This homemade clock uses a PIC16F877 Microcontroller with a 20MHz clock, it also has a DS1307 real time clock with battery backup.
169 x 700mcd diffused white LED's connected in a matrix configuration
24 hand postions which gives a resolution of 2 to 3 minutes per hand
Videos of the clock can be found on my youtube channel below, some slight alterations have been made sinse the videos were posted, changes to the patterns, flicker reduced, bugs fixed ect.
You will notice the LEDs flicker in the videos, this is the camera picking up the flicker as the LEDs are multiplexed.
Flicker has sinse been reduced further and now very difficult to spot, I cant see any flicker at all!
Version 2 HEX, build pictures & Circuit diagrams:
Version 3 is still being worked on, it will need a circuit modification, 1 LDR and 1 Resistor added and connected to A0 on the 16F877, This is a auto dimming feature for darker rooms. Also has 'fade out' added to some patterns.
Version 4 is also in the pipeline, this is a larger clock with an extra circle of LEDs, measuring 1 meter x 1 meter and uses 5mm white LEDs
Top picture shows analogue time 8:50, picture above shows digital readout 12:11
The LEDs are wired into a large matrix formation 12 columns x 15 rows. The rows are connected via current limiting resistors directly to the PIC16F877 I/O Ports C & D. The columns are connected to 0v rail via ULN2003 Transistor arrays, and controlled by the PIC16F877.
The persistence of vision technique is used to light each column one by one for a very brief time and then repeat the sequence several times a second to give the illusion that all the required LEDs are lit at the same time.