5.Electronics Design
This week for :
Group assignment:
We had to use the test equipment in our lab and observe the operation of a microcontroller circuit board
Individual assignment:
To use an EDA tool to design a development board that uses parts from the inventory to interact.
GROUP ASSIGNMENT
You can view our group assignment here!
INDIVIDUAL ASSIGNMENT
Printed circuit Board
TPCBs are thin boards that contains electrical circuits that connect multiple components to form a complete
system used to power our devices. The components are connected to the board by soldering them to the board. The
board is made up of materials with poor conductivity
the board can be of one , two or multi layers.
A PCB needs to be designed first before it cn be printed. This can be done on by PCB design CAD tools.
Components of a PCB
Switches:can either allow current or block depending if they are closed or open.
There are several different types of switches available such as slider, push button, lever, toggle, key switches
etc.
Resistors:Resistors are one of the most commonly used components in PCBs. They are used to resist the flow of
current by dispersing the current flowing into it as heat.
Capacitors: Another common component seen in PCBs. They temporarily hold electric charge and then dispersed
whenever more power is required in th ecircuit.
It functions by collecting opposite charges on two conductive layers with a insulating material in between.
Inductors: They store energy in the form of magnetic field which is formed when current flows through an coil
of wire.
They are used to block or filter out certain signals.
Diode: This device only allows current to flow from the anode to cathode i.e. only in one direction. This
helps to stop current to flow not the wrong path which may cause damage. LEDs are semiconductor light sources that
emit light when current flows through it in the correct direction.
Transistors: the are used to amplify the charge or as electronic switches. They can either be n-channel
transistor or p-channel transistors.
The NPN transistors .
Designing a PCB
We have to design and map out a PCB before it is built. To do so we have to seek out CAD tools such as
Eagle,EasyEDA,kiCAD,OrCAD etc. The software is used
for designing the PCB is
kiCAD.KiCad is an open-source Electronic
Design Automation (EDA) software that helps users to create schematic diagrams of electronic circuits and convert
them into PCB layouts and 3d models.
There PCB design can be separated into 2 categories; schematic diagram of the the PCB and PCB layout to help
design how the components will be mapped out physically on the board.
To access Fab Academy's library of symbols and footprints for KiCad, A .zip file is to be downloaded from https://gitlab.fabcloud.org/pub/libraries/electronics/kicad
Now we go to our GitLab profile and go to code and then copy the ssh key .
We now need to open GitBash in out Local kiCad folder and type in the clone command.
To add the downloaded files to the kiCad library :
To add symbol library:
1.Open KiCAD. Go to preferences.
2.Click on 'Manage Symbol Libraries'.
3.Click on "Add file" and select the symbols library that we downloaded.
Similarly to add footprints library:
1.Open KiCAD. Go to preferences.
2.Click on 'Manage Symbol Libraries'.
3.Click on "Add file" and select the symbols library that we downloaded.
I needed to add a voltage regulator circuit. So similarly as above i added a voltage regualtor,2 capacitors and
then gave connections to the ground and power supply.

we can lable the parts using the text tool from the tool bar.
I also added LEDs to make the complete circuit. Once done the schematic diagram looked like this:
Once the circuit is done we need to scan the diagrams for any errors in the connection. For this we use the 'Run
ERC' command.
This function checks and provides information if any errors are encountered.
We now proceed to go into the layout mode to start creating circuit routes on the PCB. First thing to do is connect
set the design rules which you can get into by clicking DRC inside tools menu.
Set different clearances as asked.
Open the PCB editor and click on Update PCB to load the circut board.
Designing a custom PCB
For this assignment we could create a custom PCB by ourselves. I wanted to use a 'Space Alien Invader'
video game
character as the shape of my board, because for some reason they remind me of PCB boards!
I began the project by drawing the schematic diagram first. I wanted to have a switch which will turn on 2 red
LEDs whichh would be the eyes of the crab. I used the xiao rp2040 microcontroller. i referred to the pin
out to understand the pins of the microcontroller. I added the components that
i required to create the board.
The components i used are
XIAO RP2040
2 red LEDs
2 resistors for the LEDs
Tactile switch
1x05 Vertical header pins(2nos)
1x02 Vertical header pin
Next I had to create a sketch of the outline of the character in fusion360, which I then exported as a dxf file
to
import into the PCB editor document.
I set the constraints based on the capabilities of our milling machine before creating the route traces. We can
use the routing tool from the toolbar(shortcut key 'X').
This allows us to begin the process of laying out and connecting the traces on the PCB. Manual routing took a long
time to figure out but was a fun process nonetheless and i also wanted to connect the circuit without the use of
zero resistors which was real challenge.
i had to swap the labels of the pins because i accidentally placed them on the wrong ports. i did this by going
back to the schematic
view and using the swap function. To swap between two elements right click after keeping the elements selected.
I ran DRC for errors and only minimal correction was required. The switch had a warning attached to us asking
for it to be routed , but since switches are already internally connected this was neglegible
The final routes look like this:
I opened the 3D editor to view the PCB . I had to import the correct 3D
elements to clear the missing parts. Some links were broken so i had manually fix them so that they will import
correctly.
This was the entire workflow in KiCAD from schematic to layout to the 3D model.
Finally i exported the kicad file to a .step file and opened it in fusion360 to view the 3D model
Creating a case for the PCB
I modeled a case for the PCB on fusion360. I also added a keyring hole so that it can be attached to a chain or hook.
Making a Gerber File
The file we have currently needs to be converted into a gerber file so that it can be sent for manufacturers of the PCB. Gerber is a standard file format that contains the design data for a PCB. It includes the differnt layers PCB's , including copper traces, solder mask, and silkscreen,
position of each component, such as pads, vias, and drill holes etc.
To create a gerber file Go to Fabrication outputs> Gerber

A plot dialogue box appears. On the output directory field enter "/gerber". This is done so that a gerber folder with all the files will be plotted in one place.

Click on Generate Drill files

Then click plot. Now go to
PCBway and drop the files within the gerber folder we created there. The PCB will be generated using the information.
Download files
PCB design files
References
resources.pcb.cadence.com