Electronics Design

1. Checklist

• ✅ Linked to the group assignment page
• ✅ Designed an electronic board using EasyEDA
• ✅ Documented the schematic and PCB workflow
• ✅ Exported manufacturing and editable files
• ✅ Measured board voltages using a multimeter
• ✅ Analyzed digital signals and PWM with an oscilloscope
• ✅ Included reflections about the assignment

2. Group Assignment

For the group assignment, the lab characterized and analyzed electronic behavior using measurement instruments such as the multimeter and the oscilloscope. This included observing voltage levels, signal behavior, and practical measurements on a microcontroller platform.

3. Introduction to Electronics Design

Electronics design is the process of creating a circuit that defines how electrical components interact to perform a specific function. In this week, the work included both the digital design of a PCB and the practical analysis of electrical behavior using laboratory instruments.

Some fundamental concepts are essential before starting the design and testing process. Voltage is the electrical potential difference that drives current through a circuit. Current is the flow of electric charge through conductors. Resistance limits the flow of current, and power is the rate at which electrical energy is transferred.

A simple and useful relation between these variables is commonly explained through Ohm’s Law triangle: voltage, current, and resistance are directly related by the expression V = I × R. In practical terms, this relationship helps determine how a resistor affects the current passing through a load such as an LED.

In this assignment I worked with direct current (DC), which is the type of current delivered by USB power and by the regulated lines used by the XIAO board. This is different from alternating current (AC), where voltage changes direction periodically.

4. Electronics Design Software

For the PCB development of this week, I used EasyEDA Standard Version in its online environment. EasyEDA is an electronic design automation platform that allows the complete workflow for board development inside the same software environment.

With EasyEDA, it is possible to create the schematic, search and place components from libraries, assign footprints, generate the PCB layout, verify component positions in 3D, and export manufacturing files such as Gerber, SVG, PDF, and editable project files.

One of its strengths is that the schematic and the PCB remain linked, so after defining the circuit connections, the board layout can be generated while preserving the same logical structure.

5. Schematic Design

The schematic is the first formal step in the electronics workflow. It defines the logical electrical relationships between all components, independent of their physical position on the final PCB.

5.1 Component Library

EasyEDA provides an integrated library that includes symbols, footprints, and many predefined components. This made it possible to search and place the required elements directly in the workspace.

5.3 Components Placed in the Workspace

After selecting the required elements, all components were placed in the schematic workspace to begin the electrical definition of the board.

5.4 Connections and Labels

The circuit connections were defined using both wires and signal labels. Instead of relying only on long direct wires, I used net labels to keep the schematic cleaner, reduce visual clutter, and simplify the reading of the design.

Another important point is that unused pins should not remain ambiguous. In the schematic, pins that were intentionally left unconnected were marked using the No Connect flag. This avoids false connection errors and improves design clarity.

The GND symbol was used as the common electrical reference for the board. Ground is fundamental because it defines the zero-volt reference point of the circuit. All voltage measurements are made relative to that reference, which is why connecting the measurement instruments correctly to GND is essential.

6. PCB Design

After verifying that the schematic was complete and electrically consistent, the project was transferred to the PCB layout environment. This stage defines the physical position of each component and the actual copper traces that connect the circuit.

6.1 Initial PCB Layout

Once the PCB was generated from the schematic, the components were arranged manually according to their function and the desired geometry of the board. This step is important because good component placement makes routing easier and improves the usability of the final design.

6.2 Routing

Routing is the process of creating the conductive paths that connect all components on the board. In this design, I used trace widths of 0.8 mm. This value provides a robust and easy-to-fabricate connection width for this board.

The board uses surface-mount components, which is common in compact PCB designs because it reduces overall size and supports organized routing around the board.

6.3 Ground Plane and Polygon Tool

After routing the signal traces, I used the polygon tool to generate a ground plane. A ground plane is useful because it creates a large common reference area, improves electrical stability, reduces noise, and can simplify the routing of return paths.

In this board, the ground plane was created with a clearance of 0.254 mm. Clearance is the minimum distance between the copper pour and the other traces or pads. It is important because it prevents unintended short circuits while allowing the polygon to fill the remaining copper area.

6.4 3D Visualization

EasyEDA includes a 3D viewer that allows checking the physical appearance of the board before fabrication. This is useful to confirm the component placement, general proportions, and the overall visual result of the design.

6.5 Fabrication Preview

EasyEDA also provides a preview of how the PCB would look in a professional fabrication process, including solder mask, plated holes, pads, and other manufacturing-level visual elements.

7. Measurement Instruments

After completing the design workflow, I moved to the practical part of the assignment by measuring and analyzing electrical behavior using a Fluke 117 multimeter and a Siglent SDS1052DL oscilloscope.

8. Voltage Measurements on the XIAO

The first practical step was verifying the main power rails of the XIAO. All voltage measurements were made with respect to GND, since ground defines the electrical zero reference of the board.

8.1 Measuring the 5V Rail

I first measured the 5V rail of the board. Using the Fluke 117 multimeter, the measured value was 5.066 V. On the oscilloscope, the signal remained stable around the DC level, with a recorded Vmax = 5.40 V and Vmin = 5.00 V.

8.2 Measuring the 3.3V Rail

The second measurement was the 3.3V regulated rail, which is especially important because it is the working logic level of the XIAO. Using the multimeter, the measured value was 3.295 V. On the oscilloscope, the voltage remained stable with Vmax = 3.36 V and Vmin = 3.32 V.

9. PWM Signal Analysis

One of the most useful experiments of this week was generating a PWM (Pulse Width Modulation) signal on pin D2 and observing its behavior in the oscilloscope.

PWM is a digital technique used to simulate analog behavior by rapidly switching a signal between HIGH and LOW states. What changes is not the maximum voltage, but the proportion of time that the signal remains in the HIGH state. This proportion is known as the duty cycle.

In this exercise, I tested three duty cycle levels to compare how the square wave changes while keeping the same peak logic voltage.

9.1 PWM at 25%

int pwmPin = 2;

void setup() {
  pinMode(pwmPin, OUTPUT);
}

void loop() {
  analogWrite(pwmPin, 64); // PWM low (25%)
}

9.2 PWM at 50%

int pwmPin = 2;

void setup() {
  pinMode(pwmPin, OUTPUT);
}

void loop() {
  analogWrite(pwmPin, 128); // PWM medium (50%)
}

9.3 PWM at 100%

int pwmPin = 2;

void setup() {
  pinMode(pwmPin, OUTPUT);
}

void loop() {
  analogWrite(pwmPin, 255); // PWM high (100%)
}

Comparing the three measurements made it possible to see how the waveform width changes while the logic amplitude remains defined by the XIAO output level.

10. Digital Square Wave with LED Blink

As a final practical exercise, I programmed the XIAO to turn an LED on and off every second using pin D2. This made it possible to observe a slower and more explicit digital square wave on the oscilloscope.

// BLINK DIGITAL - SQUARE WAVE (approx. 1 Hz)

int ledPin = 2;  // Pin D2

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  digitalWrite(ledPin, HIGH); // LED on
  delay(1000);                // 1 second

  digitalWrite(ledPin, LOW);  // LED off
  delay(1000);                // 1 second
}

This measurement is especially useful because it clearly shows the logic transition between HIGH and LOW states, making it easier to understand how a digital signal behaves over time.

11. Downloadable Files

12. Reflection

• This assignment helped me understand electronics design as a complete workflow rather than as an isolated PCB drawing task. I worked through the full process: selecting a design platform, understanding the role of the schematic, organizing component relationships, transferring the project to the PCB environment, defining routing decisions, and finally validating part of the circuit behavior with real measurements.
• One of the most important lessons was the difference between the logical representation of a circuit and its physical implementation. In the schematic, the priority is electrical clarity: identifying signals, defining references, and making the functional intention of the circuit understandable. In the PCB stage, the priority changes toward physical order, spacing, manufacturability, and usability.
• Working in EasyEDA helped me understand the value of an integrated EDA environment. It was useful to have the component libraries, schematic editor, PCB editor, 3D visualization, and file export tools inside the same system. This made the workflow more efficient and also helped me see how schematic decisions directly affect the physical board.
• Another important reflection was the value of keeping the schematic visually clean and technically explicit. Using net labels instead of excessive crossing wires made the design easier to read and maintain. In the same way, adding no-connect flags to intentionally unused pins was important to avoid ambiguity and show that each unused connection had been considered, not forgotten.
• The board design stage made clear that component placement is not only an aesthetic decision. The location of the XIAO module, LED, resistor, and headers strongly affects trace organization, routing simplicity, and the final usability of the board. Good placement reduces unnecessary crossings, shortens paths, and produces a cleaner board that is easier to fabricate and understand.
• Trace design was also an important learning point. Choosing a 0.8 mm trace width was not arbitrary; it reflects a balance between mechanical robustness, ease of fabrication, and practical layout clarity. This week helped me understand that routing is not only about connecting pads, but about defining reliable conductive paths that must respect space, order, and manufacturing constraints.
• The use of a ground plane was one of the most relevant design concepts of the week. Before this assignment, ground could easily be understood only as a symbol in the schematic, but now it became clearer that ground also has a strong physical meaning in PCB layout. The polygon-based ground plane helps create a common reference area, improves electrical stability, supports return paths, and can reduce noise in practical implementations.
• Defining a clearance of 0.254 mm also reinforced the idea that PCB design must follow physical rules, not only visual logic. Clearance is essential because it protects the electrical isolation between copper areas and prevents unintentional shorts. This made me more aware that PCB design is strongly tied to manufacturing capability and board reliability.
• The 3D visualization and fabrication preview stages were more valuable than I initially expected. They helped confirm not only the physical appearance of the board, but also the practical coherence between footprint selection, component arrangement, and expected fabrication results. Seeing the board in 3D and in manufacturing view gave more confidence before exporting the final files.
• Exporting multiple fabrication formats also showed that one electronic design can support different production workflows. Gerber files are intended for standard PCB manufacturing, while SVG, PDF, and monochrome image exports can support documentation, vector editing, or custom fabrication methods. This helped me understand that documentation and fabrication outputs are also part of the design process.
• On the measurement side, this week helped connect design theory with real electrical behavior. Using the Fluke 117 multimeter to verify the 5V and 3.3V rails reinforced the importance of using GND as the common electrical reference. It also made clear that voltage values are only meaningful when measured relative to a defined reference point.
• The oscilloscope practice with the Siglent SDS1052DL was especially important because it revealed behavior that a multimeter alone cannot show. While the multimeter gives a stable numeric value, the oscilloscope made it possible to observe waveform shape, pulse width, transitions, and signal timing. This was one of the strongest learning moments of the week.
• Observing the PWM signals at different duty cycles helped me understand much better how Pulse Width Modulation works. The key lesson was that PWM does not create a true analog voltage at the pin; instead, it changes the proportion of time that the signal remains in the HIGH state. Seeing the waveform at 25%, 50%, and 100% made this concept much clearer than reading it only in theory.
• The LED blink experiment was also very useful because it produced a slow and easy-to-read square wave. This made it easier to connect the programming logic with the electrical signal observed on the oscilloscope. It also reinforced practical concepts such as period, frequency, and logic transitions between HIGH and LOW.
• Another important reflection is that electronics design in Fab Academy is not only about producing a board that “looks correct,” but about creating something that can be understood, tested, fabricated, and later integrated into larger systems. In that sense, this assignment is directly valuable for future work involving sensors, actuators, control boards, and communication modules.
• Overall, this week gave me a stronger foundation in how electronic systems are conceived and verified. I now understand more clearly the relationship between design rules, schematic clarity, PCB layout decisions, manufacturing outputs, and real signal measurement. More importantly, I see electronics design as a bridge between digital planning and physical system behavior.