Base 15 Clock Design

My previous post outlined (sort of) my original idea for my digital clock. After practicing some woodwork, I realised that I am totally incapable of building what I wanted, so I decided to change my plans to work with my strengths, not my weaknesses. 

My "BCD" Design

So, a few minutes of pondering, I decided to make my own BCD display, but using symbols instead of numbers. After thinking some more, I decided that base 10 is boring, and base 15 would be a lot more interesting for time. 


I can already hear the cries of protest: Why base 15? Wouldn't 12 be better? Isn't base 12 awesome?


Well, when we think about minutes, the most commonly used times are quarter to, half-past, quarter past. These are all linked into fifteen minute intervals, hence base 15.


But, what would be an interesting way to show the most significant digit? Should I have unique symbols for them? No. How about colours?


That's right, each interval of 15 is represented in its own colour. Haven't decided which is which though, that is something I can play around with once my parts FINALLY arrive.

Base 15 symbols

I was originally going to work out 15 different "symbols" for 0 - 14, then work out the logic for it to work, but then I realised a quicker method. Hooking up each "panel" (each panel contains 3 LEDs) to a different output on the 74LS393 would generate symbols from 0 - 14 with little effort, and it would be very easy to implement.




Parts:
24 x RGB tri-colour LEDs (common anode)
12 x Dual colour LEDs (common anode)
1 x 74LS21
3 x 74LS393
5 x NPN transistors
3 x momentary on push buttons
1 x power button
1 x reset button
Various resistors
12 x 1000 uF capacitors
2 x 74LS08
1 x 5.1 V Zener Diode
1 x 9V battery