collaboration with Fabio Casu

What's behind the acronym LED?
These light emitting diodes, light emitting diodes or literally.

Wikipedia informs us, already aware of user on: "LEDs are a special type of diode formed by a thin layer of semiconductor material. When subjected to a direct voltage to reduce the potential barrier of the junction, electrons in the semiconductor conduction band recombine with the shortcomings of the valence band releasing enough energy to produce photons. Because of the reduced thickness of the chip a reasonable number of these photons can leave and be emitted as light. The LEDs are formed from GaAs (gallium arsenide), GaP (gallium phosphide), GaAsP (gallium arsenide phosphide), SiC (silicon carbide) and GaInN (gallium nitride and indium). The exact choice of the semiconductor determines the peak wavelength of the photons, the electro-optical conversion efficiency and thus the light intensity output. "(Full text at: http://it.wikipedia.org/wiki/LED)

The LEDs are set to revolutionize the field of lighting indoors?
It seems so judging from the premises: economic management, cold light, no noise or bulky ballast, long life, 100% PAR. They promise a 75% improvement in performance and cost savings cooling environment
A miracle? Maybe.

The first thing that leaps to the eye investigating on lighting to LED is the total lack of reliable material to draw from, as the monopoly of data and studies entrusted entirely to the producers themselves and therefore by definition be taken lightly.

You can draw some inference using what you have available, or the experience of farmers and technical bare and raw disseminated by manufacturers and distributors.
To begin a comparison and an objective evaluation of the first step is the classification of the LEDs based on size, power, light output and color (or wavelength of radiation).
The LEDs are on the market with sizes ranging from 3mm to 10mm: 10mm LEDs can provide a power of 0.8 to 1.2 watts and consist of about 8-10 LEDs, high power is naturally associated with a single LED and this will be more bright.

The LED lighting has widely used in civil and road, with LED efficiency by 20 lm / w to over 100 lm / w, they replace the traditional HPS offering greater durability and lower heating environment as well a stable performance over time.

For what concerns the growing number of proposals are on the market, but the most common features are these:

630nm red 40-60 lm / w% PAR50 use flowers and fruits
660nm red 30-45 lm / w% PAR100 use flowers and fruits
blue 455-465nm 20-40lm / w% using vegetative PAR100

with variable yield depending on the size of the LEDs themselves, (as happens with neon tubes: 30 lm / w for 15w tubes against 60 lm / w Tube 65W 120 cm long), frequency (a red 630 nm for example, has much higher efficiency compared with a red 660 nm), and quality equipment.

We would like to use in the field of cultivation, so it is with great interest that we welcome the note by which producers lamp, 90W can replace a 400W HPS.
What exactly can we expect?
Here are the numbers:
90W LED (80 red 10 blue 660nm 465nm) 1980 lumens with a PAR 100% = 1980 actual lumens
HPS 400w average efficiency 90-120 lm / w then 36-48000 lumens

We have seen other times what is meant when one speaks of the MLP, but in this case necessitates a summary.
The need to define the PAR was created to understand how much emitted light a lamp is used by the plant. This value explains why a high number of lumens not necessarily correspond to a high yield cultivation.
The PAR is the amount of radiation emitted in the frequency spectrum suitable for the plant and shall be eligible for the transpose, thus having a wavelength between 400 and 700nm.

However this is not sufficient to define the goodness of a light because the 400-700 range includes the wavelength of the green, which we know is absorbed in very low percentage, or almost anything from vegetables.
Then the same PAR 100, ie 100% of the radiation contained in the range 400-700, there are lamps with a spectrum lamps with a spectrum better and worse.

That is why now the popular fluorescent envirolite have actually made good: their high luminous efficiency is thus equal watt electric emit much radiation absorbed, with a dominant red or blue depending on who examines a model or 2700k from 6400K.

The red and blue LEDs have certainly PAR100%, concentrated between 460 and 665 nm and therefore correspond to absorption peaks of the plants, but the radiation values are low for this work best if combined with another type of light
or if used with great powers, precisely to 90-180 watts / sq.

Unfortunately almost all the data available have been issued by manufacturers, distributors and sellers, and never by a research institute accredited.
In the case of envirolite in place of data we met crowds of farmers, we can still consider a good sign of credibility and reliability in the case of LED lamps unfortunately still do not have it yet 'reliable studies of its' customer testimonials.

They say that LED lamps are expensive. What figures speak?
Consider the most suitable model for hobby use size and performance, available only with difficulty even in Italy, or the UFO.
This is a light compact design characteristic, with the best led.
In America shops specializing in indoor growing sales to $ 600 each, in Italy the average price is about $ 800.

In both cases the products manufactured in China, or more precisely from Shenzhen, a region that currently has earned the title of world capital of LED lighting: you can buy directly from producers certified lamps at very favorable prices, having time and will follow a shipment troubled by uncertain outcomes.

These prices are so high to be considered in light of "field tests", showing that the LEDs behave well for the vegetative stage, very bad for flowering as a crop damage amounting to one third that of using well-HPS 15 days more.
For those who primarily require support for the vegetative stage and winter waiting for the sun and take care of valuable crops completely indoors, without the aid of sunlight, could be a purchase to be considered carefully.
For the user to grips with the salad to eat for dinner or a few ornamental plants continues to be an overly expensive.

An alternative to single use is to combine T5 fluorescent lamps or HID (high intensity discarge), or the use of LEDs only the first stage and then switch to classic.
Some manufacturers to remedy this unsatisfactory behavior are studying lamps also emit white light LEDs in addition to blue and red, although it seems that for some fruits such as apples for perfect maturation are also important UV rays, not included in the PAR (photosintetically active radiaton).

Some American producers have put on the market other LED lamps under the name Pocyon and IT Smartlamp or you SMARTbite.

Again promise amazing results (even with white light spectrum), but unfortunately the only data are still those provided by the manufacturers (a Smartlamp you replace a 300 watt HPS to 600 watt with a total reactor consumes 670w, guaranteeing equal results if not better) and prices are really high.
Some say that the LEDs have a great future in lighting civil but for the crops were dead before birth because of advances in sulfur plasma, which provide very small with an average life and very high flows of 180 lm / w 100% PAR.

Related articles:

1. Lighting in indoor cultivation
2. Guide to Indoor cultivation
3. The reflectors in indoor growing
4. Indoor crops: DIY or shop?
5. Table guide to indoor growing

Tags: Growroom management , lighting , LED , products

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