Theatre Design & Technology - Summer 2017 - Public - 61

political figures like Bernie Sanders, Barack Obama, and
Donald Trump (Figure. 1). Additionally, it was suggested
that these busts interact with the performers. We saw this
as an opportunity to incorporate automation using an
Arduino microcontroller to make the head movements
hands-free and cue-able.
To turn the busts, we chose to use four motors, one for
each, so that their positions could be individually adjusted
or cued if desired. Knowing that the busts needed to turn
their heads from side to side and that the motors would
have to carry the weight of the busts themselves, mostly
foam, we explored using hobby servo motors. These little
gear motors have a wide variety of uses and come in an
assortment sizes, torque, and speed ratings. Additionally,
they run on only five volts direct current (DC), meaning we could use a simple DC power supply. One benefit of these motors is that they have position feedback
information built into them, allowing us to specifically
tell them where to turn. We looked into different motors
with a higher amount of torque to help compensate for
the weight of the busts and found that our best options for
servo motors were Futaba S3010 and S3305 (Figure 2).
The hobby servo motors allowed us a wide range of
motion that was programmable through the Arduino;
however, how far the heads could turn was limited. Hobby servos with position control have a 180-degree range
before stripping or damaging a gear. Unfortunately, due to
a programming error, we encountered this during a test
run. Realizing we had damaged one of the nylon gears of
the Futaba S3010 servos, we adjusted our coding to include software limits. This effectively limited the range of
motion, from five degrees to 175 degrees, as a safety in
case the weight of busts caused the motors to slightly pass
their initial position. As an extra precaution, we upgraded
to a Futaba 3305 servo, containing metal gears.
In order to control movement, we connected the signal leads from the motors to four of the Arduino's Pulse
Width Modulation (PWM) outputs (Figure 3). Coding
for the Arduino allowed us to send PWM signals for precise speed and position to the motors. These leads were
connected to the Arduino through a terminal block. Power for the motors was separated from the Arduino and
connected to an independent power supply preventing
the possibility of an overload. This allowed us to avoid using servo motor shields and simplified programming by
using Arduino's built in servo program library. The terminal blocks allowed for secure electrical connections and
helped with cable management between devices, allowing us to bridge terminals or connect more than one wire
to each. Cable runs to the motors were done with threepin XLR mic cable for quick connections and because of
XLR's shielding properties. The shield of the cables was
connected to the power supply ground to keep electromagnetic interference (EMI) separate from the Arduino.

Figure 2

Figure 3

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