Hardware Reference
In-Depth Information
Client #2: A Balance Board Client
Client #2 is a balance board. To control it, you stand on
the board and tilt left or right. To stay in the middle, you
have to balance the board. An accelerometer at the center
of the board senses it tilt from side to side. The physical
interaction for this controller is very different than the
last. It requires more action from you, and it takes more
physical agility to operate. However, the behavior of this
client is identical to the previous one—from the server's
point of view.
thick. Each one is two inches from the center diameter
of the circle, as shown in Figure 5-11. Glue the two circles
together with their grains opposing each other.
Next, cut two arcs 12 inches across, as shown in Figure
5-10. Glue the arcs into the slots and let them dry. Make
sure it's very solid before you try to balance on it.
The case for the balance board was adapted from the
joystick client. The differences are that the connect/
disconnect button took the place of the joystick, so the
second large hole could be removed and the whole box
made shorter. Mount the control box at the center of your
balance board, as shown in Figure 5-12.
The balance board itself is based on a design by the
Adaptive Design Association
(http://adaptivedesign.org
),
a New York City-based organization that gets people
involved—families and community volunteers—in making
safe and affordable furniture and equipment for children
with disabilities. A balance board is great for helping to
strengthen your balance, and it's fun as well.
The code for the balance board client is also very similar to
the joystick client. All you have to change is the values for
the left and right thresholds. To discover them, do as you
did with the joystick: put the accelerometer on the balance
board, program the Arduino to print out the value of the
analog input, and tilt it both ways to learn its extreme.
Then fill those values in for
left
and
right
. Everything else
stays the same. That's the beauty of using a clear, simple
protocol: it doesn't matter what the physical input is, as
long as you can map changes recorded by the sensors to
a left-right movement, and program the microcontroller to
send the appropriate messages.
The physical construction for the balance board client
case is similar to the joystick client—you can use the
same template with the same LED setup. Just make the
joystick hole smaller to hold the pushbutton, and don't cut
a second hole.
To construct the board, you'll need heavy-duty triple-wall
cardboard. Many packaging supply houses carry it. If you
can't get triple-wall cardboard, you can laminate three
sheets of regular cardboard together using white glue.
When you're gluing layers together, make sure the grain of
the corrugations for adjacent layers runs perpendicular to
each other, for added stability.
It's worthwhile to try building both these clients, or one of
your own, to look at how different physical affordances can
affect the performance of different clients, even though it
appears the same to the server.
X
Cut two circles approximately 15 inches in diameter from
a sheet of triple-wall cardboard. In one of them, cut two
slots, 12 inches long and as thick as your cardboard. In the
board shown in Figure 5-12, the slots are roughly an inch
Figure 5-10
The balance board rocker. Make two of these.
Design courtesy of the Adaptive Design Association.
2.5”
12”
