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WEEK 06 Electronics Design

GROUP ASSIGNMENT:

Understanding the Test Equipment

Multimeter

A multimeter is a device used to measure electrical properties such as voltage, current, and resistance. It helps in diagnosing circuit issues by providing precise readings of these parameters.

Oscilloscope

An oscilloscope is a tool used to visualize electrical signals over time. It displays waveforms, allowing us to analyze signal behavior, frequency, amplitude, and any distortions present in the system.

Experimental Setup & Observations

Calibration and Adjustment

  • We connected a new probe (sonda) to the oscilloscope and calibrated it for precise signal reading.

    calibration.jpg

  • By zooming in and adjusting the waveform display, we fine-tuned the compensation capacitance using a small screwdriver, ensuring minimal spikes at the beginning of each step.

Measuring Voltage Outputs

  • First, we used a multimeter to measure the output voltages of 5V and 3.3V to verify proper power supply operation.

33.jpg

50.jpg

Measuring PWM Signal

Pulse Width Modulation (PWM) is a technique used to control power delivery by rapidly switching a signal between high and low states. It allows fine control over components like LEDs and motors by adjusting the duty cycle (the percentage of time the signal is high in each cycle).

Arduino Code for PWM Output

int x = 0; // Declare x globally so it retains its value between loops

void setup() {
  pinMode(14, OUTPUT); // Set pin 14 as an output
}

void loop() {
  analogWrite(14, x); // Write PWM signal (0-255)

  x++; // Increment x

  if (x > 255) { // Reset x if it exceeds 255
    x = 0;
  }

  delay(250); // Wait 250ms
}

Debugging and Correction

Initially, we encountered an issue where the PWM signal did not behave correctly on pin 14 (A0).

pin14.jpg

To fix this we changed the output pin to pin ~3 and updated the code accordingly.

INDIVIDUAL ASSIGMNET:

KICAD

For my individual assignment, I first installed KiCad software: https://downloads.kicad.org/kicad/windows/explore/stable

Then, I attempted to reproduce the Quentorres Board: https://gitlab.fabcloud.org/pub/programmers/quentorres

I used the Fab Electronics Library for KiCad from https://gitlab.fabcloud.org/pub/libraries/electronics/kicad and followed these steps:

  1. Clone or download the repository and rename the directory to fab.
  2. Store it in a safe location such as ~/kicad/libraries or C:/kicad/libraries.
  3. Open KiCad or a KiCad .pro file.
  4. Go to Preferences → Configure Paths and add a new environment variable FAB that points to the fab library's location (e.g., ~/kicad/libraries/fab). This ensures proper 3D model loading.
  5. Go to Preferences → Manage Symbol Libraries and add fab.kicad_sym as a symbol library.
  6. Go to Preferences → Manage Footprint Libraries and add fab.pretty as a footprint library.

On the right panel, you can load elements from the library and connect them by drawing lines. If the schematic gets too messy, use TAGS instead of direct connections. This method is quite intuitive.

kicad_quantores_schemat.jpg

Once the schematic is ready, switch to the PCB design editor (1). A new window will open, where you need to update the PCB from the schematic (2), check for errors, and update (3). In my case, a footprint was missing, but for this exercise, I ignored it. If necessary, you can always upload missing libraries.

Initially, the layout is messy, but this is the fun part—designing the board by arranging components and routing connections.

kicad_quantores_schemat2.jpg

In the settings it is important to define design rules. For now I’ll just set up the track clearance and width .

kicad_quantores_pcb1.jpg

There’s also a build-in checker:

designrulescheck.jpg

designrulescheck2.jpg

KiCad is intuitive and similar to schematic design. However, remember:

  • The cutting line should be on a separate layer.
  • When exporting for CNC milling, define engraving vs. cutting correctly.

kicad_quantores_pcb2.jpg

Finally, you can visualize the 3D model of the board:

kicad_quantores_3d.jpg

FINAL PROJECT BOARD COMPONENTS

  1. REWARD MACHINE
    • XIAO ESP32-C3 – Controls logic and communication
    • **5V 2A Power Adapter** – Powers LEDs, servo, and ESP32
    • LED light stip (5 blue, 5 white, 1 green) – Visual feedback
    • Buzzer (30-50kHz ultrasonic) – Cat-friendly sound signal
    • Servo Motor (SG90) – Moves flap or dispenser
    • IR Sensor (TCRT5000) or Load Cell (HX711) – Detects treat release (optional)
  2. BUTTON
    • XIAO ESP32-C3 – Handles wireless communication
    • 3x AA (4.5V) + Boost Converter (to 5V) for long-lasting power
    • Push Button – Cat presses to trigger reward
    • 1 LED – Debugging/connection status
    • Buzzer (3-5kHz Piezo) – Connectivity feedback
  3. TREADMILL
    • XIAO ESP32-C3 – Handles sensor readings and wireless transmission
    • 4x AA (6V) + Buck Converter (to 5V) for extended operation
    • Rotary Encoder (KY-040) – Measures distance travelled
    • 1 LED – Debugging/connection feedback
    • Buzzer (3-5kHz Piezo) – Connectivity signal

  4. CLIMBING TOWER

    At this moment I’m considering adding the distance sensor into the button and making in 2in1 device and I’ll keep that possibility in mind. For now I’ll keep it simple and focus just on The Reward Machine + button + treadmill.

BUTTON

First, I tested my button circuit. My previous simulation in Wokwi had a small error:

  • I connected the button to 5V, but my instructor Ricardo (@Ricardo Marques) informed me that the Xiao ESP32-C3 pins only support 3.3V and ****using 5V could damage the microcontroller.

Here’s the corrected schematic:

kicad_button_wokwi.jpg

Power Regulation

I learned that I need a low-dropout linear regulator to connect Xiao to a battery. I found this regulator in the https://inventory.fabcloud.io/

regulator.jpg

And applied it to my schematic:

kicad_button_schemat.jpg

Here’s the PCB design and the 3D visualisation.

kicad_button_pcb.jpg

kicad_button_3d.jpg

Additional Notes from Ricardo:

  • The two sides of buttons are typically connected internally. This means you can ignore how KiCad wants to connect them—they are already connected.
  • All grounds on the Xiao ESP32-C3 are internally linked, so there is generally no need to connect them externally.

REWARD MACHINE

First, I designed this version:

kicad_RM_firsttry.jpg

Later, I realized I could use LED strip LEDs for debugging instead of adding a separate one on my board. Also, I didn’t need a power adapter since the Xiao ESP32-C3 has a USB-C port. Ricardo also suggested adding a button for convenience.

kicad_RM_schemat.jpg

Here’s the first approach to the PCB design and its visualisation (where I was expecting to see a real buzzer since in schematic I can see a speaker icon not a pin out, but maybe that’s better, I can place the speaker further from the board)

kicad_RM_pcb.jpg

kicad_RM_3d.jpg

FILES:

REWARD MACHINE

BUTTON:

CHECKLIST:

Group assignment:

  • Use the test equipment in your lab to observe the operation of a microcontroller circuit board (as a minimum, you should demonstrate the use of a multimeter and oscilloscope)
  • Document your work on the group work page and reflect what you learned on your individual page

Individual assignment:

  • Use an EDA tool to design a development board that uses parts from the inventory to interact and communicate with an embedded microcontroller

Learning outcomes:

  • Select and use software for circuit board design
  • Demonstrate workflows used in circuit board design

Have you answered these questions?

  • Linked to the group assignment page
  • Documented what you have learned in electronics design
  • Checked your board can be fabricated
  • Explained problems and how you fixed them.
  • Included original design files (Eagle, KiCad, etc.)
  • Included a ‘hero shot’