Abstract:
A system for enabling controlled plant growth of plants in containers includes linear tracks spaced apart from each other by intervening supporting plates. Each track includes an array of blue and red LEDs affixed to heat sink that can slide along the track to be positioned in a desired arrangement to the container beneath it. A controller for the LEDs is positioned between every other pair of tracks to control adjacent arrays of LEDs. The controller controls the LEDs to provide light to the plants in the containers of desired intensity and wavelength.

Description:
REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to U.S. Provisional Patent Application No. 61/699,970, filed Sep. 12, 2012, and entitled “System for Optimized Plant Growth,” which is incorporated herein by reference in its entirety for all purposes. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This application relates to technology for plant growth, and in particular to a lighting system for optimized plant growth under controlled conditions. 
         [0003]    Growing plants in a controlled environment is now a well-known technology. Greenhouses produce large quantities of flowers and vegetables that are distributed throughout the world. More recently, plans are being grown in yet further controlled environments, for example, where all of the light and nutrients are provided in a closed, essentially windowless structure. While such systems can use incandescent lighting, the reduced power consumption and higher efficiency of light emitting diodes (LEDs) have made those the preferred choice for “indoor” greenhouses. We use the term “indoor” herein referred to systems in which plants are grown with minimal or no exposure to ambient lighting; that is, systems in which essentially all of the light provided for plant growth is provided from artificial sources such as light emitting diodes. 
         [0004]    One example of this technology has been implemented by Ecopia Farms. Ecopia Farms grows herbs and vegetables in soil positioned in bins on racks inside a closed building. This allows control of light, water, and nutrients. The closed environment dramatically reduces the amount of water required, while the ability to grow the produce on shelves of stacked racks dramatically reduces the square footage required to produce a given amount of produce. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    Our system for enabling controlled growth of plants in containers includes a set of linear tracks spaced apart from each other. Supporting plates position the tracks in a parallel arrangement. Each track includes an array of blue and red LEDs affixed to heat sink which can slide along the track to be positioned in a desired position to the container beneath it. A controller for the LEDs is situated between every other pair of tracks to control adjacent arrays of LEDs. The controller controls the LEDs to provide light of desired intensity and wavelength to the plants. 
         [0006]    By making each track identical to all other tracks and making each supporting plate identical to all other supporting plates, the apparatus may be enlarged or reduced in a modular manner to an appropriate size for the configuration of the plant growth system. Positioning a light sensor in proximity to the containers and coupling it to at least some of the controllers enables adjusting the intensity and wavelength of the light from the LEDs adjusted as needed for the particular plants and stage of plant growth. In addition, if the containers are labeled with identification tags, e.g. RFID, and also providing the apparatus with a tag sensor that detects the identification tags, the system can be controlled automatically. Furthermore, in some embodiments an environmental sensor is coupled to the controller to enable the controller to control an environmental variable such as temperature or humidity. Preferably each array of light emitting diodes includes only blue and red light emitting diodes mounted on a heat sink, with a temperature sensor also mounted on the heat sink in communication with the controller. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a top view of a light emitting diode assembly for plant growth; 
           [0008]      FIG. 2  is a perspective view of the assembly; 
           [0009]      FIG. 3  is a diagram of an LED array strip; 
           [0010]      FIG. 4  is a perspective view of the assembly as implemented in a typical environment; 
           [0011]      FIG. 5  is a block diagram illustrating a controller for the system; and 
           [0012]      FIG. 6  is a diagram illustrating network control of the plant growth line. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]      FIG. 1  is a top view of a light emitting diode assembly  10  used for plant growth. Shown in the diagram are a series of tracks  20  having separated side rails. Positioned within each track is an light emitting diode (LED) assembly  30  which includes strips of LEDs affixed to a heat sink  30 . The LED/heat sink assembly is preferably not affixed to the track  20 , enabling it to be positioned in the track in a desired relationship to the container beneath it. The LEDs are electrically coupled to controllers  40  disposed on the plates  50  of assembly  10 . 
         [0014]    Each pair of tracks  20  is held in a fixed position with respect to other tracks by an intervening supporting plate  50 . The plates  50  and tracks  20  enable a modular approach to the system in which additional subassemblies consisting of a plate and a track can be added to extend the length of the assembly as needed by the particular application. 
         [0015]      FIG. 2  is a perspective view illustrating the apparatus in more detail. As shown, the individual tracks  20  each consist of a pair of L-shaped side rails  28  mounted in opposition to each other to provide a lower surface  29  upon which the LED heat sink  30  is supported. Heat sink  30  is not affixed to the track  20 , but may be moved to and fro in the track  20  as indicated by the bidirectional arrow  32 . 
         [0016]    Also illustrated is a strip-shaped circuit board of light emitting diodes  60  affixed to the lower surface of the heat sink  30 . In the preferred embodiment the circuit board of LEDs consists of a linear row of blue LEDs disposed in parallel to a linear row of red LEDs. Wires, not shown, couple the strip of LEDs  60  to the controller  40 . The intervening plates  50  between each pair of tracks provides an attachment surface for the controller  40 , and for tabs  22  on track  20 . 
         [0017]      FIG. 3  illustrates the LED circuit board  62  in more detail. Arranged in a linear manner along one edge of the circuit board  62  are LEDs  70  of a first color. Along the other edge of the circuit board are LEDs  75  of a different color. Preferably the two colors are red and blue. Each circuit board of LEDs  70 ,  75  also preferably includes a thyristor  80 , or other sensor, for measuring the temperature of the assembled circuit board and heat sink. This allows more careful control of the temperature of the circuit board and LEDs, enabling longer life for the LEDs. A connector  90  coupled to the LEDs and the thyristor enables electrical connections to be made between the assembly  60  and the controllers  40 . 
         [0018]      FIG. 4  is a diagram illustrating an application for the system described in  FIGS. 1-3 . As shown in the  FIG. 4  a rack  100  supports a series of trays  110  in which plants are being grown. Each tray includes soil with appropriate nutrients and water added as necessary. Positioned linearly above the row of trays  110  is the apparatus  10  described in conjunction with  FIGS. 1-3 . Positioned above the apparatus  10  is another row of trays  109  supported on an additional portion  120  of the frame  100 . Above that additional row of trays  109  is another LED assembly (not shown) to provide illumination to that row of trays. 
         [0019]    A series of sensors  130  are mounted along the side rails of the frame  100  to detect the light emitted by the assembly  10 , and to detect environmental conditions in the vicinity of the apparatus. The sensors  130  are coupled to the controllers  40  to provide the controllers information about the color and intensity of the light being emitted by the strips of light emitting diodes  60 . 
         [0020]    Generally most plants absorb primarily blue and red light. With appropriate experimental testing and calculations, the apparatus described here provides an optimal mix of wavelengths of light ranging from all blue to all red, each with a controlled intensity. For example, some plants grow best with primarily blue light at the beginning of their growth, and later predominately red light. The apparatus described here enables such control. 
         [0021]    The sensors positioned along the trays provide information about the color of the light being received. In addition those sensors also can provide information about temperature, humidity, reflected light, carbon dioxide content, or other parameters of interest at the location of the trays with the plants. The sensors can provide feedback to control systems within the facility to raise or lower the temperature, humidity, carbon dioxide content, etc. In this manner, water use can be limited and power consumption made appropriate for the needs of the plant at the time. 
         [0022]    Furthermore, in a preferred embodiment, an RFID tag can be added to each of the trays, and this identification sensed by an RFID sensors  160  on the frame  100 . If the RFID tag information also provides information about the content of the tray, the light color and intensity of the LED emissions can be optimized for that particular plant type, even as the trays are moved to other locations on the supporting racks. 
         [0023]      FIG. 5  is a block diagram illustrating a control system for the apparatus illustrated in  FIGS. 1-3 . As shown the bins  110  containing plants are positioned under the strips of LEDs  60  which are supported by the frame  100 . A light sensor (photo detector)  130  is positioned in proximity to the bin  110  to detect the light provided by the LEDs  60 , and relay that information over a connection  135  to a controller  40 . Depending upon the particular plants and the stage of their growth, controller  40  provide signals over bus  140  to control the color and intensity of the light by controlling the LEDs. The particular bin  110  and its contents are identified to the controller  40  by an RFID tag  150 . The RFID tag communicates with an RFID sensor  160  that provides that information to a controller  40  using a connection  165 . An environmental sensor  170  provides information to control  40  about desired environmental variables, for example, temperature, humidity, carbon dioxide, etc. By coupling controller  40  to fans, heaters, or other apparatus, the environmental conditions in the vicinity of the bins  110  can therefore also be controlled. 
         [0024]      FIG. 6  is a diagram illustrating networking of the plant growth system, and the ability to remotely control the system. As shown there, a computer or controller is coupled to the plant growth line using the Internet. The plant growth line includes sensors that report on conditions, for example, illumination intensity or illumination color, and relay that back to the computer. The LED light engines are then controlled based on the sensed conditions. The ability to sense and control parameters, such as light intensity and color, enables the plants to be grown under optimal conditions. Such a networked lighting and sensor system is explained in more detail in our co-pending U.S. Provisional Patent Application “Networked Lighting Infrastructure for Sensing Applications,” Ser. No. 61/699,968, filed Sep. 12, 2012, the contents of which are incorporated herein by reference. 
         [0025]    In the plant growth system described here, lighting control and sensing are provided using the techniques described in the above referenced patent application. In the plant growth system here, the sensors detect carbon dioxide levels, ambient temperature, ambient humidity, and both reflected light and light from the LED sources. 
         [0026]    As shown in  FIG. 6  a web browser-based interface enables the user to connect through the internet to view the status of the plant growth lines and their sensors, as well as control the lighting, for example, by turning lights on and off, changing their power levels, and changing their schedules. In some applications of the system described here, a database running on the computer shown in  FIG. 6 , or elsewhere, stores growing condition profiles for different plant species, e.g. respective red/blue LED power levels, on/off schedules, ventilation demands, etc. Desired parameters can be set and stored in a profile so that each time a plant growth line is planted with new seedlings, the user can select the appropriate profile from the database to be used by the system. The profile can contain all operating parameters and controls the LEDs until harvest time. 
         [0027]    In addition to using the system to control the LED illumination sources, the software enables recording data from the sensors, enabling determination of the effects of various parameters over time. This enables plant growth research. Successful results enable new, more optimal, plant growth parameters for profiles to be determined. 
         [0028]    Of course, while above we describe the structure and system described here in terms of an application for optimized plant growth, it will be apparent that the system described can have other uses, for example, in any circumstance in which controlling light output in a manufacturing process is important. For example, in the manufacture of products where photoresist is used, controlling the color and intensity of light can provide superior results.