Building a Large
Scr lling Display —
Part 2: Adding a Second Panel
● by Pete Smith
Buoyed up by my success in getting one panel to work,
I decided to add a second panel
to increase the impact of the
display and to make it a little
easier to read.
FIGURE 1. Wiring for
in the middle of Figure 1 (ignore
the other wiring for now), and
making a small change to the code
so that the microcontroller
recognizes the second panel.
You simply change the
command “#define DISPLAYS_
ACROSS 1” to “#define
DISPLAYS_ACROSS 2.” Load
the code onto the Freetronics
Eleven as before; now the display
will run across both panels, but at
a reduced brightness.
To restore the panels to full
brightness, you need to add a
5V power source directly to them.
I bought a small 5V 3A power
supply on eBay for about $10
(Figure 2), then connected a
power cord to it and output wires
that feed both panels (refer again
to Figure 1).
CAUTION: Line voltages are
dangerous and can injure or kill.
FIGURE 2. 5V power supply.
If you are not experienced with
how to safely connect and shield
line voltages, then get a laptop or
wall wart type power supply. Mine
will be inside a protective box in
the final display so that the high
voltages will not be accessible.
The display, however, currently
still needs the computer to be
connected to power the
microcontroller. To be able to run
the display without the computer,
you need to be able to replace the
5V provided by the USB cable.
At first glance, the Eleven
32 SERVO 03.2013