Senior Design Part 10: Making Sure the Project is Ready to Pass On

2023-06-23 | By Will Siffer

License: Attribution Non-commercial Test Equipment

Planning for a project that I may not see finished:

As the semester progresses, I am realizing that it is likely I won't see the end of this project in the way that I had hoped. At the beginning of the semester, I hoped that I would have a fully integrated device with multiple instances around campus with proven environmental testing. Those were lofty goals, but I believed that I could achieve them with the help of my team working hard every week to make sure that progress was always made in as many directions of the project as possible. These goals have turned out to be quite challenging to accomplish, especially with only seeing the whole team once per week for two hours.

So, where do we go from here?

Well, one of the beautiful parts of Purdue's EPICS is that the projects get maintained each semester until they are eventually delivered. This means that I need to make sure I am giving the next semester's team the best chance for success that I can, and that process starts now so I am not rushed to complete all the documentation at the end of the semester. As I am sure you all know, a rushed documentation phase only leads to delays in the development phase later. 

Documentation isn't the end-all of this project!

The project still has a lot of progress to be made, but we made a lot of progress this week! For one, we fixed the solar panel code to give the proper data to the server so we can analyze the device's performance while it is mounted outside. As I mentioned earlier in the semester, we are measuring the device's voltage and current trends over time, as well as the temperature on the PCB and the humidity in the device enclosure. All this data, of course, needs to be as accurate as possible in order to successfully diagnose issues with the PCB quickly.

After changing the solar panel reading code, there was quite an interesting finding. Although we thought the solar panel would charge the battery under normal device conditions, we found that it is actually quite rare to charge the battery with normal amounts of sunlight throughout the day. The pictures below show the solar current in purple and the net battery current in blue. The goal is for the blue value to go negative sometimes to indicate the battery is charging, and for the solar current to rise above 100mA to charge the battery and support the system. 

Battery Current never drops negative, so it doesn't charge.

Battery current going negative, indicating the charging circuit works, but the solar panel isn't powerful enough.

This is a lot of good data! We are learning more and more about the device and how it performs every day, and in this case, you can see that we found an issue with our 6W solar panel in that it will only provide enough power to charge the battery under some of the most ideal situations. This obviously won't work for us since Purdue is located where there are lots of clouds and minimal sunlight in the winter months. In the next couple of weeks, we are hoping to solve this issue and find a better solar panel that can support our device. 

Wait, Will, where are you going?

While it has been awesome being the Digi-Key representative and ambassador here at Purdue for the last few years, it is time for me to move on to the next chapter of my engineering career; industry work. As of the writing of this blog post, I have accepted a position that will allow me to continue my passion for vehicles, electrical engineering, and the outdoors. I won't be going anywhere for a little while though, so you are stuck with me for a little longer. Until next time, my name is Will Siffer, and I hope you discovered something new.

Here is my personal reflection for the week where I thought about the ethical implications of writing good documentation.

Recommended Reading

• Senior Design Capstone Part 1: What (or Who?) is LoRa?
• Senior Design Part 2: Using Eagle to make a custom PCB
• Senior Design Part 3: Designing a SMD PCB full of sensors
• Senior Design Part 4: Assembling, Testing, and Debugging Circuit Boards!
• Senior Design Part 5: Diagnosing PCB Issues
• Senior Design Part 6: Protecting our Power!
• Senior Design Part 7: Compressing data with Magic? (It's just math!)
• Senior Design Part 8: Squishing Bugs and Finding More
• Senior Design Part 9: Can adding a delay be a good thing?

"This week we needed a sort of re-alignment and made sure that we were making our project easily continued after I am no longer with this team. This experience gave me the opportunity to reflect on the professional, ethical implications of the project, not only when it's delivered, but also while it's being built. To me, it's important to consider the future engineers working on the project just as much as it is important to consider the end user. Whether it be a mechanic, a new designer, or a supervisor, the device needs to be able to be understood, and the documentation needs to be readable without many issues. This is important for this project, especially since it is prone to a high turnover rate of team members. Because of this, we need to make sure all our documentation makes sense. This can be brought with me to the industry when I am working on products that will eventually be in production. I need to make sure that the products are serviceable and easy to understand by those who need to understand it."