LED stands for Light Emitting Diode. Diodes are simple electronic devices with two electrodes (terminals) that allow current to flow in one direction only. An LED chip is at the heart of the LED and converts electricity into light at the chip’s PN junction. The color and wavelength of light emitted is determined by the materials of the LED chip.
LED lights have an almost endless variety of uses in residential, commercial, and industrial applications. Unique uses for LED lighting include simulating daylight conditions to assist with jet lag and improving the look of waiting areas to divert people’s attention and improve emotional well-being during long wait times. Other unique uses for LED lights in the medical field include light therapy (using specific light wavelengths or infrared LEDs for different treatments).
Generally speaking, LED lights are better than conventional lights (incandescent and CFL) because of their higher lighting efficiency, long life, and durability. However, there are some applications where LEDs are far superior to conventional lights for other reasons.
- Vibrating environments
Incandescent, halogen, and fluorescent lamps are constructed with glass bulbs. These bulbs are fragile and break readily under impact. The tungsten filaments in incandescent bulbs are also very delicate and can break under vibration or stress. LEDs are fairly sturdy and ideal for use in a rugged or vibrating environment, such as around machinery, in vehicles, or on bridges.
- Very Cold Temperature Environments
Starter switches (especially on fluorescent lights) do not work well in very cold temperature environments such as freezers. LED lights are unaffected by cold and actually work more efficiently in cold temperature environments.
- Applications requiring frequent on-off cycling
Incandescent and fluorescent lights fail sooner when turned on and off more frequently, but an LED’s operating life is completely unaffected by being frequent on-off cycling.
- UV applications
Compared with standard UV lighting applications done with HID (mercury vapor and metal halide) lamps, LED-UV lights require less operating power (~80% reduction) and do not need a large exhaust fan to avoid producing ozone.
- Replacing 2″ halogen can lights
LED lights are generally ideal for replacing halogen lights. Only LED lights can directly replace halogen lamps in small, 2″ halogen can light fixtures and match their brightness. Halogen lamps have a lighting efficiency similar to incandescent lamps; LED replacement lights have a much greater lighting efficiency.
- Vehicles needing good lighting
Vehicles such as mobile stores, large trucks, trailers, and ambulances may have special lighting requirements. Vehicle batteries usually only have enough power to provide approximately four hours of lighting for these types of vehicles. In contrast, switching to LED lighting could increase the lighting time for such vehicles to around 10 hours.
- Color tuning
LEDs are excellent for color tuning applications and can smoothly transition color temperature from 2,500K to 6,000K. LEDs have made color tuning simpler than that done with conventional lights; color tuning can even be done in a small 2″X3″ LED can light.
- Colored lighting
Conventional lights typically produce colored light by shining white light through a glass covering or filter. LED lights are much more efficient at colored lighting because they can produce any colored light directly (as determined by the materials of the LED chip and coating).
60% of the power supplied to an LED is converted to heat. While this may seem like a lot, LED lights emit much less heat and are highly energy efficient compared with conventional lights. LED lighting can save as much as 85% of the electricity used by similar incandescent bulbs and 50% of the electricity used by similar fluorescent lights.
LEDs cost more than conventional lights, but they are more energy efficient and also have a longer operating life than most comparable conventional lights, thus saving on operating, maintenance, and replacement costs. Many applications with LEDs have a fairly short payback period. For example, Sunlite’s LED replacement for a T-12 fluorescent light typically pays back in two years. Depending on the application and product type, some LEDs actually pay for themselves immediately. Sunlite’s LED Can lights do not cost more than traditional can lights.
Although prices have declined significantly in recent decades as LEDs become more widely used, LED lights still cost more than conventional lights. There are several reasons for the higher cost. LED modules are made of packaged electronic components including semiconductor chips, phosphors, silicone, covers, and wiring. These components are more expensive than those of conventional lights. LED setups also generally require an AC to DC driver and a metal heat sink.
Retrofit LED fixtures are generally used to replace bulbs in traditional light fixtures. Retrofit LEDs are usually designed to replace an Edison-base light bulb and are fabricated with a built-in driver and metal heat sink. Retrofit LEDs are generally not recommended LED products for several reasons.
Retrofit LEDs are much more expensive than traditional bulbs and also have higher fabrication costs than other LEDs. Additional costs are primarily due to the extra materials needed to make the metal heat sink. Retrofit LEDs in older fixtures also generally require larger diameter wire. In contrast, Sunlite’s low-voltage LEDs use 18AWG wire.
LED drivers (often enclosed within the fixture for retrofit LED products) contain semiconductor components and are heat sensitive. In a retrofit LED, the heat generated by the driver adds to that generated by the LED and worsens the heat dissipation problem. When the built-in driver of a retrofit LED fails, the entire fixture must be replaced. In contrast, drivers for Sunlite’s standard LED products are made separately from the fixtures they service and are easily replaced if they fail.
Retrofit LEDs often have dimming problems. Dimming retrofit LEDs is usually done using a TRIAC dimmer. When retrofit LEDs are dimmed, low voltages may not provide enough load for the LED driver and can cause the LED light to flicker.
It should be noted that LEDs are much less expensive (and sometimes are no more expensive than conventional lights) if they are used with an appropriate fixture. For example, if a traditional can fixture is replaced with a new LED fixture (instead of just replacing the bulb with a retrofit LED), the new LED fixture can usually be made much smaller and may not cost more than the traditional light fixture.
Direct lighting refers to a lighting setup in which the majority of the light travels directly from the source to the area being illuminated. Direct lighting is best for focusing light on work surfaces, tables, or countertops, and it is usually used in environments such as work offices, gyms, and warehouses.
Indirect lighting refers to lighting achieved by directing light emitted from a light fixture toward a wall or ceiling, rather than directly toward the area to be lit. Reflected or diffused light created by indirect lighting is often used to avoid glare or shadows created by direct lighting. Sunlite’s thin-profile linear fixtures are excellent for creating indirect lighting.
Evenness of lighting refers to how evenly and uniformly the light in a setting is distributed. The human eye will automatically adjust itself to even lighting in a setting, even at very low light levels. However, if an environment has uneven lighting the eye will not fully adjust and some areas will always appear darker than others. Even lighting in an environment is generally created by having many lights spread out to cover an area, as opposed to having only a few very bright lights.
When a person enters a new lighting environment, the pupil in the human eye constricts or dilates as it adjusts to different lighting conditions to allow more or less light into the eye. Objects can appear different as the amount of light reflected by an object changes. Changes in an object’s appearance are more pronounced when the percentage of total light entering the eye as reflected by the object changes significantly.
The figure below shows a mechanic’s workshop in a mobile truck store being lit by fluorescent and LED lighting. As shown in the figure, object’s reflections tend to look clearer under LED lighting than under conventional lighting because:
- Light emitted by LEDs is more focused and directional than that emitted by conventional lights. A higher percentage of the directional light emitted by LEDs is reflected by objects and enters the pupil. In contrast, the light emitted by conventional lights is less direct, and a lower percentage of more scattered light emitted is reflected by objects and enters the pupil.
- Since more indirect (scattered) light emitted by conventional lights goes directly into the human eye, the pupil will constrict to allow less reflected light to enter.
A “Before” being lit by all fluorescent lighting, “After” all LED. Note that floors, countertops, and various objects look clearer and brighter under LED lighting.
LEDs are considered a green technology and are friendly to the environment for several reasons. They contain no harmful mercury associated with CFL (compact fluorescent light) or HID (high intensity discharge) lamps. LEDs have a much longer operating life than conventional lights, and they do not generate used bulbs that get thrown into landfills. They also have a much higher lighting efficiency (lumens per watt) than incandescent and fluorescent bulbs. Overall, LEDs have tremendous cost savings and benefits to society in terms of their power consumption (with associated pollution and CO2 emission) and resources required for servicing and replacement.
While not hazardous, LEDs are made of electronic components. They should be collected separately from household wastes and treated similarly to electronic equipment for disposal or recycling.
No. LED lights instantly turn on to their full brightness and very slowly dim over their operating life.
Retrofitting a 2″ halogen lamp is not possible with LEDs, since a retrofit LED with a G4 base is typically too big to directly replace a 20W halogen lamp. The best way to replace a halogen puck light is to replace the entire fixture with a 2″ LED can light fixture. Sunlite manufactures LED fixtures as short as 1″ tall (to replace a standard 20W halogen lamp) and 2″ tall (to replace a standard 60W halogen lamp).
An LED light never truly burns out; it simply dims over time. The lighting industry uses the L70 standard rating as the life span for an LED. L70 is measured in hours until the LED reaches 70% of its original light output (30% lumen depreciation). Testing has shown that the life span of an LED under ideal conditions at a constant 25°C is theoretically as long as 350,000 hours (calculated by extrapolating test data to reach the L70). In reality, LEDs do not operate under ideal conditions and will not exist nearly long enough to find out when they would actually burn out.
Many factors reduce LED life span. LEDs are heat sensitive, and good heat dissipation is key to extending the lifespan of an LED fixture. LED fixtures are sometimes installed in areas without good air circulation, thus leading to higher operating temperature and affecting product life. Each 20°C increase in temperature typically will drop an LED’s life span by 10,000 hours. LEDs are typically enclosed with plastic protective lenses, but over time plastic lenses tend to degrade, turn yellow, and block-in heat. LED drivers (often enclosed within the fixture for retrofit LED products) typically have a warranty of 5 years and often fail before the LED reaches its L70 life span. Like the LED, drivers contain semiconductor components and are heat sensitive; outside of its rated operating range each 10°C temperature increase may reduce the driver’s lifetime by half. In a retrofit LED, the heat generated by the driver adds to that generated by the LED and compounds the overall heat problem.
If an LED fixture is well designed, the L70 life span can usually be estimated to be around 60,000 hours. This is much greater than the life span of incandescent, fluorescent, or HID lamps. Sunlite products are designed to last over 60,000 hours because they have excellent heat dissipation and are made with glass lenses that do not degrade or turn yellow over time.
No. Incandescent and fluorescent lights will fail sooner when switched on and off more frequently, but LED lighting is unaffected by being turned on and off.
Well-designed LEDs perform well under typical ambient temperatures. All Sunlite products are rated to operate well between -30°C and 40°C (-22°F and 104°F). LEDs are very sensitive to heat, and although the LEDs will still perform well under their rated operating conditions, each 20°C increase in temperature will typically drop the life span by 10,000 hours. The AC to DC driver for the LED is also heat sensitive, and each 10°C increase in temperature will typically cut the lifetime of the driver in half. Unlike fluorescent lights, LEDs are generally not affected by cold temperatures and actually work more efficiently in a cold environment because the cold helps with removal of heat.
Most insects are primarily attracted to UV rays. LEDs do not emit UV rays and attract fewer insects than conventional lights.
Yes. Natural sunlight is comprised of the entire light spectrum. Blue wavelength light generally promotes plant germination and elongation, while red wavelength light generally stimulates optimum flowering. Regulating the light spectrum with LEDs to match the plant’s life cycle can actually promote faster growing, stronger plants than those grown with natural sunlight.
Yes. Our General Lighting LEDs do not emit UV light or radiant heat. They are excellent for use in refrigerators and displaying food items.
Yes. LEDs can be configured for blinking applications and LED lighting and lifetime is not affected by being turned on and off.
When retrofit LEDs are installed in a can, air does not circulate well and heat is generated from both the LED and the driver. When the driver overheats, it shuts off for protection. When the driver turns on and off, it makes the LED light blink on and off. This is even more prone to happen in summer when ambient temperatures are hotter.
Glare refers to difficulty seeing or a reduction of visibility in the presence of a bright light. Glare may be caused directly or indirectly by natural or artificial light. Common examples of glare include that caused by headlamps at night, overhead light reflected on a computer monitor, and driving into the sun at sunrise or sunset.
A light’s glare is quantified in terms of a G rating. As shown in the figure below, it takes into account the amount of lights in the FH, BH (60-80 degree) and FVH, BVH zones (80 -90 degree) (zones in the dotted red box). While some LED lights have a very high brightness (intensity), they do not produce more glare than that caused by halogen bulbs or similar conventional lights. Glare can be controlled by selecting a product or lighting design designed to direct light only where it is needed.