Parallax has allowed me to release the code
and plans for this board, as well as another tester
I built for exceptions — the exceptions being
boards like the Home Work board, Sumo board,
and Toddler board where the Stamp is surface-mounted and cannot be removed to plug into
this test board. First, I’ll cover the test board, then
the card tester.
ExpressPCB is Fast
I needed the board in a hurry and already
had a reference schematic, so I used ExpressPCB
to quickly create the printed circuit board (PCB)
you see in Figures 1A and 1B. Using the mini-board service, we got three of these for under
$60 in three days. The ExpressPCB file can be
downloaded from the article link or from my
project page (see Resources). As you can see
from the solder side of the board, all ground
connections are part of the ground plane.
June 2014 43
■ FIGURE 1B. PCB back.
■ FIGURE 1A. PCB front.
For me, populating a PCB begins with
the smaller components. I do this to make it
easy to solder sockets and resistors, while
being able to lay the board down flat on a
surface. Once the smaller components are in,
I start working my way up. See the Parts List
for what was used.
■ FIGURE 2. One 14-pin and two
20-pin machined sockets. The 14-pin
socket mounts on the left side of the
board. The two 20-pin sockets on the
right need to line up with the ZIF socket
in the end, so I plugged it in until I got
these fully soldered. I then removed the
ZIF socket for the rest of the assembly.
■ FIGURE 3. One three-pin RA SIP header, eight 4.7K resistors,
and two 470 ohm resistors. The three-pin RA SIP header mounts on
the far left. This is where the BS1 serial adapter connects. The 4.7K
resistors run from the bottom-right of the BS1 socket about half way
up. These are connected to the BS1 I/O pins. The 470 ohm resistors
mount above the 4.7K resistors and control current to the LEDs. Note:
These (values) may be changed as needed for the color LEDs you use.