BY DAN DANKNICK
The appearance of stopping time
can be fun – and truly messy!
An associate sent me a link to a cool video
on the Internet that showed water droplets
moving upward toward the spout. No, this
wasn’t on Art Bell’s website and had nothing
to do with Nikola Tesla, zero point energy,
or the so-called Hutchison Effect. But it had
everything to do with real science known as
temporal aliasing a.k.a., the “stroboscopic
effect.” Wikipedia explains a machine
employed toward this visual phenomena as
“... an instrument used to make a cyclically
moving object appear to be slow-moving,
■ FIGURE 1. The completed Freeze Fountain.
Are you interested in building something both cool
and interactive? Would you like to learn about
microcontroller programming and basic electronics? If so,
this is the project for you! (And if your 10-year-old isn’t
already writing Web 2.0 programs in Python, this would
also make a great science fair project.)
What It Is!
The Freeze Fountain uses a submersible pump to emit
a droplet stream of water with a dissolved fluorescent dye.
It recirculates the flow into a catch bowl like a tabletop
fountain (Figure 1). As the drops fall, ultraviolet LEDs
continually strobe to excite the dye and convert UV light
to something visible. When observed in a darkened room,
groovy effects are exhibited (Figure 2). Manual controls
for droplet and illumination rates allow you to interact
with the device and have some fun. Set everything just
right ... and you can freeze the droplet flow in place.
Now that’s cool!
As a software engineer, I am well heeled in fixing
hardware problems through the magic of code. And as
a science geek, I love things that make noise, have
adjustments, and are messy. If you also feel that way, then
this is a project you will love!
52 May 2008
In any design, there is always some nuclear element
that sets the base requirements. In this case, it was
obtaining a submersible, low voltage DC powered pump.
Most of the fountain pumps I located on the Internet
were AC – either mains voltage or 12 VAC. They were
cheap because they used the AC for commutation, but
that made controlling their speed a complex problem.
Eventually, I found a nice submersible DC pump designed
for solar powered fountains. I had one directly shipped
from China and it was excellent: only 200 mA at six volts
and it came with a ton of piping accessories to tailor the
emitted water stream. I also knew that for whatever gallon
per minute (GPM) rate I chose, it would probably be
wrong so my control logic would need to PWM the
voltage to the pump to control it in some way. (Some
submersible pumps use manual occlusion shutters to
vary the flow and even before I ordered this pump, I knew
that was a liability for readers not wanting to experience
Enter the PICAXE-08M. I’d read about these for a
while but had never seen a really good project done with
one, so I ordered a chip just to play with. When coupled
with the (free) Programming Editor for Windows, you have