Controlling 24 LEDs with just 6 pins - the Berlin Clock (Charlieplexing)
Channel: Uwe Zimmermann
Date: 18/04/2022

I just received back the circuit boards I ordered for two new projects, one of which I will present here: a famous street clock in Berlin. The 24 LEDs of the display are connected to the microcontroller with just 6 GPIO pins, using Charlieplexing.

https://en.wikipedia.org/wiki/Charlieplexing
https://en.wikipedia.org/wiki/Mengenlehreuhr

This video is unsponsored and not monetized, as usual.

00:50 unboxing the package from pcbgogo
05:40 my previous prototype
08:00 the theory of charlieplexing
13:00 the schematics in KiCAD
14:10 importing an outline in .dxf-format
14:50 the layout in KiCAD
16:00 about the Berlin Clock (Mengenlehreuhr)
16:50 assembling the circuit board
30:15 first test of the soldered LEDs
32:00 soldering the components on the backside
35:00 connecting the board to an Arduino nano (clone)
37:00 starting a project in PlatformIO
40:00 the code for Charlieplexing
50:00 being halted by a defective USB cable
53:30 going to a higher refresh rate for a flicker free display

source code: https://pastebin.com/edit/WjJPFCYU

circuit boards made by https://www.pcbgogo.com/
- 1.6 mm thick
- white solder mask, black silkscreen
- lead-free HASL

other tools used:
LED Test Tweezers https://www.thingiverse.com/thing:3198136
TS-100 solder iron
Felder Iso-Core Clean Sn100Ni+ solder wire 0.5 mm
Arduino nano (clone), ATmega328 16 MHz, 5V

Software used:
KiCAD PCB layout https://www.kicad.org/
QCAD general 2D design https://www.qcad.org/en/
VS Code https://code.visualstudio.com/
PlatformIO plugin https://platformio.org/