Tunable White Application Note

This Application Note describes how to develop a Tunable White luminaire for use with the Enlighted lighting system with sensor firmware v5.4. Luminaire manufacturers, electrical engineers, and Enlighted field application engineers will find this information helpful in adequately designing and deploying a Tunable White luminaire.

Overview

With the introduction of LED “white” light sources, a new market for adjusting these light sources to mimic the sunlight's color at different times in the day is born.

Specifying Tunable White “Color”

To control the ‘color’ of an LED light source, identify the method used to determine the color. The science of Colorimetry is well established and provides us with several methods. As defined in Wikipedia, “Colorimetry is the science and technology used to physically quantify and describe the human color perception.” The main takeaway is the CIE 1931 Chromaticity Diagram and the color space it defines:

The area of the diagram that is in color is referred to as the “gamut” or “color gamut,” representing all colors that are perceptible to the human eye.  Any point (color) in the space (either inside or beyond the visible color gamut can be represented by a coordinate pair of decimal numbers (x,y). In the case of “White Light,” it is the area of the diagram indicated by the “black body locus,” which is the black line in the lower right third of the diagram. This is also referred to as the “black body line” or “black body curve” or just the “black body.” An x, y coordinate pair could specify any point on this curve, but that would be an overkill for Tunable White. 

 Black_body.png 

By Paulschou at en.wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=24903791

Another method of specifying points in the White Light region is “Correlated Color Temperature” or “CCT.”  These lines cross the black body locus and extend into areas of the color gamut that would show an objectionable hue or color. The diagram below shows a closeup of the black body locus with the CCT lines indicated.  CCT is measured in degrees Kelvin or “K,” and the basis of these values (and the black body locus) is that if an object were heated, it would start to glow; first a dull red, then a brighter red, and as the temperature continued to increase, would eventually glow orange, yellow, white and finally blue.  A CCT value specifies the ‘color’ for Tunable White systems, as long as the actual color of the source is near the black body locus. From this, it can be inferred that a system’s light output can be represented by an intensity value and a CCT value to achieve the Tunable White function, and that is precisely how the Enlighted system operates.

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https://www.waveformlighting.com/tech/calculate-color-temperature-cct-from-cie-1931-xy-coordinates

Generating Tunable White Light 

There are many methods to produce colors and white light in the color gamut, such as RGB, which is familiar to most of us from television and computer monitor displays. Unfortunately, the method using non-white primaries suffers from low efficacy (lumens/watt) and is not well suited for general illumination purposes. A simple process for general illumination is to use two different LED white light sources of different color temperatures and vary the relative intensity of these two sources to traverse the range of CCTs in between. The two sources are single points in the color space, and their combination will form a straight line connecting those points. The actual location on that line will be dependent on the ratio of drive given to each of the two sources, as shown below in the diagram. The colored background has been removed from the diagram for clarity:

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To traverse the line and ‘tune’ to different color temperatures (CCT) of white light, adjust the drive level to each of the two equal wattage sources. 

  • At 100% cool (6500K in this example) and 0% warm (2700K in this example), “cool” white light with full brightness (6500K) is achieved. 
  • At 0% cool (6500K in this example) and 100% warm (2700K in this example), “warm” white light with full brightness (2700K) is achieved. 

When the two sources are at 50%, the Tunable White light is at midpoint CCT (near 4000K) with full brightness. When both sources are driven to 100%, the Tunable White light would still be at midpoint CCT (near 4000K), producing an undesirable characteristic of the intensity varying as the CCT is changed. 

A better approach is to have both channels equal 100% intensity so that the light output is relatively constant regardless of CCT selected.  Note that this simplifies it as other considerations will affect the light output, for example, the efficacy of cool vs. warm LEDs and the effect of dimming. You cannot dim to a level that would change the warm to cool ratio since there would be a color shift as you dim, but these items can be addressed later. The ‘two-channel’ approach leads to the following system architecture: 

   mceclip4.png

While the two-channel method is a simple architecture, the implementation can be a bit tricky. The control signals for each of the drivers must be calculated from the Intensity and CCT values that represent the light output indicated by the “Color Mixing Algorithm.” The algorithm must consider the interaction between each single control input (intensity and CCT) and both dimming level outputs. 

For example, as the intensity control input is varied, both dimming channels must be reduced or increased proportionately. If further reduction of either channel changed the color mix ratio (because one of the channels has reached its minimum level), the intensity reduction would be limited. Similarly, as the CCT control input is varied, the ratio of the two channels must be altered, but in doing so, the combined output of both channels must remain constant so that there is no intensity variation as CCT is altered.

Controlling Tunable White Light

The two common methods for controlling the Two-channel generated Tunable White include:

  1. Warm/Cool (W/C) method – independent channels
  2. Intensity/CCT (I/C) method – linked channels

The decision of which method to choose depends on the driver selection; several driver technologies are available that partition the “Color Mixing Algorithm” in different ways.

1.     Warm/Cool Method

From a hardware standpoint, this is the simplest method as it follows single-channel dimming.  Combine the two single channels in a single luminaire and have the sensor control one channel as “Warm” and the other as “Cool” in the system. The Color Mixing Algorithm is implemented within the Enlighted sensor based on information provided by the luminaire manufacturer.

Advantages of Warm/Cool Method

  • Familiar components - use the same drivers as monochromatic fixtures.
  • A wide portfolio of drivers is available.

Disadvantages of Warm/Cool Method

  • Requires twice as much driver ‘wattage’ as needed for the luminaire rating (each channel must be able to drive up to 100%, but the combination of both channels can never exceed 100%. Since drivers are priced at $$/W, more watts will result in a higher cost.
  • Two drivers take up more space, and
  • Input wiring is complicated.

Refer to the Line diagram of Warm/Cool Method, 0-10V Control Interface. 

2.     Intensity/CCT Method

Drivers and mixing units are available to receive intensity/CCT control inputs. They either provide a mixing function to be used with an external driver or provide a dual-channel driver capability in a single unit. The Color Mixing Algorithm is implemented within the driver/mixing unit based on the luminaire manufacturer's information. 

Advantages of Intensity/CCT Method

  • Lowest component count – single, dual-channel driver (optional energy metering and on/off control eliminating the need for an external control unit)
  • Driver ‘wattage’ is tuned to the luminaire's requirements – the wattage is split between the two channels as required by the requested CCT.

Disadvantages of Warm/Cool Method

  • Less familiar driver SKUs

Block diagram of the Intensity/CCT Method using a separate driver and current splitter:

 mceclip5.png

Block diagram of the Intensity/CCT Method using dual-channel driver:

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The Enlighted system supports Analog (0-10V) drivers and Digital 2-wire DALI Type 8 (DT8) methods of representing these values. An advantage of using the 2-wire solution is that the wiring is simplified because the values of both channels, as well as the power to the sensor, are all communicated over the same two wires.  Additionally, the 2-wire solution also simplifies the system's setup, since the values for the CCT of the LED sources used can be pre-loaded into the driver and automatically be read by the sensor and propagated through the rest of the Enlighted system. 

Refer to the following line diagrams:

Fixture Manufacture Table (FMT)

The Enlighted system supports Analog (0-10V) drivers and Digital 2-wire DALI Type 8 (DT8) drivers. The FMT (Fixture Manufacturer Table) is only required for Tunable White if analog (0-10V) drivers are being used.

When a DT8 (digital) driver is used, the color information typically provided in the FMT is provided by the driver from values stored in the driver by the fixture manufacturer, so the FMT is not required. Enlighted Manage system automatically detects that the driver is a DT8, Tunable White, and enables the Tunable White controls. The CCT values stored in the driver know the proper range for the controls, eliminating the need for an FMT.

The Enlighted sensors with firmware v5.4 and above require Fixture Manufacturer Table (FMT) to test Tunable White fixtures in the production line (End of Line testing) when they are built to control Tunable White fixtures after they are deployed in the field. You can upload an FMT to a sensor in Manage. Refer to Configuring Tunable White for instructions on how to upload the FMT

If the FMT is not uploaded to the sensor when the Tunable White fixtures are being built in the factory, the sensors might fail the wiring test, and visual cues need to be used to verify proper wiring – the sensor will exercise (min to max intensity) both the warm and cool channel of the fixture independently. 

Controlling Tunable White Fixtures

The Enlighted’s Manage can be used for controlling the color temperature and intensity of the light to fit any setting or use case. Additionally, the system’s astronomical clock implements sunrise and sunset CCTs following natural daylight patterns. Enlighted Manage (EM) can also integrate time-of-day calculations to match or enhance occupants’ circadian rhythm patterns. For more details on controlling color temperature, refer to the Configuring Tunable White article.

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Configure Tunable White - Prerequisites

The Enlighted’s Tunable White feature allows users to adjust or modify the color temperature of Tunable White LED fixtures to help achieve the desired color tuning within specified parameters. Having the ability to color tune lights based on employees’ needs and preferences increases their productivity and focus.

Note: Tunable White feature is supported in Enlighted sensors with firmware version 5.4 or higher.

The Enlighted system supports both:

  • Analog (0-10V) Drivers: Requires the FMT (Fixture Manufacturer Table) to be uploaded, and this is a manual process. The FMT needs to be uploaded in Manage. Hence, the Digital 2-wire DT8 is the most preferred method.
  • Digital 2-wire DALI Type 8 (DT8) Drivers: When a DT8 (digital) driver is used, the FMT is not required since the color information is provided by the driver from values stored in the driver by the fixture manufacturer. Enlighted Manage system automatically detects that the driver is a DT8, Tunable White, downloads the FMT, and associates it with the Fixture Type, enabling the Tunable White controls. The CCT values stored in the driver know the proper range for the controls, eliminating the need for an FMT.

Recommended Prerequisites:

  1. Check that all sensor firmware is version 5.4 or higher. Click Devices > Sensors to view the firmware version in the Sensor Details table. The Version column lists the sensor firmware.

Devices_sens_Version.png

  1. For Analog drivers,  contact the respective Fixture Type manufacturer to obtain the FMT file in .xml or .bin format and upload the file. Refer to the article Uploading Fixture Manufacturer Table (FMT) to Fixture Type. Skip this step for DT8 drivers.
  2. Assign the Fixture Types to a floor, building, or campus facility. To begin assigning Fixture Types, read Assigning Facility to a Fixture Type.
  3. Assign the Fixture Type to sensors on a floor. Refer to the article Assigning Fixture Type to Sensors.
  4. To control the color temperature of Tunable White fixtures with scenes, see Creating a Scene with Tunable White.
  5. To adjust the color temperature, see Adjusting the Color Temperature

Note: Configuring Tunable White is not supported for sensors with firmware version 5.3 and below. See Adjusting the Color Temperature for a Sensor with Firmware Version below 5.3.

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Upload the Fixture Manufacturer Table

The Enlighted’s Tunable White feature allows users to adjust or modify the color temperature of Tunable White LED fixtures to help achieve the desired color tuning within specified parameters. This feature is supported for sensors with firmware version 5.4 or higher. Read the recommended prerequisites for configuring Tunable White fixtures before proceeding further.

Also, please note that Tunable White is not supported for sensors with firmware version 5.3 and below. If you need to adjust the color temperature for a sensor running firmware version 5.3 and below, see Adjusting the Color Temperature for a Sensor with Firmware Version Below 5.3.

You do not have to upload an FMT for the following circumstances:

    1. The manufacturer has already preloaded the FMT file (.XML or .bin formats) into the sensor mounted in the fixture.
    2. The fixture uses a DALI Type 8 (DT8) 2-wire driver. The information is already programmed into the driver and is automatically loaded by the system.

In both the above cases,  Enlighted Manage will automatically download the FMT and associate it with the Fixture Type. 

You will only upload the FMT for Tunable White when analog (0-10V) drivers are being used. Contact the respective Fixture Type manufacturer to obtain the FMT file and then upload the file.

Follow the steps below to upload the FMT file.

  1. Go to Administration -> System Management -> Fixture Type Management and select the Fixture Type tab.
  2. Select the required Fixture Types in the list. The FMT buttons above the columns get enabled.
  3. Click on Load Fixture Manufacturer Table. A warning message that the lights will dim and brighten for about one minute is displayed.
  4. Click OK to proceed.
  5. Select the FMT file provided by the manufacturer.
  6. The FMT gets uploaded, and the name appears in the Fixture Table column associating the FMT with the Fixture type.

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After the FMT is uploaded, the fixture lights will dim and brighten for about a minute while the sensors assigned to the selected Fixture Types reboot and perform a wiring test. 

Removing FMT associated with the Fixture Type

If a wrong version of the FMT gets associated with the Fixture Type, use the Remove Fixture Manufacturer Table button to remove the Fixture Type association and load the correct FMT again. If you are getting an “invalid file format” error, make sure you are uploading one of the supported valid file formats: .xml or .bin.

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Adjust Color Temperature of a Fixture

If an occupant wants a warmer or cooler light than other occupants' in the room, adjust the individual fixture's color temperature while keeping the rest of the lights in the office at a higher color temperature.

Read the recommended prerequisites to make sure that the fixtures support Tunable White.

To adjust the color temperature of an individual sensor for a specific duration,

  1. Double-click the sensor in the Floor plan view to open the Fixture Details screen.

FixtureDetails.png

  1. By default, for fixtures with firmware version 5.4 and higher, the Tunable White Fixture checkbox is disabled (unclickable) since the Fixture Manufacturer Table (FMT) is associated with the Fixture Type. The name of the FMT is displayed next to the Color Temperature slider.
  2. In the Color Temperature box, drag the slider to the required color temperature.
  3. Specify a time in minutes for the duration.

ColorTemp_drag.png

The LED fixture adjusts the color accordingly for the specified time in minutes.

Note: When both the Dimming Control and Color Temperature are set to Manual mode, the Dimming Control will take precedence over the Color Temperature. For example, if Dimming is set to 60 minutes, and Color Temperature is set to 90 minutes, the Manual mode setting will end after 60 minutes.

ColorTemp.png
When the Manual mode expires, the fixture returns to Auto mode following the Circadian option settings enabled in the Advanced option of the fixture profile. If the Circadian option is not enabled in the Advanced option, the sensor will follow the default color temperature available in the Fixture Manufacturer Table (FMT).

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You can also adjust the color temperature of one or more sensors from the floor plan. Refer to the article Adjusting the Color Temperature for one or more Sensors from the Floor Plan.

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Adjust Color Temperature for one or more Fixtures

You can adjust the color temperature of one or more sensors from the floor plan. The color temperature for the sensors is set by default to sixty minutes.

Read the recommended prerequisites to make sure that the fixtures support Tunable White.

To adjust the color temperature from the floor plan,

  1. Click on the Floor name in the Facilities left panel and click the Floor Plan tab.
  2. On the floor plan display, selecting one or more sensors displays the Override color box next to the Override Light Level box. If the Override color box does not get displayed, it could be that the fixtures do not have the corresponding Fixture Manufacturer Table (FMT) uploaded or the firmware version is 5.3 and below.
  3. Drag the Override color slider to the required color temperature. The LED fixture adjusts the color accordingly for an hour by default.

TW_override_color.png

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Switch Control for Light Fixtures

After a switch is successfully added, commissioned, and configured, it can be used to control lights and scenes based on light profiles and scenes programmed in Manage. 

Tunable White Fixtures: When fixtures are configured for Tunable White, the switch buttons three and four have additional functionality to increase or decrease the color temperature.

ERC Switch  

Refer to the ERC Switch for install details and configure a switch to control lights.

ERC_Switch_Control_TW_IconsDEsc_1.2.png

EnOcean Switch 

Refer to the EnOcean Switch for install details and configure a switch to control lights.

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EnOcean 4- and 2-button Switch for N. America and Europe

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If a switch is defective, refer to the RMA procedure:

Downloads:

Download and print the ERC quick inset card for managing room light levels.

Adjust the Color Temperature for a Sensor with Firmware v5.3

For fixtures with firmware version below 5.3, you can adjust the color temperature for a sensor in the Fixture Details screen.

  1. Double-click the sensor in the Floor Plan view to open the Fixture Details screen.
  2. Check the Tunable White Fixture checkbox to display the Color Temperature box shown below.
  3. In the Color Temperature box, drag the slider to the required light level to tune the fixture’s dual-channel LED for a specified duration in minutes. A light level value of 0% is warm-white, and 100% is cool-white.

Color_Temp.png

Enable Circadian Lighting

The Tunable White fixture’s color is automatically synchronized with the Manage's astronomical clock that provides daily sunrise and sunset times. For this feature to work, you must set the Day and Evening periods of the sensor’s lighting profile to use the astronomical clock. See Periods of a Day and Week Days to set time based on the astronomical clock.

To configure the dual-channel LED of a Tunable White fixture,

  1. Click Facilities, and select a profile from the Profile Templates navigation tree.
  2. Click the Settings tab
  3. Select the required profile instance and click the Edit button.

Profile_Templates.png

In the resulting Edit Profile screen, scroll down until the >>Advanced option is seen and click the >>Advanced option to expand the screen.

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The following Dual Channel LED options are provided:

  • Circadian Option – When selected, the fixture's color temperature is automatically changed during the day based on the astronomical clock and the selected color temperature settings. The astronomical clock provides the local times for civil twilight (when the sun is six degrees below the horizon, sunrise, solar noon (when the sun is highest in the sky), sunset, and civil twilight at the end of the day. The light color will be changed gradually over time between the settings provided, except at night when it remains constant.

The five circadian periods of the day include:

  1. Dawn – Transition from night color to sunrise color setting occurs between civil twilight and sunrise.
  2. Morning – Transition from sunrise color to solar noon color setting occurs between sunrise and solar noon.
  3. Afternoon – Transition from solar noon color to sunset color setting occurs between solar noon and sunset.
  4. Dusk – Transition from the sunset color and the night color setting occurs between sunset and end of civil twilight.
  5. Night -- The night color remains constant from civil twilight at the end of one day until the morning civil twilight before the Dawn transition starts.

Manage provides four-color settings for the five circadian periods of the day. Where 100% is the warmest (2700K) and 0% is the coolest (5000K):

  1. Sunrise Color Ratio: Set the required % of color transition that has to take place from night color to sunrise color.
  2. Solar Noon Color Ratio: Set the required % of color transition that has to take place from sunrise color to solar noon color.
  3. Sunset Color Ratio: Set the required % of color transition that has to take place from solar noon color to sunset color.
  4. Night Color Ratio: Set the required % of color transition that has to take place from sunset color and the night color.

The color set point format is represented as a direct ratio (0 to 1.0) of the two LED channels T1/T2, where T1 represents the cool CCT LED and T2 represents the warm CCT LED. In the Color Settings, enter a ratio multiple by 100 value.

  • T1 = 2700K CCT and the value is ‘0’ percentage value is 0*100 = 0%
  • T2 = 5000K CCT and the value is ‘1’ percentage value is 1*100 = 100%

For example: If a Tunable white fixture has a CCT of 3850K

  • The range fraction for 2700K is 5000K-2700K = 2300K in comparison to the baseline cool temperature of 5000K.
  • The range fraction for 3850K is 5000K-3850K=1150K in comparison to the baseline cool temperature of 5000K.
  • The ratio will be 1150K/2300K = 0.5
  • Value is 0.5 *100 = 50%.

Note that the fixture's luminance is controlled independently from the color, based on the same methods as non-tunable white fixtures. Also, the location data specified at the installation time must be accurate for color transitions to be supported accurately. To edit location data, see Edit Building's Location Data.

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