Welcome to our LED questions and answers page. Here you will find the answers to a large number of commonly asked questions relating to all things LED.
If you don’t find a question here feel free to drop us a line and we will get back to you. And we will add your question to this page.
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?
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.
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.
Why is the life of LEDs measured as lumen depreciation?
Unlike conventional light sources that reduce in output and eventually fail, LED products do not normally suddenly fail. Instead, the light output reduces over time.
The normal convention is to measure the life from when the output has reduced by 30%, i.e. when there is 70% light output remaining. This is often quoted as the L70 life and is measured in hours.
What are the factors that affect the lifespan of the LEDs?
The thermal management of the LEDs. If LEDs come on a standalone chip, appropriate heat sinks have to be designed to prevent premature failure of LEDs.
The electrical stress: Running LEDs at currents higher than specified make the LED run hot. This can happen with wrongly matched drivers. For example, if the driver produces 700mA but the LED needs 350mA, this will put stress on LED and reduce its lifespan.
Higher ambient temperatures than the ones that the LED is rated for will reduce its expected life.
Is lifespan reduced if the LEDs are frequently turned on and off?
Unlike discharge lamps, LEDs are semiconductors and their life span is not affected by the number of times they are turned on and off.
How much longer does an LED last than a conventional light source?
Typically, an LED will last four times longer than a CFL and 25 times longer than an incandescent source that puts out the same amount of light.
What is the best way to compare the output of LEDs with other light sources?
Sometimes simply comparing the lumen output of LEDs and conventional light sources may not be adequate. The amount of light falling on a specific task area (the lux) gives a more realistic comparison. You should also consider the amount illumination visible on the walls. This helps identify applications where LEDs offer better solutions than other light sources.
Does increasing the wattage of LEDs increase their output?
This may occur if you are using the same product from the same brand, with the same optics and hardware. However, in general, the nature of the components (like the optical system, the heat sink, the LED chip, and the driver) affects the output more than the wattage does. A 3watt LED luminaire from one manufacturer will have a different output to a 3watt LED luminaire from another manufacturer, even if the same LED chip is used. Hence, using a high quality chip alone does not guarantee better performance. Note that as the wattage increases, the efficiency drops slightly. An LED driven at 3W will emit slightly less than three times the output of one driven at 1W.
Why are LEDs considered more efficient than conventional light sources?
When comparing the lumen output between LEDs and conventional light sources, LEDs may have lower lumen value in many cases. However LEDs are directional light sources, all the lumens emitted from an LED are directed towards the task area. Conversely, conventional sources emit light in all directions. The light is then modulated in a given direction with optical systems like reflectors and lenses. The amount of lumens that falls in the intended task area from an LEDlight source is greater than that of a conventional light source.
What are “Cold” and “Hot” Lumens?
These terms do not have any photometric or engineering meaning. However, “cold lumens” is the light output of the LED chip alone when it is first switched on. “Hot lumens”, refers to the light output of the LED when it is fully warmed up in the luminaire. The hot lumen value may be 30% – 50% lower than the cold lumen value.
How is light produced in an LED?
Light emitting diodes produce light by the movement of electrons between the two terminals of diode, which occur 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 within 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 LEDs 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 LEDs different from other light sources in the way they produce light?
LEDs 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 ionization of gases in a discharge tube which in turn produce photons.
Do LEDs require time to reach maximum brightness?
No. LEDs 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 fluorescents 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-LEDs?
O-LEDs are organic light emitting diodes. They are made of carbon based films sandwiched between two electrodes; one is a metallic cathode and one is a transparent anode, which is usually transparent glass.
Why are LEDs considered green technology?
LEDs are more efficient than most other light sources, so they usually consume less energy for a given task or at a spesific light output. Also, they do not contain hazardous materials such as toxic mercury. Moreover, LEDs have a longer lifespan and hence reduce the frequency of disposal of lamps.
How can LED lighting help reduce CO2 emission?
LEDs 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, this helps reduce the overall CO2 emissions.
How do LED Lights save energy?
All our LED lights and bulbs are energy saving that are designed to replace incandescent, fluorescent, CFL, metal halide, high pressure sodium and halogen lights in your office, facility or business. They will reduce your energy consumption by at least 50%, and as much as 80%, depending on the light you choose and the light we are replacing. With LEDs lasting up to 100,000 hours, we can also reduce your maintenance on your lighting.
How do LEDs Work?
LEDs are comprised of 3 main components: the LED’s (the chip set that produces light), the driver (converts AC to DC) and the heat sink (to keep everything cool). LEDs take DC power from the driver and create light. The heat sink captures heat from the LEDs and the drivers. Although LEDs produce significantly less heat than the light bulbs we have been used to over the past century, the heat they produce must be managed. The better this is done, the longer the life of the product.
LED’s also performs the job of converting electricity to light more efficiently than other light sources, that is why we can replace a 400W metal halide bulb with a LED 100W solution.
What are the benefits of replacing your ordinary bulbs with the LED?
There are many benefits. Here is a list of a few:
a. An immediate reduction in your electricity bill.
b. Less heat. LED fixtures are extremely efficient converting electricity into light.
c. LED Bulbs last a very long time, typically 50,000 to 100,000 hours.
d. They are virtually indestructible.
e. They do not contain mercury or other hazardous materials
f. Highly recyclable – with no hazardous parts, you can easily reclaim most of the parts in an environmentally safe way.
How much money can you save when you convert to LED?
It all depends what you are converting. Incandescent to LED, fluorescent to LED, Metal Halide to LED. And this answer will change over time as LED Lights become more efficient and their lumens/watt get better. For now, you can expect at least a savings of 50% when you convert fluorescent lights to LED and 70% or more when you convert Metal Halide or High Pressure Sodium to LED.
Can LED bulbs be used with dimmer controls?
Yes and No. First, not all LEDs are dimmable. The driver must be designed to allow dimming. Secondly, you must purchase the right type of dimmer. Most retail stores now carry dimmers specifically designed for LED bulbs. Please note, if you purchase a non-dimmable LED bulb and try to dim it, it will cause the bulb to fail and also void the warranty.
Some of our industrial and commercial LED fixtures (high bays, floods, area lighting, retrofits) work with a 0-10V dimming system. 0-10V dimming requires special wiring and a special type of dimmer.
The two most common types of dimming is: 0-10V low voltage and Triac dimming.
Do they contain any hazardous or heavy metals like Mercury?
They shouldn’t. LED bulbs should not contain mercury or any other hazardous metals or chemicals. CFL’s and fluorescent do contain a very small amount of mercury that needs to be disposed of correctly. So when your LED bulb eventually stops to work, you don’t have to worry about costly or special disposal procedures.
What colour temperatures are available with LED bulbs?
Colour temperature for light bulbs is measured on the Kelvin scale. LED Bulbs come in a variety of colours, but the most common are in a range from 2700 Kelvin to 7500 Kelvin. The unfortunate thing is that the only consistent measurement is the Kelvin scale, Many manufacturers like to use terms like Day White, Natural White, Warm White and Cool White, but there is not a standard that defines a Kelvin temperature to associate a colour temperature with those terms. The warmer the light, the more yellow tones, the cooler the light, there are more blue tones.
In this example, we have used terms to reflect what we believe to be the right relationship to Kelvin colour temperatures.
2700 – 3200: Warm White
4000 – 4500: Natural White
5000 – 5500: Day White
6500 – 7500: Cool White
Its important to note: at home we use Warm White bulbs, in the office we use Natural White and in the Warehouse we use Day White. We rarely use or even sell Cool White LEDs.
Can LEDs be used in outside lights?
Yes. Some bulbs are designed with water-proof fittings. Others need to be kept in a water-tight fixture. Read all instructions and manuals before using a LED bulb outdoors.
The specification you need to check for is IP Rating. A bulb or fixture IP65 or greater is considered acceptable to work in a wet environment.
Will the light levels decrease over the life of the bulb?
Yes. They will fade as the bulb gets near the end of its normal operating life. But it is very gradual and hardly noticeable. This is called Lumen Degradation and is denoted on the website as L70. L70 is the amount of time the light takes to get to 70% of the initial lumen output.
How many lumens do I need to replace 400W Metal Halide fixture?
There is a lot that goes into answering this question. DesignLights Consortium has indicated in their specifications that you need at least 10,000 lumens to replace a 400W Metal Halide. Some other factors come into play, like surface reflectiion, obstructions and other source of light, such as natural light sources coming into the building.
We replace indoor Metal Halide with 15,000 to 21,000 lumens of LED.
We replace outdoor Metal Halide with 12,000 to 21,000 lumens of LED.
MyLEDLightingGuide designs light solutions. We are product agnostic, we will select the best product that meets your needs. So we have the ability to replace 400W Metal Halide with 10,000 lumens up to 30,000 lumens. We do find that you need more lumens indoors to do a proper replacement than you do outdoors. A lighting photometric analysis will determine how much you need to create the proper foot candles.
What are the steps required to replace a fluorescent tube?
There are several steps, but essentially this is no more difficult than a bulb and ballast replacement.
- Remove the fluorescent tubes, and then remove the ballast.
2. Replace the existing tombstones (only if necessary). This step may be required with single ended powered tubes if you have shunted tombstones.
3. Rewire the fixture to accommodate the LED replacement tubes. Note: there are also ballast compatible tubes that allow you to convert to LED by simply removing the old fluorescent tube and replacing it with the LED replacement tube.
Our LED internal driver Tubes use AC current, and then converts the power to DC within the internal LED driver to light the LED’s. There are some tubes that can be driven from the fluorescent ballast, but we do not supply those tubes as we see fluorescent ballasts as a maintenance item. Ballasts consume about 4+ watts per fluorescent tube installed, so leaving the ballast in place reduces the energy savings as well.
We also can supply LED externally driven tubes. With these tubes, the driver is externally housed outside the tube, and is usually installed where the fluorescent ballast was located. External drivers act the same way as internal drivers; they accept AC power, convert it to DC which is supplied to the LEDs in the tube.
In the case where you have a native DC system (such as solar systems) you are best to look for externally driven tubes and forgo the installation of the driver. You will have to make sure the DC power that is supplied to the fixture is compatible with the DC power requirement of the tubes.
When I buy LED, should I buy based on watts or lumens?
Always buy based on lumens, watts is a number that is used to determine how much energy it takes to produce those lumens. It is important to pay attention to lumens per watt, or lm/w. The higher the number, the less energy you will need to produce the light. You will notice that some lights take less energy to produce the same amount of light, and this is something you should watch for. Typically, the higher the ratio, the better.
What component of the LED system is typically the first to fail?
Almost always, it is the driver. That is why it is important to know who makes the driver in the LED fixture or retrofit you purchase. Brand names like Meanwell, Inventronics and Philips are great. A LED product with a 1 or 2 year warranty is an indication of how good the driver or product is. Typically a good driver should last more than 50,000 hours.
What is the most common reason LEDs fail?
Heat. Heat is the enemy of electronics, the hotter it is, the shorter the light. However, with good design, you can create a light or fixture that can withstand some high heat environments. Typically a fixture or bulb with an external driver will last longer than an integrated fixture that has the LEDs and driver as one unit.
What is CRI?
CRI is Colour Rendering Index. It is a measurement of the quality of light. Where as lumens is a measurement of the quantity of light, CRI is the measurement of quality. It is a scale between 0 and 100. 0 is bad, 100 is great. LED’s typically are in the 70-95 range. The higher the CRI, the more expensive the LED chip, and therefore the more expensive the product itself.
What Is Lamp Life?
Professionally branded lamps are designed and tested to strict international IEC standards and with it defined calculations as to “average life”.
Typically there are two (2) methods of calculating lamp life namely:
Average Rated Life – whereby a defined production quantity is tested using set switching cycles and when 50% of the lamps remain the result determines the rated average life.
Eg: an installation using a quantity of 100 lamps, with a 10,000 average rated life = at 10,000 hours operation 50 lamps will have failed.
Economical Life – whereby a defined production quantity is tested using set switching cycles and when the batch selected reaches a determined light output, that then determines the economical life of the lamp.
Eg: an installation using a quantity of 100 lamps, with a 10,000 average (output) life equaling a depreciation of 60% = at 10,000 hours operation the installation lighting output will be 40% of the original installed design.
It is important at the time of the lighting design to consult with your lighting professional to determine what lamp lumen depreciation factors should be included to accommodate the expected and natural deterioration of the lamp component.
Important note – For system integrity ensure you replace the lamp with a direct and approved equivalent.
What is Power Factor(pf)?
Power Factor is a term used to describe the relationship between the current and voltage in an electrical circuit. Equipment such as ballasts possess inductance which causes the current waveform to be displaced and ‘lag’ behind the voltage waveform.
A measure of this angle of displacement calculates the Power Factor. The larger the angle, the lower the Power Factor.
An ideal power factor is when there is no phase angle difference between the current and the voltage of the circuit and therefore the voltage and current are said to be ‘in phase’ at ‘unity’, resulting in a power factor of 1.
LED products with a low Power Factor mean that the operating current has to be increased from the supply source to compensate for the reduced Power Factor and to maintain constant power at the load.
How do I measure the running costs of a 12W LED downlight compared to a 50W MR16 halogen lamp downlight?
The running costs can be determined by the following. Annual running cost $ = Wattage (expressed as a % of 1000 watts, or KW) x Hours (Number of hours use per day) x cents per KWH (Cost of electricity)
Example: What is the annual savings when I compare a Crompton 12W XL-LED downlight used for 10 hours per day, 7 days per week, 52 weeks per year, with the cost of electricity at 20 cents per KW Hour ?
Annual Cost for Crompton XL-LED = 12/1000 x (10 x 7 x 52) x $0.20 = $8.74 Annual Cost for MR16 50W halogen downlight = 55/1000 x (10 x 7 x 52) x $0.20 = $40.04
*Full system losses have been used in the above example to more accurately reflect true savings
Based on a medium sized house with an average of 30 x low voltage 50w halogen downlights and a cost of electricity at 20 cents per Kilowatt hour, the annual savings would be more than $900 per year.
Can I run my LED MR16 style lamps on older halogen electronic transformers?
There are two basic types of LED drivers, both designed to run LED at their optimum parameters to protect the life of the chip: constant current and constant voltage.
A constant voltage LED driver (ie. transformer) will output exactly 12V DC. 12V MR16 Style LED lamps and other 12V powered LED modules can be connected in parallel to such a driver. Thanks to the parallel connections, if one bulb dies, the remaining bulbs will stay on.
A constant current LED driver will output a fixed current, suitable for operation of the LED chip or module. The output voltage will vary as required to maintain the specified output current with different forward voltage drops common with LED junctions.
Basically, the user needs to ensure that the LED supply you choose can handle the correct load.
Halogen transformers normally have a minimum load required and therefore (for example) placing a 12V 3W MR16 style LED bulb on a 20-60va halogen transformer that previously operated a 50W MR16 Halogen lamp is not an ideal solution, as the ‘load’ is not sufficient to start the lamp or run the lamp at its optimum output.
A number of possibilities would generally be experienced with the above such as strobing or flickering of the LED lamp or it may not work at all.
These characteristics can also be detrimental to the life span of the LED chip.
Due to the number of halogen transformers in the market with differing operating characteristics, the best solution is to always ensure that the power supply has been recommended by the manufacturer or supplier of the LED source, to ensure compatibility.
What is DALI?
DALI is an acronym for Digital Addressable Lighting Interface and has become an open standard for Lighting control Essentially, each light fitting is given a unique ‘address’ allowing digital control of the Lighting installation.
What is DSI?
DSI is an acronym for Digital Serial Interface. It is a protocol for lighting control, through the controller (mainly in commercial buildings). DSI was the first use of digital communication in lighting control, and its low voltage means it can run on relatively thin cables. One of its main advantages is that it dims to ‘off’ so does not require mains switching equipment to turn the lighting off.
What is the difference between DALI and DSI?
DSI is essentially the same technology as DALI in terms of digital communication, however DSI eliminates the individual ‘address’ aspect of each light fitting required in DALI. In DSI each unit has its own wire direct to the controller, rather than being part of a network such as with DALI.
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