■ FIGURE 9. A top view of my camera
platform. The base of the tiny CCD
imager mounts to the center of the
platform.
at the center of its extension beyond
the arm. A #2 bolt goes through this
hole and acts as the axle for the lazy
Susan platform for the camera.
The camera platform is made
from a 1/16 inch thick sheet of
hard modeling plywood. Do not use
the light ply as it’s likely to break
from stress. Cut the platform large
enough for your imager and two wing
extensions.
Drill a small hole in each platform
wing near the ends of the shelf. Piano
wires from the micro-servo connect to
these holes in the wings. So when the
micro-servo rotates, the camera’s lazy
Susan platform also rotates.
Drill a 3/32 inch diameter hole
through the platform’s center. Push a
■ FIGURE 10. A top view of the arm.
The rotation base is at the bottom, the
micro-servo in the middle, and the
camera platform at the top. Note the
pair of piano wires connecting the
extended arms of the micro-servo to
the camera platform.
#2 bolt through the hole. Place washers on the bottom and push the bolt
through the hole in the camera shelf.
Use a locking nut (a nut with a nylon
insert) to hold the lazy Susan to the
shelf. Tighten the locking nut enough
to take the slack out of the axle, but
not so tight as to restrict its rotation.
Attach the CCD imager to the lazy
Susan according to the design of your
imager. Be sure the lazy Susan can
still rotate freely after the camera has
been attached.
Now insert a micro-servo at the
midpoint of the arm and screw it in
place. I only used two screws (on
diagonally opposite corners of the
micro-servo) since there is very little
force trying to lift the micro-servo out
of its pocket in the arm.
Add a horn to the micro-servo
and compare the width of the horn to
the wings on the camera’s lazy Susan.
I added an extension to my servo horn
to make it the same width as the
camera platform. In Figure 10, you can
see that I used a strip of basswood for
the servo horn extension. The horn’s
extension is held to the servo horn
with epoxy and some wire, but you
should use small bolts in place of the
wires. Snap the servo horn (and its
extension, if it was needed), to the
micro-servo and rotate the servo to its
mid position. Remove the servo horn
and place it back onto the micro-servo and bolt it down.
Measure the distance between
the arms of the servo horn and the
wings of the camera platform. Cut two
pieces of stiff piano wire to the same
length plus an additional inch. Insert
the piano wires into the holes in the
servo horn and camera platform and
bend the ends over to keep them from
falling out. Test the rotation of the
camera platform by twisting the horn
of the micro-servo. The camera
platform must rotate without binding
up. If all the servos rotate without
binding, the exterior portion of the
BioCA is complete.
Now bring the servo and camera
wires inside the quad panel. I drilled
two holes into the quad panel. I don’t
think you can get by with just one
pass-through hole without the arm’s
rotation base binding up on wires.
Since the SSC II is mounted inside the
quad panel near the bottom, I drill my
two holes about halfway up from the
bottom of the quad panel.
After drilling the hole(s), epoxy a
shelf inside of the quad panel that’s
large enough to hold the SSC II. I used
1/8 inch thick light ply for the shelf
and used a bit of Styrofoam as a
brace. After the epoxy sets, hold the
SSC II in place and mark the location
of its mounting hole in the shelf. Drill
the holes and bolt SSC II to the shelf.
I only used two of the mounting holes
because there isn’t much force trying
to pull the SSC II off its shelf.
Pass the servo cables through the
holes in the quad panel and connect
them to the SSC II. You may have to
extend the length of the cables to get
them to reach. I extend servo cables
88
January 2006
