38 April 2017
aerospace days. So, I looked them up in the PIC Design
Yikes. The price was $29 for the belt and $54 for two
mating toothed pulleys. I debated whether I should simply
use a belt made of o-ring type rubber, which probably
would have worked fine. Figure 7 clearly illustrates that I
caved in and spent the money for the cool looking blue
belt. The final rotation rate was about 5 RPM.
Adding Bells and Whistles
Figure 8 shows how I used
several 2-1/2“ curved girders to
build a start/stop lever on the
control box. The action sort of
duplicates the actuation of the
clutch mechanism in a real Ferris
wheel, instead of using a modern
Figure 9 is the schematic of
the whole system including the
latching relay circuit for the motor.
The start/stop lever also triggers
the newly added MP3 player
board to start the carnival music.
A while back, someone
suggested that a carnival-like
sound track would be a good
addition, so I did it. The music file
came from the Internet and was
transferred to a SparkFun
triggerable MP3 player board using
Audacity. The MP3 board was not
made to directly drive a speaker,
so I dug out an old RadioShack
powered speaker that I’ve had for
years and mounted it on the rear corner of the baseboard.
I never throw anything away because you never know
when you’ll need it! Although it took quite an effort to
add the sound track to the project, I’ll have to admit that
the carnival music made a big difference. It was just like
you were walking down the midway.
One day when I was in RadioShack, I stumbled across
a bunch of addressable tri-color LED light strips for a vastly
reduced price on the closeout rack. I figured the lights
would look great on the Ferris wheel, so I attached them
around the rim and down the spokes with lacing cord. The
strips require a 24-bit serial data
stream to control the brightness
and color of the tri-color LEDs. I
chose an Arduino to do the job
because it was easy to program,
had enough memory, and was
Figure 10 is an interior photo
of the newly added chassis box
containing the Arduino and MP3
player. As you can tell, the project
was rapidly spiraling out of control.
The bells and whistles were taking
Now the big question ... how
to get power and data to the
rotating LEDs? A slip ring rotary
joint was the answer. When I was
working in aerospace, mil-spec slip
ring assemblies were very
expensive. However, a quick look
on eBay saved the day. For under
$10, I found a commercial six-conductor plastic unit from China,
and it got here in less than a week.
FIGURE 10. The red SparkFun triggerable MP3
board plays carnival music to give the project
the feel of the midway.
FIGURE 9. An Arduino microcontroller sends 24-bit serial data to the
tri-color LED strips to produce various flashing patterns.
FIGURE 8. My start/stop lever switch emulates the
manual clutch lever used on old-fashioned carnival
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