4 Digit 7 Segment I2C Display - Red
A fun way to make a small display is to use a 4-digit 7-segment display. Matrices like these are 'multiplexed' - so to control all the seven-segment LEDs you need 14 pins. That's a lot of pins, and there are driver chips like the MAX7219 that can control a matrix for you but there's a lot of wiring to set up and they take up a ton of space. Wouldn't it be awesome if you could control a 4-digit 7 segment display without tons of wiring?