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  • DIY 100 Watt LED Grow Light, Variable Output; Power and Spectrum

    For use in seed starting or growing taller plants, made with A19 household LED light bulbs and readily available medium base Edison sockets. A 12 bulb fixture is an 175 watt HID MH equivalent / 104 watts actual / over 10,000 actual Lumens / over 17,090 Lux (~ 227 PPFD) @ 18" from canopy, delivering PAR light Intensity greater than one (1) 2 ft , 6 lamp T5HO florescent fixture and costing less than $40.00 and requiring minimal wiring skills. The bulbs in this fixture are mounted on a 12 inch square pattern to create a form factor that can easily cover a 2ft x 2ft footprint (measured). The form factor (12 bulbs or modules in a 12" square pattern) is based on the Illumitex Stratus SHB5012 High Bay fixtures.

    These DIY LED lights can be made from almost any medium base E26 lamp socket and inexpensive, UL & CSA listed, Great Value A19 Edison medium socket base, 800 Lumens, 9 watt LED bulbs. In a multitude of different configurations they can provide light with increased intensity for starting seedlings or stem cuttings and growing out taller plants indoors. With the diffusion globes removed these bulbs can provide intense directional light in excess of 150 PPFD (umol/m2/s) at 18 inches from the canopy. The light intensity without the globes is equivalent to or greater than T5HO florescent bulbs with almost a third (1/3) less power usage. With or without the diffusion globes four 9 watt bulbs (36 watts total) can provide sufficient light intensity of ~ 10,000 Lux @ 6" from 1020 trays, for starting seedlings or stem cuttings in the 4 sq ft or ~ 2' x 2' footprint. A 6 - bulb Bath Light Bar could also be used for lighting two (2) 1020 trays lengthwise in a 1' x 4' footprint since the bulbs are mounted on 6 inch centers (6" apart). As with all DIY projects, proceed at your own discretion.

    For Seed starting and cutting propagation the 5000K bulbs provide a satisfactory mix of Red:Blue spectrum for shorter inter-node spacing, good early root and vegetative growth. For healthier general purpose Vegetative and flowering growth a better ratio of Red:Blue Spectrum with the available bulbs is 3:1, 2700K to 5000K. With the form factor of this fixture (12 bulbs on a 12" square) the 5000K bulbs should be placed in the corners for better color mixing. The Great Value A19 bulbs manufactured by TCP have produced over 800 lumens each when independently tested, are available as dimmable and or 1700 Lumens / 100 watt incandescent equivalents. Adding a Dimmer with the available 9 watt Dimmable bulbs could increase this fixture's versatility at a small added cost, but the 18 Watt 1700 Lumens A19 LEDs would more than quadruple the cost (to ~ $139.00 / 12 bulb fixture) and increase (double) the total heat output. To calculate the Heat output of any Light Multiply the actual Wattage by 3.412 BTU.
    For example;
    1 - 60 watt Incandescent Bulb = 204.7 Btu of heat.
    12 - 9 watt LED Bulbs = 368.4 Btu of heat
    1 - 175 watt HID (205 watts actual) = 614.2 Btu of heat.
    1 - 400 watt HID (458 watts actual) = 1,562.7 Btu of heat

    A Hard Wired Version:
    12 - A19 9 Watt LED Great value (W-mart) - $12.00
    12 - Surface mount socket bases - $18.00
    1 - Extension Cord - $4.00
    1 - pk wire nuts - $2.00
    1 - pk #6 pan head screws - $1.00
    1 - 16in x 16in base - $ ?
    Total - $37.00 , plus?

    Plug n Play Version:
    This version can be made with parts all available from Walmart. The four (4) outlets are connected in series, each is plugged into the end receptacle in the adjacent power strip. Only one power strip is plugged into the wall outlet and the lights (lamp) can all be turned on and off. by the one (1) lighted on/off circuit breaker switch.
    12 - A19 9 Watt LED Great value (W-mart) - $12.00
    12 - Polarized Sockets Adapters (W-mart) - $16.00
    2 - 2 pk Extension Cords (W-mart) - $14.00
    1 - pk #6 pan head screws (W-mart) - $1.00
    1 - 16in x 16in base - $ ?
    Total - $43.00

    Seed Starting Version: For ~ 2' x 4' coverage (for 4 - 1020 seedling trays)
    8 - A19 9 Watt LED Great value (W-mart) - $8.00
    8 - Surface mount socket bases (L-wes) - $8.00
    1 - Extension Cord - $4.00
    1 - pk wire nuts - $2.00
    1 - pk #6 pan head screws - $1.00
    1 - 16in x 40in base - $ ?
    Total - $23.00, plus?

    Can Household White LED Bulbs be used for growing plants?... Yes!

    Current technology household LED Bulbs made with Phosphor- Converted Type White LEDs (WLED) with same CRI and CCT have similar color spectrum and emit most (up to 97% ) of their light in the PAR spectrum (400 - 700 nm). WLED are not predominant in the LED Grow light industry as Sole Source Lighting (SSL) simply because most provide up to 50% of their emitted light output in the 500 - 599nm range which has been claimed (interpreted) to be "useless" for plant growth and therefore not energy efficient, this premise has been scientifically proven false, as shown by the McCree 1972 Plant Absorptance spectrum and subsequent horticultural research. The science is that on average ~ 70% of the "useless" Green 500 - 599 nm spectrum is utilized by plants, with a measured low of ~ 50 % in lettuce to a high of ~ 90 % in Fir trees and in thick layered canopies the Green spectrum penetrates down to the lower leaves more effectively, providing energy for photosynthesis. Due to electrical "efficiency" the Commercial Horticultural Industry typically utilizes targeted color spectrum which include Green and or WLEDs as supplemental spectrum.

    The Phosphor type white LED bulbs currently on the market can output well over 100 Lumens per watt, those with diodes facing the plant canopy are more efficient than CFL, Tube Florescent bulbs and many lower wattage HID fixtures (less than 400Watt). In fact the A19 bulbs (with globes removed) configured in a High Bay Light fixture format have approximately the following equivalent outputs.
    12 bulb - 108 watts LED ~ 175 Watt Metal Halide Fixture = 205 Actual Watts
    18 bulb - 162 watts LED ~ 250 Watt Metal Halide Fixture =290 Actual Watts
    24 bulb - 216 watts LED ~ 400 Watt Metal Halide Fixture = 458 Actual Watts

    The current NASA LED & Horticultural research findings conclude the following;
    ... LED lights are efficient and versatile Because of their durability and long life, they are ideal for space missions where resupply of things from Earth is limited.

    Blue light (400 - 499 nm)... Plant-growth functions that seem to be particularly sensitive to blue light in SSL (single source lighting) situations include stem elongation and leaf expansion, with “too much” blue inhibiting growth in both cases. Other plant responses having an absolute requirement for blue light include phototropism, stomatal aperture, leaf thickness, and chlorophyll content.

    Green light (500 - 599 nm)... Because chlorophyll has major absorption peaks only in the red and blue regions, researchers initially selected first red, later blue, LEDs for first-generation LED arrays to support plant growth. However, intact leaves do absorb considerable green light, and in a relative quantum-efficiency curve for photosynthesis vs. PAR wavelengths, some wavelengths of broad-band green actually are more efficient than certain wavelengths of the blue band.

    Red light (600 - 699 nm)... In general, red light promotes stem elongation, leaf expansion, biomass accumulation, and contributes to a phytochrome photostationary state (PPS) that can determine flowering, dormancy, and other important photomorphogenic responses of plants, including seed germination.

    Far-red light (700 – 799 nm)... Although FR (far-red) and blue wavelengths can have opposite effects on stem elongation and leaf expansion, they both lower PPS, which may trigger accumulation of desirable phytonutrients in leafy greens. Like green light, FR wavelengths pass through upper layers of a closed leaf canopy. Unlike green light, FR wavelengths have mostly photomorphogenic effects.

    White light (400 - 700 nm)... The often confusing issue regarding which colors or proportions of colors to select for SSL applications with LEDs can depend on species, cultivar, stage of development, and intensity of available light. In some ways, the use of LEDs for SSL is causing us to rediscover the value of white light for plant growth and development. It actually would be more electrically efficient to make white light from monochromatic RGB LEDs than to use white ones. Nevertheless, inclusion of a few white LEDs on an array may have utility in terms of achieving certain proportions of broad - band color in case green LEDs are not included.

    1. http://leds.hrt.msu.edu/assets/Meeti...l-spectrum.pdf
    2. http://www.inda-gro.com/IG/sites/def...M-KJMCCREE.pdf
    3. https://ntrs.nasa.gov/archive/nasa/c...0150009399.pdf
    4. http://hortsci.ashspublications.org/.../1947.full.pdf.
    5. http://hortsci.ashspublications.org/.../1951.full.pdf
    6. http://cpl.usu.edu/files/publication...b__4124704.pdf
    7. http://agi32.com/blog/2014/12/10/pho...hotosynthesis/
    8. http://www.amjbot.org/content/100/1/70.full.pdf
    9. http://pcp.oxfordjournals.org/content/50/4/684.full.pdf
    10. http://liltomatoconcepts.com/images/...eet-3-2014.pdf
    11. http://galileo.graphycs.cegepsherbro...a/app/en/lamps
    12. https://www.reddit.com/r/HandsOnComp...t_light_meter/
    13. http://www.myledlightingguide.com/le...tween-unequals
    14. https://www.reddit.com/r/Head2HeadMG..._color_choice/
    15. http://illumitex.com/wp-content/uplo...d_spec8.16.pdf
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    Last edited by AscPete; 02-10-2017, 06:16 AM. Reason: edited Photo Album
    Pete R - Hudson Valley, NY - zone 5b