So all white LEDs start off as blue LEDs. An electrical charge is put through an anode, which jumps over to a cathode and emits energy at a certain frequency. In the case of nearly all white LEDs, the diode produces a bright blue light in the 450-460nm range. This blue light is then scattered using red and green phosphors which appear as the yellow "coating" you see on LEDs, such as the ones below.Intrinsic wrote:Thanks Prawn, My old growing area in the attic between joists is 4' x 8' perfect for this size.
Ahh i forgot abut the low UV thing with leds. tho i think leds can be engineered to produce a wide range of frequencies, but don't know if there are any out there with sufficient UV for our plants. if so perhaps an improvement in yer panel for the future.
Red phosphor + Green phosphor + Blue light = white (RGB colour).
The more red phosphor, the warmer the white colour. If you look at the LEDs below - which are incidentally one of the LEDs used in the new boards - you'll see the ones on the left are a bright yellow, and the ones on the right are more of an orange colour.
The yellow LEDs have less phosphor coating that allows more blue light through, as well as more green than red phosphor - together making 5000K-6500K (blue or cool) white light.
The orange LEDs have more phosphor coating and more red than green to convert more of the blues to reds, making 2700-4000K (red or warm to neutral) white light.
[image]http://www.nichia.co.jp/img/product/led ... isolis.jpg[/image]
Why am I telling you all this? Just bear with me . . .
The amount and type of phosphor determines efficiency as well as colour temperature (kelvin) and colour rendering (CRI) - all of which have a bearing on plant growth
As most of us know, THC and other cannibinoids are a bit like sunscreen for plants - they are produced in response to UV (not just genetics), and break down under UV, thus protecting the plant - and most importantly, the seed casings. Which is why buds have the most THC. That's the simple explanation.
Now individual LEDs can be produced in colours other than white - depending on the frequency, they can emit almost any base colour.
UV LEDs do exist (both UVB and UVA). They emit UV light and have little or no phosphor coating on them. But UV light is destructive, so UV LEDs - in addition to being very expensive to produce - do not last long.
One of the cheapest forms of UV light at the moment is fluorescent, or compact fluorescent. Mercury vapor lights are also high in UV, but not very efficient. In fact, CFL/fuoro is a type of mercury vapor lamp that produces UV as its base colour, which is then converted to white light using phosphors - which is why the bulbs are a white to yellow-white colour, due to the phosphor coating on the inside.
A few LED companies have developed a white LED based on a UV (or near UV) base light. This light is emitted at about 400nm - which is at the end of the UVA spectrum and start of the visible light spectrum. These LEDs use Red, Green and Blue phosphors to make white light, but they also emit violet light.
These are the LEDs that are used in the new boards. They have most of the efficiency and longevity of traditional blue-white phosphor LEDs, but produce a good amount of light in the UVA and near UVA spectra that is not produced by blue-white phosphor LEDs.
So this is all a long way of explaining why we are using a violet-white phosphor LED and not a dedicated UV LED. Some LED panel produces do use dedicated UVA lights on their boards (usually around 385nm), but they require a separate driver (added cost), are not as efficient, and have a shorter life expectancy, diminishing the lifespan of the entire boards. They also do not add other colours (spectra) to the board, so have no real photosynthetic value.
Ideally, if you are serious about adding UVA/B light to your grow - and there is also the matter of adding too much, which can damage your plants - you would use a UV reptile bulb, or fluoros or CFLs or MH/CMH light.
But even a little bit of UV appears to be beneficial to plants grown under LED, and so that is why this is perhaps the first near UV/UVA white phosphor LED grow panel produced, as we don't know of anything similar.