PAGE 05 PAGE 07
WEEK #06

ELECTRONICS DESIGN

Drawing the nervous system. From digital blueprints to copper paths.

ALL ACCESS MISSION FILES (GITLAB REPO)

MISSION BRIEFING

This week's goal is to design a Printed Circuit Board (PCB) from scratch using an Electronic Design Automation (EDA) software. I will build the first brain of my Smart Goal project, adding a XIAO RP2040, a button, an LED, and expansion pins for an OLED screen.

For this mission, I chose KiCad because it is open-source, powerful, and strictly logical.

02. THE ARSENAL (INSTALLING FAB LIBRARIES)

To ensure my digital design matches the real components we have in the Fab Lab inventory, the first critical step was installing the official Fab Academy Library in KiCad.

Installing KiCad Fab Library
Adding the Fab footprint and symbol libraries in KiCad's Plugin and Content Manager.

03. THE BLUEPRINT (SCHEMATIC DESIGN)

I started placing my components in the schematic editor. I added the Seeed Studio XIAO RP2040 as the main brain, a 1206 LED, a tactile button, and headers for the future OLED screen.

Placing Components
01. Placing components.
Wiring the Schematic
02. Connecting pins.

ASSIGNING FOOTPRINTS

ERC CHECK

COMPONENT LOGIC & CALCULATIONS

Before wiring the schematic, I needed to define the specific values for my components to ensure the circuit works safely. The brain of the board is the XIAO RP2040, which operates at a 3.3V logic level. For visual feedback, I am using a standard 1206 SMD LED.

LED Resistor Calculation:
To prevent the LED from burning out, I needed to calculate the correct current-limiting resistor using Ohm's Law (R = V / I).

  • Source Voltage (Vs): 3.3V (Output from the XIAO RP2040)
  • LED Forward Voltage (Vf): ~2.0V (Standard for a Red/Green LED)
  • Desired Current (I): 10mA (0.01A) for a bright but safe light

R = (3.3V - 2.0V) / 0.01A = 130 Ohms

Since 130 Ohms is the absolute minimum required, I chose a standard 330 Ohm resistor from the Fab Lab inventory. This slightly higher value keeps the LED perfectly visible while saving power and ensuring a long lifespan for the component.

05. THE SECRET IDENTITY (INKSCAPE TO KICAD)

I wanted the PCB to have the shape of the Puebla soccer team shield! Importing a complex SVG directly into KiCad's Edge.Cuts layer often causes double-line errors. I used Inkscape to clean it up.

Original Reference Image
This was the original logo reference for my board's shape.

now let´s go to import the schematic.

04. THE COPPER LABYRINTH (PCB LAYOUT)

With the logic defined, I crossed the portal to the physical world by updating the PCB from the schematic (F8).

ESTABLISHING DESIGN RULES

Before routing a single track, I had to establish the Design Rules in KiCad's Board Setup. Since we are milling this board locally on a Roland SRM-20 instead of ordering it from a commercial factory, the physical size of our cutting tools dictates our digital rules.

  • Minimum Clearance (0.4 mm): This is the most critical constraint. The endmill used to isolate the copper traces is 1/64 inch (approximately 0.4 mm) wide. If the space between two traces is less than 0.4 mm, the machine's endmill physically cannot pass through, and the traces will remain connected, causing a short circuit.
  • Track Width (0.8 mm): Milling puts mechanical stress on the copper layer. While 0.4mm is the minimum, I set my default net class width to 0.8 mm. This guarantees highly robust paths that won't rip off the fiberglass board during cutting or when applying heat with the soldering iron.

06. 3D INTERACTIVE REVEAL

Final 3D Render
The final 3D Render from KiCad.

"Smart Goal v1.0" by Javier Vega on Sketchfab