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ELECTRONIC DESIGN

TOOLS

KiCad
KiCad
Electronic Design Automation

Installation

The first step is to install a suitable software for circuit design. In my case, I used KiCad, as it is an open-source tool that allows seamless integration with other platforms for PCB post-processing.

I´ve installed the KiCad FabLib library using the Plugin and Content Manager. This library includes standardized symbols and footprints that correspond to the components commonly available in Fab Labs, making it easier to move from design to physical fabrication.

Electronics Schematic

Once the Fab library was installed, I began selecting the required components directly from the symbol editor, which allows the use of compatible footprints.

This workflow makes the design process faster as the selected components are already aligned with fabrication constraints during the PCB design stage.

You can also modify the values of the components directly within their properties, allowing you to adjust parameters such as resistance, capacitance, or other specifications according to the design requirements.

The following schematic was developed based on previously used designs in Fab Academy, built around a SAMD11C microcontroller. It represents a basic system that integrates power supply, USB communication, and input/output components. Working with this design helped me understand the PCB design workflow, as I did not have prior experience in this type of development. Around it, different subsystems are connected to enable its operation:

  • Power Supply System: The circuit receives 5V from the USB connector, which is regulated down to 3.3V (VDD) using a voltage regulator (LM3480). This voltage powers the microcontroller and the rest of the components. A capacitor is included to stabilize the voltage and reduce noise.
  • USB Communication: The USB connector provides both power (5V and GND) and data lines (D+ and D-), allowing communication between the board and a computer.
  • Programming Interface (SWD): A pin header is included for SWD programming, using signals such as RST, CLK, and DIO.
  • Input System (Button): A push button is connected to one of the microcontroller pins. A resistor acts as a pull-up, ensuring a stable logic state when the button is not pressed.
  • Output System (LEDs): LEDs with current-limiting resistors are included, serving as visual indicators for testing and verifying the system’s operation.
The schematic can be transformed into a PCB design using the board editor. All components are imported with their corresponding footprints in an unorganized layout, which becomes a challenge in the workflow, as it requires proper arrangement to route traces efficiently and avoid unnecessary crossings.

In my case, I had to modify the trace design parameters, since with the default configuration it was almost impossible to connect all the components on a single board. However, to solve this issue I adjusted the design rules to connect all the components. This change affects the fabrication process, because reducing the trace width and spacing requires the use of a 0.2 mm milling bit in order to mill the traces properly.

Before exporting the design, it is necessary to verify that the PCB has no connection errors or design rule violations using the Design Rule Check (DRC) tool.

Finally, I used the 3D viewer to visualize and verify the dimensions of the PCB.

Circuit Simulation

The simulated system was developed using Circuit Simulator, where the necessary components to properly control a solenoid were included. However, since the solenoid component was not available in the schematic library, a 30 Ω resistor was used to represent the electrical path of the load.

The simulated circuit represents the control of a solenoid, which functions as an electromagnetic actuator. The MOSFET is used as an electronic switch that allows the solenoid to be turned on and off through a control signal. When the MOSFET is activated, current flows from the 12 V supply to the solenoid coil, generating a magnetic field that produces the movement of the mechanism. When the MOSFET turns off, the energy stored in the coil attempts to keep the current flowing.

Because the solenoid is essentially a coil, the current does not appear instantaneously and part of the energy is temporarily stored in its magnetic field. To prevent voltage spikes that could damage the transistor or the microcontroller in the project, a flyback diode is used. This diode provides a safe path for the current and allows the energy stored in the solenoid coil to dissipate safely.