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Twain’s Status Report for 2024/02/24

This week, I created a prototype for the piezoelectric energy harvesting. I cut one of the pieces of spring steel into one inch strips, prepped the surface, and attached three of the piezo tiles to the surface at locations suggested by the paper, leaving room to attach other tiles at the angles suggested to have more voltage output upon flexion. I then hooked each tile up to an oscilloscope and studied the outputs upon flexing the spring steel small amounts at the bend angles that would be likely to be seen when wearing the watch. Additionally, I began to figure out how to attach the watch straps together so that they can be reformed for our purposes.

My progress is on schedule, as this week was dedicated to creating a prototype of the energy harvesting.

In the next week, I hope to test this prototype more and to help Carson implement the other form of energy harvesting that we are looking into.

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Gary’s Status Report for 24 Feb 2024

Progress

This week I finalized the barebones breadboard prototype of the GPS watch: a lot of the time was spent on debugging the UART failing to connect (the issue was that the baud rate I configured the GPS to had been reset, as the GPS doesn’t actually have persistent settings). In the end, we have a GPS setup that’s printing the coordinates out to the screen!

Pacing

I’m about on pace for my tasks: by the end of this week I was scheduled to be done with the firmware needed to get GPS data on the screen, which is what I’ve done.

Planning

Next week I plan to work on more of the firmware functionality, mainly the timekeeping via the RTC. I’ll also help Carson and Twain iterate on the energy harvesting after the success we had this week with the motor-based design.

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Gary’s Status Report for 17 Feb 2024

Progress

This week, I made more progress toward writing the boilerplate firmware needed to get the microcontroller to communicate with our various peripherals. This includes another pass at the SPI transaction handling for the display, and a preliminary serial setup for receiving GPS data.

Here’s a screenshot of my newly rewritten function for efficiently updating the display by sending only changed lines:

Pacing

I’m a bit behind schedule in terms of producing our actual prototype board, but I have at least shown the fact that the various hardware we’ve been planning to integrate will work together, which was needed in order for Carson to start designing the board schematic.

Planning

Next week our GPS module should arrive, so I can actually properly do GPS integration rather than sending test data. After that point, I should finally be done with our “breadboard prototype” step, at least in terms of firmware.

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Carson’s Status Update for February 17th, 2024

Progress

My primary accomplishment this week was in making a first (very rough!) draft of the board schematic. It is missing a few connectors and features useful for testing (jumpers, test points, spare pins, etc.), but it’s very useful for checking if there’s any major design details we’ve overlooked. Thankfully, there weren’t any.

Pacing

I am roughly on pace right now.

Planning

By next week, our components should have arrived. This means I can start testing the energy harvesting setup and experiment to find the optimal setup, and then get real numbers on how much power we can source.

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Team Status Report for 2024/02/17

The biggest risk we see right now is the timing on the shipping of necessary components. We have accounted for this as part of our general shipping time / slack in our Gantt chart, but we will mitigate similar future risks by attempting to figure out what we need earlier, and by utilizing Slack to communicate these needs earlier.

We did not make any specific changes to the existing, but we decided to make a design decision on our battery system: we will move forward with a LiPo battery. The only costs from this are in purchasing one such battery.

There have been no changes to the schedule.

For this status report, we were asked to answer additional questions. A was written by Twain, B was written by Gary, and C was written by Carson.

Part A: Our product solution addresses a critical need in the context of public health, safety, and welfare. The prolonged battery longevity ensures that individuals, especially those engaged in outdoor activities or requiring continuous location tracking, can rely on the device for an extended duration without the concern of sudden power depletion. Simultaneously, the watch’s emphasis on user privacy safeguards individuals from unauthorized access to their location data, mitigating potential risks associated with personal information exposure and contributing to the psychological well-being of the user. By prioritizing both functionality and privacy, this GPS watch contributes to the overall well-being of users, aligning with the broader goals of public health and welfare by providing a secure and dependable tool for personal tracking without compromising privacy or safety.

Part B: The most prominent existing solutions to the issue of a user wanting to keep track of their own location history involve sending the user’s location data to a companies who have stipulated in their privacy agreements that they are free to sell the data to others as they wish. To many people, this is an uncomfortable arrangement, as over time, more and more fears surrounding “big data” and data-selling arrangements like this have become prevalent. Our watch addresses this issue, as it allows the user to track their path while all of the data involved is stored on the watch itself, without ever being uploaded to the cloud.

Part C: Current watches that integrate both GPS and energy harvesting technology are very expensive (e.g. the Garmin Instinct II, which sells for ~$400). Other watches that have GPS technology (e.g. the Google Pixel Watch, at ~$200) don’t integrate energy harvesting, and thus have limited battery life as a result. Landhopper’s feature set is specifically designed to fill the niche of a wearable but long-lasting GPS, while trimming out features like Bluetooth and phone connectivity to avoid expensive transceiver modules and additional processing requirements.

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Twain’s Status Report for 2024/02/17

This week, I spent significant time working on the slideshow presentation for the design presentation. I also helped create the list of parts we needed to order, and then submitted all of the ordering paperwork and dealt with the issues that arose in the order. Additionally, I helped Gary with the firmware for the GPS, looking at Rust crates for parsing NMEA 0183.

My progress is on schedule, assuming that the parts needed to test the energy harvesting show up quickly enough for me to get to prototyping, which is my main task for next week. I will need to figure out how to cut the metal, make it safe to wear, and attach it to the wristwatch strap and the piezo tiles to the metal.

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Gary’s Status Report for 10 Feb 2024

Earlier this week, I worked with my teammates to review possible paths to follow for our energy harvesting design, and also worked on composing a purchasing list for our initial prototypes.

Later in the week, I started working on the breadboard prototype for the watch, along with the firmware: most of this time (around 9 hours) has gone into setting up our build environment and debugging the peripherals we need to use in the firmware. So far the display is implemented, and I’m also currently working on the UART for the GPS and the real-time clock. I am a little bit behind schedule as we had originally planned for me to finish with the breadboard prototype this week, but we’d failed to account for when we’d be able to order parts. However, I don’t think this should be an issue since I’ve been using my time to get ahead on the firmware (my task for next week), and progress should be faster on said firmware with Twain helping next week. Once the remaining parts we need for the breadboard prototype arrive (mainly the GPS), it should be pretty quick to finish the prototype (the wiring is pretty much just a few UART lines) so we can start testing the power systems.

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Team Status Report for 2024/02/10

The most significant risks we see right now are with the energy harvesting and its interaction with the GPS. The energy harvesting method we intend to employ may not be as efficient as we were hoping, since we were unable to find the correct kind of piezo tile, and generally we would not expect to get the same results as the paper. We are managing this risk by looking into alternative sources of energy harvesting. The other risk that we see right now is that GPS is a very finicky system, and we are worried that the voltage jumps from the piezo tiles will create a large amount of noise that may throw off the GPS signal. This is also being mitigated by looking into other potential sources of energy harvesting.

No set changes have been made to the system as of right now.

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Twain’s Status Report for 2024/02/10

This week, I gave the project proposal talk on Wednesday. I helped my teammates finalize a list of materials that we would need to purchase for this project, and additionally helped figure out which exact items we would need and where we could purchase them from. I looked into a paper to help figure out how to get energy harvesting working, and was able to figure out a better plan of action in terms of materials to buy and sources to look into.

My progress is slightly behind schedule; I didn’t realize that I wasn’t going to be able to order parts on Friday, and we were hoping to put in an order for the sheet metal and piezo elements, at least, by the end of this week. However, we should be able to get that done this week, and shipping should take a short enough amount of time that it should not be a huge detriment.

In the next week, I intend to help Gary with getting the minimal firmware done for the project. Depending on shipping time for our parts, I will also start to work with figuring out how to mount the piezo tiles on the metal band, and the metal band on the wristwatch strap.

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Carson Swoveland’s Status Report for February 10th, 2024

Progress

This week I did literature review for the energy harvesting part of the project. I made a number of interesting notes from these papers, with the most important ones being:

Piezoelectric energy harvester impedance matching using a piezoelectric transformer

Though sourcing a piezoelectric transformer is infeasible, this paper did give some insights on some of the challenges to getting optimal power transfer from piezoelectric elements. The major concern was the fact that at low frequencies (the typical frequencies of human motion), the impedance of a piezoelectric element is largely capacitive. The inductance required to match this capacitance is typically infeasibly large to achieve on a wearable device, so instead mostly resistive matching is done.

A Coaxial Wrist-Worn Energy Harvester for Self-Powered Internet of Things Sensors

This paper proposed the use of a motor and weight for energy harvesting. Surprisingly, it achieved power generation of ~3mW average at a normal walking pace, which far exceeds the capability of the state of the art in piezoelectric generators (as far as I could find). Originally we discarded the idea of using a motor for energy harvesting due to mechanical complexity, but after some discussion we realized that we may be able to use a standard gimbal motor and 3D print a planetary gearbox for the top. We will be experimenting with both methods to see which one is more effective.

Low-Power Design of a Self-powered Piezoelectric Energy Harvesting System With Maximum Power Point Tracking

This paper presented the most thorough design for the voltage regulation and conversion that I’ve found so far,  and goes into great detail on the design considerations for implementing a circuit for low-power use. I expect that my design will be primarily based on the techniques discussed here.

Pacing

I am roughly on pace right now.

Planning

Next week, I will start the more detailed design of the energy harvesting circuit, and do some hands-on testing of piezoelectric elements I have laying around. My goals are:

  • Create preliminary design for Boost/Buck Impedance Matching
  • Test Boost/Buck Impedance Matching on Breadboard