March
2005, Issue 176
Joystick
Technology
E-Switch
makes the JS1100AQ, which is a five-position joystick
navigation switch. It's essentially five switches in
one. A vertical press makes one set of contacts. A tilt
makes contact with one or two of the four-corner contacts
in a similar fashion to Atari's digital joystick.
The
JS1100AQ is a surface-mount part, measuring approximately
0.3" square. If you mate the switch to Maxim DS1869
digital potentiometers, tilting the JS1100AQ toward
a corner will engage a single switch (see Figure 1).
Opposite corner switches are tied to the increment (up)
and decrement (down) inputs of the same DS1869. This
allows for the independent action of each digital potentiometer
or a combined action of adjacent switches by tilting
to a side.
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(Click
here to enlarge)
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Figure
1—By connecting a JS1100AQ to multiple DS1869s,
the directional switch closures can enable the
internal incrementing and decrementing features
of each of the digital potentiometers.
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The
DS1869 has 64 taps over its total resistance (available
in 10, 50, and 100 kW). It will automatically increment
or decrement at a rate of 100 ms if an input is held
for at least 1 s. Each of the potentiometer's resistor
chains is connected across the 5 V and ground supplies
in the circuit (although you could use other voltages
as long as they fall within the chip's supply limit
of –8 to 8 V). Unfortunately, this is the only manually
operating digital potentiometer I've found. If you need
more resolution, you must add some smarts.
