?
The thickness of the phosphor layer and the wavelength of the blue chip influence the Colour Temperature of the LED.
What are the standard comparisons used to evaluate the colour quality of light sources?
- Color Rendering Index – CRI indicates the accuracy with which a light source such as anLED can reveal the various colors of an object. The standard CRI system is based on eight colors across the spectrum.
- Additional R-values of CRI are used to represent certain colors. The appropriate R-values are application specific. For example R9 represents red and is good for lighting for lighting flesh. It also tends to make the light Warmer.
- Color Quality Scale CQS is a new system that uses a wider palette of 15 reference colors as against the smaller palette of 8 reference colors used for the CRI system.
Why do some white Led start emitting an almost bluish tone over time?
The white Led 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.
Why has the color appearance of the Led changed after some period of use?
There are several possible reasons why this happens as follows:
- TheLed are being overrun by the use of inappropriate driver
- The application temperature is different from the operating temperature noted in theLED
- There may be heat build-up due to improper thermal management.
- The phosphor may have degraded due to overheating or other reasons.
What does SMD mean?
SMD means surface mounted diode. This is a better technology that the first generation DIP Led. The SMD type Led are mounted on an aluminium substrate and enveloped in an epoxy resin.
What are the advantages of SMD over DIP Led?
The advantages of SMD over DIP Led are:
- Smaller size
- Morelumen output
- Better heat dissipation
- Lowerlumen depreciation
- Longer life
What are the various types of LED chip packages available in the market?
The basic types of chip Led are:
- SMD (Surface mounted diode) is a standalone chip on a ceramic base that can be integrated into various packages for linearLED strips or downlights.
- COB (chip on board)LED comes as a high powered chip in direct contact with a printed circuit board optimal thermal management.
- MCOB (multiple chips on board)Led are multiple COB Led integrated to form a single chip. This is used in LED bulbs and tubes.
- MCCOB (multiple chips and cups on board) are used for high bay fixtures and floodlights.
Which developments in Led have reduced the number of components in a system?
- The chip on board (COB) package enables mounting the package directly on a heat sink instead of relying on aLED board manufacturer.
- In many designs the heat sink is designed to be a part of theluminaries housing design which reduces the number of components in the system.
- Developments in more stable mains voltage ACLED drivers is offering solutions that can reduce wiring requirements and overall dimming cost.
How environmentally friendly are Led?
A study of the ecological balance of LED lamps by OSRAM Opto Semiconductors shows that the latest generation of lights is already extremely environmentally friendly. In the context of the study, the entire life cycle was investigated. Research was carried out into how much energy and how many raw materials the lamp consumes during its manufacture, use and disposal and what environmental impacts this has. The service life of the lamp – 25,000 hours – was used as the basis for comparison. This means that a Parathom LED lamp was compared with 2.5 energy saving lamps and 25 incandescent lamps. The result: Current LED lamps achieve the same ecological balance values as compact fluorescent lamps and are miles ahead of conventional incandescent lamps.
The study, compiled in cooperation experts from Siemens Corporate Technology (Center for Eco Innovations), shows that: As with compact fluorescent lamps, LED-based lamps consume over 98 percent of the energy supplied during operation, i.e. in the generation of light. Less than two percent is used in production. This disproves the fear that manufacturing Led in particular can be very energy intensive. In contrast to the primary energy consumption of the incandescent lamps of roughly 3300 kWh, less than 700 kWh is used for manufacturing and operating LED lamps. Therefore the LED lamps are considerably more efficient than conventional incandescent lamps. As the efficiency of the Led is continually increasing, we can expect even better ecological balance results of the LED lamps in the future.
How much can we save with Led?
With regard to current consumption, CO2 emissions and maintenance costs, Led offer huge potential for savings – without making any reductions in light quality. When the longer service life is taken into account, the overall balance is clearly positive, even if the procurement costs are comparatively higher than conventional incandescent lamps. Depending on the system solution, clever technical solutions can reduce power costs by up to 80%.
Led are very efficient when compared to standard lights such as incandescent lamps or halogen lamps. Whilst incandescent lamps offer efficiency of a good 10 lm/W, and halogen lamp around 20 lm/W, the efficiency of white Led is between 70 and 100 lm/W (depending on the type and light color). Fluorescent lamps have an efficiency of 70-90 lm/W. In the laboratory, the efficiencies of Led are over 140 lm/W. Depending on the type, the power consumption is only 0.1 to 15 W. This means: Even small Led can provide powerful lighting.
However, a sound efficiency comparison is only meaningful in a complete, functioning system, as the efficiency of electronics and optics also have a decisive role to play here. In addition to that, standardization committees take system efficiencies into consideration, as a detached observation is not sufficient.
Whilst a white incandescent lamp converts only five percent of the input energy into light, with Led, this value has already reached around 35 percent. In the case of colored light, the ratio of 0.5 to 40 percent comes down even more in favor of Led. And whilst the incandescent lamp has reached the end of its development, this is certainly not the case for the LED. There is still the potential to increase efficacy, in order to make Led even more efficient light sources than they are today.
What advantages do Led have over conventional light technologies?
Led are point light sources and emit targeted light. They are extremely small and allow great design freedom for lighting applications. In contrast to incandescent lamps, their light and heat components are separate. Led have neither UV nor infrared components in their light. This means that they can be used more flexibly, particularly in heat sensitive areas, such as lighting for food or cosmetics, or in applications with very limited space.
Led have a considerably longer service life than other light sources. A white LED with more than 50,000 hours will last between three and seven times longer than conventional fluorescent and energy saving lamps and 50 times longer than an incandescent lamp.
Led are “green” products: They do not contain any environmentally harmful substances such as mercury or lead. The life cycle assessment for LED lamps has confirmed the environmental friendliness of Led, even during manufacture.
Led shine in saturated colors, allowing a very wide variety. There is no need for color filters. They can also be dimmed infinitely and with low loss.
White Led offer better color reproduction than many conventional light technologies. In street lighting, where yellowish sodium vapor lamps are frequently used, their color reproduction index is noticeably better.
In some areas, the total cost of ownership – the costs viewed over the entire life cycle of the application – is already lower than that of conventional lamps. These include illumination of chilled cabinets, in museums and street lighting.
What are ballasts and why can you save energy with them?
Energy-saving lamps require a ballast to operate. The ballast provides a high initial voltage to initiate the discharge, then rapidly limits the lamp current to safely sustain the discharge. Without a ballast, the discharge lamp would quickly burn out.
There are basically two types of ballasts: conventional and electronic. Ballasts can make an important contribution to saving energy. Electronic ballasts are the most energy efficient, and they are increasingly gaining in popularity on the market. They use less energy and significantly increase the service life of the lamp – while still achieving the same level of lumen output as conventional ballasts.
Experts estimate that replacing all conventional ballasts with electronic ballasts would reduce energy consumption in Germany (taking into account the operating life of the lamps) by 6.5 billion kilowatt hours a year. Installing sensor-controlled, electronic dimming ballasts would increase these annual energy savings to an impressive 10 billion kilowatt hours. This is roughly the equivalent of the electrical power annually consumed by 2 million 4-person households in Germany.
WHAT IS AN LED?
Light emitting diodes (LED’s), are small diodes that are comprised in LED lamps and fit easily into an electrical circuit. But, unlike incandescent bulbs, they do not have a filament that will burn out, and they do not get especially hot. They are illuminated solely by the movement of electrons in a semiconductor material, and last just as long as a standard transistor.
A diode is the simplest sort of semiconductor device. A semiconductor is a material with varying ability to conduct electrical current. Most semiconductors are made of a poor conductor material that has had impurities (atoms of another material) added to it. The process of adding impurities is called doping.
In the case of LED lamps, the conductor material is typically aluminum-gallium-arsenide (AlGaAs). In pure aluminum-gallium-arsenide, all of the atoms bond perfectly to their neighbors, leaving no free electrons (negatively-charged particles) to conduct electric current. In doped material, additional atoms change the balance, either adding free electrons or creating holes where electrons can go. Either of these additions makes the material more conductive.
HOW DOES A DIODE PRODUCE LIGHT?
A diode emits light as the electrons drop from a higher orbital to a lower one. Different materials will determine the size of the drop which in turn determines the color of light being produced.
The wavelength (in nanometers) of the light emitted = the COLOUR of the LED.
WHY IS IT SO IMPORTANT TO HAVE GOOD HEAT MANAGEMENT WITHIN YOUR LED LAMPS?
The heat management of an LED lamp is critical to its efficiency and longevity. When an LED produces light some of that electricity is actually turned into heat. The job of the heat sink is to move that heat away from the lamp in order to ensure the LED lamp does not run at a high temperature, which decreases efficiencies and life.
Without having an efficient heat management system and heat sinking in place, there can be many negative effects on the LED lamp’s characteristics, including the following:
- Decrease in forward voltage, which could strain other LED components causing them to increase their temperature.
- Optical wavelength can shift, which can consequently cause coloured LED lamps to appear different colours.
- Overall loss of efficiencies and light output
DO LED LAMPS EMIT ANY UV OR INFRARED RADIATIONS?
No, LED lamps provide cool light that is free from any harmful UV and infrared emissions. The lack of these emissions means that there is no discoloration of items under this light.
WHAT IS LM79 TESTING USED FOR?
LM79 standard, published by the Illuminating Engineering Society of North America (IESNA), tests the photometerics of the lamp, including lumen output, color temperature, CRI, watts and lumen efficacy.
WHAT IS LM80 TESTING USED FOR?
LM80 standard, published by the Illuminating Engineering Society of North America (IESNA), lights up an LED array for 6 000 hours and based on those initial results, extrapolates that data to calculate a lifetime for the LED lamp. It is often used as the primary method for calculating lumen depreciation.