And now for something that seems incredibly complex but is quite the opposite - a device that can sort Skittles or M&Ms into separate colours. Thanks to the availability of inexpensive colour sensors, this device can control the flow of candy as they approach - determine the colour, then move a servo-controlled chute to the appropriate colour's cup.
The work behind the project is mostly the 3D-printer parts and assembly, however the electronics are quite simple and could be gathered for less than a hundred dollars. It made a great educational project and I'm sure lives to this day to amuse and feed onlookers. Here's the sorter in full operation:
If you're looking to learn how to use an Arduino to sense and control certain environments, you can't go past "Arduino Workshop - A Hands-On Introduction with 65 Projects” by John Boxall.
Arduino Workshop takes the reader from having zero knowledge about the Arduino platform, electronics and programming and leaves them with the know-how and instructions on everything from blinking an LED, to robotics, wireless data, cellular communications, motor control, sensors, Internet connected systems and more. For more information including a sample chapter and table of contents, visit the book page.