Creating a working PCB badge from a visual design

In this video, I show you how I created a working PCB based on some visual designs. The process involved some schematic design and some PCB layout and design.

Challenges and solutions

So, I got a PDF file with some drawings and some “schematics” in it, which I had to turn into a working PCB Badge for PCBWay’s upcoming 11-year anniversary. The design itself is nice and it was easy to work with it, however, the electronics part required some extra work.

First, the power rails were a total mess. According to the drawings I got, the battery’s positive pole was connected to the microcontroller’s ground connection. Furthermore, the positive (VCC) pin of the microcontroller was not connected to anything. And then maybe this can still be mentioned under the “power rail issues”: the switch did not have a proper function. According to the drawings I received, it is supposed to cut the circuit from the negative side of the battery. But all these connections went towards the LEDs, and there was no connection towards the microcontroller whatsoever. So, the switch was not designed to cut the power to the chip in any way.

If I assume that the battery should have the opposite polarity, the circuit would be almost good if I neglect the missing VCC connection to the microcontroller. In that case, the LEDs would be “high-side-driven” and the GPIO pins would sink the current that passes through the LED. However, there are still issues with this:

• The polarity of the LEDs is not marked on the drawings

• The code I received for driving the LEDs was written in a way that the GPIO sources the current

Further issue is that the author connected an LED to the PB5 (5) pin. This pin is the reset pin of the microcontroller, and without reprogramming the reset fuse in the microcontroller, it won’t work as a GPIO pin. However, if the pin is used as a GPIO pin, we lose the reset functionality, and the chip cannot be reprogrammed by simple tools, such as another Arduino microcontroller. Therefore, instead of making things complicated, I will add this single LED to the next bunch of LEDs.

Received “schematics” with all its flaws

KiCAD work

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Silkscreen layer

This layer of graphics was used as the front silk screen.

Importing as KiCAD graphics

The previous picture was imported to KiCAD’s image converter tool. The image had to be inverted (“negative”) since KiCAD uses the black graphics as active layer.

Front mask layer

This layer of graphics was used as the front copper mask.

Importing as KiCAD graphics

The other layer was also imported using the image converter tool. Here I did not invert the image, but I had to use the maximum threshold value to show the image properly.

KiCAD schematics

A simple KiCAD schematics describing the whole circuit. The LEDs are grouped together and their group numbering is shown next to each group. These numbers are in fact the port numbers (PBx) of the microcontroller.