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grow led diy

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honeybadger:
So what is the best red-blue combo and what PPFD/watt it gives? Currently for full spectrum about 2.1 PPFD/watt is the limit.


https://gn.uk/guides/par-ppf-ppfd-and-dli

So why is there such a difference between the absorption spectrum and the action spectrum if chlorophyll is responsible for photosynthesis? The answer is simple: Chlorophylls are not the only photoreceptors that are responsible for photosynthesis. There are other types of antenna photoreceptors (mainly carotenoids) which also promote photosynthesis, and by utilizing narrow band red/blue LEDs in sole-source lighting conditions these pigments are not able to optimize their light harvesting capabilities. Also, it should be noted that green light does in fact promote photosynthesis in chlorophylls, quite efficiently in fact. Recent work has shown that green light is able to penetrate deeper into leaf surfaces to drive photosynthesis in chloroplast located towards the bottom surface of the leaf, in fact, more efficiently than red light at high PPFD.

Zero999:
I honestly don't know the answer to that question. I agree that other wavelengths as well as red and blue are used by plants and haven't disputed this. I've just noted the majority of photosynthesis seems to occur in the red and blue regions. I believe the optimum spectrum depends on the plant, the stage of development and is something which is the subject of ongoing research.

If you look at the spectrum of a typical white LED, you'll find it looks nothing like that of any grow lamp, hence why I believe it's not optimum, although I can understand why you might prefer it for practical reasons.
https://www.cree.com/led-components/media/documents/ds-CXB3590.pdf

It also depends on whether you're growing solely under artificial light or supplementing ambient light. If it's the latter then I imagine it's not too critical.

In any case the efficiency of converting electrical energy into different optical wavelengths needs to be taken into account, as well as photosynthesis.

metrologist:
Solar powered grow lights   ;D

Zero999:

--- Quote from: Irukandji on March 15, 2019, 08:27:45 pm ---Sorry for the late response.

Thanks for your feedback so far.
I found these LED's on ebay, but im not sure if they have enough power for my little grow box.
Link
https://www.ebay.com/itm/10-x-High-Power-LED-OSRAM-OSLON-SSL-660nm-hyper-red-Platine-3W-Pflanzenwachstum-/172846213449

All in all its for some garden plants like Physalis, paprika and chili.
The box size is 90 x 60 x 60 cm. Im not quite sure if i get enough light out of my LED' stripes. They running with 5050 smd LED's.

Link:
https://www.ebay.com/itm/5pcs-SMD-5050-LED-Grow-Light-Strip-Lamp-for-Indoor-Veg-Flower-Plants-Hydroponic/264077183863?hash=item3d7c3a0b77:g:Mn4AAOSw3fxcCiz-&frcectupt=true

--- End quote ---
Why not stick with branded produces from reputable distributors? I don't think this is the sort of thing you should be trying to save every penny on.

I'd probably go for the LEDs on little aluminium PCBs mounted to a large heat sink.

Either something like this:
https://www.digikey.com/product-detail/en/thomas-research-products/132541/1121-1640-ND/7693230

Or separate red and blue modules: four red and one blue in the middle.
https://www.digikey.com/product-detail/en/led-engin-inc/LZ4-40R208-0000/1537-1042-ND/4976732
https://www.digikey.com/product-detail/en/led-engin-inc/LZ4-40B208-0000/1537-1037-ND/4976727

With a suitable LED driver module.

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