see that the female USB connector’s
+5V line (pin 1) is located near the
top of the layout at C2 (rather than
near the bottom, as it was in the
The short C2-D3 jumper on the
bottom of the board connects the
+5V power line to pin D3 on the
switch. As a result, when we move
the lever of our “reversed” switch to
the “up” position in the layout, the
switch electrically connects pins D4
and D5. Therefore, the short D5-E5
jumper on the bottom of the board
connects the +5V power to the two
power pins at E2 and E5.
The second difference is that
we’re using six full traces this time
(because they fit under the female
connector), so all six traces are
labeled in the layout. Again, all the
necessary parts are available on my
website, but you may already have
what you need. As before, read
through the complete list of assembly
instructions that follows to be sure
you understand the entire procedure
before beginning to assemble the
• Cut a piece of stripboard to
size (six traces with six holes each).
• Cut traces C and D as shown
in the layout.
• Using a 5/64” drill bit, enlarge
the two holes at B1 and B6. Drill
both holes from the bottom of the
stripboard to avoid tearing out excess
copper from trace A.
• Use pliers to straighten the two
large “pins” on the connector case.
• Snip the two data pins (pins 2
and 3) from the connector.
• Insert the female USB
connector firmly onto the stripboard.
Clamp it firmly in place and make
sure it’s parallel to the board. Do not
solder it in place yet.
• Cut a piece of wire for the B6-
F6 jumper, allowing a little extra on
the B6 end so the jumper can be
bent back on the bottom of the
stripboard, as shown in the bottom
view of the layout.
• Install the jumper, bend it back
from B6 to C6 on the bottom of the
board, and snip the excess length so
that it doesn’t extend beyond trace C.
• Solder the jumper at B6, C6,
and F6. At B6, heat the pin on the
case of the USB connector for a few
seconds before applying solder.
• Solder the other USB case pin
at B1. Again, preheat the pin.
At this point, we’re ready to
install the switch, but there’s a
complication that we need to address
before doing so. The top of the
switch is lower than the top of the
female USB connector, making it
difficult to access. I’ll describe how I
solved the problem, but if you find a
simpler solution, go for it!
I first tried to raise the switch by
snapping a three-pin piece from a
long male header, pulling the three
pins out of the black plastic, and then
inserting the black plastic onto the
pins of the switch. That raised the top
of the switch above the top of the
female USB header, but it didn’t
leave enough pin length on the
switch to enable it to be soldered
onto the stripboard.
Next, I removed the black plastic
from the switch pins, held it firmly
with a pair of pliers so the three
holes were on the exposed surface,
and the jaws of the pliers were
positioned so that about half the
height of the plastic was exposed.
Then, I used my bench-top disc
sander to (carefully!) remove a little
less than half the height of the black
plastic. In other words, the black
plastic — which is normally 0.1” in
height — ended up being about 0.06”
in height. When I inserted the plastic
back onto the pins of the switch and
installed the switch back onto the
stripboard, there was just enough pin
length on the bottom of the
stripboard to enable me to solder the
switch in place.
If this little complication hasn’t
discouraged you, let’s continue:
• Insert the modified switch (no
polarity) onto the board as shown in
the layout, and solder only the
middle pin at D4. Do not solder the
pins at D3 or D5 yet.
• Cut a 3/4” piece of thin
jumper wire (e.g., a lead from a
1/6W resistor), bend it in half at its
center, and use small needle-nose
pliers to crimp it onto the bottom of
the board as shown in Figure 8.
• Snip the excess leads so they
do not extend beyond trace C, and
then solder the jumper in place at C2
• Install the capacitor as shown
in the layout (no polarity).
• Solder its leads at E4 and F4.
• Install the resistorized LED as
shown in the layout (observe
• Solder its leads at E3 and F3.
• Snip all pins and excess leads
on the bottom of the board as close
as possible. (Do not yet snip the
unsoldered switch pin at D5.)
• Sand and clean the bottom of
• Snip off the short ends of the
pins from the two reverse-mounting
16 January 2015
■ FIGURE 8.