Шахматные часы

https://www.wholesalechess.com/blog/chess-clock-timing-modes/ - Chess Clock Timing Modes

http://digitrode.ru/computing-devices/mcu_cpu/612-chasy-na-arduino-bez-ispolzovaniya-modulya-rtc.html - простейший вариант

http://wiki.amperka.ru/slot-box:digital-chess-clock - Часы Фишера для быстрых шахмат

http://www.instructables.com/id/Arduino-Chess-Clock/ - Arduino Chess Clock

http://www.tested.com/art/makers/456717-how-build-timer-clock-and-learn-arduino-process/ - How To Build a Custom Timer Clock and Learn Arduino In The Process

https://github.com/jamiebull1/arduino-chess-clock - Chess countdown timer for Arduino with an LCD keypad