Project 21
Space War
Build the circuit shown on the left, which
uses the space war IC (U3). Activate it by
flipping the slide switch (S1) or pressing the
press switch (S2); do both several times and
in combination. You will hear an exciting
range of sounds, as if a space war is raging!
Project 22
Use the preceding circuit, but replace the slide switch (S1) with the
phototransistor (Q4), with “+” toward U3. The circuit immediately makes noise
(unless the room is very dark). Cover and uncover the phototransistor to
change the sound, or push the press swtch (S2). Do both several times and
in combination.
Note: the phototransistor is very sensitive, and even a small amount of light
may be enough for it to activate the space war IC. You may need to be
covering/uncovering the phototransistor in a relatively dark room.
Photo Space War
The upper-right snap of the space
war IC is like an electrical gate,
opening and closing quickly to let
small bursts of electric current flow
in. The bursts of electric current also
flow through the speaker (which
produces sound). The space war IC
produces the different sounds by
adjusting the pattern of two
separate current bursts through the
speaker.
Like the other integrated circuits, the
space war IC is a super-miniaturized
electronic circuit that can play a
variety of cool sounds stored in it by
using just a few extra components.
In movie studios, technicians are paid
to insert these sounds at the precise
instant a gun is fired. Try making your
sound occur at the same time an
object hits the floor. It is not as easy
as it sounds.
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