■ FIGURE 8. The Cowlacious ST-200b kit and
■ FIGURE 9. Tin snips used
to remove a small part that
blocks the mounting bracket.
■ FIGURE 10. Rotary tool used to smooth
out the servo bracket mounting spot.
to take home. Of course, having some experts on hand
(i.e., my buddies from The Robot Group) certainly doesn’t
hurt since they can help troubleshoot any issues that arise.
A Make and Take is a lot of fun and is very effective in
both learning new things and getting things done.
After my announcement on the mailing list, I counted
up the RSVPs and it looked like we had about 10 folks
from all around central Texas that wanted to make talking
skulls, with some folks signing up to build a pair! To meet
the demand (and to make sure I had one for myself), I
ordered 12 complete Cowlacious Talking Skull kits with
red LED eyes. (Note: See the Resources section to order
a kit for yourself in time for Halloween!)
The weekend of the Make and Take arrived and we
set up the center island in my kitchen as the “skull prep”
area (Figure 5). The kitchen table was set up with three
soldering stations for circuit board assembly (Figure 6).
We also had some speakers and a small MP3 player for
testing the finished units (Figure 7).
I opened the kits and was happy to see that each one
was bundled with a full-color multi-page instruction guide
(Figure 8). If you’d like to have a look, the instruction
books are available directly from Cowlacious (see
Resources) as PDF documents. The booklet had detailed
instructions and photographs on how to modify the fourth
class Bucky skull to hold the servo motor and allow a
piece of piano wire to reach the jaw. There were also
detailed step-by-step instructions on how to assemble the
audio servo board in a separate color booklet. As you can
see in the photos, we were all using these guides constantly
as we went along and they were VERY helpful!
Though the skull modification guide is very detailed,
the actual modification is fairly simple and can be
recapped in short order: A small piece of plastic is
“snipped” away from the bottom of the skull to make
room for the servo bracket mounting screw (Figure 9).
A rotary tool is used to smooth an area inside the skull for
the servo bracket (Figure 10). The springs that hold the
jaw to the skull are removed, then holes are drilled in the
skull to allow clear plastic wire ties to act as hinges for the
jaw (Figure 11). The servo bracket is attached to the skull
with a nut and bolt (Figure 12) and then a hole is drilled
to allow the piece of stiff wire (i.e., piano wire) to be
threaded from the servo down to the jaw (Figure 13).
Finish by attaching the servo horn to the servo (Figure 14)
and you have a modified skull ready to go (Figure 15).
While some folks were busy modifying the skulls, the
soldering area was in full swing (Figure 16). The first board
was completed by Paul Atkinson (Figure 17) and we took
it to the test area to try it out. We powered it up and uh, oh,
the servo refused to budge! After a bit of head scratching,
connection testing, and taking readings on the board using
a meter and an oscilloscope (Figure 18), we found that
two pads on the circuit board had a solder bridge. Once
that was fixed, the board worked fine.
■ FIGURE 11. Zip ties used to create
a hinge for the jaw.
■ FIGURE 12. Attaching the servo bracket
to the skull.
■ FIGURE 13. Piano wire push-rod
threaded through hole to jaw.
September 2008 37