PICAXE PRIMER
■ FIGURE 12. Stripboard layout for SMD version.
■ FIGURE 11. Top view of finished board.
■ FIGURE 14. SMD
board in breadboard
circuit.
transistors raised the display about
0.1” above the surface of the strip
board. When I decided to make a
second display, I wanted to see if I
could eliminate that small gap, which
is how SMDs became involved in
this project.
I redesigned the strip board
layout and placed SOT-223 versions
of both transistors on the bottom of
the board; the resulting layout is
shown in Figure 12 (again, a larger-sized version is available at the
article link).
Unfortunately, the pins of the
SMD transistors are in a
different order than those
of the through hole
versions, so I also had to
make a couple of minor
modifications to the strip board
wiring. If you compare the two
layouts (Figures 10 and 12), you’ll
see what I mean.
Figure 13 is a photo of the two
SMDs soldered to the bottom of the
strip board. You can tell that I
soldered them in place after sanding
the bottom of the board and, again, I
used a little too much solder (filling
■ FIGURE 13. Bottom view of
finished SMD board.
two holes in the process). The board
was already fully populated, however,
so it doesn’t matter.
Figure 14 shows the completed
board inserted into a breadboard,
directly in line with a 20M2
processor. After I completed both
versions of the board, I used the
Count2Digits3Tasks.bas program
(from the April 2013 Primer) to test
them. Guess what — both boards did
June 2013 21
