Do you remember herctrap from the "LFS data on my Dashboard with Arduino"? Well, yesterday he posted another electronic project. This is the result from his experimentation with shift registers-that's why he did not use matrices. Unfortunately, there is no schematic for the design as he did not use one. He promised though that on Monday he will send us the PCB! The PCB can be found in this link.
He uses Arduino fr time keeping, and each second the time is saved in the EEPROM. Upon next startup, a switch determines if the clock will start from 00:00 or prom the previously saved time. It also shows the date and calculates if the month days and leap year. It carries a battery backup in case of power failure. Finally, a speaker sounds once every hour -as many times as the hour- and every half hour -once-. Here is the schematic for the speaker friving circuit.