Week 6 – Electronic Design

2. Definitions of Technical Equipment

3. Electrical Fundamentals

3.1 Ohm’s Law

Ohm’s Law relates voltage, current, and resistance:

V = I × R

Where:
V = Voltage (Volts)
I = Current (Amperes)
R = Resistance (Ohms)

Derived forms:
I = V / R
R = V / I

3.2 Electrical Power

Power is the rate at which electrical energy is consumed.

P = V × I

Alternative forms using Ohm’s Law:
P = I² × R
P = V² / R

Where:
P = Power (Watts)

Example – LED with ESP32-C3

ESP32-C3 GPIO = 3.3V
LED forward voltage ≈ 2.0V
Desired current = 5mA (0.005A)

R = (3.3V − 2.0V) / 0.005A
R = 260Ω

Standard value used: 220Ω

Power dissipation in resistor:
P = V × I
P = 1.3V × 0.005A
P = 0.0065W (6.5mW)

A 1/4W resistor is more than sufficient.

4. Using the Multimeter

4.1 Measuring Voltage

Purpose: Verify correct power supply levels.

1. Turn on multimeter.
2. Select DC Voltage (<20V range).
3. Connect black probe to GND.
4. Connect red probe to measurement point.

Measurements performed:
Working battery → 8.9V
Dead battery → 1.2V
ESP32-C3 3.3V output → 3.2V

This confirmed proper voltage regulation.

4.2 Measuring Resistance

Purpose: Confirm resistor value.

1. Power off circuit.
2. Select Ω mode.
3. Place probes across resistor terminals.

Measured value: 220Ω

4.3 Testing Continuity

Purpose: Ensure circuit connections are closed and solder joints are correct.

1. Turn off power.
2. Select continuity mode (beep symbol).
3. Touch probes across GND connections, LED terminals, PCB traces.

Beep indicates closed circuit.

4.4 Measuring Current

Purpose: Determine actual current consumption.

Current must be measured in series.

1. Disconnect power.
2. Open power line.
3. Set multimeter to DC mA mode.
4. Insert multimeter in series.
5. Reconnect power.

Measured value for blinking LED circuit: 5.4 mA

5. Using the Oscilloscope

5.1 Setup

1. Turn on oscilloscope.
2. Select DC coupling.
3. Adjust Voltage scale (Volts/div) and Time scale (Time/div).

Calibration was required to properly visualize the waveform.

5.2 Observing GPIO Blink Signal

The ESP32-C3 was programmed with a blinking LED (100 ms interval).

Probe connections:
Tip → GPIO pin
Ground clip → GND

Observed waveform:
Square wave
0V (LOW)
3.3V (HIGH)

5.3 Changing Frequency

LOW = 500 ms
HIGH = 100 ms

The waveform width changed accordingly, demonstrating duty cycle variation.

5.4 Observing Serial Communication

We transmitted character “K”. ASCII binary: 111101011

Oscilloscope displayed Start bit (0), Data bits, Stop bit (1).

This confirmed correct digital serial transmission.

6. Key Learning Outcomes

• How to safely use a multimeter.
• How to measure voltage, resistance, current, and continuity.
• How to validate power integrity in a microcontroller board.
• The difference between DC average measurement and time-based waveform visualization.
• How digital signals appear as square waves.
• How theoretical calculations compare to real measurements.

7. Individual Contribution – Diego Zhindón

7.1 XIAO Board Used for Measurement

For the practical measurements, I used a XIAO board. This board works mainly with 3.3V logic, while it can also expose the 5V USB rail depending on the power source. These two voltages were used as the first measurement points in this practice.

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%)
}

10.2 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%)
}

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. Reflection

• This group assignment provided practical experience using laboratory test equipment to analyze a microcontroller system. By validating electrical parameters on the ESP32-C3 board, we reinforced fundamental concepts such as Ohm’s Law, power dissipation, signal integrity, and digital waveform behavior.
• These skills are essential for the upcoming PCB design and fabrication stages, where electrical validation becomes critical before hardware deployment.
• 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.
• 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.