Diode is an electrical device or component with two electrodes (an anode and a cathode) through which electricity flows – characteristically in only one direction (in through the anode and out through the cathode). Diodes are generally made from semiconductive materials such as silicon or selenium – substances that conduct electricity in some circumstances and not in others (e.g. at certain voltages, current levels, or light intensities).
What is LED Lighting?
A light-emitting diode is a semiconductor device that emits visible light when an electrical current passes through it. It is essentially the opposite of a photovoltaic cell (a device that converts visible light into electrical current). Did You Know? There is a similar device to an LED called an IRED (Infrared Emitting Diode). Instead of visible light, IRED devices emit IR energy when electrical current is run through them.
How Do LED Lights Work?
It’s really simple actually, and very cheap to produce…which is why there was so much excitement when LED lights were first invented! LED lights are composed of two types of semiconducting material (a p-type and an n-type). Both the p-type and n-type materials, also called extringent materials, have been doped (dipped into a substance called a “doping agent”) so as to slightly alter their electrical properties from their pure, unaltered, or “intrinsic” form (i-type).
The p-type and n-type materials are created by introducing the original material to atoms of another element. These new atoms replace some of the previously existing atoms and in so doing, alter the physical and chemical structure. The p-type materials are created using elements (such as boron) that have less valence electrons than the intrinsic material (oftentimes silicon). The n-type materials are created using elements (such as phosphorus) that have more valence electrons that the intrinsic material (oftentimes silicon). The net effect is the creation of a p-n junction with interesting and useful properties for electronic applications. What those properties are exactly depends mostly on the external voltage applied to the circuit (if any) and the direction of current (i.e. which side, the p-type or the n-type, is connected to the positive terminal and which is connected to the negative terminal).
When an light-emitting diode (LED) has a voltage source connected with the positive side on the anode and the negative side on the cathode, current will flow (and light will be emitted, a condition known as forward bias). If the positive and negative ends of the voltage source were inversely connected (positive to the cathode and negative to the anode), current would not flow (a condition known as reverse bias). Forward bias allows current to flow through the LED and in so doing, emits light. Reverse bias prevents current from flowing through the LED (at least up until a certain point where it is unable to keep the current at bay – known as the peak inverse voltage – a point that if reached, will irreversibly damage the device). While all of this might sound incredibly technical, the important takeaway for consumers is that LEDs have changed the lighting landscape for the better, and the practical applications of this technology are almost limitless.
LEDs have swept the conventional lighting marketplace for a variety of reasons, most notably their extended lifespans, reduced energy consumption and lower maintenance requirements. By 2030, the DOE estimates that LED lighting could save 190 terawatt hours of electricity per year, which equates to a whopping $15 billion. As the purchase price of lamps and fixtures continues to fall, more and more facility managers are looking to upgrade their lighting systems with LEDs, given their many benefits compared to traditional technologies. Following are eight advantages for all store decision makers to consider:
1 | Energy efficiency
LED lights use about 50 percent less electricity than traditional incandescent, fluorescent and halogen options, resulting in substantial energy cost savings, especially for spaces with lights that are on for extended periods. LEDs also aim light in a specific direction unlike conventional bulbs, which emit light—and heat—in all directions (because LEDs are mounted on a flat surface, they emit light hemispherically rather than spherically). This directional lighting capability reduces wasted light and energy.
2 | Extended life
Unlike incandescent lighting, LEDs don’t “burn out” or fail, they merely dim over time. Quality LEDs have an expected lifespan of 30,000–50,000 hours or even longer, depending on the quality of the lamp or fixture. A typical incandescent bulb lasts only about 1,000 hours; a comparable compact fluorescent lasts 8,000 to 10,000 hours. With a longer operational life, LEDs can reduce labor costs of replacing bulbs in commercial situations, achieving a lower maintenance lighting system.
3 | Cold temperature operation
LEDs love the cold unlike fluorescent lamps. At low temperatures, higher voltage is required to start fluorescent lamps, and luminous flux (the perceived power or intensity of light) is decreased. In contrast, LED performance increases as operating temperatures drop. This makes LEDs a natural fit for refrigerated display cases, freezers and cold storage spaces in addition to outdoor applications such as the parking lot, building perimeter and signage. DOE testing of an LED refrigerated case light measured 5 percent higher efficacy (the efficiency of a light source in lumens per-watt, like miles-per-gallon) at -5°C, compared to operation at 25°C.
4 | Durability
Without filaments or glass enclosures, LEDs are breakage resistant and largely immune to vibrations and other impacts. Traditional lighting is usually contained in a glass or quartz exterior, which can be susceptible to damage. LEDs, on the other hand, tend not to use any glass, instead they are mounted on a circuit board and connected with soldered leads that can be vulnerable to direct impact, but no more so than mobile phones and similar small electronic devices.
5 | Instant on
Most fluorescent and HID lamps do not provide full brightness the moment they’re switched on, with many requiring three minutes or more to reach maximum light output. LEDs come on at 100-percent brightness almost instantly however, and with no re-strike delay. This can be advantageous following a power outage or anytime employees open a building during early morning hours when it is still dark outside.
6 | Rapid cycling
Traditional light sources tend to have a shorter lifespan the more they’re switched on and off, whereas LEDs are unaffected by rapid cycling. In addition to flashing light displays, this capability makes LEDs well suited for use with occupancy or daylight sensors.
7 | Controlability
It can take more than a few dollars to make commercial fluorescent lighting systems dimmable, but LEDs, as semiconductor devices, are inherently compatible with controls. Some LEDs can even be dimmed to 10 percent of light output while most fluorescent lights only reach about 30 percent of full brightness. LEDs also offer continuous, opposed to step-level, dimming (where the shift from 100-to-10-percent light output is smooth and seamless, not tiered).
8 | No IR or UV Emissions
Less than 10 percent of the power used by incandescent lamps is actually converted to visible light; the majority of the power is converted into infrared (IR) or radiated heat. Excessive heat and ultraviolet radiation (UV) presents a burn hazard to people and materials. LEDs emit virtually no IR or UV. Rapid advancements in LED lighting technologies, with more improvements on the horizon, have resulted in lowered costs and increased reliability of LEDs. And while it may be tempting to assume LEDs are the right choice for all applications because of their energy efficiency, selection should be based on a combination of factors, including light quality and distribution, dimmability, and expected lifetime.
LED vs. CFL
If you’re still on the fence over which energy-efficient alternative to choose, you’re running out of time. Incandescent bulbs are being phased out and will be a thing of the past by next year. Since lighting our homes accounts for about one-quarter of our electric bills, the new energy-efficient bulbs are going to save us money in the long run. But which should we choose?
LED lights last longer, so even though you’re paying more at purchase, you buy fewer bulbs over time. These bulbs fit in standard light fixtures with no adaptor necessary. LED makes very nice lighting for effect and decorative purposes.
LED lights generally cost more to buy than CFLs, but manufacturing technologies are lowering these prices continually. These lights are directional, meaning they are excellent for lights under cabinetry, but not as suitable to table lamps. Some of the newer LED lights come with diffusers, which helps some.
CFL, or compact fluorescent, is simply a mini version of a standard fluorescent light bulb, However, these bulbs fit in standard light sockets without any adaptor. The light appears much like the incandescent light we’re used to, and looks nothing like the harsh lighting we associate with offices or school buildings.
The primary disadvantage to CFL lights is the mercury contained in the bulb. This is ordinarily not a problem, but if the bulb breaks clean up is a hassle. Mercury is a dangerous heavy metal, and proper cleanup and disposal of CFL bulbs is critical. Never put a used CFL bulb in with the rest of your trash. Contact your local waste management company to learn how to properly dispose of used CFL bulbs.
Making Your Decision
Most people make the decision between LEDs and CFLs with their pocketbook. LED costs more at purchase, but lasts longer. CFLs are cheaper, but if broken become not so convenient very fast. Other people decide that CFL lighting is closer to what they’re used to and therefore choose these bulbs to replace incandescent bulbs as they blow out.
Both are efficient ways to light your home, and both work with all the sockets, lamps and fixtures you already own. If you enjoy a directional light for reading, cooking, or working at home, you might prefer the LED bulbs. For general home lighting, such as illuminating a room, CFL might be best.
Of course, you can always use a combination of these technologies in different parts of your home according to the lighting needs in different rooms. This is also a good way to compare the lights to decide. Try some LEDs in the kitchen over your workspaces and over the home office desk. Use CFLs in the living room and bedroom lamps. In time, you may develop a preference, or find you like one for certain applications and the other for other activities.
Side effect of LED lighting
Light pollution has increased worldwide because of the prevalence of energy saving LED lights. However, the problem isn’t with the lights themselves — but the fact that the world is getting brighter because LEDs are illuminating places we didn’t bother to light before. And that has its own environmental cost. The findings were published in the journal Science Advances, and found that artificially lit outdoor surfaces grew at a pace of 2.2 percent each year between 2012 and 2018.
In recent years, the tidings of LED bulbs have taken over the international lighting market with gusto and changed it unrecognizably. Lately, however, questions have been raised as to whether this type of lighting is, in fact, a revolutionary and beneficial one that does not bring disadvantages or health risks with it.
In a recent survey conducted by the Israeli Ministry of Health it was found that at this point in time, there is insufficient scientific evidence indicating a correlation between exposure to LED light and a negative effect on people’s health.
Therefore, and in accordance with what is customary in other countries, the Ministry of Health does not find any justification at this stage for restricting the use of LED lighting or recommending limiting the exposure to such lighting within buildings (houses, public buildings, etc.).
The illumination power of lighting fixtures used in open public space is much higher than that used in closed buildings. The French Agency for Health and Safety of Food, Environment and Employment expressed concern about the damage that could be caused to the eye due to direct exposure to fixtures emitting highly intense light. In health ministries in other countries, no such risks or others have been defined.
Due to the concern that in the future additional scientific knowledge will be accumulated and since the establishment of infrastructure at a cost of millions of shekels requires various economic calculations regarding domestic use of such lighting, the Ministry of Health recommended adopting a conservative approach. Thus, if they discover (say in a decade) that there is a health risk, municipalities will not have to remove all the lighting infrastructure.
With regard to domestic use, as mentioned above, this light is less powerful and is also not close to the human body and therefore (according to information currently available) does not pose a health risk. If in a few years there is information indicating a health risk, then the replacement of bulbs (rather than systems or infrastructure) will be simple and easy to implement. It should be emphasized that apart from the risk of damage to the eye due to direct exposure to high intensity light, no causal relationship was found between exposure to light and other adverse health effects, including cancer.