Tag: engineering

  • Mechatronic Project – Arcade Game Machine

    One of the most fun and interesting projects that I’ve worked on during undergraduate was for a mechatronic class where I and my team designed and built and arcade game machine from scratch. The project inspiration started with the extra LED lights leftover from the midterm project. Our team wanted to exploit the power of LEDs and utilize them for the final. Many different ideas were considered, and we initially settled on a TV screen. The TV screen can be used for displaying animations and music videos, but the idea of a video game was enticing. Combining the two concepts, we started to work on wiring the LEDs to a prototype PCB. As the screen was being made, the idea of developing an Arcade cabinet to turn the TV screen into an Arcade machine inspired the team and this became our final project proposal. I was responsible for building the Pacman game and assisted with electrical wiring as well as programming music. Below is an embedded Youtube video of our final product.

    Arcade Cabinet Construction and Design Functionality

    The Arcade Cabinet was designed to mimic the functionality of a real video arcade machine. Functionality includes ergonomic joypad, ease of access for maintenance, glare shroud, electrical inner storage, and aesthetics. The main materials of the cabinet include popsicle sticks, hot glue, foam poster board, felt padding, a cup holder, and Rubbermaid plastic.

    The ergonomic joypad was covered in felt padding for comfort and was designed to be separate from the main cabinet to provide ease of access for maintenance. The maintenance access is essential for wire assembly and troubleshooting. The joystick and button wires feed under the joypad and into the electrical inner storage area, which is located at the base of the arcade cabinet. The electrical storage area is home to all the wires connecting to the uc32 microcontroller board. It is also home to a dual battery power source and twin speakers. A fun highlight of the team’s arcade machine is a cup holder for the user’s beverage. The cupholder is located on top of the cabinet, which sets just above the video screen.

    Electrical Design

    Wiring Diagram

    The size of the LED matrix was determined by the number of I/O pins available on the uC32, using all the pins on the right side and leaving the left side open for other devices. The arcade machine uses all but 3 I/O pins available.

    All wiring and routing is done on the prototype PCB, this eliminates the need for a breadboard and creates a more compact design, male and female headers are used to make connecting the prototype PCB to all other components easy and organized.

    LED Matrix

    The common anode RGB LEDs are wired in a matrix as depicted above. This method allows us to control 189 individual LEDs using only 30 pins. To turn on an LED, the desired row (C1-C9) is set to HIGH and the desired colors are set to LOW. while it’s possible to set the entire row at once, each LED is scanned individually as the uC32 cannot supply enough power for multiple LEDs at once without losing color accuracy.

    Joypad

    The joypad is a simple input device consisting of a joystick and 3 separate momentary switches. Though it would have been possible to wire the buttons in a matrix to use less pins, the increased complexity was not worth opening a single pin. All inputs are digital and pulled down to ground when not activated and can be used simultaneously.

    Speakers

    The speakers were originally connected directly to the uC32 and ground. Due to the low but audible sound, a transistor was implemented to amplify the signal. In addition, potentiometers were added before the amplifier to control the volume of each speaker individually. Though it would have been possible to use the DAC on the uC32 for more sophisticated control of the speakers, however, the simpler control method suited the needs for the project.

    Featured Games

    The Arcade machine menu is a selection of games consisting of Tetris and Pacman. The Tetris game is played with two push buttons and the joystick. The push buttons are used to change the block orientation and the joystick allows the block to be moved left, right, up and down the screen. There is no level up in the game. However, the game difficulty increases with each additional line completed. The Pacman game utilizes only the joystick as physical input. The user can move Pacman in four directions, left, right, up and down the maze. The game has four main built-in levels with increasing difficulty in the maze pattern and in the ghosts’ speed. From the main menu, the user can also listen to Jingle Bell while watching the colored Christmas tree being displayed on the screen.

  • Geometric Dimensioning and Tolerancing

    Image from Autodesk, Geometric dimensioning and tolerancing (GD&T) in design and manufacturing

    In the past couple weeks, I attended another training session at work on Geometric Dimensioning and Tolerancing (GD&T).

    GD&T is a symbolic language used in engineering drawings to define and communicate tolerances or allowable variations in a part. GD&T is governed by ASME Y14.5 standard and is widely used in industries requiring high-precision components such as aerospace and automotive.

    GD&T is a topic that I had briefly learned about in my undergraduate curriculum but had never had the proper training to fully understand the tool. In my early career, it was discouraged to use GD&T in my engineering because it tends to increase the cost of the parts due to high inspection requirements. However, if use correctly, GD&T can reduce the total manufacturing costs by removing ambiguity in the interpretation of design intent, improve assembly fit by allowing functional tolerances and reduce scrap rate. It provides a way for companies to control the quality of parts received from the suppliers and prevents disputes that might lead to increase in procurement cost.

    GD&T History

    The concept of GD&T was developed by Stanley Parker, an engineer at the Royal Torpedo Factory in Scotland during World War II. He observed wartime production issue where many parts were being rejected due to imperfect measurements. Even in cases where the discrepancy is small, the parts still fail to meet functional requirements. Parker then came up with the concept of true position (the theoretical exact location of a feature on a part) and tolerance zone (the specific 3D space or boundary that constrain the variation of a feature). In 1940s, the U.S. military developed the first standards for GD&T, MIL-STD-8. In 1982, the American Society of Mechanical Engineers (ASME) released the Y14.5 standard, which inherited and modernized those principles established from the original MIL-STD-8. The latest revision of ASME Y14.5 standard was released in 2018.

    Image from Metal Craft Industries

    GD&T Feature Control Frame

    Image from Fictiv, GD&T 101: Our Guide to Geometric Dimensioning and Tolerancing

    The GD&T feature control frame is used to specify the tolerance values acceptable for a feature of a part. The tolerance value is the difference between the minimum and maximum dimension limits. For example, in the image above, the size of the feature is specified using a diameter symbol with a value 9 and a tolerance zone of plus or minus 0.25. The feature modifier Ⓜ is used to define additional tolerance of 0.500 at maximum material condition (smallest hole or largest pin). The feature is inspected relative to datum features A, B and C (a physical surface or an edge used as a physical contact point for inspection equipment) in order of importance, primary, secondary and tertiary datums.

    GD&T Pros and Cons

    Image from Eziil, What Are Tolerances in Engineering?

    GD&T provides a clear and complete way to communicate part design intent. It is universally interpretable, meaning that it can be understood in the same by all engineers, suppliers, manufacturers and quality inspectors. GD&T maximizes manufacturer’s freedom and thereby reduces costs.

    One disadvantage of GD&T is that it adds complexity to the drawings during design and review. The language might not be interpret and understood correctly by all manufacturers if not property trained.

    References

    “GD&T Basics – A Comprehensive Introduction to Geometric Dimensioning and Tolerancing.” Five Flute, www.fiveflute.com/guide/gd-t-basics-a-comprehensive-introduction-to-geometric-dimensioning-and-tolerancing/. Accessed 7 Mar. 2026.

    “Geometric Dimensioning and Tolerancing (GD&T) in Design and Manufacturing.” Autodesk, www.autodesk.com/solutions/geometric-dimensioning-and-tolerancing. Accessed 7 Mar. 2026.

    Lindenberger, Chris A. “Definition of Terms- Tolerance Zones.” Metalcraft, 11 Nov. 2018, metalcraftind.com/definition-of-terms-tolerance-zones/.

    “Precision Edge: Bilateral & Unilateral Tolerance.” EZIIL, eziil.com/tolerance-types/. Accessed 7 Mar. 2026.

    Willson, David, et al. “GD&T 101: Our Guide to Geometric Dimensioning and Tolerancing.” Fictiv, www.fictiv.com/articles/gdt-101-an-introduction-to-geometric-dimensioning-and-tolerancing. Accessed 7 Mar. 2026.

  • My Career

    I am a mechanical engineer with over five years of work experience in design development. I am currently working as a Structural Design Engineer on wing leading/trailing edges and winglet team for Boeing 737 program. Prior to joining the airframe team, I have also worked in payloads where I was responsible for designing interior commodities including windscreen, closet, partitions, class dividers, etc. I find engineering challenging but also rewarding because there is always something new to learn and I enjoy getting to understand how things work.

    Image from Marissa Nall via Puget Sound Business Journal

    Before Boeing, I’ve also worked for a smaller company called Sekisui Aerospace where I was involved in design development for a 777 passenger to freighter conversion program. As a design engineer, I get to work on the initial concept development and follow through the entire process from manufacturing to installation of the final products, supporting production as well as airline customer in troubleshooting in-service issues.

Kim Nguyen – IS 5320