LED Lighting Knowledge

How to best build an illuminated stretch ceiling with LED modules

The light ceiling or illuminated stretch ceiling is a new and very interesting trend in interior lighting. By using a translucent material of many square meters in size with a backlight system a diffuse, uniform and relaxing illumination of interior space can be created. The main advantage of this type of lighting is the absence of glare, as the light sources are spread over a large area and hidden behind the material.  

Illuminated ceilings usually use as the backlighting source LEDs of low or medium brightness (5 to 50 lumens) placed on strips or modules.  As the illuminated surface has a wide area such low power lighting is the best choice. Illuminated stretch ceiling with LEDs, inside an office

Illuminated stretch ceilings can have personalized shapes and even can feature translucent images. Such, they can influence the overall design of a space much more than other lighting fixtures. From the lighting design point of view the uniform light should be complemented with spotlights or lamps that could attract attention to certain areas or objects.

Properly designing and installing an illuminated ceiling has a unique set of challenges which we will address in this article. 

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How to create lines of light or linear light fixtures with LED strips

A new trend in lighting is the line of light, made with an LED strip inside an aluminum profile with translucent white cover. Such a linear light fixture can be many meters long, form geometric shapes, and is a type of direct lighting.

Line of Light with LED strip inside a profileCompared with indirect cove lighting, also a popular trend in lighting design, lines of light are more energy efficient but can have greatly increased glare. For this reason direct lighting with lines of light should be designed with care and almost always be dimmable. 

Let's see how we can achieve the best results with lines of light.

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Cove lighting with LED strips

A cove luminaire is a light line that can be made via an LED strip that is hidden within a Cove in the wall or ceiling that illuminates an adjacent surface. Light is reflected from this surface into the room to be illuminated. For this reason, light lines are generally referred to as cove or indirect lighting.

Cove lighting is a popular trend in lighting design, focusing on human nature and the behaviour of natural light. It is widely used today, with light lines as the main method of lighting interiors.

The attraction is the similarity with the natural light. With the right light source we could imagine that the bay is actually a hidden window to the outside from which the sunlight streams in.

Let's see how we can achieve the best results with cove lighting.

1. Use of energy-efficient light sources

Choose LED modules or strips with high energy efficiency, at least 100 lm/w, and place them within the coving light so that most of the emitted light uses the reflective surface, wall or ceiling that directs it into the interior. Waste of energy for lighting the interior of the bay should be avoided. LED strips with 120-180° are recommended, which should be placed at an angle if possible:

Surfaces that are more absorptive than reflective, like dark paint or wood should be avoided unless the design is primordial to energy efficiency. White ceilings produce the best results.

2. Select an LED light source with the correct light output.

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How to choose the light with the right CRI for your project

The Color Rendering Index or CRI, for short, is a one number quantification of how good (or bad) an artificial source is at reproducing colors, compared with reference standard illuminant modeled after daylight. The highest number is 100, for daylight and incandescent lamps/halogen lamps, while gas discharge lamps are between 17 and 96, with even a negative value for sodium low pressure (the yellow type used in street lamps).

It was introduced by the International Commission on Illumination (CIE) in 1974, because of the wide variation in the ability to reproduce colors with the white light emitted by the many types of gas-lamps then on the market.

Today, with over 40 years of use, the CRI index is firmly rooted in the lighting industry and among professionals. However, it has failed to gain much traction among the general public due to the fact that soon after its introduction it became not really relevant when making a purchase decision for lighting.

The reason was that most lamps were built for specific applications that required a minim CRI value so one could not go wrong with the choice of lamp.

From 2000s onward, LED technology changed this. It is the first lighting source that can be used for every application and have the full range of performance and quality level, including the ability to accurately reproduce colors. Therefore, it is imperative you choose the LEDs with the correct CRI level for your application. CRI comparison

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IP wateproof rating explained. Recommended IP levels for the bathroom/


What IP rating is required in the bathroom it depends on the IP zoning, which we will explain by dividing the bathroom into areas or “zones“, which are classified using the numbers 0, 1, 2 – see the illustration below.

IP protection zones for bathroom

LED strips or luminaires – the bathroom lights – are then assigned a certain “IP rating” which indicates how much protection they provide against ingress of water and other particles. Each zone has a minimum IP requirement that must be met if a fitting is to be installed in this area.

  • Zone 0 – Inside the bath or shower. Any fittings used here must be SELV (Separated Extra Low Voltage – max. 12Volts) and have a minimum rating of IPX7 (IP67) (protected against immersion in water – total immersion proof);
  • Zone 1 – Above the bath or shower to a height if 2.25m. Recommended IP rating: IP65. In this zone, if there is likelihood of water jets being used for cleaning purposes, a minimum of IPX5 is required. Also, subject to IP rating, SELV or 240V luminaires may be used in this zone; ff the fitting is 240 volts, a 30mA residual current device (RCD) must also be used to protect the circuit in this zone.
  • Zone 2 – The area stretching to 0.6m outside the bath or shower and above the bath or shower if over 2.25m. An IP rating of at least IPX4 (IP44) is required. In this zone, if there is likelihood of water jets being used for cleaning purposes, a minimum of IPX5 is required. Also, subject to IP rating, SELV or 240V luminaires may be used in this zone. In addition, it is a good practice to also consider the area around a wash basin (within a 60cm radius of any tap) as Zone 2.
  • Outside the zones – anywhere outside zones 0, 1, and 2. Where water jets are not to be used for cleaning purposes, the general rules of BS7671 apply. Here, there is no requirement for any lighting solutions to be protected against particles or solid objects, e.g. IPX4 – no IP rating required.

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Innovative SunLike Natural Spectrum LEDs by Seoul Semiconductor

SunLike LED techology from Seoul Semiconductor and Toshiba

Seoul Semiconductor’s SunLike Series LEDs are the world’s first natural spectrum LEDs, as they produce light that closely matches the spectrum of natural sunlight.

SunLike LED package design

This achievement comes from using a new LED architecture, with a purple emitter in combination with a red, green, and blue (RGB) phosphor mix, unlike conventional white LED that use a blue emitter and yellow phosphor.  By removing the blue LED light source and replacing it with a purple light LED chip, lighting technology is fundamentally transformed. For the first time it is possible to render colors accurately with very low energy use and positive effects on health. Compared with other LED lights, the new SunLike Series does not have a blue energy peak associated with eye discomfort and poor sleep patterns.

Furthermore, an ordinary LED spectrum is very different to sunlight, whereas SunLike’s spectrum is very similar. Thus, the light sources with SunLike Series LEDs will more accurately show the color of objects, as they would appear in natural sunlight. It's natural light spectra has color rendering of CRI-97 – close to CRI-100 of sunlight, and much higher than the CRI-80 of conventional LEDs.

The SunLike packaged LED technology from Seoul is based in part on a Toshiba phosphor technology called TRI-R. By using the TRI-R, the LEDs deliver a uniform and broad spectral power distribution (SPD) that is more like sunlight than are typical phosphor-converted white LEDs.

The applications of this new LED technology, with its diminished blue light peak, similar spectral curve to sunlight, accurate rendering of colors and reduced scattered reflection and glare are many, from Human Centric lighting for our home and office to commercial and art lighting.

Human Centric lighting

‘Human-centric lighting’ describes lighting that is designed to work with the human body’s natural rhythms. It relies on the well-established fact that the human eye detects the presence of a particular wavelength of blue light in the spectrum that makes up sunlight, and uses this to judge what time of day it is. In this way, light helps regulate our sleep–wake cycles and other bodily rhythms, and has a significant impact on our mood and well-being.
Color temperature of sunlight
Human-centric lighting harnesses this effect by adjusting its brightness and colour temperature during the day to mimic natural light. To achieve its purpose, human-centric lighting must have a spectrum that resembles that of real sunlight, with just the right level of the crucial blue wavelength that triggers the body’s response. Most solutions described as human-centric do not have a spectrum that resembles that of real sunlight, so they end up providing too much or too little blue.

Seoul Semiconductor’s SunLike Series LEDs are different, as are the first LEDs to be closely matched to real sunlight, so they have the right level of blue that trigger the desired biological stimulus.

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Home lighting guide with LED strips and fixtures

Home lighting with LEDRISE Lumistrips in covelights

Careful design of the lighting for your home will ensure that the right amount of light is gets where and when it is needed and can be switched on conveniently. Lighting should avoid over-lit areas, and give control and flexibility to create lighting effects for different situations. Well-designed lighting will be inherently easier to use and will function in an energy-efficient way.

The best approach to home lighting design is to use three levels of lighting: general lighting, task lighting and accent lighting. By combining these three levels, the recommended lighting level for each room or activity should be obtained, as below: 

Recommended lighting levels for the Home  in Lux
Living rooms general 50-150
Casual reading 150
Study 150-750
Bedroom general 50-150
Kitchen general 150
Kitchen working areas 400
Bathrooms 150-300
Halls and landings 100-150
Stairs 100-150
Dining rooms 150-450

The three levels of lighting

General lighting should ensure a sufficient minimum level of light in the room. There are plenty of LED light sources that can be used for this purpose: LED modules, strips, luminaries or spotlight. Decide on the desired illuminance level (lux). In living rooms and bedrooms in particular, give a certain degree of flexibility (through control settings/dimmers) so that occupants can raise or lower the general lighting around the set level. Design for the upper end of the Lux ranges in homes with elderly occupants, which generally appreciate a higher level of general lighting. A minimum level of general lighting is required for safe movement in the home, especially on the stairs, but sufficient general LED lighting is considered important for general well-being.

Workplace lighting is needed for certain activities at home, such as reading, preparing food and working from home. LED lamps must be carefully selected, correctly positioned and controlled. Recommended are LED spot lights and high flux LED modules. Lamps or sockets are needed in the right places to ensure flexibility in the availability of work and accent lighting. Depending on the task, LED workplace lighting may be required at different levels. The colour rendering of the light is also very important for some activities and we recommend LED lights with CRI 95 or more.

Accent lighting contributes to the ambiance of a house and is usually done with LED spots and strips. As with workplace lighting, LED luminaires (or sockets) are placed in the right places to emphasise architectural features, furniture and ornaments. Accent lighting is a more personal matter, and depending on the circumstances, spotlighting or floodlighting can be useful.

For each of these levels of lighting, controls can provide a range of lighting options. So in an living room there could be separate controlled circuits for:

  • general lighting 
  • task lighting (typically positioned under the wall units) 
  • accent lighting 

Similar control patterns can be considered in other rooms, with dimmers providing a different lighting atmosphere in salons, dining rooms and bedrooms. Advanced controls, sometimes controlled by a mobile phone or a tablet app, that allow remote adjustment of the amount of light and its color are increasingly popular. Lighting is establishing itself as a lifestyle statement and houses with new and innovative lighting systems are perceived as a marketing advantage.

Lighting of each room in detail:

Living rooms

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Human Centric Lighting

Human Centric Lighting (HCL) is an illumination specially designed to have a positive physiological and/or psychological effect on humans. It consists of adjusting the colour and intensity of the light throughout the day using adjustable white LED lighting solutions.

HCL supports human health, well-being and performance by considering and properly planning the implementation of a lighting system according to the desired visual, emotional and above all biological effects of light. Human Centric Lighting focuses on the needs of people for their living, leisure and working environment. The study is based on the properties and effects of natural light, a dynamic source of changing tone and brightness that changes throughout the day and seasons. 

A combination of white LED light sources, usually warm white (2700K) and cold white (6500K), is used to provide adequate human-centred lighting. This solution is also called Tunable White lighting. By adjusting the intensity of each individual, bright or dull white light with a hue between 2700K and 6500K can be achieved. It is a new way of using and implementing artificial light, corresponding to the changes of natural light and research on the effects on humans.

1. More light, more productivity

Increased lighting intensity allows people to work more concentrated, less tired, make fewer mistakes and more accurately identify mistakes. And what makes life more pleasant for the individual is more lucrative for the company as a whole.

2. More concentration and creativity

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Heat management of LED lamps

The optimal use of a product based on LED technology can be difficult due to an important factor: How the operating temperature can lead to a significant difference between the announced and actual performance of an LED-based product.
Important factors for this effect are LED quality, product design and heat management: how much of the heat generated during operation is dissipated.

If the heat is well managed, an LED-based lighting product will have the announced performance, long life and energy efficiency.

The basics of LED heat management

LEDs use electricity and this process generates heat. This heat must be conducted away as efficiently as possible from the LED in the environment. The design of the LED itself and the luminaire for this purpose is referred to as thermal management. The heat to be dissipated is directly proportional to the luminous flux and power consumption of the LED.

The heat is dissipated via a heat circuit.

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LED operating temperature and lifetime

For LED technology, heat is the biggest enemy. From LED chips to related products such as LED lamps, modules and fittings, high operating temperatures can lead to mechanical failure or a significant drop in performance.

The behaviour of the LED at higher operating temperatures is directly related to the LED quality. High-quality LEDs (such as Nichia or Cree) work within parameters and high temperatures, while low-quality LEDs fail, change color, lose brightness, or form a combination.

However, most people are not aware of this fact. They usually give heat and warmth a positive connotation. The misunderstanding that heat is good also comes from the fact that the sun and classic incandescent or halogen lamps have a warm ray. The heat comes from the considerable amount of infrared radiation in its spectrum, which can be high enough to keep food in fast food restaurants warm with light bulbs.


The spectrum of the LED (blue line), the fluorescent tube (green line) compared to the sun (orange line) and the incandescent/halogen lamps (violet line).

Heat and LED technology

Such a setup is necessary because high temperature operation must be avoided at all costs with LED technology. If you do not do this while doing so, lead to at least one of the following points:

  1. Complete failure of the LED
  2. The light output is permanently reduced (lumen degradation), even if the problem with the high temperature is solved.
  3. The light output is reduced in time, while the LED operates at a high temperature.
  4. The color temperature of the white LED changes

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