Electronic Design

Basic Electrical Concepts

Charge is a fundamental property of subatomic particles. Protons carry a positive charge, electrons are negative, and neutrons are neutral. Atoms, the building blocks of all elements, have a nucleus made of protons and neutrons, with electrons orbiting around it.

Voltage appears when electrons are unevenly distributed, creating a potential difference. It’s measured in volts (V) and represents the energy applied per unit charge. This imbalance is what pushes electrons to move and try to restore equilibrium.

Current is simply the flow of electrons caused by that voltage difference, and it’s measured in amperes (A).

Direct current (DC) flows in one steady direction.
Alternating current (AC) periodically changes direction.

Resistance describes how easily electrons can move through a material. It’s measured in ohms (Ω). High resistance restricts current; very low resistance allows a large current, sometimes too large, leading to a short circuit.

Ohm’s Law ties voltage (V), current (I), and resistance (R) together:

V = I × R

The Multimeter & Breadboard

A multimeter measures voltage, resistance, and current in a circuit. It’s also your best friend when debugging, especially for continuity checks.

A breadboard is a rapid-prototyping tool that lets you connect components without soldering, making it perfect for quick circuit testing.

Electronic Design

Designing electronic systems means understanding components and how they interact.

Starting simple:

Resistors Passive two-terminal components that provide electrical resistance in a circuit.

Capacitors Two-terminal passive components that store energy in an electric field. Their main job (in our case) is smoothing out high-frequency noise on power lines.

Diodes Two-terminal devices that conduct primarily in one direction: low resistance forward, high resistance backward.

Oscillators Circuits that generate periodic signals.

Regulators DC linear regulators keep output voltage stable even when the input supply fluctuates.

Transistors Essentially controlled switches. For example: letting a microcontroller drive a higher-power load like a light.

Each component comes with specific electrical limits and recommended operating conditions. The datasheets is where the real truth lives, always check it.

Electronic Design Automation

EDA tools help design and simulate circuits. In FabAcademy we’re using KiCad, an open-source tool for schematics and PCB layout.

Key concepts:

Symbols → logical representation in the schematic
Footprints → physical pad layout on the PCB
PCB (Printed Circuit Board) → the actual board where everything connects

The PCB is where the magic happens.

Designing My First Board

This week I finally sat down to design my first board on my own. I’ve worked around electronics before. but proper PCB design always felt like unexplored territory.

Rather than overcomplicating things, I deliberately kept the scope small. The goal was simple: understand the workflow end-to-end and build confidence through something manageable.

I went with a minimal setup:

1 button
1 LED
1 ATtiny microcontroller
current-limiting resistors for the LEDs
1 decoupling capacitor
USB-A for power
UPDI for programming

Nothing extravagant, just a clean foundation to build on.

Requirements

The ATtiny line is well suited for compact, low-pin-count designs, which made it a natural fit for this board.

With that decided, I opened KiCad, created a new project, and moved into the Schematic Editor.

From there:

Preferences → Manage Symbol Libraries

I loaded our local FAb Lab libraries and disabled the default KiCad ones. The idea was to avoid selecting components that we don’t physically stock.

After that, pressing A on the canvas brought up the symbol browser.

I selected the ATtiny412. A quick check of the datasheet confirmed it operates at 5 V, so powering the board from USB-A (5 V) was perfectly valid.

I then added the remaining components until the schematic was complete.

Design Reasoning

The ATtiny412 provides 8 pins in total:

VCC → 1 pin
GND → 1 pin

That leaves 6 GPIO pins available for the design.

Power considerations

Since the board is powered from USB, I added a Unpolarized capacitor to smooth potential supply noise.

Chosen value: 10 µF This value is commonly used in similar reference designs and provides adequate bulk decoupling for a small board.

Programming interface

Using USB data lines would have consumed two I/O pins. Instead, I selected UPDI, which only requires:

1 data pin
plus VCC and GND

This keeps the pin budget efficient.

Button input

The button was assigned to a dedicated GPIO pin with a pull-down resistor to ensure a defined logic state when the switch is open.

From Schematic to PCB

Connection labels were added to clarify signal routing (available from the right-hand tool panel).

Once the schematic was validated, I moved to the PCB Editor using the top-right shortcut.

If the PCB view appears empty, updating from the schematic populates the board with the components.

Routing followed next, manually laying out copper traces between components. It’s a careful balance between readability, spacing, and manufacturability.

After roughly an hour of routing and cleanup, the board layout was complete.

For this iteration I kept the board outline simple. More experimental shapes can come later once the fundamentals are fully internalized.