the SD card readers that it works
with. It doesn’t work with the SD
drive in my laptop, but it will work
with an external SD drive.
I haven’t used a Mac to format
an SD card for a RaspPi, but based
on the research I’ve done it doesn’t
seem like there are the same
problems that Windows has.
Once you have the SD card
formatted, you need to copy the
Falcon Pi Player software over to
the card. This can be done with a
simple drag-and-drop from the .ZIP
file you downloaded from Falcon
Christmas over to the SD card.
The first time you set up the
RaspPi, you need to plug in the SD
card, the USB drive, the network
cable, and a speaker. There won’t be any animations or
songs on the USB drive at this point. The directories will
be created when the Falcon Pi Player is first turned on.
Once you have everything connected, you can
connect 5V to the USB port to start up the software. If the
red PWR LED on the RaspPi is the only LED that’s on, you
haven’t pushed in the SD card far enough. It will take
about eight minutes for the software to install itself the
Once it’s done, the IP address for the local Falcon Pi
Player website will be announced over the speaker. The
default IP address is 192.168.0.10. You can connect to the
RaspPi via a web browser to check if it’s working. Alan
Dahl made a pretty good video tutorial page on how to
set up the Falcon Pi Player if you need more help. Those
tutorials are available at http://falconchristmas.com/wiki
Building the Raspberry
There are two custom printed circuit board (PCB)
types for the animated display: the RaspPi connector and
the LED controller. Each face will have three LED
controllers: one for each eye and one for the mouth. So,
there’s a total of four circuit boards. The parts and PCBs
can be ordered from the Nuts & Volts webstore.
The RaspPi connector attachs directly to the RaspPi
via a 26-pin header (Figure 10). This board takes power
from a 12V source. You’ll need a 12V power supply that is
used to power the LED strips. I added reverse circuit
protection with the Q1.
There’s a clever video on You Tube that explains
exactly how this P channel MOSFET protects the circuit
without a voltage drain that a diode would take. Watch it
at http://youtu.be/IrB-FPcv1Dc. The RaspPi uses 5V, so
the 12V input needs to be converted to a voltage that the
RaspPi can use. The parts in the green box on the
schematic do this. I tried to use a simple LM7805 voltage
regulator, and it got uncomfortably hot. The LM2576 is a
much better choice as it doesn’t get hot at all.
The AND gate in the 7408 doesn’t look like it’s doing
much. However, the output for the RaspPi is 3. 3 volts, and
we need to have five volts to guarantee the correct high
voltage. The 7408 provides the line level conversion.
Lastly, there’s a standard RJ11 phone jack on the
circuit board to connect to the LED controller circuit
boards. Since the boards can’t use the telephone to talk to
each other, I used the RJ11 connector because it’s still
pretty easy to find standard telephone cable even in the
age of the smartphone. The four pins used are 12V,
ground, a data clock, and a serial interconnect bus (SDO).
When assembled, the RaspPi connector looks like
what you see in Figure 11 You’ll notice there are leads
that are standing from the GPIO header. Don’t cut those
off; they’re used to stack any additional boards to connect
to the RaspPi.
Building the Controller
The LED controller takes the signals from the RaspPi
and turns on the LED strips; see Figure 12. The heart of
this controller is the WS2801 from WorldSemi. The
WS2801 is very powerful despite its small size. Each IC
has its own address based on its position in the series. Not
only can each light be turned on individually with a simple
two-wire interface, you can also fade lights with 256
degrees of intensity. The WS2801 chip is commonly used
to change the color of a single RGB LED, but it’s also
powerful enough to switch a series of LEDs. The IC can be
used anywhere from LED decorative lighting to LCD TV
back lighting. This IC sounds too good to be true, right?
September 2014 49
FIGURE 11. FinishedRaspber y Pi connectorPCB.