Q&A
motor itself.
Like the previous question, you
have to provide the audio interface.
Just make sure that the voltage
sweep on pin 5 is between the Vcc
and GND limits or you’ll fry the
555 chip.
This input is not linear over this
range, which is okay for the type of
output you desire. Also, 5 µF may not
be ideal for your particular pumps.
Play with it until it works right for your
display.
MAILBAG
Dear TJ,
In reference to the thermocouple
answer (November 2004), back
when I was still gainfully employed,
we routinely made thermocouples
for plant use. The process consisted
of twisting the two materials together
so that they were in intimate
contact and discharging a large
capacitor through the junction.
Dave Schoepf
via Internet
Dear TJ,
If you put 12 amps through a 1 Ω
resistor, it better be 144 watts instead
of 10 W (November 2004 issue)!
Charles D. Geillker
Professor of Physics
Response: That would be true
if the current flowed 24/7, but the
thermocouple welder shown in that
answer has the current flowing for
about 1/10 of a second while the
user taps the wires to the carbon
rod. This isn’t nearly enough time
for the resistor to heat up to even 10
watts. It’s called duty cycle. — TJ
Dear TJ,
Your block diagram for a slide
viewer will indeed invert negatives,
but the color will not be correct. All
negative color film uses an orange
mask that corrects for impurities in
the magenta and cyan dyes. This will
make the inverted image appear to
have a sickly blue cast.
Bill Runkle
via Internet
Cool Websites!
Learn to speak Aussie.
www.aussieenglishcd.com/
multimedia_samples.php
Lots of high voltage stuff.
http://205.243.100.155/frames/
lichtenbergs.html
What’s up? Kennedy Space Center.
www.ksc.nasa.gov
2005
March 6– 10, 2005
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