Arduino Circuit Analysis Results

Team: Manuel Ayala-Chauvin, Sandra Nuñez-Torres
Institution: Fablab - Universidad Tecnológica Indoamérica
Year: 2025

2. Measurement Results

Measured Parameter	Obtained Value
Voltage at Arduino digital output (control pin)	4.96V
Voltage across LED (anode-cathode)	1.85V
Voltage across resistor	3.11V
Current through LED (calculated with Ohm's Law)	9.42 mA

3. Analysis of Results

• The measured voltage at the Arduino output confirms the microcontroller is providing a 5V signal, verifying the digital configuration.
• The voltage drop across the LED is around 1.85V, which is typical for red LEDs.
• The calculated current using Ohm’s Law \( I = \frac{V}{R} \) with \( R = 330Ω \) is 9.42 mA, which is within the safe range for the LED.
• The LED remained ON without variations, indicating that no blinking code was executed in the Arduino.

Wokwi simulation

3.1. Experiment Objective

The goal is to use the oscilloscope to visualize the PWM signal generated by Arduino. This demonstrates how the duty cycle of the signal changes over time, affecting the LED brightness.

Wokwi simulation

3.2. Tools Used

• Arduino Uno → Generates the PWM signal on pin 6.
• Oscilloscope → Allows us to observe the signal and verify its variation.
• Connection wires → To connect the oscilloscope to the circuit.

The images show an experiment using an Arduino Uno and a Siglent SDS 1202X-E oscilloscope to observe the PWM signal generated by the microcontroller.

The oscilloscope displays a flat line at 3.3V, indicating that the measured pin is in a constant HIGH state (no PWM modulation visible yet).

The oscilloscope shows a 5V signal, meaning the measured pin is in HIGH state without variations.

A pulsed (PWM) signal appears, with transitions between 0V and 5V. This confirms that Arduino is correctly generating the PWM signal.

3.3. Code Explanation

The Arduino code implements a progressive fading effect on an LED connected to pin 6 using PWM (Pulse Width Modulation).

- Variables:

• led = 6; → Defines pin 6 as the LED output.
• brillo = 0; → Stores the LED brightness level (PWM value from 0 to 255).
• aumento = 5; → Defines how much the brightness increases or decreases in each iteration.

- Initial Setup (setup)

pinMode(led, OUTPUT); → Configures pin 6 as an output.

- Main Loop (loop)

• analogWrite(led, brillo); → Sends a PWM signal to the LED.
• brillo = brillo + aumento; → Increases or decreases brightness.
• If the brightness reaches 0 or 255, the aumento direction is reversed.
• delay(100); → Waits 100 ms before the next update.

3.4. Expected Behavior

The LED gradually increases in brightness until it reaches the maximum (255). Then, it gradually dims until it reaches 0. This cycle repeats indefinitely.

Arduino Code Screenshot

3.5. Arduino Code Download

Click the link below to download the Arduino code:

PwmLED.ino

4. Additional Observations

• No voltage fluctuations were detected in the circuit power supply.
• The LED is correctly oriented (anode connected to the Arduino output pin, cathode to the resistor).
• To further analyze the circuit, the Arduino code could be modified to make the LED blink and observe the waveform using an oscilloscope.

5. Conclusion

The circuit functions correctly based on the performed measurements. The LED receives the appropriate voltage, and the current remains within the recommended limits. Further testing could involve programming variations in the Arduino output signal and using an oscilloscope to visualize the waveform.

• The PWM signal generated by Arduino was successfully visualized.
• The oscilloscope confirmed how the signal changes according to the control code.
• The experiment demonstrated how microcontrollers generate PWM signals and how to measure them using laboratory equipment.

Individual Assignment: Development Board Design Using an EDA Tool

Objective

The goal of this assignment is to design a custom development board using an EDA (Electronic Design Automation) tool, incorporating components from the inventory and enabling interaction and communication with an embedded microcontroller.

1. Selection of Components

For this project, the following components were selected:

• Microcontroller Module: Seeed Studio XIAO RP2040
• LED Indicators: Two 1206 SMD LEDs
• Resistors: Two 1206 SMD resistors
• Buzzer: To provide auditory feedback
• Connector for Servo Motor: To allow control of external actuators
• Pin Headers: For expandability and debugging

2. Schematic Design

Using KiCad, the schematic was designed with:

• The microcontroller module as the central unit
• LED indicators connected via resistors for status feedback
• A buzzer connected to a digital output
• A servo motor interface
• Proper grounding and power distribution

Schematic Capture

The schematic was created in KiCad, ensuring proper electrical connections and component placement.

This circuit operates by using digital pin D5 of the microcontroller, which when set to HIGH allows current to flow to both a buzzer and two LEDs connected in parallel. Each LED is paired with a limiting resistor (R1 and R2) to protect the components from excessive current. When D5 is HIGH, the LEDs turn on and the buzzer emits sound, providing both visual and audible indication that the system is active. When D5 is set to LOW, the current is cut off, turning off the LEDs and silencing the buzzer, indicating the system is inactive.

3. PCB Layout Design

After verifying the schematic, the PCB layout was designed:

• Two-layer board to optimize routing
• SMD components for compact design
• Vias and traces optimized for signal integrity

PCB Layout

The placement of components ensures short signal paths, proper spacing, and clearances for manufacturability.

3D Visualization of PCB

A 3D render of the PCB was generated to inspect the component placement and board design.

4. Final Adjustments and Verification

Final adjustments included:

• DRC (Design Rule Check) Analysis to detect potential issues.
• Footprint Validation to ensure correct component dimensions.
• Connections Review for proper routing.

5. Conclusion and Next Steps

The board is ready for fabrication and assembly. Further improvements could include:

• USB connectivity
• Additional sensor interfaces

The design meets the project requirements for embedded microcontroller interaction and peripheral communication.

Reflection

This project provided a hands-on approach to designing a custom development board using EDA tools. It enhanced skills in:

• Schematic design and PCB layout
• Component selection and integration
• Design validation and debugging