STAMP APPLICATIONS
you check for gross errors and
ExpressPCB will link to your
schematic to show you what
connects to what. This is a huge
timesaver and way to prevent
headaches. A friend of my recently
skipped the link step and created a
board manually — and then ended up
sorry for it as he had problems with
that board.
One of the latest features of
ExpressPCB is the ability to add
a flooded plane to the top or
bottom layer of the board. I decided
to use this for ground instead of
running traces. When you make
your own boards, it’s usually best
to lay out the components and
other traces first, then add in
the flooded plane. To connect a
component to my ground plane, I
had to right-click on the pad, then
select Bottom Layer Pad Shape, then
select the connection type; I used
Thermal Pad to Filled Plane. For
vias that are not soldered, you
could select a solid connection to
the plane.
As Figure 5 shows, the plane
goes everywhere except where
there are traces and pads and
where you explicitly tell it not to be
(I removed a couple stranded
islands). When you build the board,
you need to be very careful about
solder bridges from a pad to the
plane — it’s easy with no solder-mask
... I found out the hard way. On
my initial test of the board, I found
that control output 1 didn’t work;
with a loupe I discovered a hair-thin
solder bridge from RC.0 to the
ground plane. Thankfully, the SX28
is a tough dude, and removing
the solder bridge fixed the problem;
the pin did not seem damaged. The
lesson here is to use a clean iron
with a sharp tip, and lift it straight
up instead of dragging it away from
the pad.
Figure 6 shows the completed
controller — as you can see, I now
have animatronics control in the
palm of my hand! The photo shows
that I stood resistors R7-R14 on
end. If you’re comfortable with
SMD soldering (I’m not, yet), you
can probably fit SMD resistors
between the top pads.
TESTING THE
ANIMATRONICS
CONTROLLER
To test the unit, I wrote
a simple Visual Basic program,
as shown in ■ FIGURE 6.
the source code Animatronics
included in the controller.
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