DIY Plant LED Light Prototype Lights Up The Winter

With winter on the way, our thoughts turn to indoor hacks. And what could be better in the cold winter than fresh veggies? This can be done by replacing the sun with an LED light, and [Margaret Johnson], aka [Bitknitting] has been working on building her own LED plant light.

She’s using a combination of red and blue LEDs that produce the ratio of light frequencies that plants thrive on, and has been experimenting with how bright to make them and how long to run them. This combination of factors determines how much light the plants get every day, called the Daily Light Integral, or DLI, and has a huge effect on how well the plants grow.

Her latest prototype uses nine red and two blue 3 Watt LEDs which run for about twenty hours a day. These lights shine onto the growing area, a bucket filled with nutrient solution. [Margaret] has done an excellent job of outlining why and how she made the choices she did and providing lots of links to more information for the home grower. It’s a great place to start for anyone looking to get something growing indoors in the depths of winter.

25 thoughts on “DIY Plant LED Light Prototype Lights Up The Winter

      1. Hello bitknitting, I was wondering what happens with plants if there is never a “night”? IOW, do plants need to “sleep” and why? If there is some internal repair mechanism going on for them like there is for animals, then is there some special “night sap” that could be interesting for pharmacology and if so, where would it be produced? Should we pick our green leafy foods during dark to get more healthy nutrients? Are there any herbivores who do graze after dark? How about plants in vicinity of streetlights having very little to no daily dark time, are they more stressed?

        1. Datapoints, not much grows in the Arctic and Antarctic circles where they have 6 month long “day” all summer…

          … I mean some quibblers might point out it’s the cold that does this, but meh.

        2. there’s this thing called photoperiodism which notes some plants need different amount of light hours in order to flower (or go dormant). This article discusses it:

          i am not an expert on if there is an environmental optimum regarding light/dark to get more nutrition when eating a plant. Regarding streetlights, the actual light a plant gets is next to nothing because plants use very specific light wavelengths for their processes. A good google term for this would be PAR. Great questions. Thank you.

  1. i was reading a book on marijuana cultivation (which is totally legal where i live) seeing what kind of leds would be needed. red and blue were the sweet spots. throw in a couple ir and uv leds for other useful abilities. one kills harmful fungi and bacteria, and the does something else that slips my mind (weed has that effect). and since plants do expect some other wavelengths to be present (leds are rather narrow in their spectra), id toss in a few white leds. i also read that green leds can be used to observe the plants while they should be in darkness, so you can monitor them at “night” without interfering in the plant’s day/night cycle. while i am confident i could build a lighting system, i came to the conclusion that gardening wasnt really something i wanted to do. after all we should have a weed shop opening in couple months.

    1. Hello Lord Nothing, Green light is indeed interesting. It seems to be added to LED grow systems to do as you suggest – make looking at the plants easier than staring at the purplish. The challenge with green LEDs is they use a much higher amount of energy…I’ve seen this referred to as the green-gap. Some papers also note green has a greater affect on the plant leaves than I would have assumed on plant studies. But as you point out, if gardening is something you don’t want to do – no need to do it :-).

      1. green leds are rather funky. i was building a fire control box for use in various games. with a bunch of illuminated arcade buttons. i had a notorious time getting the greens to match the brightness of the other colors dispite being paired with the lowest resistor value i had on hand. i ended up doubling them up, but that didnt help much. the only thing i can really do is decrease the current limiters and run them in overdrive (leds in my box were charlieplexed so each one was only on for a small slice of time and they have time too cool down).

        of course for lighting thats not really an issue . human eye is most sensitive to green, and you just need a few ultrabrights and a good current regulator to run them as high as their specs allow. you cant just turn on all the lights when you want too, that kind of thing can make your plants go vegitative and wont produce decent buds. its not so much a dont want to do as it is a cant afford to do.

  2. It seems the high-end led grow lights don’t use green at all. I have several systems from California Light Works. Their latest Solar System uses R,B,W LEDs; no green. All 3 are separately adjustable and programmable. The productions from these lights is incredible.

  3. We raise orchids indoors under artificial lights, and switched over to LEDs six years ago. We’ve learned a few things:

    Flowers look sick under any light that is not a fairly true warm white (3000K-4000K), making it hard to judge how they’re doing. HPS light was an ugly greenish gold, and bluish-white LEDs are also bad. But red/blue LED lights emit their own heinous purple glow that makes us almost nauseous. That’s obviously not a problem for veggies who are enjoyed on a dinner plate, but the enjoyment of orchids derives from their looks.
    Many orchids had stunted growth after a year under red/blue LED grow lights. Normally, veggies are grown and eaten in the same season, so this also may not be a problem for an indoor gardener. But it did suggest that something was missing from the light.
    LED fixtures are 2x as efficient as high output T5 fluorescent lights, but the initial costs are so much higher that the T5s are cheaper to own (even after factoring in the much shorter tube life and replacement costs.) This will remain true until the cost of electricity exceeds about $0.35/kWh, or until the cost of LED fixtures drops below $0.05/lumen (the streetlights I use cost over $0.10/lumen.)
    The LED streetlights we bought have a two year warranty, and both have needed service. One was out of warranty, so service cost $350, plus it was gone for over a month during its round trip to China. I have not yet realized the expected 7 year lifetime of the LEDs. On the plus side, in neither case was the problem due to the chips; it was the power supply that failed in one, and a solder joint in the other. The chips may still deliver their 7 years of service.

    1. Thank you for your reply. It excites me to learn from folks like you. Indeed, the light quality (red/blue/warm white/green) “adjustment” will be dependent on what is being grown – particularly in leafy versus flowering. So it makes sense to me that solely red/blue for orchids might be less than ideal. And as you point out, the purplish light is hard to look at. I’m going to try a build that uses two XP-E2 warm whites instead of the blues. For two reasons: 1) get a light that is not only pleasing to the plant but also to the eyes 2) folks have been pointing me to articles about the benefits of green / warm whites…in fact, there seems to be a trend of warm white COB LEDs instead of discreet red/blue. I intend to explore COBs too.

      Do you check your PAR/DLI?

      All the best.

        1. many busts did not even need the far-IR cameras.

          when you have a long appartment complex (two story) with multiple units attached side-by-side, and a SMALL amount of FRESH snow, the growhouse(attic) will be the only unit with NO snow, it will be clear as black(roof-shingles) and white(snow) and you can see it from all the way down the street with naked eyes during the middle of the day.

          search on youtube

    1. really nicely done, CONGRATS!! Are you monitoring many plants? How has your monitor helped with growing? I’m always curious to know if technology is actually helping. Seriously, great job and thank you very much for sharing the link.

      1. Well, I’ve got 4 sensors (full sets with oled screen). one in my orchids terrarium, and 3 others on orchids pots on different location. We’ve more than 30 orchids, some need a lot of luminosity and humidity, and some other need a cooler environment.

        So this module help me to monitor every location and make adjustements if needed.
        I’ve still got some issues with this design, the ESP8266 heat and fake temperature sensor, so for the moment the temperature sensor is outside the block,

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