professional. Where does someone
start who is interested in electronics?
I checked with a local school, but they
wanted thousands of dollars in tuition
costs. I would appreciate any
information you can provide.
#2043 Lodrick Price
Does anyone have a schematic
for a well-regulated and efficient (little
wasted energy) 120 VAC
transformerless power supply (no
step-down transformer of any kind —
just diodes, resistors, caps, and
voltage regulators) with an output of
9 or 12 VDC at 40 mA?
We are searching for a solution to
the problem of the ultrabass sound
from stereos in cars that drive down
the busy street we live on. The loud
bass noises and vibrations penetrate
our house, setting off resonances that
rattle our walls and windows. The
rumbling from other vehicles —
buses, trucks, and trains — is also an
Is there a technology available, or
one that could be easily developed,
that could cancel out these noises?
Or, perhaps, is there a metal screen
that could be plastered into the walls
and have applied to it a charge that
would cancel out the low frequency
sound waves, similar to the screen
embedded in the glass of the
microwave oven door?
We would appreciate help with
this problem, which is becoming
I noticed that your magazine is
for the beginner, as well as the
I have several USB flash memory
sticks that I like to use simultaneously.
Most USB "hubs" have the (typically,
four) receptacles so close that, at
best, I can get three USB sticks in, and
sometimes only two. What I need are
some short (preferably about eight
inches or less) USB extension cables,
but the shortest I've seen are three
feet and the "retractable" USB cables
are typically very pricey ($12.00+).
Does anyone know either of a source
for short USB cables or a source for
USB cable connectors to allow me to
roll my own?
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I'm looking for a composite video
level generator that sweeps from
black to white, to simulate the output
of an iris control circuit in a video
camera. Any assistance would be
I have a standard personal
computer that has serial inputs. Is
there an adaptor I can build, or
purchase, to add USB ports to my
Ken Johnson W9BIH
NUTS & VOLTS
I need to generate a 0- to 5-volt
triangle wave. I tried to obtain this
from a 555 timer chip, but it only
produced a waveform that varied
from 1/3 to 2/3 Vcc. Can anyone help
me out with a circuit?
#2047 Huseyin Akgul
The last two batteries on my
Compaq Armada M300 notebook
have died and replacements are
wickedly expensive. A simple
alternative would be to supply an
external 18. 5 V at 2.5 A, with some