Week 16 - System Integration

The objective of this week was to integrate the electronic system into the final project in a clean, safe, and functional way. For this task I designed a case that holds the custom PCB of the project and organizes the wiring that connects the board with the motion sensor used in the Smart Lean Cell.

The case was designed in Fusion 360 and fabricated with a Bambu Lab 3D printer. The final object protects the PCB, keeps the connectors accessible, and allows the electronics to be presented as part of the final system instead of remaining loose on the table.

Before fabricating the enclosure, I defined a system integration plan for the Smart Lean Cell. The goal was to transform the electronics from a set of exposed components into a packaged subsystem that could be installed, inspected, connected, and presented as part of the final product. This plan considered the PCB footprint, the XIAO ESP32-C3 USB-C access, HC-SR04 sensor wiring, power lines, cable routing, visibility, maintenance, and the physical position of the module inside the final workstation.

1. Define interfaces: identify which elements had to connect to the PCB: USB-C power/programming, HC-SR04 sensor cables, status LEDs, power pins, and jumper connectors.
2. Design the package: create a Fusion 360 enclosure with internal clearance for the PCB, cable exits, front visibility, and an inclined angle for presentation.
3. Fabricate and test fit: print the enclosure using a Bambu Lab 3D printer and verify that the board, headers, and cables fit without mechanical stress.
4. Integrate with the final project: mount the packaged electronics in the Smart Lean Cell so it is accessible, protected, and visually consistent with the rest of the prototype.
5. Document and reproduce: publish CAD screenshots, photos, videos, and downloadable 3MF/STL files so the enclosure can be reviewed or fabricated again.

The system integration work was not limited to designing a protective enclosure. The enclosure was one subsystem inside the complete Smart Lean Cell, a learning station where children interact with an assembly process while the electronics measure what happens in real time. The complete integration connects the physical workstation, the organized Lean tools, the sensing system, the custom PCB, the embedded firmware, the Blynk dashboard, and the user feedback elements.

Architecture Diagram

The diagram below shows how the main subsystems interact. The child performs the assembly activity in the workstation, the sensors detect inventory and finished parts, the PCB processes the signals with the XIAO ESP32-C3, and the software layer sends live values to the dashboard. The case designed in this week packages and protects the control board so it can be safely installed as part of the final product.

Integration Flow

1. Preparation: the physical Lean tools organize the parts before the activity begins. This supports 5S and reduces searching time.
2. User interaction: the child takes a part from the inventory area and starts the assembly challenge.
3. Sensor event: the inventory HC-SR04 detects when the part leaves or enters the inventory station.
4. Embedded processing: the custom PCB receives the sensor signals through protected input lines and the XIAO ESP32-C3 runs the cycle logic.
5. Status feedback: the firmware updates status LEDs and sends process values through WiFi.
6. Software interface: Blynk receives the values using virtual pins and displays distance, cycle time, average time, pending cycles, inventory, finished parts, and productivity.
7. Finished part event: the second sensor detects the completed assembly and the system closes the cycle measurement.
8. Learning feedback: the dashboard gives immediate information so the learner can compare attempts and understand improvement.

Subsystem Interfaces

To validate system integration, I checked that the mechanical station, sensors, PCB, firmware, dashboard, and user interaction worked together. The goal was not only to verify that the printed enclosure fit the PCB, but also to confirm that the packaged electronics could operate inside the Smart Lean Cell while the user performs the assembly activity.

The integration required the mechanical case, the electronic control board, and the components needed to connect the sensing system. The BOM was kept simple because the goal was to make the electronic subsystem easier to mount, inspect, and maintain.

The design started by measuring the PCB and defining the internal volume required to place the board without pressing the headers or the USB-C connector. The case needed enough clearance for the cable connectors, the sensor wires, and the power/programming cable. For this reason, the design includes side and rear openings for routing cables.

In Fusion 360 I first created a rectangular sketch based on the PCB footprint. Then I added the external frame, the internal cavity, mounting slots, and a front opening that allows the board to be visible. The case also has an inclined body so the PCB can be presented at a readable angle in the final project.

After finishing the model, the case was exported for 3D printing and prepared for fabrication on a Bambu Lab printer. PLA was selected because it is rigid, easy to print, and strong enough for a protective electronics enclosure. The print was oriented so the main cavity remained clean and the front frame had a good surface finish.

During printing, I checked the first layers and the adhesion to the build plate. This was important because the case has a flat base, thin walls, and long slots that need to remain dimensionally stable to fit the PCB correctly.

Once the print was finished, the PCB was placed inside the case to check the fit. The board was aligned with the internal rectangular area and the slots were used to route the cables without bending them sharply. The front opening makes it possible to inspect the PCB, verify the connections, and access the USB-C port of the XIAO ESP32-C3.

The HC-SR04 sensor was connected to the PCB using jumper wires. The sensor was positioned in the final project so it could detect object presence near the assembly area. The case works as the electronic control module of the project: it groups the board, protects it, and separates the electronics from the moving or handled parts of the prototype.

The final integration connects the mechanical, electronic, and sensing parts of the project. The printed case gives the PCB a defined location inside the Smart Lean Cell, while the HC-SR04 sensor detects movement or object presence near the working area. This makes the electronics easier to present, debug, and protect during demonstrations.

The case also improves the visual presentation of the final project. Instead of showing loose wires and an exposed PCB, the electronics are organized as a module that belongs to the system. This is important because the final project is not only a set of separate parts; it must work as one integrated prototype.

The packaging method was based on a simple requirement: the electronic system had to be protected without hiding its function. For this reason, the PCB is visible from the front of the case, but the board is no longer exposed to direct handling. The enclosure creates a defined boundary between electronics, cables, sensors, and the learner interaction area of the Smart Lean Cell.

The printable case files are available below. The 3MF files preserve the slicer-ready geometry used for the PCB enclosure, while the STL files provide a more universal format that can be opened in most CAD viewers and 3D printing slicers. Both formats are included to improve accessibility and reproducibility.

This week helped me transform the electronics from a functional prototype into an integrated subsystem for the final project. Designing the case in Fusion 360 allowed me to consider the real size of the PCB, the position of the connectors, cable routing, and presentation inside the Smart Lean Cell.

The Bambu Lab 3D print produced a rigid case that protects the board and makes the electronic module easier to install. The final result integrates the custom PCB, cables, HC-SR04 sensor, and printed enclosure into a more organized and professional system.