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When comparing lights for horticultural use you should know:
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The standard for measuring brightness is based on human eye sensitivity at 555nm, green/yellow. Where Energy Flux is equal to Photon Flux as shown in the Sun Spectrum graph.
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Plant sensitivity is in the ranges absorbed by chlorophylA and B, less than 500nm and more than 600nm, Blue and Red as shown in the Absorbtion and Rate graph.
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The total amount of light produced in these ranges or fPAR range.
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Steradian beam coverage conversion factor for converting between candela and lumens.
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LED
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Total:
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306 LEDs
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Input Voltage:
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120VAC 12W 240mA
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Working Voltage:
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12VDC 18W 1.5A Max
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(Mfr spec sheet)
Red 640nm BIN U 1825 mcd ea (Note:Color BIN R8 is not on this chart)
Blue 455nm BIN V 2565 mcd ea
Pink Blue chip, Red phosphor Mixed 470nm+630nm BIN X 5020 mcd ea
LED BeamAngle 30°
1/(2PI(1-cos(30°/2)))
Derived Steradian 0.214
Coverage Conversion Factor 4.671
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3 Types:
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162Red+144Blue
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= 665010 mcd = 3106.26 lumens 258.85/W
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162Red+72Blue+72Pink
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= 841770 mcd = 3931.90 lumens 327.65/W
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162Red+144Pink
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= 1018530 mcd = 4757.55 lumens 396.46/W
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LED output is 100% in fPAR range
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LED output is "pure" frequencies. Lamps can be tuned to specific needs.
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LED is warm to the touch, no heat hazzard, low humidity.
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LED is focused directional emitter, no reflector.
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LED uses 12VDC very low shock risk.
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LED can use batteries and solar panels.
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LED lumen maintenance 75% @ 50,000 hrs!
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LED lifetime 100,000 hrs!
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HPS
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Total:
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1 Lamp
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Input Voltage:
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120VAC 1000W 10A
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Working Voltage:
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1000VAC 1000W 1A
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(Mfr spec sheet)
LU1000 HPS
Lumens: 140000.
Max Candela: 63479.0
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Derived Steradian 0.453
Coverage Conversion Factor 2.205
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lumen/2.2 = candela (63479)
candela*2.2 = lumen (140000)
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HPS produces roughly 25% of total lumens in the 600nm - 700nm range
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HPS produces roughly 5% of total lumens in the 400nm - 500nm range
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HPS maximum lumens is at 555nm green/yellow
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HPS output in fPAR range is about 42 lumens per watt
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HPS has a 'spheroid' radiant pattern
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Fire due to high temprature, energy for cooling
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Electrocution due to high voltage and current
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Injury due to breakage or contact, burn risk
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Elevated humidity promoting mold and fungus
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Bulb replacement, rising energy costs
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~ Reference ~
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PAR: Photosynthetically Active Radiation, normally quantified as µmol photons/m2/second, which is a measure of the photosynthetic photon flux (area) density, or PPFD. PAR can also be expressed in W/m2. Because photosynthesis is a quantum process PPFD is generally used by plant biologists, but W/m2 measurements are important in energy balance considerations for photosynthesis. (not to be confused with PARabolic or Polished Aluminium Reflector ,as some lamps are advertised with these labels a "PAR" lamp may have no corelation with plant needs but looks bright to humans)
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fPAR: The Fraction of Absorbed Photosynthetically Active Radiation (FAPAR, sometimes also noted fAPAR or fPAR) is the fraction of the incoming solar radiation in the Photosynthetically Active Radiation spectral region that is absorbed by a photosynthetic organism. This biophysical variable is directly related to the primary productivity of photosynthesis.
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1 Candela is defined as 1 Lumen per Steradian.
Lumen/Steradian = Candela
Candela*Steradian = Lumen
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Steradian beam coverage conversion factor = 1/(2PI(1-cos(BeamAngle/2)))
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Steradian: (sr) is a unit of solid angle measure in the International System of Units. It is defined as the solid angle of a sphere subtended by a portion of the surface whose area is equal to the square of the sphere's radius. A sphere subtends 4PI(r2) (steradians) about the origin. The number of steradians in a sphere is equal to the surface area of a sphere of unit radius. Steradians can be converted to square degrees by multiplying by the square of the number of degrees in a radian.
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A radian is (180/PI), or about 57.296 degrees.
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A steradian is (180/PI)2 or about 3282.8 square degrees.
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Unit Sphere = 4PI Steradians
Square degrees 4PI(180/PI)2 = 41253
1 Steradian is 1/4PI or 7.96% of the surface area
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L E D L U X 
