Tunable Broad Spectrum Lighting

Our previous blog post introduced the concept of tune-able spectrum lighting; this post focuses on the merits of tune-able broad spectrum lighting, which incorporates every wavelength in the photosynthetic active radiation range, while allowing for control over specific wavelengths relevant to horticultural outcomes.

Traditionally, many LED grow lights have utilized only red and blue LEDs, resulting in the pure magenta colored light typically associated with indoor farms. The red + blue LED approach is based on conventional knowledge, which attempted to match the wavelengths at which photosynthesis is most efficient with the emission spectrum of the LEDs in the fixture. Unfortunately, this approach prioritizes only photosynthesis over other plant functions, such as accessory pigment development. This lighting approach is broadly recognized as an inefficient method of growing healthy plants with desirable characteristics, such as rich turpene profiles, high concentrations of accessory pigments, and potent flavors.

Since red/blue LED grow lights, sometimes referred to as ‘blurple’ lights, are largely considered outdated within the industry, many LED grow light manufacturers have responded by blending white LEDs with single color (or monochromatic) LEDs in the red, blue, and far red spectrum. Some manufacturers even offer grow lights with only warm white LEDs for flowering applications. As of this writing, very few manufacturers offer tune-able horticultural lighting products which combine both narrow spectrum and broad spectrum LEDs while allowing for a wide dimming range across each channel. Tune-able broad spectrum horticultural lighting allows growers to take advantage of all of the benefits of broad spectrum horticultural lighting while also tailoring the spectrum toward their needs, such as manipulating flowering,

How to specify tunable LED grow lights

Along with the introduction of energy saving LED technology in controlled environment agriculture comes tunable, or programmable, LED grow lights, which are capable of producing nearly infinite spectrum combinations. These spectrums are able to spur vegetative or flowering growth stages, manipulate flowering, influence the shape, color and appearance of crops, affect the nutritive and medicinal aspects of crops, and target a wide variety of crop outcomes.

Controlling horticultural lighting with specific spectrums along a schedule introduces yet further opportunities to influence crop outcomes – GrowFlux calls these spectrum-schedules Light Formulas; for more information on GrowFlux Light Formulas, check out our blog post on this subject. Click here to learn more about GrowFlux’s cost effective tunable broad spectrum horticultural lighting products.

Selecting tune-able spectrum horticultural lighting requires growers to make some decisions about their growth techniques and goals, since tunable spectrum lighting usually comes at a cost premium and may have some key drawbacks, which we will discuss in detail in this post. First, and most importantly, growers should determine their lighting density goals

Broad spectrum vs. narrow spectrum

Control options

Far red

PAR output vs. tunability range

Designing your own spectrum

Product design for ingress protection

<microscope image of silicone sponge>

Equipment designed for challenging environments such as greenhouses and indoor farms face the constant threat of dirt and moisture ingress due to exposure to humidity and wet conditions caused by maintenance, rain, and irrigation. Horticultural lighting products in particular can be negatively impacted by ingress of moisture and dirt which severely impact the performance and longevity of the product. In many cases, ingress of dirt and moisture happens despite the equipment manufacturers best intentions- such as sealing an equipment enclosure with air and water tight seals and implementing IP 5x or 6x ingress protection.  So what goes wrong here?

Ingress happens when atmospheric pressure changes act on a sealed equipment enclosure. As the pressure changes, a small amount of positive or negative pressure develops inside the enclosure. These atmospheric pressure changes can cause a daily shift in the differential pressure between the enclosure and its environment. When negative pressure develops inside the enclosure – due to increasing atmospheric pressure – a small vacuum is formed inside the enclosure. Over time, the daily shifts in atmospheric pressure also cause wear and tear on enclosure seals. If a seal becomes compromised at any point due to stress, vacuum pressure inside the enclosure will draw moisture and dirt into the enclosure.

Standardized tests for ingress protection can be performed informally by the manufacturer or can be performed by a certified third party lab. Ingress protection ratings are classified by ISOXXX, and involve a two digit rating, where the first digit classifies the dust ingress protection, and the second digit classifies the liquid ingress protection.

<IP 5x-6x chart>
We should note here that these tests are typically done once, in absence of cyclic changes in atmospheric pressure and normal wear and tear. Further, these tests typically won’t catch ingress of water vapor, which can later condense into liquid water, causing condensation and damage. Water vapor can also penetrate joints, seals, and materials much more effectively than liquid water since it lacks the surface tension of liquid water.

Based on our experience working with horticultural equipment and lighting, GrowFlux believes the best design practice for ingress protection is to consider the challenges presented by changing atmospheric pressure, wear and tear, material performance over time, and water vapor ingress. In designing its horticultural lighting product line, GrowFlux has employed several design features to boost our ingress protection:

Pressure equalized enclosures
Mitigating differential pressure in an enclosure is easily achieved by designing in a specialized vent which allows only a small amount of air to pass while blocking moisture and liquid water. Not everyone in the industry is doing this as it increases cost and assembly complexity, however in our experience protective vents pay for themselves. The protective vents we install in every product with a hollow enclosure incorporate PTFE fabric at the core, passing only the amount of air necessary to remove pressure from sealing gaskets. These vents are also commonly installed in high quality LED street lights.

Fully potted power supply
Our FluxScale Series fixtures use the Meanwell HLG AC/DC driver, which offers the highest efficiency of any 300-600W driver we have seen on the market. This driver is also fully potted (or filled) with thermally conductive, high temperature silicone which protects the electronics inside the driver from water, dust, and moisture while also dissipating the small amount of heat created by the driver – resulting in its high efficiency. These drivers were originally developed for stadium lighting applications, and are well suited to challenging agricultural use.

Gasket material selection

Gaskets, O-rings, and other compressible seals can be made of a wide variety of materials. Proper material selection and extensive design for manufacturing is critical to maintaining ingress protection in a seal; designers must consider manufactured part tolerances, material properties at operating temperature, degradation mechanisms in the seal materials, and the sealing material's ability to resist permanently compressing over time (called compression set resistance), among other factors.

Microscopic view of an engineered silicone foam we use to seal FluxScale from the elements. Ball point pen shown for scale. 

Microscopic view of an engineered silicone foam we use to seal FluxScale from the elements. Ball point pen shown for scale. 

GrowFlux encases LEDs in our FluxScale product in extruded T60603 aluminum and anti-reflective coated glass for optimal protection from the elements. We use an engineered silicone foam which is die cut into several custom sealing gaskets; these materials maintain their mechancial properties at high temperatures and compression force for very long periods of time. Wear and tear due to differential pressure in the enclosure is mitigated with protective vents.

Potted fans & sealed connectors

The GrowFlux FluxScale 600AC is a fan cooled horticultural lighting product; compared to passively cooled fixtures, lights with fans exhibit better heat dissipation, resulting in higher efficiency, smaller size, and a lighter weight fixture. To ensure that our fans are reliable in wet, humid, and condensing environments, GrowFlux directs its manufacturers to apply a a potting compound to the entirety of the fan drive circuit, rotor and winding, and internal electrical connections, protecting these sensitive components from corrosion and moisture. And since our fans are user-serviceable (in the very rare event we experience a fan failure during the 10+ year design lifetime of FluxScale), we use sealing connectors inside FluxScale to connect our fans. 

Rated liquid tight cable fittings

GrowFlux installs high quality liquid tight cord grips in its LED engines, control modules, and fixture housings to protect cables and to further prevent ingress of moisture, water and dust.