Intelligent, Value-Based Research & Development

A Grow Light's Efficacy (ability to achieve a desired result) is a culmination of how well all the parts work together as a whole.  At Hydro Grow we prioritize our R&D on aspects that have the greatest impact on results, such as absorbable light wavelengths and optimized spectral ratios.  

All secondary contributors to performance such as driver type, driver brand, driver efficiency, LED package, LED chip size, LED Brand and LED Bins are chosen based on a cost to performance ratio.  A component must offer a comparable increase in performance to it's cost to be used in our LED Grow Lights.   This ensures you the highest performance per watt per dollar spent.  

Developing the Penetrator XB Series

A New Decade of Horticultural Dominance

In a 2019 online survey we asked growers what they wanted from a LED Grow Light.  The overwhelming response was simple:

  • Low Cost (Under $2/watt)

  • At Least 2.5 µmol/Joule Efficiency

  • External Drivers that can Operate Outside Your Room

  • A Square Panel for Square Dispersion

  • Evenly Spread PPFD over Target Coverage Area

  • A Dimmable Driver Option

Penetrator XB was developed specifically to answer these requests with the highest quality and performance.

Step 1: Choosing the Right LEDs

There are many factors that contribute to the overall output and efficiency of a LED:

  • LED Package (SMD, High Power, COB)

  • Optical Lens

  • LED Chip Size

  • LED Chip Positioning

  • LED BINs (Voltage, Brightness)

  • LED Brand

  • Drive Current

Step 2: Optimizing Performance

The primary factors that determine the efficacy (yield/watt) of a LED Grow Light:

  • Light Wavelengths

  • Spectral Ratios (quantum balancing)

  • LED Output (µmol/Joule)

  • Optical Lensing

  • LED Spacing

  • Operating Temperature

  • Driver Efficiency

Step 3: Reducing Overall Costs

The primary factors that determine the final cost per watt of a LED Light:

  • Driver Brand

  • # of LEDs per PCB

  • # of LEDs per Driver

  • LED Brand

  • LED Spectrum

  • Drive Current

  • Heatsink Requirements

Step 1: Choosing the Right LEDsNext > Optimizing Performance

Selecting a SMD LED Package

Surface Mount Diodes (SMD), also referred to as "Mid Power LEDs" are the most efficient LEDs on the market for grow lights due to their low drive current which allows the LED chip to operate at a lower temperature.  

The size of a SMD Package affects thermal and optical characteristics that impact the overall performance of a LED chip.  

At Hydro Grow we test the same chip loaded into different packages in our custom integrating sphere, which measures the µmol output of an individual LED.  We then compare the cost of each completed LED to its output to determine which package provides the best cost to performance ratio.  

Selecting Optics, Chip Layout & Chip Size

A LED chip without a lens emits light at 180°.  Optical lenses allow light to be focused within a set pattern.  By focusing the dispersion pattern of a LED from 180° to 120° with a lens, we can increase the amount of light being directed to our targeted coverage area.  

How many chips are placed in a package will affect the performance of a lens.  The more centered the chip is to the lens and the less chips per lens, the better the optical performance.    

The size of the chip affects performance and cost of the LED.  The larger the chip, the more surface area it has which improves it's thermal performance and efficiency at an increased cost.  The standard chip sizes for a 0.5W SMD are 14mil², 18mil², 20mil² and 24mil².  

 

LED Brand, BIN and Voltage

Every LED manufacturer specializes in specific wavelengths of chips.  Brand name LEDs (Cree, Osram, Luxeon) are usually a lot more expensive without offering much if any additional performance. 

 

Example: Cree specializes in white and blue chips, despite also making packaged red LEDs.  What most don't know is the red chips used by Cree are made by Epistar, and thus you can save a lot of money by using Epistar LEDs to achieve the same performance as Cree.

 

LEDs are divided into BINs based on wavelength, brightness and voltage.  The higher the brightness and lower the voltage, the higher the cost.  

 

The voltage and brightness BINs affect the overall efficiency of the LED.  Lower voltage means less watts, resulting in higher the output per watt.    

 

Why We Collect LED µmol Data

The LED test data from our integrating sphere is useful in two primary ways:

  

  1. It allows us to determine which LEDs in every wavelength have the highest relative µmol output per watt, among countless brands and configurations.

  2. It allows us to determine how many LEDs of every wavelength are required to achieve our quantum balanced spectrum of 75% red, 15% green and 10% blue.   

 

The Problem with relying on manufacturer spec sheets for LEDs is that almost every brand uses a different testing facility with different sensors and calibrations.  It is possible to send the same LED to two different labs and get different results.  Most LEDs are likewise not rated in µmol, which is the only measurement that tells you how many photons of light are available to your plants.  

Because our sphere and sensor is the same for every test, the data from one LED to the next can be compared, as well as data from year to year.  This allows us to see how different brands perform over time and improve their technology against one another.  Without this type of data it is nearly impossible to know if the LEDs you are using truly give the best performance per watt per dollar, or to calibrate a proper photosynthetic growth spectrum.    

LED Selections for Penetrator XB Series

The 2835 SMD package offered the best cost to performance ratio. 

One centered LED chip per package was chosen with a 120° wide-angle silicon lens.  

Epistar, EpiLEDs and Optotech offered the best cost to performance ratio (varied by color).  

The 20 and 24mil chip sizes provided the best cost to performance ratio (varied by color).

133mA drive current provided the best cost to efficiency ratio.

The lowest voltage & 2nd highest brightness BIN offered the best cost to performance ratio.  

Step 2: Optimizing PerformanceNext > Reducing Overall Costs

Optimal Light Wavelengths for Photosynthetic Growth (Part 1 of 2)

Knowing the µmol output a LED has does not tell you how well it can grow plants.  Plants have evolved to absorb certain wavelengths at very high levels, while others have little to no absorption or benefit.

The photosynthetic response curve tells you how efficiently chlorophyll A and B, as well as secondary light-harvesting pigments like carotenoids absorb various wavelengths.  The wavelengths with the highest absorption are known as photosynthetic peaks, found at 439nm, 469nm, 642nm and 667nm, with secondary peaks at 460nm and 520nm.  

After photons are absorbed by light harvesting pigments, photochemical efficiency tells us how well plants then convert captured photons into sugars (fuel) for photosynthetic growth.  

Optimal Light Wavelengths for Photosynthetic Growth (Part 2 of 2)

Quantum Efficiency/Yield tells us how efficiently a plant converts CO2 into oxygen, which is a byproduct of photosynthesis.  Research has proven that green light (525nm in our tests) has a higher quantum efficiency than red or blue light, as it can penetrate deeper through chloroplasts.  

First observed in 1957 by Robert Emerson is a secondary pigment and light reaction system that absorbs light beyond the PAR range of 400-700nm.  Emerson discovered that when far red light (680-750nm) is shown simultaneously with deep red light (660nm), photosynthetic rates were far greater than when either wavelength was shown independently.   In fact growth increased by as much as 30%.  

Green Light.jpg
Emerson Enhancement.jpg

Quantum Balancing Spectral Ratios

Matching LEDs to wavelengths with the highest absorption is only part one of spectral science.  Part two is balancing your ratios of each wavelength on the quantum level (µmol) and then each region of PAR (Red, Green, Blue).  

A NASA published research study (CP-05-3309 Pg 47), originally carried out by the Institute of Biophysics in Russia, documents how spectral ratios affect overall growth and yield of both cucumbers and tomatoes.  

The study showed that proper balancing of red, green and blue light had a dramatic impact on growth and yield.  The best performing ratios for tomatoes (75% red, 15% green, 10% blue) had plants ready to harvest in 30 days sooner than the slowest ratios.  These plants were also producing up to double the yield of the lowest yielding ratios.  

 

NASA Spectral Variance Tomato Results.pn

LED Spacing and Lensing

How much light a LED can emit (µmol/Joule) is a limited number, and therefore how that light is dispersed plays a huge role in the efficacy of a grow light.  

If a 200W light is meant for a 1m² area, it's dispersion pattern should match 1m² at a standard 12" to 18" hanging height.  Achieving a 1 meter spread at 12"-18" of hanging height requires a 120° dispersion pattern, and thus a pattern above 120° will result in light being wasted on areas like walls where plants are not growing.  To optimize performance, all available light should be directed to the targeted coverage area via a lens or reflector.            

How the LEDs are dispersed over the target coverage area also plays a huge role on peak intensity and how evenly intensity is spread from edge to edge.  The closer the LEDs, the higher intensity becomes in the center known as a "hot spot", and the less even intensity is spread over the area as a whole.  The wider you space the LEDs, the more even the intensity is divided over your targeted area.  This gives you more consistent results from edge to edge without intensity being too strong for plants to use in the center.

Operating Temperature

The hotter a LED becomes, the less light it emits and the shorter it's lifespan becomes.  The extent of this affect is determined by a LED's color.  

Blue and Green LEDs maintain brightness over a wide temperature range, while red LEDs lose brightness the fastest.  Optimal temperature for our lights is therefore 100°F (38°C) or lower to achieve at least 95% of our initial brightness and full lifespan of the red LEDs.  

Testing on our red SMD samples mounted to a Star MCPCB weighing only 1.1g, showed a junction temp of 94-100°F at 120mA drive current, in a room where the ambient temp was 85°F.  This means we need at least 1.1g of aluminum material to keep a red LED operating optimally.  

Optimization Selections for Penetrator XB Series

440, 470, 525, 640, 660 and 740nm were selected to match photosynthetic peaks, increase quantum efficiency and elicit the Emerson enhancement effect.

Spectral ratios of 75% red, 15% green & 10% blue provide the highest yield in the lowest time.  A 4:1 ratio of R to FR was chosen for Emerson enhancement.

PCBs are spaced on large heat plates to reduce hot spots, reduce temperatures and spread intensity more evenly over larger areas.

Light engines were created to blend the spectrum evenly.  LEDs are spaced to eliminate hot spots in the center of each light engine.

Light engines are spread evenly over large PCBs to create a more even spread of intensity with lower operating temperatures.

Operating temp is lower than 100°F at the chip thanks to 1.65g of PCB aluminum per LED plus a 2-3mm aluminum heat plate. 

Step 3: Reducing Overall Costs

Developing a Lower Cost LED Driver

The driver overall has the least impact on the efficacy of a grow light.  Research shows a properly calibrated and balanced spectrum can increase yields by 50%.  Testing shows a lens can increase intensity more than 70%.  LED testing shows that one brand over another can alter intensity by another 50%.  By comparison, most LED drivers are between 88% and 94% efficient, offering only a 6% difference between brands.

 

A decade of building LED lights has demonstrated that the most reliable configuration is one driver per LED PCB.  This design also guarantees that if a driver fails, the rest of your light continues working, which is vital to any grower.  

Most SMD grow lights use a single driver to power multiple circuit boards.  If this driver fails, your entire light turns off with it causing devastation to your crops.  

To increase reliability, ensure your entire light never fails, and reduce costs Hydro Grow developed our own custom LED driver at 88% efficiency.  The driver itself is modular and made of multiple internal power supplies.  Each is replaceable via simple clip-in connectors.  This driver has been in use since 2016 with a 0.2% failure rate and was adapted for use in 2019 with XB.    

Reducing Costs by Maximizing Driver Utilization

Drivers are limited in how many volts or amps they can supply.  Our driver is limited to 900mA drive current and 65V, or per 58.5W per PCB.   The closer you push the driver to its limit, the hotter it becomes causing a drop in efficiency.  

Drivers have a fixed cost no matter how hard you push them.  Our prototype XBoard was designed for light engines with 24 LEDs; however these LEDs in series only consumed 47.7V, well below the 65V capacity of our driver.  

To decrease the overall cost per watt of our production models, a new light engine was developed with 32 LEDs, consuming 62.1V.  Because the driver cost is fixed, this change allowed us to drive 25% more LEDs for the same price.

LED testing showed the best cost to performance drive current at 133mA, despite prototypes being made at 100mA.  Increasing the current also increased wattage, lowering the cost per watt again.  This gave our driver the ability to support a maximum of 6 light engines at just under 50W per PCB.   

Reducing Costs by Eliminating Heatsinks

Printed Circuit Boards (PCBs) also have fixed machining costs.  Whether a circuit board is 1" x 1" or 10" by 10" it still has 4 cuts, and thus the larger the PCB the lesser percentage the machining cost makes against the whole.  

The cost of your PCB becomes a fixed cost when considering the # of LEDs contained on said PCB.  The more LEDs you load on the PCB, the lower the cost per watt; however operating temperature also increases.  The higher the operating temperature, the more heat sinking is required.  

 

Compared to heat sinks, PCBs are rather inexpensive, and thus there is a fine balance between how many LEDs can be loaded onto a PCB before the need for additional heat sinking is required. 

 

Our 192-LED PCBs are over-engineered to ensure the PCB itself has enough aluminum weight to keep every LED operating below 100°F without the need for additional heat sinking.  This reduces costs, allowing us instead to affix each PCB to a thin aluminum heat plate for rigidity and even spacing.      

Cost Reduction Selections for Penetrator XB Series

LED Chips were sourced & packaged to deliver  better cost to performance over Brand-Name LEDs.

A custom LED driver was developed to reduce cost, increase reliability and prevent down time.

Thermal planning allowed for LED mounting plates instead of heat sinks, reducing overall costs.

The # of LEDs increased from 144 to 192 per driver, allowing 25% less driver cost per watt.  

Drive current increased from 100mA to 133mA per LED, allowing 33% less driver cost per watt.

An integrated LED driver on Micro XBoards allows  for similar cost per watt to much larger models.