Elenco Electronics 202 - Manual (Page 25)

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Project #19
OBJECTIVE: To introduce you to the space war integrated
circuit and the sounds it can make.
Build the circuit shown on the left, which uses the space war integrated
circuit (U3). Activate it by turning on 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!
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.
Space War
Project #20 Light Switch
OBJECTIVE: To show how light
can control a circuit using a
photoresistor.
Use the circuit from project #19 above, but replace the slide switch (S1)
with the photoresistor (RP). The circuit immediately makes noise. Try
turning it off. If you experiment, then you can see that the only ways to
turn it off are to cover the photoresistor, or to turn off the lights in the
room (if the room is dark). Since light is used to turn on the circuit, you
might say it is a “light switch”.
The photoresistor contains material that changes its resistance when it
is exposed to light, as it gets more light, the resistance of the
photoresistor decreases. Parts like this are used in a number of ways
that affect our lives. For example, you may have streetlights in your
neighborhood that turn on when it starts getting dark and turn off in the
morning.
Project #21 Paper Space War
OBJECTIVE: To give a more dramatic demonstration of using the
photoresistor.
Use the same circuit as for project #20. Find a piece of white paper that
has a lot of large black or dark areas on it, and slowly slide it over the
photosensitive resistor. You should hear the sound pattern constantly
changing, as the white and dark areas of the paper control the light to
the photosensitive resistance. You can also try the pattern below or
something similar to it: