Component choices and general advice for a sensor fusion device for soil quality measurement

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Joined Jun 29, 2020
For a university project, I am designing and am further required to build a sensor fusion device for soil quality measurement in agricultural soil. The device will measure the volumetric water content (VWC) in the soil, the temperature of the soil and the light levels that the soil is exposed to. The device will be battery powered and is required to have extended battery life (at least 6 months). As the device is meant to function in an agricultural setting (with no guaranteed GSM), the device is required to store the sensor data onboard and communicate the data over long ranges using LPWAN technology (I have access to a Weightless-P kit, that I have no prior experience with). The data is required to be downloaded onto the user's device whenever they want to view the data and display the data in a meaningful way to a person with limited software experience. Using Python, the data from the individual VWC sensors needs to be fused and using Bayes Inference, prove that the fused VWC sensor readings have greater accuracy than the individual sensors themselves. The temperature and light sensors are used to paint a broader picture of the state of the soil. The device is also required to be locatable/retrievable from the field where there are no discernable landmarks to use as a guide. For this, I am wanting to use an RF transmitter module on the device and then design an RF receiver device (battery-powered, handheld) that will have a bidirectional antenna (3D printed) to show the user whether they are moving closer or further away from the device. I have attached a rough system architecture diagram and a functional block diagram for a better picture of the subsystems to this design.

I am hoping that someone has experience with any of the subsystems I have mentioned above and can advise me in moving forward with my project, components or designs that they have used in the past and have had success (or not) with. The advise that I am looking for is along the lines of:
  1. What microcontroller should I consider using for my device
  2. What components/materials do I need to build a TDR sensor and simulate the results
  3. Is the Weightless-P kit going to be a good choice or do I need to look into using a different LPWAN technology
  4. Any links to research papers/websites/tutorials that will assist me
  5. RF transmitter/receiver designs
  6. How to store the data onboard and download it on the user's end
  7. What complications should I be looking out for
  8. Literally anything that you think could be useful to me

Finally, I just want to say thank you for any help that you can give me. I do not have a lot of experience with electronic design, and a massive project like this is somewhat overwhelming. I am not trying to find someone to do this project for me, just help and answer questions that I may have. If you are interested then I will keep you posted with the progress of the design and build of the device as I move forward and hopefully have a working prototype by October. I am looking forward to this journey.



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