"HOLOGRAPHIC" VIDEO HALO
I've found a way to trigger creativity: fall half-asleep
while taking a
air. Zone out in an airliner while intending to have some weird ideas.
Bring a blank notebook along of course,
so you can quickly record anything interesting that pops into your mind.
I suspect that this is
similar to a purported shaman technique for triggering odd dreams: fall
asleep in a hammock.
2006 W. Beaty
ANYWAY, while flying to Florida for 2005
was sitting there with a blank pad of paper and wondering what cool
stuff I could build someday, when I had a detailed vision of an
attention-getting device to sell at SF
conventions: glowing advertisements which float around your head with no
apparent cause. Very
appropriate for cons: it's a kind of propellor-beanie with lots of
whirling LEDs. The perfect geek fashion accessory, one which screams
"huge flaming Nerd."
(Actually I think I had a similar
LED-propellor-beanie idea many years ago at a con, but that was long
CPUs or ultra-bright LEDs existed ...and I didn't write it down.)
A motor spins a cylindrical rotor having vertical stripes of ~20 LEDs
driven by a PIC/AVR/etc. The rotor must be fairly smooth and low-speed
so it doesn't drain the batteries by acting as a fan. Rather than
dangerously spinning just one LED array at 60Hz/3600RPM, multiple
synchronized LED stripes allow low RPM with little flicker: 24Hz flicker
isn't too bad, and with six arrays it gives four rotor revs per second.
Most important: the mechanism and rotor would be almost invisible. It
wouldn't be very bright, so it would only work indoors. Walk up to
victims and "talk" by triggering stored sentences responding to typical
questions. "IT'S A MECHANICALLY-SCANNED LED ARRAY." "YOU CAN'T BUY
THESE, IT'S ONE OF A KIND." "NO, THERE ARE NO GLOWING LETTERS HERE, YOU
MUST BE HALLUCINATING." "HI THERE, DO YOU COME HERE OFTEN?" Display a
personal ad, or rent out the space to advertisers?
A DC motor is mounted on a transparent, heat-formed "plexiglas yarlmuke"
adhered to my bald scalp. Even though the transparent rotor spins at only
a few revs per second, it's almost invisible because it's built from
multiple transparent "blades." As with bicycle wheels, slow rotation of
numerous spokes causes invisibility via total blurring.
My first prototype had six blades made of adhesive tape supporting a
transparent 12" dia. cylinder about 3" tall. It spun at three or four
revs per second, and the six white stripes I stuck to the cylinder would
totally vanish at this low speed. I demonstrated it at 2005 december
Dorkbot in Seattle.
I didn't get very far beyond the crude proto of the rotor section
wo/LEDs. I hope to use (six?) synched, phase-shifted POV strips to allow
low, non-dangerous RPM. The rotor structure is made from bent 1/64"
transparent acrylic sheet taken from a Walgreens "poster frame." A 4"
plexi disk on the small DC motor's shaft has six horizontal blades
supporting the cylinder. The cylinder is very visible in this case, but
if large diamond-shaped "teeth" are cut in the edges of the cylinder, the
edges (and therefore the entire cylinder) will become nearly invisible.
With low mass at this low RPM, the edge moves at 10'/sec or 7MPH and can
be safely stopped with a finger. Even at this low speed it drew a few
hundred mA at a few volts (it takes lots of work to stir the air.)
Letters composed of red LEDs, 6x20 = 120 LEDs at 20mA would draw two or
three watts. More brightness and more wattage: each strip could be three
LEDs, RGB, with tiny phase-shift to lay the color LED flashes on top of
other. Next task: adapt a Radio Shack 4-conductor slip-ring
"phone cord untangler" to supply signal and power to the rotor section.
The real challenge would be to align all the LEDs so the six
images appear very static, and don't jump around vertically per each
revolution. Stretched tape
is the wrong idea: the supporting
"blades" need to be stiff in order to prevent distortion of the rotor or
vertical wobble of the
cylinder. Another challenge: to walk around without moving my head (since
any head-tilting causes a huge gyroscopic effect!)