We chose to use the KiCAD software since it came equipped with some of the symbols and footprints of pieces we knew we would need. Since many of the chips we needed were quite specific, we did end up having to outsource other libraries in search for the correct parts. We were able to find the majority of the missing components on the Snap EDA website.
To illustrate a simple improvement made with the Pi HAT, consider the ultrasonic sensor. When hooked up normally, the ultrasonic sensor would require an external breadboard equipped with two resistors acting as a voltage divider in order to be safely connected to the Pi, but our PCB design alleviates the need for external components as shown in the top left corner of the above schematic where we specify the needed resistors.
After many iterations of KiCAD schematics, we were finally satisfied with our connections. The next step was to create the actual board layout which required individually placing each component and drawing the corresponding wire connections. Things that we had to keep in mind in order to successfully complete this task included verifying sizing of each component and carefully selecting wire traces of appropriate thickness to assure that connections were thick enough to carry voltage supplies.
Common Name | Part Number | Quantity | Size |
680 uF Capacitor | 1 | 10×10.5mm | |
220 uF Capacitor | 1 | 8.3×8.3mm | |
Diode | 1N5821 | 1 | 15.24mm Horizontal |
2×20 Connector | 1 | ||
8 Pin Connector | B8B-XH-A | 6 | |
4 Pin Connector | 292161-4 | 1 | |
2 Pin Connector | B2B-XH-A(LF)(SN) | 7 | |
33 uH Inductor | 3631G | 1 | 12x12x8mm |
1k Resistor | 1 | 0402_1005 | |
1.3k Resistor | 2 | 0402_1005 | |
2k Resistor | 1 | 0402_1005` | |
4.3k Resistor | 2 | 0402_1005 | |
PWM | PCA9552PW | 1 | 4.4×9.7mm |
DC to DC Converter | LM2596S-5 | 1 |