What are LEDs??
LEDs are light emitting diodes. These are electronic components that convert electrical energy directly to light through the movement of electrons within the material of the diode. LEDs are important because due to their efficiency and low energy, they are beginning to replace most conventional light sources.
Why is LED technology classified as solid state lighting??
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 agaseous discharge medium to initiate production of light.
What is binning??
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.
What is a light engine??
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.
What makes LEDs more robust than other light sources??
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.
Why do LEDs have a higher initial cost than conventional light sources??
LEDs are made of electronic components that 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 LEDs require further tests for calibration and standardization.
What are the economic advantages of using LEDs over conventional light sources??
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.
Is it true that LED lights do not attract insects??
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.
What does a life of 50,000 hours mean in the case of - LEDs??
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.
Are all retrofits main voltage??
Most retrofits have the appearance of a conventional lamp and are used as direct replacement for the existing one. i.e. they have a screw or bayonet cap base. With downlights and spotlights, it’s common to have a 50mm dia reflector lamp. The mains voltage ones are usually called GU10, which refers to the flattened pins on the base. However, some are available for 12V supply fed from a transformer, e.g. Direct replacements for 50mm dichroic LV downlights. These will have thinner pins and are often called MR16 or GU5.3 lamps..
Will the light output be the same??
As with complete LED luminaires, it is important to ask the supplier for the lumen output and to compare this with the unit you are replacing. If it is a spotlight, compare the two lamps side by side. Poor quality sales literature often states the output from the LED chip and not the complete lamp.
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 cause damage to lamp sockets, circuitry and lamps, and in extreme circumstances, it can even melt fixtures and floor coverings.
Can I put a retrofit in an enclosed or sealed luminaire??
The general answer is NO. The electronics in the retrofit will overheat and lead to a short lifecycle. A better solution is to use an LED module with a remote driver.
What does SMD mean??
SMD means surface mounted diode. This is a better technology than the first generation DIP LEDs. The SMD typeLEDs are mounted on an aluminum substrate and enveloped in an epoxy resin.
What are the typical types of LED modules available in the market??
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.
How has LED lighting contributed the usage of light in healing??
The saturated and concentrated light beams of specific wavelengths that LEDs can produce have opened up a new area of healing with LED light. Special LED lighting is used to heal wounds like skin ulcers from diabetes, serious burns and oral sores from radiation and chemotherapy. Certain wavelengths of LED light can also help to remove brain tumors. Infrared LEDs promote cell regeneration and help to healing lacerations.
How are LEDs used as light therapy for the skin??
The layers of the skin have a high content of blood and water that allow absorption of light with each wavelength having positive yet different benefits to the skin. Light therapy is an advanced technology that uses specific wavelengths of light to offer the following benefits:
Infrared – replenishes dermal and epidermal cells. Used to rejuvenate skin and heal wounds, cuts and damage.
Red light – stimulates collagen product and promotes circulation. Used for skin rejuvenation. Used to reduce lines, wrinkles, scars and even the skin tone.
Orange light – revitalizes skin, bringing out the glow in skin for special occasions.
Yellow light – reduces swelling, redness and inflammation. Used to treat sunburns.
Green light – creates a calming effect on skin with anti-inflammatory properties. Lightens hyper pigmentation of spots revealing a brighter complexion.
Blue light – displays anti-bacterial properties. Used for acne, to purify the skin, regulate oil glands and soothe inflammation.
How has LED technology helped make care facilities more comfortable for elderly residents??
Case studies have been conducted where introduction of custom designed amber LEDs with occupancy sensors permitted turning on of lights when residents got out of bed reduced the number of falls. Dimming LED lighting to a low level also helped minimise the discomfort and glare issues that arose when nurses turned on bright overhead lights during nightly rounds.
Why is the heat sink design critical for the performance of an LED fitting??
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
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 LEDs to produce more light also reduces lumen depreciation. Junction temperature is affected by the driver current, the thermal path, and the ambient temperature.
Is it true that LEDs do not produce heat??
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 luminaire is hot to touch. Why is this??
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.