This time we will have a look into the schematic and the PCB Design. Once the simulations are done and the schematic is fully validated, we need to elaborate the schematic into CAD software (In this case, KiCad as we support Open Source software) and to elaborate the PCB before sending the gerbers to the manufacturer. Let's start!
The schematic is showed next:
As you can see, the design is pretty straightforward: The PIC drives some NPN transistors, which allow the display to turn on-off. Same for the buzzer.
As you may know, the display has four displays in parallel, so we will need to have a high-frequency refresh rate to mock the human eye and create the illusion that all of them are on at the same time.
For the buttons, an RC filter made of a 10K resistor and 100nF capacitors will filter any bouncing effect. However, this creates a big disadvantage in terms of producibility and scalability, which will be explained in the last chapter of the project.
Once the schematic is clear, the components are placed into the PCB in an organized manner: (Decoupling capacitors near to the ICs, RC filters just at the end of the buttons...):
Now comes the pros&cons of the routing. In this case, I used the auto-route utility of Kicad, which has the following issues:
- You need to spend a lot of time tuning the parameters to get an acceptable PCB.
- Strange and larger paths compared with manual routing.
- A good component placing is crucial.
- When you have 4 or more layers in a PCB, it can be worth it to save plenty of time.
In the end, We do not recommend use auto-routing when making PCBs with only two layers or very specific requirements are needed. Still, We used it in our first revision, and we will talk about mistakes&improvements in the last chapter. Being everything said, here you have:
The last step is to create a GND copper plate:
Finally, a good 3D representation help you to figure out what will you receive at the end:
And with the help of our Sponsors, we got the PCB:
Thanks for reading! Hope you find this article interesting ;)