Integrated LED/Imaging Illumination Panels Demonstrated within a Small Plant Growth Chamber

For this project, an aeroponic small plant growth chamber was designed, constructed and demonstrated that incorporated a new type of illumination panel that integrates multi-color Light Emitting Diode (LED) clusters with small imaging cameras. Engineering design trades were conducted to optimize illumination quality and uniformity prior to fabricating this portable growth unit. The LED nodes within the illumination panel consist of small clusters of multi-color red, green, and blue (RGB) LEDs. The LED nodes were designed so that a single cluster could be replaced if required, significantly reducing the time and expense currently required to replace LEDs on commercially available LED panels. For this growth chamber, a single panel housing twelve LED nodes was constructed. The panel was designed to provide two levels of illumination: (1) for small plants just germinated, lower intensity light and (2) for maturing plants, brighter light. Additionally, to observe plant growth and enable unobstructed viewing and time lapse photography, two small imaging cameras were integrated into the array of LED clusters. The imaging camera can also provide a means to measure illumination levels so that individual colored LEDs can be modulated to provide the correct illumination spectra and intensity. The LED nodes and imaging camera were designed to be powered with low voltage DC power. Low voltage DC power is safer, cleaner and less susceptible to power surges. For safety purposes, the AC powered DC power supplies were placed above all potential wet areas within the growth unit. LED light sources are ideal for plant growth systems. However, commercially available multi-color LED illumination panels are designed and manufactured to produce a single particular illumination. These panels have very specific LED colors arranged in a very specific fashion. This limits the amount of color mixing, intensity variation, and spatial arrangement that is possible, precluding passive precision illumination. There is no feedback mechanism to detect spectral shifts caused by LED aging and additionally, there is no mechanism to modulate LEDs. It is also not possible to integrate an imaging system into these panels. Furthermore, these panels are commonly operated using high voltage AC power sources, which is not ideal in a potentially wet environment. Therefore, to address these issues, custom LED illumination panels were designed and developed for this project's plant growth chamber. A systematic approach was taken to determine the general size, specifications, and shape of a portable plant growth unit. Once the general size and shape were finalized, the detailed design of the support structure, aeroponics, and lighting subsystems were developed. Particular attention was given to heat transfer and the expected LED thermal environment. Additionally, a computational analysis was performed to determine optimal LED nodes placement so that two different uniform illumination fields could be yielded: (1) for germinating plants, lower intensity light, and (2) for larger maturing plants, a brighter one. Also, aeroponic studies were reviewed to identify an efficient and user-friendly system that would require minimal user involvement. More »