required. The top and bottom
stripboard layout — which is shown in
Figure 6 — is all we really need.
(Large versions of the layouts for
both of this month’s power supplies
are available for downloading at the
In the layout for the male power
supply, the connector’s +5V line (pin
1) is located near the bottom of the
board at B5. The short B6-C6 jumper
on the bottom of the board connects
the +5V power line to pin C5 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 C4 and
C5, and the short C4-D4 jumper on
the bottom of the board connects the
+5V power to the two power pins at
D2 and D5.
The only other components on
the board are a .01 µF decoupling
capacitor and a 3 mm resistorized
LED (which are both placed between
the +5V and ground output traces),
and the two two-pin headers (which
are the longer reverse-mounting type
that we usually use to connect a
stripboard circuit to a breadboard).
All the necessary parts are available
on my website, but you may already
have most of them on hand.
In Figure 6, note the half-trace
on the left side of the stripboard. If
you refer back to Figure 2, you will
see a small notch in the case of the
male USB connector, just above the
large “pin” on the connector’s case.
In order to be able to fully insert the
connector into a stripboard, the
stripboard cannot extend beyond that
notch. A half-trace is about all that
will fit underneath the male
connector that’s available on my site.
(If you use your own USB connector,
check to see how far the stripboard
can extend underneath it before
cutting it to size.)
Also, note that the half-trace is
not included in the column labels.
As usual, read through the complete
list of assembly instructions that
follows to be sure you understand
the entire procedure before
beginning to assemble the board:
• Cut a piece of stripboard to
size (5-1/2 traces with six holes
• Cut traces B and C as shown
in the layout.
• Using a 5/64” drill bit, enlarge
the two holes at A1 and A6. Drill
both holes from the bottom of the
stripboard to avoid tearing out excess
copper from trace A.
• Install the B6-C6 jumper, then
solder both leads on the bottom of
• Use pliers to straighten the two
large pins on the connector’s case.
• Snip the two data pins (pins 2
and 3) from the connector.
• Use a stripboard chisel to
remove the two small plastic nubs on
the bottom of the USB connector.
• Insert the male 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 A1-
E1 jumper, allowing a little extra wire
on the A1 end so that 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 A1 to B1 on the bottom of the
board, and snip the excess length so
that it doesn’t extend beyond trace B.
• Solder the jumper at A1, B1,
and E1. At A1, heat the pin on the
case of the USB connector for a few
seconds before applying solder.
• Solder the other USB case pin
at A6. Again, preheat the pin.
• Install the capacitor. Only solder
the ground lead at E4; do not solder
or trim the positive lead at D4 yet.
• Install the resistorized LED
(observe polarity). Solder and snip
• Install the switch (no polarity).
Solder the pins at C3 and C5. Do not
solder the pin at C4 yet.
• Bend the capacitor lead from
D4 to C4. Use a small screwdriver to
press it flush against the bottom of
the board so that it touches the
middle pin of the switch at C4. Snip
the excess lead so that it does not
extend past trace C, and solder the
leads at D4 and C4.
• Snip all pins and excess leads
on the bottom of the board as close
• Sand and clean the bottom of
• Snip off the short ends of the
pins from the two reverse-mounting
• Insert one header from the top
of the board at D2 and E2. (You may
need to bend the LED slightly so the
header sits flat on top of the board.)
• Turn the board over, hold it in
place with a plastic clamp, support
the header with a small piece of
scrap wood, and solder it in place
(using a minimal amount of solder).
• Insert the other header from
the top of the board at D5 and E5,
and solder it in place using the same
approach as the previous instructions.
• Insert the completed power
supply onto a breadboard as shown
in Figure 4. If any of the solder
connections prevent it from sitting
flat on the breadboard, remove the
power supply and further trim or file
those connections until the board
can be seated properly on the
• Again clean the bottom of the
board to get rid of any possible
When you have completed the
USB male power supply, test it with
the USB power sources you intend to
use, and measure the voltage level to
make sure it’s less that 5.25V.
Constructing a USB
Female Power Supply
The female version of our USB
power supply project is very similar
to the male version that we just
discussed, but there are two
differences that are important to
keep in mind. First, if you look at the
stripboard layout in Figure 7, you can
January 2015 15