Circular LED Display
The framework to build a cheap circular LED display.
This is based around the led matrix displays using the MAX7219 driver chip, these boards cost about £1 each and can be found on ebay by searching for MAX7219.
The display is driven from a microcontroller such as an Arduino.
There is a bracket to mount an Arduino Uno to the top or bottom of the display, assuming you use 16 display segments.
Display overview and build - https://www.youtube.com/watch?v=cu6kMsd_Y8M