I made a small error in the original
schematic for my July 2017 brain
hacking project that I provided Nuts &
Volts, in which I showed pin 4 of the
7660 connected to ground. In this
configuration, the device is functional,
and will put out the minimum voltage
required for a good tDCS session.
However, you can choose the
higher voltage output recommended in
the article by simply moving the ground
wire from pin 4 to pin 3 on the 7660.
(Pin 4 will be left unconnected.)
A small number of articles detailing
tDCS research have indicated that
"more is not necessarily better," and
that finding the minimum voltage that
works for you actually produces
So, I've decided to pretend this
was a fortuitous error, and mention that
you might like to give it a try both
ways. If you do, I hope you'll let us
know what you think.
My apologies to the readers of
Nuts & Volts for the schematic error.
Did I overlook something on page
55 in the June 2017 Near Space
1) The LM355 shows a lead going
left to NO connection.
2) The 24LC256 shows a lead
going right to NO connection.
Crescent City, CA
That's correct for the LM355. The
third lead in the LM355 is a
temperature adjust pin and not needed.
Since the temperature is being digitized
by the PICAXE, any necessary adjust to
the sensor reading can be made by the
PICAXE code or in a spreadsheet.
Pin 7 of the 24LC256 is a write
protect pin. It prevents the memory
chip from being written to in an
accident. That pin should be connected
to ground to enable the write, so that is
a mistake on the schematic.
Thanks for asking.
Getting Real Again
I sure can identify with Bryan
Bergeron on the movement to
subscription software as he talked
about in his June 2017 Developing
Perspectives’ editorial. I refuse to use it.
Last year, I took advantage of the free
Windows upgrade to move my five
year old computer to Windows 10. At
the time, I had a queasy feeling that
there was going to be a catch.
Generosity was not something I
ever associated with Microsoft.
Eventually, I realized what at least part
of the catch was. Successive Windows
10 service packs uninstalled some of
the Windows utilities and other
programs which I had used under
Windows 7 and before. Other bug-laden updates disabled Windows 10
features which were supposed to work,
e.g., I cannot get Windows Store to
function and the only solution is
apparently to do a clean install – and in
the process lose all of my software.
There is added pressure to only
use software purchased (or leased!)
through the Windows Store.
Fortunately, a lot of what I need is
available as free or open source
software for Linux. Unfortunately, I am
a software developer with customers
using software I developed for
Windows. So, there will be no new
computer on my immediate horizon.
Bergeron’s comment about having
been a proponent of SDR also struck a
chord. I recently attended a local Mini-Maker Faire. The reason I went was
because there was someone from the
local ham radio club exhibiting. I was
hoping to see some actual ham
communication and some neat gear,
I was pretty disappointed when the
6 August 2017
Amps ( www.boothillamps.com).
Expect to pay about $130 for the
components, circuit board, and
chassis for a 5F1 kit, and $200 for the
5E3. You’ll have to add magnetics, a
speaker, and a cabinet. These three
items can easily overshadow the basic
amplifier kits in cost.
Even so, the 5F1 and 5E3 kits are
simple to build. The schematics are
easy to locate on the Web, and they
sound great when completed.
Moreover, most of the kits out there
use the old school point-to-point
wiring found in boutique amplifiers. I
can’t hear a difference between an
amp with components mounted on a
printed circuit board vs. one with
components dangling in space, but
many players swear by the design.
Although I don’t have first-hand
experience with full kits that contain
everything from a cabinet, tubes,
speaker, and components, this is
usually more economical than cherry
picking from several suppliers and
then paying shipping fees for each
group of components. I’ve heard
good things in the forums about the
5E3 guitar amp kit from Tube Depot
( www.tubedepot.com). At $600,
however, the cost begins to overlap
with current off-the-shelf Fender tube
amps — not to mention amps on the
When it comes to DIY electronics
— whether tube or silicon-based — it’s
impossible to compete on price
alone. You’re paying for the
experience and satisfaction of
building it yourself. A complete 5F1
amp from Monoprice sells for $99,
which is about $250 less than what
you would pay for the parts in kit
form. However, when it’s time to
replace a blown capacitor or tube on
the Monoprice, you won’t know
where to begin to look. With a DIY
tube amp, you know every wire,
component, and solder joint.
Please consider sharing your tube
journeys with others in the Reader
Feedback section. NV