Technical description of some of the displays
and the outside sign
At present, this section is a rambling brain dump of preliminary ideas
on what the displays would need technically, plus some sketches of
concepts. The detailed design is yet to be worked out, with the help of
the people who will actually be assembling the experiments. I expect
that helpers qualified to build these will also know how to fill in
many of the blanks. I will work closely with people to refine the
designs as details become apparent.
The numbering here is the same as in the "list of experiments" page. Order is random.
0. The sign/facade
The public presence of this installation will be defined by the sign
people see when they walk by. It has to compete with all the other neat
stuff, yet convey the sense of the place if only to warn the unwary. It
is basically the facade of the building/tent that houses the displays,
and so is large and needs to be structurally sound. Assuming the tent
is about 22-25 feet across, that's the sign dimension. The letters need
to be visible in day or night, with probably the best appearance at
night, as things are always more interesting in BRC then. One could
fall back on just shining light at it, but I imagine letters
self-illuminated with linear light sources, either rope lights (for the
large letters) or electroluminescent wire (for small letters and
decorations). As indicated in the drawing, one can allow the linear
lights their safe radii of curvature (about 2 inches for rope light)
while maintaining a good square appearance to the corners of the
letter. The decorations tell more of the story as regards the attitude
of the place, making it seem fun and mysterious. These can be
fabricated the usual elwire way, with screens. Maybe the decorations
flash off for a moment periodically, making the ensemble of them sort
of sparkle. If there is a convenient multi-channel driver with control
inputs available, then do it, otherwise they could all just simply glow
off of one power supply. Issue here might be capacitance of all of them
in parallel. Optimize cost and time, as always.
Sign has a frame of square steel tubing or maybe water pipe, holding
screen material where letters are attached, and guy wired to the ground
in four places to prevent movement in any direction. Letters are
separate units, steel wired on to the screen or frame. These have to
withstand wind force, of course.
See a drawing of a suggested configuration here.
8. Uncertainty principle
The experiment consists of two parts: an optical part and a sound part.
The optical part will be built from parts anyone can find at home: a
laser pointer and a wire cutter. The laser pointer beam is narrowed
down as the jaws of the wire cutter are closed, possibly by a screw
adjust to make it easy to close by small increments and leave there.
The narrowed beam goes about 3 feet to a white piece of plastic. This
size experiment would have to be on a special 3 foot by maybe 6 inch
board, bolted to the text panel. A pushbutton turns the laser on
momentarily.
The sound part would have an oscilloscope (a cheap, low frequency one,
probably from some electronic swap meet, but with trigger capability),
and some knobs to control sounds that the visitor could hear through
speakers. A sine wave audio oscillator (frequency variable by knob)
would be gated on and off to produce pulses, repeating at abour 5Hz.
The pulse width could also be varied by a knob so that the repeating
beeps can be made shorter or longer. (This could all be turned off when
not in use, so it is only occasionally annoying.) As the beeps are
decreased in duration, the carrier (oscillator frequency) gets harder
to discern, so that the carrier frequency could be varied over some
range and the listener wouldn’t be able to tell. The text would
suggest to get someone else to vary the knob, so that a person
wouldn’t fool themselves. The oscilloscope would display the
audio pulse waveform. Maybe the pulse rise and fall times should be
gradual (1 or 2ms rise and fall), so as not to introduce too many high
frequencies. Let’s say audio from 500 to 1000Hz, and pulse width
from 100ms to 5ms, to start with. Needs to be played with to get the
right effect. The gating pulse should probably be synched with the
audio carrier, so that the oscilloscope picture is consistent. Trig the
scope on the gate and see the same waveform every time. Knobs on front
of panel, with scope behind acrylic window.
See a block diagram of a suggested circuit here.
4. Game of life
A computer is needed that can play the “game of life”, that
old math game from Scientific American in the 1970s. Using a mouse and
a menu, the visitor can load or delete cells, or load complex patterns
like glider guns. This is primarily an interface design task, so that
the viewer doesn’t have to do much to get interesting results,
then things clean themselves for the next person. The softwave might
already be available, and a little customizing is all that’s
needed. Interface is standard mouse. Issue is that current software
might need a recent computer, and a discarded junker is what’s
more desirable for security reasons. Graphics should be ultra simple
and ugly, using junkyard monitor.
See a drawing of a suggested configuration here.
7. What is a wave?
People have to play with two sine waves, which add to produce a third
wave. All three are on an oscilloscope, which narrows the range of
possible cheap scopes that can be used. Maybe there is another way of
displaying them, such as on a cheap, used computer with a DAC card, as
these waves are low frequency. In that case, maybe it can all be
digital. But the suggested embodiment is a couple of voltage controlled
sine oscillators, an attenuator, and a phase shifter. One can switch
one of the oscillators to be in both legs in order to assure they are
the same frequency. Then the phase is mainly what matters. With
frequencies in the mid-audio range, the listener can hear "beats" and
adjust frequencies accordingly. The frequency that's not changed in
amplitude is the reference, and goes to the trigger.
See a drawing of a suggested configuration here.
2. Black boxes of reality
Three boxes have two pushbuttons on one end and a light on the other.
The top can be flipped up to reveal the mechanism inside, but is
typically held down by a magnetic latch or gravity. The two buttons
need to be pushed at the same time to light the light. One box has two
electronic switches in series with a light. Another has two pushbuttons
connected to two ends of a cross bar with its center attached to a
switch that activates the light (a mechanical way of realizing the
“and” function). The third box has the pushbutton switches
connected to a logic gate IC, and it drives the light. The IC is
labelled “black box.” It would be nice if the switch
contact mechanism was visible, due to the design of the (off the shelf
or surplus) switches.
See a drawing of a suggested configuration here.
3. The white crow
The viewer pulls a lever like one on a jackpot, and a wheel spins and
stops, showing a black crow, most of the time. Many crows on the wheel,
all black except for one white one. Maybe the wheel is rigged to never
stop on this one. Not sure if they are all visible when it’s
spinning, but if so, that would justify rigging the wheel. An old
mechanism from a real jackpot would be ideal, with no parts except for
the lever and one wheel, and the eventual stopping mechanism. If
multiple wheels needed to be used (due to how the mechanism is
constructed), all black crows are applied to all wheels except one
white one on one wheel. Other mechanisms could be constructed, using
parts from old bicycles, for instance. Anything that realizes the
spinning wheel randomizer principle, on which can be put a large number
of crow images. Not desirable to do it electronically, as that’s
too mysterious, even more untrustworthy. One likes to see the white
crow and never have it come up.
See a drawing of a suggested configuration here.
8. Optical illusions
Three illusions here. One is a nice transmission hologram illuminated
by a laser.
These are the most convincing holograms, with lots of depth and
resolution. The viewer can put their hand in the space of the 3D image,
without touching the hologram itself or the laser. Or maybe they wave a
fixed object on a pivot point through the image by grabbing a lever.
Hand is better, because it seems more direct.
See a drawing of a suggested configuration here.
The second illusion is that of color, produced by three LEDs of RGB
primary colors. The LEDs would have one control knob each to vary the
brightness. Viewer could make any color, while knowing that all it was
was three colors. All LEDs are behind a diffuser that mixes the colors,
though this diffuser can be flipped up to show the
three LEDs.
The third illusion is a classical optical illusion on paper. An
illusion of motion from concentric circles made of zigzags, or spots
appearing at intersections of white lines. Some nice
illusions will be collected and evaluated.