opening salvo such as:
"Last time we met, we enlisted
the aid of a couple of old standbys
— the 74-165 and 74-595 shift
registers — to expand I/O in our
projects. We even managed to craft
some PASM code to provide PWM
on multiple x595 outputs ... "
Well, by then, my eyes were
glazing over and I searched for some
lexical help, but there was none to
If you truly intend to capture the
interest of (well, for example, me)
those to whom you make reference
in the magazine editorial, then
please give us a fighting chance with
One the other hand, the Fred
Eady article was easily graspable, as
was the article by Joe Pardue. There
were more that I could grasp, but
when a secret language is used, I
fear you will only preach to the choir
and thereby limit your readers to
those who know the secret
Don't slip on a slithey tove!
May 2014 53
I have gotten several good comments about the solar design article
featured on the March 2014 cover. However, one reader pointed out that
the MOSFET has a reversed diode and will not totally turn off, which could
allow the battery to drain into the solar panel. I totally missed this on the
part I specified and ask forgiveness.
Some solar cells come with a blocking diode built in and others don't.
To prevent discharge, I have added a blocking diode (not included in the kit)
which should be placed in line with the positive wire from the solar panel.
Use a Fairchild SB1245 or equivalent. Please see the corrected schematic at
the article link on the NV website. The cathode should go toward the board.
Due to this change, I have also revised the code. The revision is at the
link, as well.
There is an error in the published parts list regarding R5 and R6. The
correct value is 910 ohms and has been corrected on the parts and source
list on the website.
R1 and R3 are correct with their values at 8,200 ohms. However, the
published part number is incorrect and will give you 18.2K. The correct part
number is 271-8.2K-RC and has been corrected also.
NOTE: If you put a voltmeter on the battery, it will reflect the charging
voltage and not the battery voltage. Always keep in mind that the higher the
voltage to the battery, the more power is being put into it. Make sure you
fuse the unit.
One reader noted that you should be able to parallel two MOSFETs
being driven by the same circuit. I had thought about this when writing the
article, however, wanted to take one step at a time.
Several readers pointed out that when the solar panel goes below the
battery voltage, a buck boost circuit could be used to continue the charging.
This was not called for in the specifications and would probably increase the
cost 3-4 times due to the size of the components needed.