28 May/June 2018
BUILD IT YOURSELF
Last time, we looked at a test circuit that had 12 LEDs. Using Charlieplexing, we ran
those LEDs with only four I/O lines and determined that expanding the LED matrix to
14 I/O lines would enable us to individually control 182 LEDs. We also looked at
how to incorporate the reading of four pushbuttons by connecting them to the LED
matrix with a handful of other discrete components. This allowed us to read the
buttons without using any additional I/O lines. The final two I/O lines will be used to
run the alarm buzzer and read the 60 Hz coming from the AC-to-AC wall wart.
Build an Analog-Style
LED CLOCK
By Robert Gill
Part 2
