Project 78
Pop On, Pop Off
The speaker uses electromagnetism to create
changes in air pressure, which your ears feel
and interpret as sound. Think of the speaker
as creating pressure waves in the air just like
waves in a pool. You only see waves in the
pool when you disturb the water, so the
speaker only makes sound when the voltage
changes.
Turn the slide switch (S1)
on and off several times.
You hear static from the
speaker (SP2) when you
turn the switch on or off.
Project 79
Crazy Combo
Build the circuit shown. Turn it on, press the press switch (S2) several
times, and wave your hand over the phototransistor to hear all the sound
combinations. You can make the sound from the music IC louder by
replacing the 100
W
resistor (R1) with the 2.5V lamp (L1).
Project 80
Alien Alarm
Build the circuit shown on the left and turn on the slide switch (S1).
Press and hold the press switch (S2) to make the lamp (L1) brighter.
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