Carnegie Mellon ECE Capstone, Fall 2025 – Safiya Bainazar, Tedd Jung, Crystal Huang
I was able to get the LEDs to vary in brightness demonstrating a PWM signal. I am experimenting with different approaches to get 4 servos moving in parallel.
I am behind schedule. I will try to put in more hours to get more progress. Next week I hope to be able to have 4 servos moving in parallel.
A – Our product is a low cost alternative to other motorized pin displays. Our low cost and modular approach enables accessibility that can be sourced internationally, allowing replication in museums worldwide. This open and scalable approach encourages cross cultural collaboration in art installations. The ease of use enables users who are not well versed in technology.
B – LivePin is designed with sensitivity to cultural diversity and inclusivity in communication and collaboration. As an interactive system for museums and for children/adults, the device enables users to communicate three-dimensional ideas without reliance on a shared language or cultural context. This visualization system reduces the potential for misinterpretation of visual or linguistic descriptions and promotes equality regardless of language proficiency. Moreover, by enabling hands-on, physical interaction with digital content, LivePin aligns with cultures that value craftsmanship and learning. The design also respects differing cultural expectations of professional communication by providing a neutral, technology-driven medium for expression and art.
C- Our solution addresses the need for rapid, tangible 3D visualization in classrooms and small exhibits without generating one-off physical waste. Instead of printing and discarding plastic prototypes for every iteration, the system renders forms on a reusable pin board, then resets for the next concept. This directly reduces consumables (no filament, supports, or failed prints) and cuts the time and material tied up in single-use models, while still giving viewers a clear, physical sense of shape and depth.
Environmental considerations are built into the design. The frame uses durable, recyclable aluminum. The guide plates are laser-cut for low scrap, and the pins are wooden dowels that are inexpensive, repairable, and biodegradable. During operation, staged actuation keeps power draw modest relative to continuous additive manufacturing, and the system produces no consumable byproducts once a visualization is complete, the board simply resets. Taken together, the design conserves materials, lowers operational waste, and supports responsible end-of-life handling through reuse and recyclability.
A was written by Crystal. B was written by Tedd J. C was written by Safiya
This week I started getting the STM32 setup by configuring the timers and GPIO pins to generate a PWM signal. This has not been successful yet, but I will verify the setup by output putting the PWM signal to an LED.
I am slightly behind on schedule due to workload from other classes. I will put in extra hours this weekend to get the LED to vary in brightness with duty cycle, demonstrating the PWM signal.
Next week I hope to be able to have 4 servos moving in parallel.
After further designing our project, we identified several risks. A big concern is actuator reliability. The RC servos may stall, strip gears, or fail to deliver our desired accuracy under load. To mitigate this we will do early bench testing of the servos with the rack and pinion to see if they can deliver the desired results. Another concern is gantry misalignment.
A significant change we made to our design is scaling up our design from 16 x 16 pins to 32 x 32 pins. This change was necessary due to concerns of low resolution. Though you can see Abraham Lincoln with 16 x 16 pins (image below). We originally decide to only have 16 x 16 pins to comfortably afford 16 actuators, but with a more detailed bill of materials we concluded we could afford 32 actuators.
Part A:
The primary purpose of our solution is for entertainment that brings a familiar pin toy concept into a dynamic, automatic form. From a health and well-being standpoint, it offers a playful, low-stress form of interaction. Unlike more physically demanding entertainment technologies, the system is hands-free and does not require repetitive strain, making it safe and comfortable for users of all ages.
Safety is carefully addressed in both mechanical and electronic design. The pins are covered by an acrylic pane to prevent accidental pinching or injury. Furthermore the reset button acts moves the device into a safe state where pins are reset. Protective housing and controlled motion paths further reduce hazards, ensuring that the entertainment experience remains safe and reliable.
Part B:
Our product solution is designed to foster social connection and shared experiences through entertainment. By transforming the classic pin-art toy into an interactive, automated and affordable display, it creates a platform where groups of people can gather, observe, and engage with the visual output together. This collective interaction encourages conversation, collaboration, and bonding. The system therefore becomes more than just a device. It becomes a medium for social engagement.
Part C:
A big focus of our project was creating a 2D to 3D display while being affordable. As any projects that were done before that had actuating pins were extremely expensive and thus making it out of reach for casual applications and environments, such as schools and homes. To accomplish our goal of a live pinScreen, we had to create a mechanism that would push each row of pins, which is mechanically more difficult, but in the long term it is cheaper and more accessible.
Additionally our design controls cost by using a shared actuator head instead of one motor per pin, so resolution scales mostly with low-cost passive parts rather than expensive motors, drivers, and power. Major cost drivers are the frame/linear hardware, a small set of servos, and the depth-camera/Pi. Operating costs are low , and the architecture lets us scale up affordably by adding pinScreen tiles without redesigning the actuation/control stack.
A was written by Crystal, B was written by Tedd and C was written by Safiya.
This week I continued designing the actuator subsystem of the project. We decided to use a RC servos to power rack and pinions that will actually push the pins. However, each servo would need their own continuous PWM signal and using 32 independent channels directly on one STM is impractical. This means we need an external PWM driver IC.
We are still on schedule. We hope to order parts by the end of next week.
So far, I’ve worked on shaping the project by carefully identifying the right components and mechanisms to make it feasible. I started by analyzing the cost and scalability issues of giving each pin its own actuator, realizing that this would exceed our $600 budget, so I explored alternatives like row-based actuation and column scanning. This week I listed different position based actuator parts we could use and narrowed it down to a few. On the electronics side, I mapped out how to divide responsibilities between a Raspberry Pi (for real-time depth capture and heightmap processing) and an STM32 (for deterministic actuator control), since the Pi can’t handle precise timing and the STM32 can’t handle heavy vision workloads. I also investigated specific ways to test latency, weighing options like software timestamps versus high-speed video, to ensure I can measure each subsystem’s delay as well as the full end-to-end pipeline.