Maker.io main logo

Senior Design Part 11: Strengthening Integration with Testing

2023-07-07 | By Will Siffer

License: Attribution Non-commercial

Designing a project to break

As we reach the end of this semester of design changes and validation phases, it is time to complete some limit tests that evaluate if we are meeting our design constraints. As with any design, we are susceptible to having tunnel vision and forgetting key aspects of our design specifications that are crucial to designing functionality. Constant testing ensures a cohesive product that will work in all conditions and use cases, allowing us to have fewer failures in the delivery phase.

What does this mean for a radio device? We need to evaluate and prove that it can handle every situation that it can be expected to operate before it is expected to succeed. Kind of like when you have training wheels and barely need them, but are still happy they are there in case something bad happens. For this project, we have a variety of tests, including:

  1. Radio Range Testing
  2. RFID Range Testing
  3. RFID Field-of-view testing
  4. Solar Panel output voltage
  5. Solar Panel output current
  6. Battery capacity testing
  7. Enclosure Waterproofing
  8. Mount weatherproofing (wind/rain/sleet/ice)
  9. PCB Heat soak test
  10. PCB cold soak test

Wow, that sure is a lot to do just for a senior design project, but for my team, we hope to develop this device into something that researchers at Purdue can use to measure aspects of campus life passively and adapt the sensors to meet their needs. 

For this blog post, I am going to keep most of these explanations brief and only go into detail on tests that we've already completed.

1) Radio Range Testing: This one is pretty simple; we were able to put our radio base station in a tall building with lots of windows and test the signal around Purdue's campus. What we found was that the biggest enemy of our range was the height of the base station! Below is the map of a successful range test that we completed: The blue shape is everywhere we were able to get a successful signal from our device, with the star representing where the base station was located.

range

2/3) RFID Range/Field of View testing: This test we just recently completed last week. The Scheme-it below outlines the test plan graphically, but the basic idea was to check that the RFID tags could still be read from a distance and record if the scanner could see the tag. We found that the system was not strong enough to scan tags over 10 feet on battery power, but on computer power, we could achieve much higher distances. 

 

 

4/5/6) Solar Panel / Battery voltage and current tests: These tests were done continuously over the last couple of weeks, and I went into more detail in the previous week's post. The basic finding was that the solar panel was not powerful enough to charge the battery in cloudy conditions, which made it difficult for us to validate that the system would work through the night or recover from a low battery. We did achieve almost a full amp of charging at one point, but it didn't last long since the sun went behind a building. 

7/8) Enclosure tests: These tests were to determine if the enclosure was capable of keeping the device safe from water and any other foreign object intrusion. This test turned out to be straightforward since all we had to do was put the device outside during extreme weather events and watch the data stream. So far, we have had the device in 1 tornado watch and 1 tornado warning with extreme winds and rain, and it transmitted successfully through the entire event (until the battery died).

9/10) Heat/Cold soak testing: This test is fairly simple to conduct in theory, but is also the one that we have not had the time to complete yet. The idea is that since the board is expected to handle well below-freezing temperatures and well over 100 degrees, we could test beyond the ranges of what's expected for shorter periods to prove that the system could handle the stress. This proved difficult to accomplish this semester since we struggled to find chambers for hot and cold baths. 

 

Overall, I am happy with this testing experience and I feel that I have learned a lot. I hope this blog post served as a way for you to learn and remind yourself of tests you may need to complete for a project that you are working on as well! Until next time, my name is Will, and as the Digi-Key ambassador at Purdue University, I hope you find something to learn today.

This week I had the opportunity to reflect on my personal development in the semester so far and how my priorities were challenged. These reflections are important to me because they connect the work that I am doing to the real reason why I am doing it, to become a better engineer. 

Recommended Reading

"This week we started more testing and explored more options for the solar charging system since we are getting more and more data that is showing that the solar panel isn't powerful enough to charge the system. In order to best prove that we are making the best effort on the device side to use as little power as possible, I measured all the things that use a lot of current like the LEDs and the RFID chip. After measuring the different points, we found that we couldn't meaningfully reduce the current consumption without also reducing functionality. This situation reinforced my belief in the specifications of the device and that it was performing to the standards that we set for the project. I would say that it challenged my priorities because I was focusing on getting the device working so fast that I never asked the question of how much power we actually had available. I will remember to bring this idea with me to the workplace when working in the industry. I need to remember to consider aspects of the design outside of my own so that in the end we have the most functional product we can."

TechForum

Have questions or comments? Continue the conversation on TechForum, DigiKey's online community and technical resource.

Visit TechForum