Razr Behary have been working on his Arduino based clock project. He had spare Arduino Mega2560 so it served as main processor. DS1307 RTC took care of precise timekeeping. He didn’t spare any LED seven segment displays and used a lot of them. Additionally Razr added another four 16 segment displays to show some other textual info like ‘date’, ‘alrm’ or ‘time’. Displays are controlled using NPN transistors with bases connected to Arduino digital pins.
Another interesting feature of clock is alarm function. Arduino is connected to Samsung DVD player using optoisolators. Once alarm is triggered DVD starts playing song to wake one up. Turning off is simple – by pressing power button of DVD. All set up is soldered using through hole prototyping boards, so it caries a bunch of wiring that barely fits on DVD player itself.