PROJECTS: SOLAR XYLOPHONE
makezine.com/12/xylophone
X-PHONE SPEX
HOW IT WORKS
A regular xylophone fits inside of a solar-powered
player box that holds a mallet over each of its
8 chime tubes. Each mallet is powered by a system
that includes a solar cell, a simple Solarengine
circuit, and a small motor. The systems work
in parallel; the brighter the sunshine on each
panel, the more frequently its corresponding
tube will be struck.
The sun
shines upon
your project.
The 8V 44mA
epoxy solar
cell collects
light energy,
converts it
to DC, and
trickles it
into the
circuit. The
more light
it sees, the
more power
it delivers.
The circuit,
a Miller
Solarengine,
collects the
energy in
a 4,700µF
capacitor until
its voltage
exceeds 5V.
Then a voltage
trigger opens
and discharges
the capacitor
into the motor.
A smaller 1.0µF
monolithic
capacitor
sets the
discharge’s
duration.
With each pulse
of voltage, the
pager motor
pulls its mal-
let down with
a bent paper
clip. The motor
has a spring on
the shaft that
inhibits rotation
beyond 60°.
This means
it gives one
strong momen-
tary nudge
rather than
rotating con-
tinuously. This
is useful for our
application.
A counterweight, made
of plumbing
solder, makes
it easy for
the motor
to keep the
mallet head
lifted off the
tube between
strikes.
When the
mallet is
pulled down,
it strikes its
chime tube.
The 2 balance
strips that
run along
either side
of the instrument hold
the mallets
and serve
as a fulcrum
for them to
swing around.
The chimes
are tuned
to cover 1½
octaves using
a pentatonic
scale. This
keeps the
notes sounding pleasant
and not
dissonant in
random combinations.
Illustration by Nik Schulz
100 Make: Volume 12
