DS1307 (RTC) Gives the time to ATmega8, It Convert the time to Binary and through a 74HC164 8-Bit Shift register It is shown on 24 LED. Each Column of LEDs is 1 Decimal Number, so we have HH:MM:SS. RTC is backed up with a CR2032 Coin Battery, so if the Main Power is off RTC will not forget the clock, although the LEDs will be off. 2 Push Buttons are for adjusting the Hour and Minute, the Potentiometer is for adjusting the brightness of LEDs manually and the LDR (Light Dependent Resistor) is for adjusting the brightness of LEDs automatically.
Here is your Shopping List: ATmega8 x1 DS1307 (RTC) x1 74HC164 (8bit Shift Register) x1 16Mhz x1 32.768kHz Crystal x1 20 pF Ceramic Capacitor x2 100 ohm Resistor x6 10 Kohm Resistor x5 100 Kohm Resistor x2 LDR x1 100k Potentiometer x1 3mm LEDs x24 2N2222 NPN Transistor x12 USB Type-B Female Port x1 CR2032 Coin Battery x1 Coin Battery Holder x1