Choosing the right linear solution

Considerations when choosing the right linear solution.

As part of the Lumascape education series, we recently interviewed Lumascape’s Technical Director, Cameron Spiller, on essential considerations when choosing a linear fixture for façade projects and to ensure the best results for any applications.

While there are more considerations depending on the type of project, here are just some of the main ones that can assist when choosing the right linear solution.

What are some of the considerations a lighting designer or consultant should take into account when choosing the right fixture for a project?

  • Application:

First, decide if the fixture will be used for a grazing, wall-washing, or direct view application. For grazing and wall-washing applications, the fixture needs to be photometrically flexible so that an optic and LED engine can be selected that best meets the needs of the specific application.

  • Scale of Lighting Task:

The scale of the fixture’s desired effect has a direct correlation on the performance needs and lumen outputs required by the luminaire.

  • Color:

More and more lighting designers and consultants critically examine the effects they want to achieve with each lighting solution. They must consider if the application requires a luminaire that is single color, white, or something more dynamic.

  • Capabilities:

The capabilities of the light engine and control considerations can mean the difference between an ideal product and one that is simply okay. Key determinations include the following:

a) The maximum number of luminaires that can be connected to a single cable and lighting controller. It is important to have a product that imposes minimal restrictions on electrical design and installation.

b) A luminaire that delivers a homogenous beam with no color separation either in mixed colors or static whites. This comes down to the precision engineering within the optics.

c) It may also be important to consider other technologies including thermal control suited for difficult environments. This ensures that the luminaire has a long life and that it will perform well after the project is over.

d) Material selection is also important with considerations including, but not limited to, whether plastics are used in construction and the UV stability of the external material. Glass and UV stabilized materials are required on external facades and in harsh environments to maximize the life and performance of the luminaire.

d) Mechanical and technical elements of the fixture being specified should be considered on any applications including the IK rating, IP rating, vibration ratings, load ratings, and operating temperature ratings. There are many other elements in this group to ensure that luminaire is the best choice.

Why not a single LED chip concept?

For mixed colors, there are two ways of getting mixed or dynamic color from a luminaire onto a surface. One way is for a fixture to have individual LEDs of different colors such as red, green, blue, and white or amber built into the luminaire. Lumascape incorporates this design strategy in all linear fixtures to ensure a superior light fitting. The other way is to design a fixture that incorporates a single RGBW LED chip or a RGB LED chip with a separate white LED.

Why use individual LEDs in Lumascape fixtures?

There are several factors for using individual LEDs. These include:

a) Thermal resistancebetween the junction, which is where all the magic happens, inside the LED and at the base of the LED, is the critical path to get the heat out of the LED is far more efficient for the individual color LEDs as apposed to a multi-die which has a very high thermal resistance. It is harder to get the heat out of the fixture. They run hotter, are less efficient, and if they are driven hard, it can be difficult to expel this heat.

b) When selecting an RGBW or amber LED or mixing colors together, having individual chips lets engineers select from a full color palette with a high number of RGB colors. Selecting the most appropriate, the richest, and the highest efficiency for each individual color makes Lumascape luminaires superior in quality. If using a quad chip or tri-chip, customers get what is in the LED.

c) When using the quad or tri-chip, the optic has a focal point in the chip. This focal point needs to coincide with the position of the LED, which is called the L.E.S. (Light Emitting Surface). The L.E.S. should be in the focal point. Otherwise, the light won’t be focused accurately or correctly. If it is off to the side, the beam will be wonky. If it is too high, the beam will spread and create an unattractive color wash. A quad chip or tri-chip has three light emitting surfaces on the same plane as the focal point, which makes it impossible for them to be in the focal point. For example, if you had red on one side and blue on the other, neither of them are in the focal point. Both are on the side, resulting in uneven beams that don’t overlap each other or color split. One way this is solved is with extra diffusion. However, there is a disadvantage with this approach: loss of efficiency each time the light goes through another surface. The light is refracted, the luminaire loses energy, and a very narrow beam cannot be achieved. When individual LED chips are designed under four different lenses, as with all Lumascape luminaires, the beams overlap and a very narrow beam, down to 10° can be achieved with decent color mixing. It is not possible to get a narrow beam angle as low as 10° with the quad or tri-chips.

There is an argument is that is often made that if the four LEDs are inside the same lens, the colors should mix better. However, this is actually incorrect. They are inside the same lens but are operating through different optic positions, so they don’t mix.

How does Lumascape cut the scallop effect within our fixtures?

Lumascape resolves this effect with several approaches:

a) Through the development of our own optics. The optics that are purchased and the optics that are used are designed by Lumascape engineers specifically for the LEDs and fixtures. This means that our optics are far more effective. We know the lens will refract nicely and emit light in the beams that we want.

b) Lumascape fixtures include spreaders. While the spreaders don’t send light back and forward, they do make the beam narrower on one plane and wider on another plane. This provides better overlap of beams on the illuminated surfaces.

c) Where you have an RGBW there are gaps depending on what color it is based on and the construction. With the LEDs that are constructed by Lumascape, the height and thickness of the base are adjusted to make sure the light emitting surfaces are all at the same height.

Do we have an option MacAdam 3?

MacAdam ellipses help explain the color point specification of lamps by providing guidelines about a person’s (trained or untrained) vision and how they distinguish between different spectrums of color. (Out of the Woods: MacAdam ellipses, Mike Wood, Protocol Fall 2010, pages 15–18).

Generally, the acceptable color deviation for lighting applications is the three-step MacAdam ellipse. All Lumascape colors and CCT codes are tested to ensure they fall within the three-step MacAdam ellipse of color as standard.

It is possible to design a fixture board with enough LEDs that if tested can fall toward the two-step or closer. At Lumascape, all LED boards are tested in an integrating sphere during the production stage before they are shipped to customers. This ensures they fall within the three-step MacAdam ellipse. No product ever leaves the production facility if the color tests indicate the LEDs are not within the three-step ellipse.

How does Lumascape maintain uniformity of color output?

When fixtures are placed into the integrating sphere for testing, every color within the luminaire is calibrated to verify the ratio of RGBW is the same on all fixtures across the entire installation and project. For dynamic color, this individual calibration process ensures a consistent and superior product. For the RGBW, we test the level of the individual color and where it falls within the ellipse when they are all turned on. For whites, selection of the three-step MacAdam ellipse and testing during production ensure we fall within the ellipse.

Furthermore, the color LEDs are calibrated and checked. All whites within the luminaire are also  selected and checked.

What things does Lumascape consider when designing a linear facade lighting solution?

Lumascape considers a full spectrum of factors when designing linear façade products. Various design considerations make Lumascape products the most innovative solutions available on the market. They transform architectural installations of all scopes into dazzling displays of performance art.

Major factors that must be considered in the beginning stages of product development include, but are not limited to the following:

a) Proper material selection ensures every luminaire can be used effectively in the harshest environments around the world.

b) Use and development of robust electronics must be considered, as luminaires are often installed in a tough outdoor conditions, from the heat of the Middle East to the cold of Canada. All Lumascape luminaires are designed for peak performance and reliability at high and low temperatures for extended periods.

c) Standards and compliance requirements are always considered when designing any luminaire.

d) Photometric performance drives the development of the optics, the selection of LEDs, and the design of the final product.

At Lumascape, we have a range of linear luminaires that can be used in a large range of applications. Our technical team assist our customers with design right through to specification and product selection.

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