details of how to install the necessary
jumpers. Figure 5 is a photo of my
completed UPS board; you may want
to refer to it as you construct this
project. (Before we continue, I need
to mention something about the
photos in this article. My digital
camera recently “died,” and I have
been too busy to replace it yet, so I
used a webcam for all the photos. As
a result, they aren’t as clear as I
would like — sorry about that!)
After you’ve built the UPS, it
would be a good
idea to check and
shorts and other
you’re ready to test and apply power,
you will need a way to support it in
an inverted position so that you can
use a multimeter to check for the
correct voltage (+5V) at the USB
connector. I used a small piece of
1.5” square scrap wood for this
purpose (see Figure 6), but you can
use any arrangement that holds the
completed stripboard in a stable
To do the testing, connect the
main power supply and the battery
pack to the board, and carefully
invert it so that it sits reliably, and is
in the same orientation that’s shown
in the layout of Figure 3. Locate
points J13 (+5V) and M13 (ground),
and carefully (because the board is
powered) determine that a voltage
very close to +5V is being supplied
to those two points. If it is, remove
the main supply connection and test
those two points again.
The same voltage should be seen
because the battery pack is now
supplying the circuit. If your board
does not pass these two tests, you
need to do some troubleshooting.
When you’re sure the board is
functioning correctly, we’re ready to
move on to final testing of the UPS
when it’s actually powering the Pi.
However, before doing that, you may
want to secure the battery holders,
batteries, and the UPS stripboard on
some sort of mounting board, as
well. I used a piece of 1/2” plywood
for this purpose (see Figure 7).
In the photo, the odd-looking
eighth “battery” is actually a wooden
dowel with a bolt running through its
center. You can just solder a wire in
its place, if you prefer.
12 June 2014
■ FIGURE 5.
Top view of
■ FIGURE 6. Testing the UPS board.
■ FIGURE 7. Completed UPS on mounting board.