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Backlighting with LEDs is considered optimal when the individual LED's light is not noticeable, while the total luminous flux meets the project's requirements. 

The most common backlighting applications are linear lighting fixtures, luminous ceilings and illuminated signs. In all cases, the LEDs are placed behind a diffuse cover.

Uniform backlighting depends on the LED pitch (L) and the distance between the LEDs’ emitting surfaces and the diffuse cover.

Linear LED light fixtures and LED tubes also feature a cover that protects the LEDs and diffuses the light. This cover is usually made of polycarbonate (a resin) and sometimes of glass. 

The cover has a certain light transmission rate that impacts the light's luminous flux and glare. If a cover has a high transmission rate, it will minimize the depreciation rate of the lamp’s luminous flux by reducing the light diffusion. However, the light of individual LED’s can be visible, increasing the glare effect.

Below, we present an evaluation of four covers to showcase light transmission and glare.

	Cover A	Cover B	Cover C	Cover D
Image
Material	Resin	Glass	Resin	Transparent Resin
Light Transmission Rate(%)	57	67	77	90

 

For the test a LED strip with the following specifications is used:

Item	Specification
Size	1,000mm
LED Model	Nichia 757
Quantity of LED	140pcs (LED pitch 7.1mm)
LED Strip Luminous Flux	2,958lm
LED Strip Voltage	24V
LED Strip Power	19.2W
LED Tube Efficacy	150lm/W
Color Temperature	5,000K
General Color Rendering Index (Ra)	80

 

The luminous flux with Covers A, B, C, and D was measured to evaluate their impact. Also, it was evaluated the light diffusion (light evenness through each cover). Each item was measured just after the LEDs were operated to eliminate the thermal impact due to the cover.

		Cover A	Cover B	Cover C	Cover D
Lamp’s Luminous Flux(lm)		2,692	2,779	2,868	2,940
Luminous Flux Depreciation Rate(%)		9.0	6.1	3.0	<1%
Light Diffusion (Unevenness) (LED Pitch 7.1mm)

 

The relation between the transmission rate and the luminous flux depreciation for the non-transparent covers is also be summed up in the below graph:

Based on the evaluation results, the highest luminous flux was obtained with Cover D, followed by Cover C which had the highest light transmission rate from the non-transparent covers. For Cover C, the luminous flux decreased by only 3.0%, but the individual LED’s light are easily noticeable when the LED strip is on.

The luminous flux decrease was highest with Cover, but the individual LEDs are not noticeable, the light being evenly diffused, like a fluorescent lamp.

This shows the relationship between the light transmission rate, luminous flux and light diffusion. For optimal diffusion, a cover with a transmission rate around 55-60% is required. A light diffusion of 75-80% is a good tradeoff, with high luminous flux, acceptable diffusion and greatly reduced glare. Transparent covers maximize luminous flux but also glare. 

It should also be mentioned that covers with lower the light transmission rate can cause color shift of the LED light. Using the milky white covers with 55-60% rate, the color could shift slightly toward yellow. Another possible effect of milky white covers is slight decreases in Blue light, without any effect to the General CRI (Ra).  When designing a linear light source for mass production, the possible color shift and CRI changes should be considered when choosing the cover.

 

Nichia UV LED product line update

Nichia is the world's largest LED manufacturer, leading the supply of innovative LEDs to all markets, including UV and UVC LEDs. Durability, brightness and homogeneity are among the major strengths of the Nichia brand. Furthermore, the fine selection allows greater added value for professional processing.

The UV portfolio of Nichia has new additions:

• New UVC LED: NCSU434A at 280nm and 17.5mW for 0.5W power
• Update of UVC LED: NCSU334B, radiant power increased from 55mW to 70mW at 280nm for 1.8W power
• New UVA LED: NWSU333B, with an amazing radiant power of 4900mW at 365nm for 12.25W power

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.

The information below is extracted from the research paper: "Fluence (UV Dose) Required for up to 99% disinfection from Viruses, Bacteria, Protozoa and Algae"  that can be downloaded also on our website at the links below:

PDF: Fluence (UV Dose) Required to Achieve Incremental Log Inactivation of Bacteria, Protozoa, Viruses and Algae

Germicidal action of UV radiation

The effectiveness of sterilization or disinfection with UV light depends on the exposure, time, wavelength and irradiance.

• Exposure or fluence (sometimes called dose) is measured in mJ/cm² (where 1 mJ/cm² = 10 J/m²)
• Exposure time is measured in seconds (s), minutes (m) or hours (h)
• Irradiance is the flux of radiant energy per unit area, in other words how much of the UV radiation power (measured in W = 1000 “miliwatts” mW = 1.000.000,00 “microwatts” μW ) reaches the surface. Irradiance is measured in mW/cm² or W/m² (1 mW/cm² = 10 W/m²) and is dependent on the radiant power, distance and dispersion of the radiation emitted by the lamp source.

Many studies that show the effectiveness of UV light in disinfection or sterilization present in their findings the inactivation of virus or bacteria for a given Exposure in an amount of time, for a given UV wavelength. However, it is difficult to centralize or build a database with so many variables. The most common solution to this problem is to present the fluence required to achieve a log reduction from 1 to 5.

 Log reduction explained

"Log reduction" is a mathematical term (as is "log increase") used to show the relative number of live microbes eliminated from a surface by disinfecting.  For example, a "5-log reduction" means lowering the number of microorganisms by 100,000-fold, that is, if a surface has 100,000 pathogenic microbes on it, a 5-log reduction would reduce the number of microorganisms to one, equal to 99.999% kill rate.

Series and parallel electrical circuits

To power a string or array of LEDs from one LED driver, the LEDs must be connected into an electrical circuit. This can be a series or a parallel circuit. 

We will explain the two types of circuits with examples using our popular LinearZ 56 cm LED strips, with SunLike TRI-R CRI97+ LEDs, Nichia Optisolis CRI98+ LEDs or special Nichia Rsp0a Horticulture LEDs:

Series connection with LinearZ Sunlike CRI97+ LED strips:

One LinearZ 56 cm Toshiba-SSC LED Strip Zhaga Sunlike CRI97 warm white 2700K has the recommended current at 350mA, reached at the voltage of 39.5VDC.

A series circuit with two, three or four LinearZ LED strips is shown below:

Effective and cost efficient disinfection or sterilizing of surfaces, water and objects has become of huge importance. The current COVID-19 (coronavirus) pandemic made this extremely clear. It created a extreme buying spree for everything that can be used in fighting it.  Never before seen shortages of disinfectants, surgical masks, gloves, ventilators and more, happen all across the globe.

The situation is made worse by the fact that many of the materials used for sterilisation are single use and have to be disposed afterwards. More have to constantly produced, exacerbating supply issues. It is time for a more efficient way of killing virus and bacteria, it is time for disinfection with UV light.

"UV light annihilates viruses and bacteria by destroying their ability to reproduce. "

Using ultraviolet (UV) light to disinfect or sterilize¹ has actually been embraced by some hospitals since years, by using large, industrial-grade machines to kill microorganisms (including COVID-19) in hospital rooms or on furniture, objects, clothing or instruments. However, such machines are prohibitively expensive for private or business use, as a mobile platform with UV lamps can cost more than 60.000 USD². They are also dangerous for people and have to be used only in empty rooms.

 

 

With the current advance in UV LED lighting technology, smaller versions of safe to use UV disinfection lamps can now be available to consumers and companies looking to clean pretty much everything, from office spaces, elevators and living rooms, to phones, computers and even toilet seats.

Widespread use of UV light to fight virus and bacteria can now happen with the technology of continuous disinfection with low intensity UVA light from lighting emitting diodes (LEDs).

Growing plants under artificial lighting in closed and fully controlled environments is a method of growing use and global impact.

Industrial scale indoor agriculture could become the main factor that keeps at bay famine and related conflicts. With increasing population, diminishing area of agricultural land, pollution, global warming and migration to grow plants in a reliable, predictable and efficient way will become even more important in the future.

Basic science concepts related to Horticulture lighting

A key factor in the success of indoor plant growth is the efficiency of the lighting system in the process of inducing plant growth, compared with sunlight. 

To build a very efficient lighting system some basic scientific concepts should be known.

Plants grow via a process called Photosynthesis that converts electromagnetic radiation – light – into chemical energy used for growth and development. The other ingredients needed are carbon dioxide (CO2), nutrients and water. The process itself is not particularly efficient, with only 4 to 6 percent of the absorbed radiation converted into chemical energy, but this is the engine that drives most life on the planet.

Photosynthesis and PAR radiation

The electromagnetic radiation required for Photosynthesis is defined as Photosynthetically active radiation (PAR), with the spectral range of 400 to 700 nanometers. Only radiation in the above interval can be used by photosynthetic organisms in the process of photosynthesis, to fix the carbon in CO2 into carbohydrates.

We should note that the electromagnetic radiation called visible light or simply light for a typical human eye has a spectral range from about 380 to 740 nanometers.

A common unit of measurement for Photosynthetically active radiation PAR is the photosynthetic photon flux (PPF), measured in units of moles per second. For many practical applications this unit is extended to PPFD, units of moles per second per square meter.

Growing plants in closed and fully controlled environments, under artificial lighting is method of growing popularity. There is also increasing competition to have results at a low cost and as fast as possible, thus the lighting system plays a crucial role.

Below you will find a quick guide how to build the most efficient lighting system.

1) Research, research

Understand what spectrum and intensity of light your plants need.

You can start by reading our detailed article about horticulture lighting here

2) Choose the right PPFD and light color for your plants

With the latest technology achievements, special or full spectrum white light LEDs are the most efficient and cost effective light sources for plant growth. With 3000K white color temperature you will have more pleasant looking plants while with 5000K you obtain faster growth.

With our Nichia 757 Rsp0a LEDs with white light for special spectrum for plant growth or full spectrum Nichia Optisolis CRI98 LEDs your plants will grow up to 50% more than conventional light, including standard white LEDs, a combination of red and blue LEDs or a fluorescent tube, for lower energy consumption.

According to the standard EN 12464 Light and lighting - Lighting of workplaces -Indoor work places, the light level recommended for office work is the range 500 - 1000 lux - depending on activity. For precision and detailed works the light level may even approach 1500 - 2000 lux. For ambient lighting the minimum illuminance is 50 ulx for walls and 30 lux for ceilings.

Recommended light levels for different types of work spaces are indicated below:

Read more about recommended lighting levels for the home in our blog article.