neatly under the eight-pin socket for the MAX1811 and it
is shown as a close-up in Figure 6. Any interconnect
technique should work fine using this plated through hole
board. My favorite two methods are shown in Figure 7,
but use any connection technique you prefer.
The current flowing through the connections is very
low so you can use a thin gauge wire that will make it
easier to cover up with the faceplate. Keep in mind that
with a plated through hole board, the interconnect can
happen on either side. I used whichever side was easier to
solder and kept most of the connections on the side that
had the most components. By using 30 AWG magnet
wire, the component leads and wire can fit in the same
hole before and after soldering.
To build this circuit, the prototyping board must have
plated through holes. The reason for this is because
components need to mount on both sides of the board,
so a single-side plated board will not work. To cover up
the solder points on the top side of the board where the
pushbuttons and display are mounted, I used a piece of
high gloss black plastic I bought at a hobby store. The
problem with this is that you have to drill holes in the
plastic to allow the pins from the display and leads from
the buttons to feed through.
I used a fine-tip pen to mark the locations on the
plastic and used a 1/16” inch drill bit to make the holes.
The matrix leads just make it through to the backside of
the circuit board for soldering, but the leads on the
buttons are too short. This problem can be easily fixed by
soldering extensions onto the leads as shown in Figure 8.
The screws included with the standoffs have built-in lock
washers that need to be removed to allow the threads to
reach through the faceplate. The design needs to have a
bottom board; this can be anything you like. I used the
same black plastic that was used as a cover plate.
This board performs two tasks. It covers the mounted
components and provides a back plate to hold on to
when playing the game. Another possible benefit is that it
can be used to mount a larger lithium battery if you want
a longer period between charges. You can easily fit a
1,000 mA battery in the space between the threaded
standoffs. I listed the catalog number for this as optional in
the Parts List. SparkFun sells a pack of 12 key caps
specifically for the tactile switches used for the circuit;
they help add a real professional look to the game.
Checking Your Work
Once you have mounted all of the components, it is
time to test the circuit. Before you insert the 28x2, turn
the slide switch to the on position and test the supply
voltage from either ground pin to the +V on pin 20 of the
PICAXE. If the supply voltage is fine, insert the processor
and connect the programmer to the audio jack. Load the
test routine to exercise the buttons, sound, and matrix
Once loaded, there should be a blinking square in the
center of the display. Depress the left and right buttons,
and the square should move from left to right. Press the
center button, and the box will extend outward with a
changing tone as it expands. This test guarantees a
working display, button control, and sound. The code for
40 October 2013
■ FIGURE 7. Interconnect techniques with plated through holes.
■ FIGURE 8. Parts placement for the top and bottom side of the board.