5. PREPARE A BASE (OPTIONAL)
Your Storm Globe will work fine without a base.
But I decided to make a Mars-themed version, so
I designed a base from the 3D model of the Block
Island rock mapped by the Opportunity rover on
Mars, and 3D printed it. The STL file is available at
github.com/grajohnt/StormGlass.
6. CODE THE BLUEFRUIT
There’s an excellent Adafruit Learning Guide that
explains everything about getting a Bluetooth
Snow Globe up and running. Read it at learn.
adafruit.com/snow-globe-bluefruit-cpb. Then
download the Storm Glass code from github.
com/grajohnt/StormGlass; it’s a lightly modified
version of their demo code.
The stormy section of the code lights up the
LEDs on the Bluefruit in such a way that it looks
like a lightning flash. This has some random-
ness included in it, so no two lightning flashes are
the same (Figure
G
).
7. START YOUR STORM!
Magnetic stir plates typically include a speed
control, which allows you to start the stirring
process gradually. This one doesn’t, so you must
be careful to get your stir bar stirring correctly.
If you look underneath the snow globe, you
should be able to see your stir bar. Tilt the globe
around until the stir bar is more or less in the
middle, and then place it on top of the assembled
base. Then plug the Bluefruit into a USB port to
start the stirring effect. If the stir bar flings off to
one side or just rattles around, you may need to
try again or adjust the distance slightly between
the fan and the base of the snow globe.
GOING FURTHER
There are a lot of ways you can experiment with
your Storm Globe and make it your own. Can
you make a better lightning animation or more
interesting LED lighting effects? Mount one on the
end of a staff for an outstanding wizard costume
effect? Maybe put waterproof lights inside the
sphere? Connect it to a Lightning Detector
circuit (Make: Volume 71, page 105) or trigger
it with real-time lightning notifications from
lightningmaps.org/apps?
I’ve noticed that the mica tends to eventually
settle up against the walls of the globe. Easily
fixed with an occasional shake and reset, but
perhaps maybe a different stir bar would create
enough turbulence to prevent it? (There’s a good
overview at makezine.com/go/stir-bar.)
Unfortunately we can’t control speed directly
from the Bluefruit, since the current draw of most
fans is too high for it. However, you could certainly
build a small circuit with a transistor to control
the speed with the Bluefruit. This could be used
to add a speed control knob or to slowly ramp up
the stirrer.
I’d love to see what you can do with rheoscopic
fluids and lighting effects; feel free to show off on
Twitter and let me know @grajohnt!
def lightning(cong):
start_time = time.monotonic()
last_update = start_time
while time.monotonic() - start_time < cong[‘duration’]:
if time.monotonic() - last_update > cong[‘speed’]:
for _ in range(random.randint(1,8)):
pixels.ll(0)
pixels.ll(cong[‘color’])
time.sleep(0.02+(.001*random.randint(1,70)))
pixels.ll(0)
time.sleep(.01)
time.sleep(5+random.randint(1,5))
last_update = time.monotonic()
VIDEO RESOURCES
•
My proof-of-concept video shows the
swirling effect of a back-lit Kalliroscope:
youtu.be/k0StfsKO8_U
•
Video of the Atmospheric Movement
exhibit at the Glasgow Science Centre
that inspired this project: youtu.be/
LYTtutG0StU
71
makeprojects.com
G
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