Our idea was to put a buzzer that
produces a steady tone on a string that one person could
swing around in a circle
while someone else stood outside the circle. The person
in the middle of the circle should hear a uniform tone.
The person outside the circle should hear a rising and
falling pitch - higher as the buzzer approaches and lower
as it recedes.
We found
a small electric buzzer that could be powered by a 9 volt battery. For
safety, we enclosed the battery and buzzer in a tennis ball.
The idea
is to help
prevent damage to the components should the ball hit something, and should
that something be a person, it would help prevent injury. Still, if you
build and
use this device, make sure that no one is in the way when you are swinging
it in circles.
- Electric Buzzer (we used RadioShack item 273-060)
- 9 volt battery
- 9 volt battery connector
- tennis ball
- string
- rubber bands
- heat shrink tubing or tape
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Using a small knife we made a slit about 1/3
of the way around the ball. Opposite the slit we
made a small hole for the string to go through.
We forced the end of the string through the hole
and then pulled it out of the ball through the
slit. We left about 20cm of string hanging out
from the slit and about 5m from the side with the
hole.
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Using a wire stripper we removed about 2cm of insulation
from the ends of the wires attached to the buzzer
and to the battery clip. |
We put a 2cm length of heat shrink tubing on each
wire from the battery clip and then twisted the battery
clip and buzzer wires together, red to red and black
to black.
|
 We soldered the connections, trimmed the excess
wire and moved the heat shrink tubing over the soldered
joints. Then we held the joints at a distance over
the flame on a gas range to shrink the tubing.
Soldering
and working with heat shrink tubing should be done
only with adult supervision. You can skip these steps
and your device will still work. Just make sure the
wires are well twisted together and cover them with
tape for insulation instead of heat shrink tubing. |
The next step was to tie the end of the string
that emerges from the slit in the ball to the buzzer.
This
knot must be very secure. Our buzzer has two extensions
with holes in them, convenient for tying.
|
Next we used two rubber bands to secure the battery
to the buzzer.
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OK, now we have all the pieces together. |
Next, we pushed the battery and buzzer into the ball
with
the terminal end of the battery facing towards the
slit. This is so the battery clip can be easily attached
and removed from the battery. |
Since the tennis
ball muffles the sound of the buzzer we used a knife
to cut a hole in the ball so that the sound element
of the buzzer is exposed. We also stuffed the excess
wire into the ball through the slit.
|
 That’s
it. Now out to the park to give it a try. We pressed
the battery clip onto the battery to start the buzzer
buzzing and then twirled the buzzer ball around. The
cameraperson who took this picture heard a rising and
falling tone while the twirler heard a steady pitch.
The biker and the runner would also have heard a rising
and falling pitch if they had been paying attention.
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