Testing LEDs with tobacco seedlings

Other plants we have or landscape elements like ponds.

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Tarzanus
Posts: 1457
Joined: Sun Jan 16, 2011 12:05 am
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Location: Ljubljana, Slovenia

Testing LEDs with tobacco seedlings

Post by Tarzanus »

I've tried growing (mostly bamboo) seedlings under LED bulbs up to 20W and I didn't really know if they work or not, because they always got some natural light as well. I decided to try different approach with box, inside covered with aluminium foil. Same box showed good results with 20W bulb directed onto the plants and with aluminium foil cover that deflected any light that would want to escape. Plants (tobacco and peppers at that time) grew slowly, but none of them had elongated weak stem - all of them grew nice thick strong stems.

Then I replaced the 20W bulb with two 50W (Chinese seller said they were 100W diodes, but when I calculated volts and amperes, I figured out they were 50W models) diodes, one cold white and one warm white.
I wired everything up to an old computer PSU, change voltage from 12V to 30V, attached the diodes onto old processors heatsinks with active cooling, somehow attach the darn things onto the box and turn the whole thing on. LEDs seriously heat up and without large coolers, they wouldn't last more than 10 seconds. Light inside the box was bright. Extremely bright!

After two weeks I noticed difference in leaf colors under lights with different wavelength. Warm white LED made tobacco leaf grow a bit yellow, cool white LED, on the other hand, managed to trigger the leafs chlorophyll and turn them dark green. Leaf size was not affected.


And there was one other thing I found out. Tobacco plants literally exploded. They started as tiny tiny seedlings, but with strong light and some extra heat from the lamps, they thrived. I'm going to post two images, taken 2 days apart. I did managed to burn one leaf a bit with too strong light, but they seem healthy. The one in the greenhouse is almost dead and didn't grow since I've taken it out of the box (firs batch of test seedlings) almost 2 weeks ago.
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Tarzanus
Posts: 1457
Joined: Sun Jan 16, 2011 12:05 am
Location info: 0
Location: Ljubljana, Slovenia

Re: Testing LEDs with tobacco seedlings

Post by Tarzanus »

It's too early to tell, but it looks that warm white LED diode exposed seedling started to turn yellow (same yellow as ripe tobacco that gets dried). I removed it now, along with all the yellow leaves. Hopefully I'll see all green leaves again.
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