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LED Grow Lights
In this document we will endeavour to give an overview of terminology in relationship to growing plants
under LED lights, we will do some comparisons between different products and show the range of
products that we offer.
The nature of light
The energy produced by the sun reaches the earth as electromagnetic radiation. Light and other forms of
electromagnetic radiation are considered to have both a wave nature and a particle nature. Particles or
packets of light (its particle nature) are known as photons(the smallest divisible unit) light depends on the
number of photons absorbed per unit time. Each photon carries a fixed amount of energy which
determines the amount that the photon vibrates. The distance moved by a photon during one of its
vibrations is referred to as its wavelength and is measured in nanometres. Electromagnetic radiation spans
a broad range of wavelengths. At the one end of the spectrum of electromagnetic radiation there are
gamma rays which have a wavelength of 10 nm and at the other end, radio waves which have a
wavelength of 1012nm. A very small part of this spectrum can be seen by the human eye i.e. between the
wavelengths 380 and 750 nm. This part of the electromagnetic spectrum is called visible light. Almost all
life depends ultimately on this part of the spectrum for its energy. Humans perceive the different
wavelengths of visible light as different colours. Within the spectrum the longer the wavelength of the
radiation, the slower the vibration of the photons and the less energy each photon contains. Thus photons
of ultraviolet light, at the blue end of the visible spectrum, have shorter wavelengths and contain more
energy than red light and infrared radiation. Sunlight contains 4% ultraviolet radiation, 52% infrared
radiation and 44% visible light. Why is only visible light used by plants?
Light and photosynthesis
Chlorophyll does not absorb all the wavelengths of visible light equally. Chlorophyll a, the most
important light-absorbing pigment in plants, does not absorb light in the green part of the spectrum. Light
in this range of wavelengths is reflected. This is the reason why chlorophyll is green and also why plants
(which contain a lot of chlorophyll) are also green. Note in the graph below that the absorption of light by
chlorophyll a is at a maximum at two points on the graph 430 and 662 nm. The rate of photosynthesis at
the different wavelengths of visible light also show two peaks which roughly correspond to the absorption
peaks of chlorophyll a. Plants do not depend only on chlorophyll a in their light harvesting machinery but
also have other pigments (accessory pigments) which absorb light of different wavelengths.
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One of the first questions we are asked is “how bright are the LED lights that you sell?” and what is
their measure in lumens.
Firstly you need to remember that Lux meters (lumens) are designed to measure brightness in relationship
to the human eye, i.e. designed for use mainly with cameras etc, so it is described as a subjective measure,
which is not really of great concern to a plant, there are other meters that measure the actual photons as
they reach the plant and their relevance to the photosynthetic reaction, but this gets all very complicated,
for instance even though blue light registers far less in brightness on a Lux metre when it comes to
photons absorbed by the plant blue actually has more energy then the red spectrum. These type of
measurements are therefore much more accurate when comparing the energy required from light by
plants, however they are still not accurate because they still give value to the wavelengths of light that the
plant may not be using. Unfortunately everybody needs to use the same units for these comparisons to be
of any use, at the moment most people use Lux meters which still have some value as long as you are
comparing similar things, ie two LED lights with the same ratio of blue to red LEDs or if you are
comparing two HIDs, but not really relevant if you are trying to compare a red and blue LED lamp with
an HID.
Also we must remember that we are only talking about the new high power LEDs that run at 1 W or
greater not the smaller LEDs that flooded the market over the last year or so, which will be fine for
growing seedlings but do not really have enough power ie intensity, for a plant to go into flower and fruit
stages successfully.
Probably the best and most expensive LED light on the market at the moment is an American device
called the Procyon see a grow test between a 400 watt high pressure sodium bulb HPS and a Procyon 100
at http://www.homegrownlights.com/testing.html
At this site http://www.greenpinelane.com/hgl_procyon_test.aspx you will see where tomatoes have been
grown to flower and fruit using this device, they have also done Lux measurements (scroll to the bottom
of the page) over a 3’ x 2’ or 0.9 m x 0.6 m, roughly half a square metre, you see that the intensity
decreases towards the edges but if you take the highest measurement in the centre at say 18 inches above
the test meter, the highest reading is 7820. Below we have done some similar measurements using our 7
W (1B6R) with 30° lenses LED light and at 18 inches the greatest measurement is 11470 and the 7 W
(6B1R) 30° lenses LED light and at 18 inches the greatest measurement is 4420, the lights on the Procyon
use a ratio 2Red to 1Blue so combining our lights gives a reading of 9120. The Procyon users 56 LEDs
without lenses, they run their LEDs at just under 2Watts giving slightly higher brightness than the ones
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that we use, that are run at 1W, however the LEDs that we use will last slightly longer (because they
are not running as hot), and as can be seen by the brightness tests below, by using lenses you can
achieve the greater brightness levels and, this is even more so when you add extra lights together as
you do not get the drop off at the edges e.g. in the Procyon at the edge of the 2 foot square rectangle
the measurements are down to around 2000.
You will see below where the 3x7W (6R1B) LED lights have been placed in a row you see that it
covers the same length as the Procyon without the diminished brightness at either end, being focused it
does not cover quite as much width, but we would suggest using 3x12W (8R4B) LED lights, which
would give you a similar spread, and higher intensities over a more uniform area, and the same ratio of
red to blue LEDs ie 2:1.
The other advantage of using these smaller lights is that not only do they work out cheaper as we have
demonstrated, using lenses gives you higher intensities, but you also have the flexibility of changing
the lenses to suit your particular application, you can even remove the lenses for widespread closer
applications.
7Watt (6Red1Blue):- Mix of light with 3 different lens angles
Angle
Height
24inch
18inch
7pc 50°
LUMEN(LX)
Intensity
4340
7170
7pc 30°
LUMEN(LX)
Intensity
7370
11470
1pc 50° + 6pc 30°
LUMEN(LX)
Intensity
7020
10640
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7Watt (1Red6Blue):- Mix of light with 3 different lens angles
Angle
Height
24inch
18inch
7pc 50°
LUMEN(LX)
Intensity
720
1490
7pc 30°
LUMEN(LX)
Intensity
2200
4420
1pc 50° + 6pc 30°
LUMEN(LX)
Intensity
1450
2500
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3x7Watt (6Red1Blue):- The coverage of 3 lights
Coverage
Height
24inch
18inch
Length(mm)
Width(mm)
900
800
550
350
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100
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Eye Response Curve
0
20
Ire(%)
60
40
80
White 6000K
400 425
500 525
550
575
600
625 650
675
700
725
750 775
Wavelength (nm)
We also supply a 7W White LED light, these can be successfully used in a number of
applications, as can be seen from the graph above the main area in which they supply their energy is in
the blue spectrum, this is the type of light energy used mostly in the vegative stage of growth ie leaf
development so these lights can be used successfully to grow salad Greens, they can also be used to fill in
and supplement other areas of the spectrum where the plants require much smaller amounts of energy,
kind of like trace elements in fertiliser. We have now also added a small number of another type of white
LED which has its energy peaking in the 440nm and in the Orange part of the spectrum.
For the indoor gardener who would like to grow salad greens in their living space, then this is an ideal
solution because it would give you very good results and your plants will look green ie natural, when
growing under red and blue dominant grow lights the plants will not look green they will have a purple hue.
New 12W LED Grow lamp with wider spectral coverage.
These lamps consist of 12 x 1Watt high-intensity LEDs :- 4xRed630nm(30°) + 4xRed660nm(30°) +
2xBlue(40°) + 2xWhite(40°), they are designed to fit the colour spectrum required for plant growth.
As you can see from the LED makeup we have added a mix of two different red frequencies better
matching the chlorophyll production needed in the flowering & fruiting stage of growth.
Also instead of having 4xBlue LEDs we have opted for 2xB & 2xWh, the
White LEDs have most of their energy focused in the blue end of the
spectrum, as can be seen by the graph for the white LED lights, but the
main reason we included these was that they give a sprinkling of
frequencies right across the light spectrum that’s why they appear white,
these frequencies are not used to any great extent by the plant, but for some
plants they appear to be like trace elements, as they are only needed in tiny
amounts.
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All the lights pictured below are now available in 110/220/240V 50/60Hz.
see:LED Grow Lights Free Shipping Worldwide
http://www.livingapartment.com.au/Products/LED-Grow-Lights-Free-Shipping-Worldwide
If you have further questions & are interested in purchasing these lights whether for retail or personal use
please contact us at info01au#livingapartment.com Note change the # to a @ (spam problems). Delivery
time approximately 2 weeks after order is confirmed.
Each light pictured is a mixture of Red(630 & 660nm 1:1.5) and Blue (460nm) LEDs and a new White that
has its energy peaking at 440nm & in the Orange part of the spectrum. These sites also comes with 60°
lenses, this ensures that the intensity of light is greater than that achieved by lights with 120° spread, which
end up with a hotspot in the centre and then diminishing rapidly at the edges. If you are comparing these
lights with what is on the market remember that when we say 96W & 144W etc we mean 96 & 144 x 1W
LEDs, 120° based lights which are advertised at 120W & 300W are actually 112 & 288 x 1W LEDs.
440 -
- 460
630 -
- 660
Chlorophyll a
Chlorophyll b
Plant absorption Spectra
White LED
48W
288W
96W
144W