https://www.instructables.com/id/DIY-Solar-Phone-Charger-5-Portable-100-Batter/ This is a solar phone charger that you can make that won't cost much over $20. This is solar powered so you have to have...

This is a robot car you can build that can run bluetooth off the HC-05 Bluetooth Module. The car is controlled through a device that has bluetooth connected to it. This relates to engineering because this...