Is a scratch build line following robot around the Pololu QTR8D sensor bar that I had found in my parts pile.
The challenge for me was to build a chassis from scratch and code my own QTR8D class, Motor class and all that in a single day.
Raspberry Pi 3 (Will also work with Pi4 and most likely also Pi Zero Wifi) L298N H-Bridge 11.1V Lipo for motor pow4r power bank for the Pi
The chassis was made with some spare 1.5mm thick styreen
Links to components: