10 µA of current, I did some
additional experimentation to
see if I could disconnect the
voltage divider from the
batteries whenever the 08M2
was not making an ADC
reading — which would be
about 99.99% of the time!
In the process, I
happened upon the
CPC1002N which is an SMD
solid-state relay (SSR) that
contains an optically coupled
MOSFET transistor. The
CPC1002N is capable of
switching up to 700 mA of
current, so it’s a useful
device to keep in mind. Not
only for our UPS, but also for
a variety of other PICAXE or
Pi projects.
Figure 11 presents a
close-up photo of a
CPC1002N that I soldered to
a small scrap of stripboard
and inserted into a
breadboard. I added the
CPC1002N to my
breadboard circuit for the
UPS and was easily able to
control the connection to
the voltage divider circuit.
When the SSR was open
(99.99% of the time), there
was no measurable current
flow through the resistors.
Whenever the program
temporarily closed the SSR
and measured the ADC
voltage of the battery pack,
the results were in line with
our earlier results. So, I
decided to keep the
CPC1002N in my UPS
circuit.
We don’t have enough
space left this month to
discuss the CPC1002N in
more detail, but if you want
to experiment with it, it’s
June 2014 15
■ FIGURE 11. CPC1002N SSR on breadboard.
■ FIGURE 12. RazzPi-LCD board. ■ FIGURE 13. RazzPi-LCD and RazzPi- 20 boards.
