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Phototherapy--Grow Lights

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  • Phototherapy--Grow Lights

    We know based on Photosynthesis (Chlorophyll A & B) that the plants utilize primarily 439nm, 469nm, 642nm, and 667nm, (4-bands) while most other wavelengths are use a little. Aside from these colors we know that humans must see their plants to monitor their health, which requires the use of white or green light (1-band) in small quantities will work, as these reflect off the plant. Lastly a light should contain 740nm far-red (1-band), which triggers flowering within the plant during a 12/12 light cycle. 740nm also stimulates the Emerson Enhancement effect, which increases photosynthesis rates up to 30%! UV light in the region of 285-315nm also has a benefit for resin-producing plants such as poison ivy or cannabis.

    The visible colors of light from shortest to longest wavelength are: violet, blue, green, yellow, orange, and red. Ultraviolet radiation has a shorter wavelength than the visible violet light. Infrared radiation has a longer wavelength than visible red light. White light is a mixture of the colors of the visible spectrum. Here is a summary of wavelengths (nm).

    200 – 280 nm UVC ultraviolet range which is generally harmful to plants. LEDs in this spectrum are non-existant or very expensive. You can see on the bar graph below that it borders with X-ray wavelength.

    280 – 315 nm Includes harmful UVB ultraviolet light which causes plants colors to fade. This is the part of spectrum reaching Earth around noon.

    315 – 380 nm Range of UVA ultraviolet light which is neither harmful nor beneficial to most plants.

    380 – 400 nm Start of visible light spectrum. Process of chlorophyll absorption begins. UV protected plastics ideally block out any light below this range.

    400 – 520 nm This range includes violet, blue, and green bands. Peak absorption by chlorophyll occurs, and a strong influence on photosynthesis. (promotes vegetative growth)

    520 – 610 nm This range includes the green, yellow, and orange bands and has less absorption by pigments.

    610 – 720 nm This is the red band. Large amount of absorption by chlorophyll occurs, and most significant influence on photosynthesis. (promotes flowering and budding) The ratio of red (660nm) to far red (730nm) in sunlight is about 1.2:1

    **As with exposure to
    continuous far-red radiation, blue light also promotes flowering through the mediation of
    cryptochromes photoreceptors

    720 – 1000 nm There is little absorption by Chlorophyll here, but Phytochrome uses a nice portion. Flowering and germination is influenced. Near and above the higher end of the band is the Infrared spectrum, which can also be heat and could cause elongation or affect water absorption/transpiration.

    **The phytochrome photosystem includes the two interconvertable forms of phytochromes, Pr and Pfr, which have their sensitivity peaks in the red at 660 nm and in the far-red at 730 nm, respectively. photosystems: photosynthetic, phytochrome and cryptochrome or blue/UV-A (ultraviolet- A). In the photosynthetic photosystem, the existing pigments are chlorophylls and carotenoids. Chlorophylls are located in the chloroplasts’ thylakoids located in the leaf mesophyll cells of plants. Here, the quantity or the energy of the radiation is the most significant aspect, since the activity of those pigments is closely related to the light harvest. The two most important absorption peaks of chlorophyll are located in the red and blue regions from 625 to 675 nm and from 425 to 475 nm, respectively. Additionally, there are also other localized peaks at near-UV (300 – 400 nm) and in the far-red region (700 – 800 nm). Carotenoids such as xanthophylls and carotenes are located in the chromoplast plastid organelles on plant cells and absorb mainly in the blue region. They are also known as auxiliary photoreceptors of chlorophyll. Photomorphogenetic responses mediated by phytochromes are usually related to the sensing of the light quality through the red (R) to far-red (FR) ratio (R/FR). Phytochromes are probably the most intensively investigated group of photoreceptors . In Arabidopsis there are five identified phytochromes: phyA, phyB,phyC, phyD and phyE . The importance of phytochromes can be evaluated by the different physiological responses where they are involved, such as leaf expansion, neighbour perception, shade avoidance, stem elongation, seed germination and flowering induction. Although shade-avoidance response is usually controlled by phytochromes through the sensing of R/FR ratio, the blue-light and PAR level is also involved in the related adaptive morphological responses. Blue- and UV-A (ultraviolet A)-sensitive photoreceptors are found in the cryptochrome photosystem. Blue light absorbing pigments include both cryptochrome (cry1, cry2) and phototropins (phot1, phot2). They are involved in several different tasks, such as monitoring the quality, quantity, direction and periodicity of the light. The different groups of blue- and UV-A-sensitive photoreceptors mediate important morphological responses such as endogenous rhythms, organ orientation, stem elongation and stomatal opening, germination, leaf expansion, root growth and phototropism. Phototropins
    regulate the pigment content and the positioning of photosynthetic organs and organelles in order to optimize the light harvest and photoinhibition. As with exposure to continuous far-red radiation, blue light also promotes flowering through the mediation of cryptochromes photoreceptors. Moreover, blue-light-sensitive photoreceptors (e.g. flavins and carotenoids) are also sensitive to the near-ultraviolet radiation, where a localized sensitivity peak can be found at around 370 nm.

    UV LEDS:
    Although radiation of wavelengths below 300 nm can be highly harmful to the chemical bonds of molecules and to DNA structure, plants do absorb radiation in this range.


    Last edited by blackchisel97; 07-21-2013, 07:42 PM.

  • #2
    Well, its time to get the seeds going again so the tomato and pepper plants are ready to go in the ground in the spring. Just thought I'd share a few tips that worked last year and that I am going to do again this year. Special thanks to Bob for helping me with my solid state LED drivers and trouble shooting as well as to Patrick for his Lite lenz circuit, it is an awesome led driver. enjoy, hope it helps you all start plants cheaper than the old way.

    First grow light was standard technology.

    First grow light:
    3" pvc sawn in half, drilled lots of little holes and poke leds through.
    pvc bottom.jpg
    then put rails on and series 3-5 rows depending on how many volts you have to supply. I used a 9 volt transformer.
    standard 9volt led light.jpg
    not too difficult here is a closer pic of the meters
    standard light with meters.jpg
    not bad 2 watts, but with bedini, we can do better



    • #3
      So the last light had 4 rows of 19 paralleled LED's

      To change that to bedini style we want high voltage low currant.

      To make the load that way is easy, series the LEDs.

      Lots of things to consider when sizing ssg circuit/coil/input to load, and lots of trial and error on my part, but the skinny of it all is I wanted to be able to use either a battery as the source for my lights or the wall ac, yet keep cost to run the lights way down.
      I first made this panel....

      having trouble uploading pics? worked a minute ago

      Well I made a test panel and put lots of them in series and then marked what voltage would turn them on at which point so I could test both the ssg circuit or the lite lenz circuit and adjust things.

      standby for pics...

      original led panel.jpg

      use basic uploader.
      Last edited by aln; 02-21-2015, 02:48 PM. Reason: add pic


      • #4
        Light #2

        Once I figured the voltage I wanted the output to run at I strung a series of 38 LED's and hooked up my ssg.
        pvc for light array.jpg

        the circuit is a vanilla ss ssg

        ss ssg.jpg

        heat was a major problem with the circuit w/ a 12 volt input, tried parallel rows, caps in parallel with the led's and lots of stuff, Bob helped lots. I finally ended up lowering the input voltage to control the heat best.

        Here is a 5 volt cell phone charger plugged to wall then to ssg input with 2 paralleled rows of 38 (76 leds) as the output.

        76leds 5 volt.jpg

        the meter is showing current.

        Here is another paralled 38 LED's (114 all together) same input voltage.

        114leds 5 volt.jpg

        Here is another paralleled 38 LED's (152) same watts to power it.

        152leds 5 volt.jpg



        • #5
          Here is a 6 volt battery to ss ssg input with 152 LED's as output.
          6 volt leds.jpg

          Here is a 12 volt input with all 4 rows in the light 152 led's.
          12 volt.jpg

          12.25*0.23=2.8175 watts

          I built better ones with better LED's but this was a fun project to get me going and thought someone might see some value in it. maybe i'll put a video up if there is interest. Aln


          • #6

            would ther ebe any advantage to mylar chrome tape as a reflector on the inside of the PVC? very interested in anything you have to share on this subject. this is real world use of pulse technology!!

            Tom C

            experimental Kits, chargers and solar trackers


            • #7
              Originally posted by Tom C View Post

              would there be any advantage to mylar chrome tape as a reflector on the inside of the PVC? very interested in anything you have to share on this subject. this is real world use of pulse technology!!

              Tom C
              Yes to the chrome tape as far as reflective ness, but would have to be careful to not let the legs of the LED's short out on each other if it conducts.

              Sizing the SSG was actually the most time consuming. I ended with a 5 k pot with like 1k or 2k base resistor I think, and small coils. I originally put the driver in this tin can
              finished ss bedini.jpg
              but the noise drove my wife crazy. I also had to go w/o cores, it hummed with them too. Since it isn't being used for charging you don't want the CPD mod, you want as little current as possible.

              But then... Things progressed to the cheapest, easiest, simplest driver; Patrick's liite lenz circuit as described in The Ultimate Cap Dump thread.
              An AC cap and 4 diodes.
              That's it!

              As long as you have your load sized it can be driven by the Bedini or the FWBR cap (Lite Lenz) method. The circuit is also called the "Capacitive Battery Charger" by George Wiseman.



              • #8
                I suppose you could insulate the legs with tubing, or install them from the back.... what is the ratio you ended up with blue to red? did not look like it was equal from one of the pictures

                Tom C

                experimental Kits, chargers and solar trackers


                • #9
                  White actually reflects the light better than silver/mirror/mylar,etc. for the purposes of growing plants.
                  Aaron Murakami

                  You never change things by fighting the existing reality. To change something, build a new model that makes the existing model obsolete.” ― Richard Buckminster Fuller


                  • #10
                    Thanks for chiming in Aaron. I know the white works as this was all done last year and tested but did not know that it was any better than silver.

                    I decided to throw a few videos up on youtube that I made last year for Bob when I was getting the project going. Don't know if I will keep them up very long so enjoy in the next couple weeks if you want to see them. Nothing special, Just a look at my project in action.



                    • #11


                      • #12


                        • #13
                          Here is the last video that has anything in it people would want to see. I use the old 3pmp kit to drive 2 panels. Aln


                          • #14
                            Originally posted by Tom C View Post
                            what is the ratio you ended up with blue to red? did not look like it was equal from one of the pictures

                            Tom C
                            To answer you question: More red than Blue, the deeper the red the better to a point as mentioned in the first post of this thread. I have some white/tiney bit of uv/some blue and /most red. I will not say that I did what is best, but it worked for the purpose I had.
                            Lets not ask what I did so much as ask what should be done which I bet Aaron could do much better at than me. Here is a helpful chart for anyone interested, it is from the Stealth Grow Light website.


                            • #15
                              Hey Aln-

                              I hooked up an led grow light today to get the process of starting some seeds going, and then thought how I could make it more efficient using some bedini tech. And then here you go posting all this info. Thank you for that.

                              I am interested in replicating what you have done exactly. How much is that array of Rapid LED's pulling? Are they from this site: ?

                              I have a small solid state SG I can use to test this out...but then you mentioned a separate driver? How does that connect to the SG and then to the LED's?

                              I also have a small 3 pole kit. Are you just running one master coil and then a gen coil driving the LED's?