The initial project, and certainly the one to which many were inspired is that of Doug Jackson.
also inspired by
Step 1: The Materials
The list of materials for the board depends on how you plan to make the electronics, if you want an Arduino standalone or an Arduino UNO or 2009, however, this is what I used.
Step 2: 1) the Materials- LED and Resistor
To realize the proposed scheme are needed:
98 White LED
98 Resistor 470 ohm
I chose these resistors for this reason:
LED (ultrabrightness white) http://www.robot-italy.com/product_info.php?products_id=421 forward v is 3,3v and 25ma
,the clock will run to 9v and i want that the led will be drived at half current 12,5ma (no needs too much brightness), so:
(9-3,3)/0,0125= 456, correct misure is 470 ohm resistor.
Step 3: 2) the Materials -Standalone Arduino
On the web and on Instructables you will find several examples , these are the materials I used for my own PCBs, I plan to switch directly the ATMega 328 bootloader included with that my own Arduino UNO.
-2 ceramic capacitor 22pF
-quartz 16 mhz
-2 elettrolitic capacitor 100 nF
-5v regolator voltage 78L05
Step 4: 3) the Materials – Integrated
3- HCF4094 shift register
4- ULN2003A Driver
ATMega 328 with bootloader
For more details: My Arduino Word Clock