6
People that are deaf need lights to tell them
when a doorbell is ringing. They also use
circuits like this to tell them if an alarm has
been triggered or an oven is ready.
Can you think of other uses?
Different sounds that can easily be
changed are very important when
designing games and toys.
Wave & Watch
This circuit does not use the noisy speaker (SP) but instead uses a
nice quiet LED (D1). Turn on the slide switch (S1), the LED ickers.
Wait a few seconds, and then cover the photoresistor (RP), and the
icker stops. The icker is controlled by the photoresistor; uncover it
and the icker resumes.
Switching Sounds
Build the circuit shown on the left.
When you close the slide switch (S1),
the integrated circuit (U2) should start sounding an up-down siren. This
is just one more sound effect that this integrated circuit is designed to
produce. Switch the sound on and off quickly and see if you can create
even different effects. This mode will create many robotic sounds if
switched quickly.
Project 70
Project 71
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