Here is a cool digital clock made using LEGO Mindstorms blocks. Time Twister by Hans Andersson has two LEGO Mindstorms bricks that communicate via Bluetooth. The master brick keeps track of the time and the minute digits while the slave brick takes care of the hour and second digits. Each digit is made up of five layers, which each layer capable of rotating 360 degrees. The below video shows how this digital clock works:
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