22 March 2018
BUILD IT YOURSELF
Several years ago, I read about a technique called Charlieplexing where you can
control a large number of LEDs individually with a relatively small number of I/O
lines. I immediately thought that a good use of this technique would be to make a
clock. It would have three circles of 60 LEDs each. The outer circle of LEDs would be
for representing seconds, the middle circle for minutes, and the inner circle for hours.
Although only 12 LEDs would be needed to display hours, I thought it would be
more symmetrical if I used 60 and advanced it every 12 minutes. I had envisioned
using both T1 ( 3 mm) and T1-3/4 ( 5 mm) LEDs; the larger LEDs would be used every
fifth position at each hour mark.
Build an Analog-Style
By Robert Gill