Remote Volume Knob

Remote Volume Knob
Paulo Rebordao | Make Vol. 16- 2008 | Pdf | 2 pgs | 1 mb

There's nothing like hard work to get your mind
running. Having to get up from the couch to adjust
the volume on my old stereo amp several times
each night got me thinking. I didn't want to buy
a new stereo, so I came up with a plug-in remote
volume controller that you can easily adapt to
anything with a reasonable-sized volume knob.

My circuit uses a Picaxe-08M microcontroller,
which is programmable in BASIC, and a TSOP2238
infrared receiver, which sees signals from any
Sony (or compatible) TV remote. The removable
device hangs off the volume knob, attached with
velcro.

At the top, an R/C servomotor turns the knob
through about 180° of travel, which should be
enough range for most environments. At the
bottom, 3 AA batteries act as a "keel," weighing
that end down so that the knob is forced to turn.
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G-Meter and Altimeter

G-Meter and Altimeter
Double-duty aerospace instrument on a shoestring budget
David Simpson | Make Vol. 16- 2008 | Pdf | 4 pgs | 2 mb

Here's an aerospace instrument you can build for
$5 that will measure the crushing forces that a
model rocket withstands and the rarified strata it
attains. It isn't exactly six-sigma technology in
terms of accuracy, but it's darn fun.

The device, which you install in the rocket's
payload compartment, uses 2 small bands of
heat-shrink tubing that slide over a dowel to record
the maximum G-force and altitude attained. As
the rocket accelerates, the G-force band is pushed
down by washers on a spring, and as the rocket
rises, the altitude band is pushed down the rod by
the expansion of a pressure chamber made from a
pill bottle and a rubber-balloon membrane.
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Chladni Plate

Chladni Plate
Edwin Wise | Make Vol. 16- 2008 | Pdf | 11 pgs | 3 mb

BEATIFUL ACOUSTICS
Use a broken speaker, bits of wire, and
tape to prepare a coneless voice coil
driver, then use it to generate standing
waves on a sheet of metal, making
sound visible. Magic!

My knowledgeable friend Robin once
said that you don't need to worry about
having too big an audio amplifier,
because speakers are usually damaged
by under-powered amps working too hard
and clipping the signal, creating rough
square waves with too much power.
I learned that this is true when I melted
a speaker's coil by running a strong
20Hz signal through it, to drive a vortex
cannon (MAKE, Volume 15, page 114).

On the bright side, I now had a nice
speaker magnet to use as the foundation
for something else I wanted to try,
a Chladni plate!
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DIY-brary

DIY-brary
Rick and Megan Prelinger couldn't find a library
with what they wanted, so they made their own
R.U. Sirius | Make Vol. 16- 2008 | Pdf | pgs | mb

It's an overcast Monday afternoon as I arrive at
8th and Folsom in San Francisco's seedy, bohe-
mian SOMA district. I find 3018th Street and then
buzz Room 215. A voice says hello. I tell him who
I am and he buzzes me in. I take an elevator to the
second floor, walk past several closed offices, and
enter a small room packed to the rafters with four
rows of shelves filled with books stacked 15 feet
high. This is not your typical 21st-century urbane.
haute-culture library.

The Prelinger Library (prelingerlibrary.org) is
the brainchild of Megan Shaw Prelinger and Rick
Prelinger. Founded in 2004, it's a DIY, appropriation-
friendly, intuitive, and highly personalized context for
organizing and sharing this couple's books, periodi-
cals, printed ephemera (like obscure government
documents from the Department of Indian Affairs),
and - most of all - their obsessions. In addition to
its physical presence in San Francisco. it has an on-
line presence of more than 3.000 scanned volumes
at the Internet Archive (archive.org).
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Wheelchair Safety System

Wheelchair Safety System
Bryant Underwood | Make Vol. 16- 2008 | Pdf | 1 pgs | .4 mb

My daughter Katy uses an electric wheelchair
and last year she went off to college. Her mom and
I were concerned about Katy's safety in navigating
the campus -- she might get her chair stuck or have
some other type of trouble and not be able to get to
her cellphone.

So I used a Parallax microcontroller to control
a GSM cellphone as a "telematics" system for her
wheelchair. Inside the gray box mounted on the
back of her chair. I use the phone in speakerphone
mode with an external microphone and speaker.
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