Digital Wandering Pen
The Wandering Pen is the result of a one-week rapid prototyping sprint at Brown and RISD’s Master of Arts in Design Engineering (MADE) program. I reimagined the conventional measuring tape to improve convenience, robustness, and versatility. Over multiple iteration rounds, I arrived at a more refined prototype: a digital pen that tracks the distance it has been rolled over a surface. This project was an excellent practice of rapid prototyping, user research, design refinement, and mechatronics.
I aimed for breadth in my initial visualizations. These were narrowed down for prototyping based on novelty, personal challenge, and feasibility of prototyping. I also polled my classmates on which tools they would want to use, given that the target audience was design engineers aged 20-30.
Then, I made low-fidelity prototypes until I was blue in the face.
I composed a list of constraints and specifications to select the best prototype:
| Constraint | Specification |
| 1. Quick to use | Time from pocket to measurement <15s |
| 2. Simple to use | <3 steps to measure |
| 3. Accurate | Measures test piece to within ⅛” |
| 4. Visually appealing | <75% of cohort polled agrees |
| 5. Novel | No other cohort member is making a significantly similar product; not recognizable as a product on market by cohort |
| 6. Technical | Displays >3 technical skills for a portfolio |
| 7. Compact | Fits in a 6” pocket |
Electronics
This was half a day’s worth of work, and surprisingly the least troublesome part of the project. Due to the short timeline, I only used electronic components I had on hand: an encoder, an Arduino Nano, a 16x2-char LCD display, a 9V battery, and a power management breakout board. I tested encoder readings with two different Arduino libraries, then added in a display readout of the encoder’s distance traveled. While less sleek, I preferred the LCD over a 4-digit 7-segment display because it only uses 2 pins.
Measurement Wheel
My biggest challenge in this project was the measurement wheel. My first prototypes slipped on most surfaces and decreased the accuracy of the measurement. I tried many different materials to increase the grip, and eventually settled on the spoked wheel. This worked the best on the chipboard block the class was given to standardize our measurements.
Results
My initial vision was to use the device as a pen, although I also considered more horizontal computer-mouse-type orientations. I handed prototypes to my cohort members and saw where they gripped it, which led to dimension adjustments for various parts of the case. The most important feedback I received was that the device was top heavy due to the battery placement. The final device has a resolution of about 0.1”. When tested on multiple different surfaces, slipping brought the accuracy to 0.25” on average, which was more than sufficient to meet the challenge of measuring a 3’ chipboard test block.
Final Prototype and Future Iterations
Higher-fidelity prototypes would be made with soldered connections, which would eliminate the need for the power supply board and the excess wires. The device requires very little power, so I would use a much smaller battery and display, with the battery moved much lower to better distribute the weight. This would shrink the entire setup and allow the device to be much more like a pen. I would also like to examine a wider variety of materials for the scroll wheel than what I had on hand, with a focus on manufacturability. A production-level design should succeed on multiple surface materials and with a much smaller wheel for higher accuracy.