Covert NFC Wearable

Contract Project


Define customer needs


A Harvard professor wanted to record patients (users) taking notes on their cancer treatments. This was to ensure they were following up on their treatment.

The objective of the device was to covertly log the opening and closing of patient notebook. This data had to include timestamps, be quickly cleared and read from the device, and most importantly, below $20 a notebook.

The project was conducted was in 6 stages.

  1. Determine the specs and scope.
  2. Calculate the cost and bid for a price.
  3. Agree on the contract cost and timeline.
  4. Develop prototype.
  5. Check in with customer and solicite feedback
  6. Complete project with delivered units.

Electrical Design


Microcontroller

The first design decision was to choose which microcontroller to use. We wanted something that was low power (50uA), low height (0.55mm), easy to program (STM32IDE), and affordable ($1.38).

Thus, we settled on the STM32L011F4. One will also notice ports were connected with test points to allow for future expandability.


Programming

The debugger chosen was the JLINK basic as it was used in previous projects. (899-1004-ND)

We also wanted a low cost programming port, so the use of the Tag-Connect programmer was a must. (TC2050-ARM2010, TC2050-IDC)


Magnetic Switch

Starting out a reed switch like the MDSM-4R-12-18 seems like a good choice. It was low profile and relatively low cost.

This was until we found the A3213ELHLT-T Hall effect sensor. It's cost is far less, it's more reliable, lower profile, smaller footprint.


Battery

Chooseing a battery was critical to the project. Thus the following table was made to search for the optimal part. The one chosen was the CR-2016/F2N

Fix the table

Battery Height (mm) Cost ($) Power (mAh) Height (mm)
CR2030 ML614-TZ21 ML-614S/FN MS412FE-FL26E CR-2016/F2N
3.56 1.4 1.5 1.2 1.6
0.85 2.12 1.96 1.82 1.12
225 3.4 3.4 1 90
20 6.80 6.8 4.8 20

NFC

Used STEVAL-SMARTAG1 as a reference design


Layout

Mention Antenna Design https://my.st.com/analogsimulator/html_app/antenna/#/


Rendering

Submitted order and BOM to PCBWAY... on Costs


Implementation

Recieved DigiKey Parts and PCBs, built up test


Software

The Unity game engine enabled the rendering of a 3D enviroment to navigate with either a controller or a full VR system (HTC VIVE). Signals were routed by Uniduino to the Arduino RF dongle via USB

As a player, the goal was to navigate the maze with vision. Then naviagte a randomly given maze blindfolded (visionless) with the use of the VIEW system.


Enclosure

OnShape was used to design the enclosure. To view the enclosure, follow this link.

Design considerations were as follows:

  • Snap fit PCB
  • Space for LiPo battery + Connector
  • External Power Port
  • Programming port
  • Snap fit enclosure top
  • Belt loop on back of enclosure

This enclosure was manufactured by MakeXYZ with a .step file

Results

Blindfolded users experienced drastic improvements navigating through the course with haptic feedback. While navigating through a two-dimensional space, users found difficulty monitoring their speed. As a result they were given audio feedback when moving. Subjects with more experience playing video games were able to complete the two-dimensional tests with less difficulty than those who did not play games. However, subjects globally completed three-dimensional mazes with fewer collisions using the feedback system. Once in a three-dimensional test, test subjects were able to navigate with more comfort. In the virtual test setting, users had a much stronger sense of speed and spacial awareness when walking in real life instead of using a controller.

Future Contracts


1st Place

2017 Capstone Competition

Northeastern University

With strong competiton, competing aginst 12 other teams, the VIEW team took first place overall.

Link to formal website