What is LED?
LEDs or Light emitting Diodes, as the name states, are diodes. A diode is a semi-conductor device that permits current flow in one direction. Semiconductor diodes are a junction of two materials. One material has a surplus of positive charge (holes), and the other a surplus of negative charge (electrons). When you apply a forward voltage, the electrons and holes are brought together. They combine and release light energy. This explains the ‘light emitting’ part in the term, LEDs.
Why use LEDs?
The future of lighting rests with LEDs. These Light sources consume almost 90% less electricity than standard incandescent bulbs, last up to and beyond ten years and produce an even spectrum of light that is unparalleled. These lights will soon be used in every home and office. In anticipation of this, we offer LEDs to light your indoor and outdoor spaces.
Is an LED a bulb?
LEDs do appear to be bulbs, but in fact are not. LEDs are tiny semiconductors encapsulated in plastic which protects their components and helps to focus the light.
What is the difference between an incandescent bulb and LED?
Incandescent bulbs create light through filaments. When power is applied, the filament glows and generates heat - which in turn produces light. LEDs are just the opposite. LEDs create light through a 'cold process'. When power is applied to semiconductors (usually gallium, arsenic and phosphorous), they're stimulated by the movement of electrons, this creating photons. Photons are the light that is visibly seen by humans.
Do LEDs have a wire filament?
No, LEDs operate using entirely different components. LEDs are diodes - they only allow power to move in one direction. The anode (+) is where the current comes in and the cathode (-) is where the current goes out, much like the positive and negative terminals of a battery. Incandescent bulbs project light in every direction (Omnidirectional) as opposed to LED lights which project light in specified directions (such as 20, 50 and 120 degrees) due to their package design and layout.
Why do LEDs use such little power?
LEDs don’t use a filament where a conductor is heated and light is created. Filament based lighting consumes more power than the light produced. LEDs produce very little amounts of heat and do not use filaments making them far more efficient in consumption and output.
Do LEDs produce heat?
LEDs produce very little heat. If LEDs are hot to the touch, they are being overpowered due to improper circuitry.
Can LEDs be damaged if hooked up backwards?
Yes, they can. LEDs are diodes and only allow power to pass in one direction. To ensure a long life out of our LED devices, we add additional circuits to prevent this from happening in both AC and DC applications.
Are LEDs affected by extreme conditions?
LEDs are geared for harsh environments. LEDs function from -40C to 180C. There is no delay or required "warm up time" for LEDs to function.
Do LEDs attract insects?
No, they do not. Insects see entirely different spectrums of light and are attracted to ultraviolet light. A side note - flowers create "nectar guides", invisible to the human eye and ultraviolet light attracts insects to flowers for reproductive purposes. This is not to say that all bugs aren't attracted to LED lights, but most can't see the light that LEDs produce.
How long do LEDs last?
LEDs are rated by manufacturers to operate under normal conditions for approximately 10 years or 100,000 hours of continuous use. As LEDs get older, they tend to dim and fade but aren't susceptible to blinking like incandescent or fluorescents.
LEDs are more expensive than other lighting options. Why?
LEDs can operate as stand-alone devices, but when grouped or clustered they require additional steps to operate properly. LEDs need proper components such as a circuit board, driving components and some cases and housings to endure the elements. LED circuits can be designed rapidly, but to ensure that they operate correctly and for long periods of time they require testing. All components used to make LED luminaires make LEDs more expensive than other lighting sources.
Can LEDs be dimmed?
It's useful to think of an LED as a current-driven device. Instead, pulse width modulation presents a technique to safely dim an LED from 0 - 100% of its nominal brightness. By pulsing the LED with current, and varying the duty cycle of the current waveform, the LED rapidly transitions between on and off, and the relative times spent give the impression of being dimmed.
How do you get more light out of an LED?
LEDs are made by a process that deposits the junction materials on a substrate material. One of the limitations of LEDs is that imperfections in the material deposited on the substrate reduce the efficiency. Improvements in the manufacturing process have given us brighter LEDs, as have new junction materials.
To a certain extent, you can also make the junction larger to get more light. But you can't extend that very far, mainly due to those imperfections. Their accumulated effect prevents a junction from growing much bigger than a square millimeter. So we won't likely see larger LED junctions without some advance in materials science to overcome that limitation.
Where have LEDs been used in the lighting industry?
LEDs are commonly used in aesthetic, effect, or specialty lighting applications, including architectural highlighting. Most traffic lights and exit signs, for example, now use red, green or blue LEDs.
Have LEDs always been used in general illumination lighting?
No. Early attempts to apply LEDs in general illumination lighting failed because they didn't meet the lumen-per-watt output or color requirements. Technology has advanced to the point where using LEDs for general illumination is now viable. Lighting industry experts are gaining a better understanding of how to capitalize on that technology.
What is CRI, and what does it mean for LEDs?
CRI=Colour Rendering Index. This is the level to which colours appear natural under a specific light source. A light source with CRI of 100 means that all colours will appear exactly as you would expect under normal daylight conditions. A warm white LED gives a CRI of approximately 90 which gives an excellent perception of colour. LEDs are currently under development with a CRI >95 (watch this space).
Why have past attempts to create general illumination LEDs failed?
Conventional approaches to developing general illumination LEDs often involved retrofitting existing fixtures to house the new LED technology. Instead of investigating the benefits and challenges of LEDs, many early attempts simply used traditional lighting standards and housings. The problem was that LED technology breaks all traditional rules, and it quickly became apparent that old thinking couldn't be applied to this new technology.
Why don't LEDs function as efficiently in traditional fixture housing?
An LED module may physically fit into an existing housing, but that housing doesn't leverage the inherent qualities of the LEDs. Standard housings can't handle the challenges of LED thermal management, which is vastly different than thermal management for traditional incandescent or fluorescent lighting. Also, the optical design used in most traditional fixtures doesn't maximise the LED's efficiency.
What is junction temperature?
Junction temperature is the temperature at the point where an individual diode connects to its base. Maintaining a low junction temperature increases output and slows LED lumen depreciation. Junction temperature is a key metric for evaluating an LED product's quality and ability to deliver long life. The three things that affect junction temperature are: drive current, thermal path, and ambient temperature. In general, the higher the drive current, the greater the heat generated at the die. Heat must be moved away from the die in order to maintain expected light output, life, and color. The amount of heat that can be removed depends upon the ambient temperature and the design of the thermal path from the die to the surroundings."Heat management and an awareness of the operating environment are critical considerations to the design and application of LED luminaries for general illumination. Successful products will use superior heat sink designs to dissipate heat, and minimize junction temperature. Keeping the junction temperature as low as possible and within manufacturer specifications is necessary in order to maximize the performance potential of LEDs."
Why Does Thermal Management Matter?
To maintain the extended life of the fixture, LEDs need to shed heat that builds inside the fixture. A low junction temperature is key to effective thermal management. The heat sink assembly contains heat thermally conductive material that move heat away from the LEDs and the circuit board quickly and effectively. Through this effective thermal management design, the fixture is guaranteed to operate at the proper temperatures
Are 2 Watt, 3 Watt and 5 Watt LEDs available?
Yes, there are whole hosts of different power LEDs available. Ranging from 0.01W right up to several hundred watts. There has even been a 1kW LED produced. The higher power LEDs are generally not a single LED, but rather an array of lower power LEDs which are combined over an area to give the perception of high power. It is not the power of the LED which is important but rather the amount of light produced. The amount of light produced measured in Lumens. There are many low quality 5W LEDs which produce significantly less light than quality 1W units.
Do I have to replace LED diodes?
An LED does not burn out like a standard lamp, so individual diodes do not need to be replaced. Instead, the diodes gradually produce lower output levels over a very long period of time. If one LED fails, it does not produce a complete fixture outage.
Why are LEDs of some colours are more expensive than LEDs of other colors?
The reason is that different semiconductor materials are used for different color LEDs, and some semiconductor materials are more expensive than others; another reason is that manufacturing costs are different. White LEDs are the most expensive because red, green and blue LEDs are combined together to make a white LED.
Does a colour shift occur in the LED over time?
Colour shift occurs with all light sources over time. Typically if a bulb is replaced it will appear a different colour to adjacent bulbs. The colour shift pattern of LEDs is only very slight and colour shift is virtually eliminated with correct thermal management of the fittings. Dimming can cause colour shift with conventional light sources (if you dim a filament/ halogen bulb down it appears red). This is not experienced with LEDs due to the special techniques used in LED dimming systems.
How is an LED installation wired?
This depends on the installation and the products used. Traditional low power LEDs are provided with a constant voltage then a resistor is used to regulate the current to each LED. High power LEDs requires a more sophisticated method to regulate the current to each LED.A typical 1.2W LED requires a regulated constant current of 350mA, the LED itself will self-regulate its voltage. If a chain of LEDs are used then they must be wired in series, so each LED receives the required 350mA.The 350mA is provided by specialist power supplies often referred to as Drivers.