62 January 2017
READER - TO - READER TECHFORUM
>>> QUESTIONS
Uno-Known Device
I’ve used the Arduino IDE with
a genuine Arduino Uno board
for experiments for a few months
without trouble. Recently, I wanted to
permanently put an Uno in a desktop
project, so I purchased some budget
Arduino Uno compatible boards. The
budget boards seem fine, but the
Arduino IDE doesn’t recognize any of
them. When connected, the boards
show up as an “Unknown Device.”
I am using Windows 7 32-bit. Does
anyone have any pointers on how to
make this board work?
#1171 Michael Allison
Camden, NJ
Trainsformer Needed
I found a bargain at a local thrift
store and now have a 1959 Marklin
HO Scale train, cars, and track. The
set didn’t come with a transformer, so
I thought it would be a fun project to
build from scratch. Does anyone have
a schematic or suggestion for a DIY
train transformer they can share?
#1172 Alfred Thompson
Kingsport, TN
Turn Signal Signal
I have a newly restored 1971
Honda CB350 motorcycle that I
ride for fun on the weekends. One
problem is forgetting to turn off the
turn indicators. I have found a kit that
“beeps” every time the indicator lights
up, but it's very annoying as I sit at a
light. I would like a circuit that would
alert me only if the turn indicator
stays on for more than two minutes.
Schematic would be welcome!
#1173 Leland Collins
Gulfport, MS
How Much Tolerance Is Enough?
When designing circuits, is there
a rule of thumb for picking voltages
and tolerances of components? For
example, if my power source is 12
volts, is an electrolytic capacitor with
a 24V rating “better” than one with a
16V rating? What do good designers
use as a margin?
#1174 Enrico Gutiérrez
Panama City, FL
>>> ANSWERS
[#9162 - September 2016]
What’s The Deal With Ultra Caps?
I am looking to experiment with
“ultra capacitors” as a replacement
for AA batteries. Is this possible to
do and, if so, what kind of capacitors
would be a good place to start?
#1 The short answer is NO. The
main function of ultra caps is for
TEMPORARY backup of memory
type devices (i.e., clocks in DVD
players) during brief (i.e., less than a
day) power outages. They are NOT
suitable nor designed to replace
batteries simply because, as they are
electrolytic capacitors, they need
recharging when their stored energy
is depleted. Also, they’re not really
designed for current loads greater
than a couple hundred microamps.
This subject has come up a few times
in the past couple of years and I
believe N&V had an article comparing
ultra caps to batteries (primary and
rechargeable).
Ken Simmons
Auburn, MI
#2 This is only practical when the
current draw is very low. A coulomb
is one amp-second. By definition, a
one-Farad capacitor charged to five
volts can deliver five coulombs. A
single AA battery can deliver at least
1,350 coulombs. This is because the
material of the battery is consumed
when it is delivering current. The
capacitor isn’t consumed; it’s just a
tank for electricity. About the only
practical use of a small ultra capacitor
is to maintain a CMOS memory while
the set is unplugged.
Chip Veres
Miami, FL
[#9163 - September 2016]
Cassette to MP3
I have a box of cassette audio
tapes that I want to convert to MP3
format. What’s the simplest way to
do it? I have a Windows 10 PC and a
Nakamichi CR-2A cassette deck.
#1 There is a very good little box
made just for transferring LPs and
CDs to MP3 or wave format. It’s
made by DAK and costs $69.90.
See the link: www.dak.com/
reviews/ 2021story.cfm.
The box accepts stereo input
from any source (including a
microphone), provides for balance
and loudness adjustment, digitizes
it according to the resolution you
want, and prepares a file for a CD.
You can name the flie and see the
audio as it is played. This is especially
useful in that you can ensure that
the signal is not being clipped. One
can then run the file(s) through a
hiss and click reduction program,
which is especially good as it is based
on an algorithm rather than just
clipping spikes. Thus, it works on low
amplitude as well as high amplitude
signals.
The latest software also has a
feature which will automatically take
out the large gap one may have
between sides of tapes or LPs, leaving
only, say three seconds. I have found
the whole process very satisfactory
though time-consuming, as one
must — of course — pay a certain
amount of attention to whether the
tape or LP is finished when doing the
conversion. The ideal thing is to have
two screens on your computer so you
can keep your eye on the conversion
