Hardware Reference
In-Depth Information
Figure 1-14:
Wiring up an
LED.
When you know the circuit works, disconnect from the ground and then connect to the tran-
sistor via one of the output terminals - such as output 0. When the transistor is turned on,
it will allow the current to flow to ground and complete the circuit, so the LED will illumi-
nate. Turn the output on from the emulator and check that it lights.
Playing with the Reaction Timer
Now that you have connected an LED and switch, rerun the reaction timer program. Again
the LED should light after a random time and the switch should stop the timer. Now that
you know your wiring and circuit works, you can really start to have fun - try different out-
put devices, wire up a buzzer instead of the LED and see if your reactions to sound are
quicker. You could perhaps mount a feather on a motor and test your reaction to touch. You
might find this reaction to be quicker. This is because the inputs (nerves in the skin) can send
a message to the outputs (muscles) without going through a complicated processing system
(your brain) - the principles of computing apply to lots of other systems too! Experiment
with different input switches too - you could attach a switch to different parts of your body
and see if they respond as fast as your hand.
Have a go at making your own switch! Instead of a pre-made switch, you could wire up pieces
of aluminium foil as the contacts and detect when they are connected. Maybe you could
make a pressure pad for your foot, or have pieces of foil taped to your knees and complete
the circuit by bringing them together.
