I designed this sensor using an Arduino Nano, ten LEDs and resistors, an ultrasonic sensor, and a breadboard. It emits ultrasonic waves that bounce off the car, records the time it takes to bounce back, and lights up the LEDs based on that time. The more LEDs there are, the closer you are to being fully parked.

This robot has antennae on a daughter board at the front that detect objects in the robot's path, so as it walks, it can turn to avoid obstacles. The trick with this project was getting the gearbox right, as several gears would spin freely without very careful alignment.

I made a multimeter that functions just like one you can buy at the store, as long as you press on the battery the right way (battery snap issue). For this project, I had to solder resistors upright very close together, get the dial working without damaging the contacts, and connect an LCD screen.