by cwik @instructables
This is a guide to building an Arduino-powered clock that uses LEDs to display a 24-hour clock (hours and minutes) as binary digits, an analog meter to display the seconds, a switch to toggle between time-display and time-setting mode, and 2 knobs for setting the hours and minutes. This was designed from scratch, but is an improvement over other Arduino binary clocks that miss milliseconds here and there. This clock is extremely accurate and can be used and trusted.