In a world where global warming is a growing issue, new solutions need to be found to reduce the carbon footprint. The same is true for the seed breeding industry, which uses energy inefficient ways of disinfecting seeds using hot water baths. A more eco-friendly solution would be the use of cold plasma treatment. This thesis proposes two designs for high voltage generators to achieve this goal. These include the supercascode switch for high voltage pulsed DC operation and the high voltage transformer driven by a ZVS driver to create high voltage AC. Simulations were performed from which it was verified that the supercascode circuit could switch an input DC voltage of 10 kV at 20 kHz. The ZVS driver-transformer combination was shown to be able to generate up to 10 kV peak with a frequency up to 22 kHz depending on the load. Experiments were conducted with the ZVS driver and transformer which was able to match the simulations. However, the transformer turned out to have a coupling coefficient of 87%, which was not enough to be able to generate plasma, as a coupling of around 95% would be required.

Disinfection of seeds is a method used by the seed industry to remove pathogens. However, conventional methods have their shortcomings in terms of energy efficiency and yield. This thesis focuses on the design of a fluidized bed setup with sensors for the purpose of DBD plasma disinfection.
Two configurations were investigated, namely a spouted bed and a bubbling fluidized bed, where the bubbling fluidized bed produced the best results. Additionally, the fluidized bed was equipped with motor speed control, and with sensors for the measurement of ozone concentration, temperature, humidity, air speed, and ion density. These sensors were integrated in an easy readout system using displays, making the system ready for testing of disinfection performance.

As a novel alternative for conventional seed disinfection methods, a new design has been proposed in this report using a surface dielectric barrier discharge (SDBD) fractal electrode. The discharge mechanism for this electrode is a diffuse microdischarge under AC or short-pulsed DC mode operation. In this way, cold plasma could be generated that is applicable for seed disinfection. Furthermore, the electrodes were designed to be part of a proof of concept fluidized bed reactor with a reactor size of 10×20×20[𝑐𝑚] for disinfecting cabbage seeds with a diameter of 2𝑚𝑚. Because of this application, the efficacy of seed decontamination using plasma with its generated reactive agents was discussed. The used gas mixture in which the electrodes created plasma was ambient air without increased humidity. This means that the main reactive agents for sterilisation are reactive oxygen species (RON) like ozone (O3) and reactive nitrogen species (RNS). The electrical and physical parameters required to make cold-plasma were investigated to come up with a proper design for the electrode. From this theoretical analysis, five different initial designs emerged. The analysed designs include a wire-to-wire, wire-to-sheet, multi-hollow DBD, fractal SDBD and a coplanar DBD fractal electrode. All electrode designs were made based on the state-of-the-art dielectric barrier discharge principle. Moreover, in the design consideration, different materials for the conductor and dielectric were discussed, mainly based on electrical properties, plasma generation and manufacturing possibilities were considered. Based on previously set trade-off requirements, together with the results of measured power and turn on voltage of the plasma electrodes, the best designs tested design for seed disinfection are the double-sided 5𝑡ℎ order Hilbert fractal with a 1.6 𝑚𝑚 barrier and the single-sided 5𝑡ℎ order Hilbert fractal with a 0.8 𝑚𝑚 barrier.

This thesis describes the design and implementation of a LED Driving and Sensing Unit, one of the parts of a UV-C LED sterilization machine for the disinfection of plant seeds. The purpose of this part is to drive LEDs which can destroy different structures of pathogens. While doing this, certain parameters like temperature and ozone generation are being measured.
The report covers many design choices such as the choice to put the LEDs in arrays that are a combination of series and parallel circuits, or how SPI addressable variable resistors were used, in order to have full control over the LEDs and the sensing part. Furthermore, through a MATLAB script, it was discovered how the arrays of LEDs must be placed in specific manner to obtain a uniform radiation pattern. From this, it follows that using two arrays with radii of respectively 17 and 41 mm would work best. Furthermore, a literature research was done on UV-C and on what wavelength is theoretically the best for destroying pathogens on seeds. The focus was set on wavelengths of 255 nm and a combination of 275 nm and 285 nm. Also a 395 nm (UV-A) LED was used to investigate whether pathogens can be awakened from a hibernation state with the help of this type of light.
A boost converter capable of controlling the intensity of the LEDs by changing its gain with the aforementioned variable resistors was designed. Finally, the entire unit was tested successfully. The result of the research is a fully working LED driver module that can sense all parameters that need to be measured, completed with the design of a 3D CAD casing, which has all been manufactured and fabricated. This thesis does not include test results of the disinfection of plant seeds. This information will be included in the supplementary seed testing results report.

This thesis presents the design and development of a UV-C LED-based seed treatment machine aimed at enhancing seed quality by the extermination of pathogens. The research covers design choices, including a round irradiation pattern, consisting of two rings with three and nine LEDs for the inner and outer ring respectively, the use of a quartz plate as a holding plate for seeds for its high UV-C light permeability capabilities, the use of a vibration motor underneath the main operational stack for seed movement, and the use of Ethernet ports for power distribution and communication. The thesis discusses a comparative study between square and circular plate configurations, evaluating their performance using simulation results. Safety considerations were prioritized in the design, and appropriate precautions were implemented throughout the design process. The thesis also highlights the iterative design process for the mechanical system, discussing challenges encountered and improvements made to achieve a functional and robust prototype. Results demonstrate successful integration of components and achievement of objectives. The thesis concludes with discussions on the strengths, limitations, and future enhancements of the UV-C LED-based seed treatment machine. The research presented in this thesis provides valuable insights for further advancements in seed treatment technology, contributing to sustainable agricultural practices. Due to time constraints, conclusive results of testing on seed with this machine could not be obtained yet.

In this thesis for the Bachelor’s Degree in Electrical Engineering, a Control Unit (PCB and software) is designed for inside the UVC Seed Disinfection Machine of Team UVO. The machine consists of four modules: the Control Unit, the LED Driver, the motor controller and the power supply. The Control Unit allows a user to input the intensity per wavelength (for possible wavelengths: 255 nm, 275 nm, 285 nm and 395 nm), the exposure time and the motor speed.

The design of the machine, including all the modules, is aimed at achieving the optimal wavelength for inactivation and maximum and uniform irradiance, with the ability of changing radiation settings according to the desire of the user.

The Control Unit manages communication with the other modules, data storage, the User Interface, safety checks and system enabling. The thesis covers the design choices regarding the entire design, with an in-depth analysis of the hardware implemented safety checks, the graphical user interface and the design of the communication protocol.

Due to difficulties regarding uploading the code onto the PCB, not every developed functionality could be tested or implemented. However, the functionalities that were tested, did perform as expected. In addition to this, after the thesis has been submitted, more time will be spent on debugging the PCB, implementing and testing its features.

The objective for the graduation project of Team UVO is to provide a proof-of-concept of disinfecting cabbage seeds (Brassica oleracea capitata) from Alternaria using UVC LEDs. This thesis describes design process of the Control Unit module. The results of the decontamination process are provided in
Appendix F.