Elenco Snap Circuits SOUND &reg - Manual (Page 60)

Use the preceding circuit, but add the 0.1 m F
capacitor (C2) over the keyboard (U26)
using a 1-snap wire, as shown. Press a blue
and a green key at the same time, while
turning the TUNE knob.
Watch the colors on the color
LED (D8), and listen to the
sound.
Normally the color LED doesn’t work
when you connect it backwards, but in
this circuit it does. The changing
voltage produced by the keyboard
actually goes both ways (positive and
negative), so here the color LED will
work in either direction.
Project 112
Backwards Color
Sound
Use any of the 3 preceding circuits, but reverse the
direction of the color LED (D8). The circuit works the
same, but the sound may not be as loud and the LED
may not be as bright.
Use the preceding circuit, but use the 1 m F
capacitor (C7) instead of the 0.1 m F capacitor
(C2). Press a blue and a green key at the
same time, while turning the TUNE knob.
Watch the colors on the color LED (D8), and
listen to the sound.
Next, replace the 1 m F capacitor (C7) instead
of the 470 m F capacitor (C5). Press one of
the green keys and hold it down. Every few
seconds, the color LED flashes and you hear
a click from the speaker.
Build the circuit and turn the slide switch
(S1). Press any key on the keyboard
(U26), but just one key at a time. The
color LED (D8) lights (mostly red), and
you hear a tone from the speaker (SP2).
Now press one blue key and one green
key at the same time, to produce 2
tones on the speaker. Watch the color
LED (D8) closely; you should see more
green and blue color than before. Try
viewing it in a dimly lit room.
Now turn the TUNE knob while pressing
the blue C key and the green C key at
the same time. Slowly turn the knob
across its entire range, and see how the
LED color changes.
The spectrum of LED color here
depends on your batteries. With strong
batteries you will see more green and
blue. With weak batteries you will mostly
see red.
Project 109 Color Sound
Normally the color LED changes colors, but here
it doesn’t, why? The U26 keyboard produces a
changing voltage, intended to produce sound on
the speaker. The color LED is designed for use
with a stable voltage (like the batteries); when
used with the changing voltage from the
keyboard, it gets confused and blurs its pattern.
Red is the easiest color for the color LED to
produce, and blue is the hardest. So when the
voltage to it is weak, the more difficult colors get
dim first.
The keyboard produces separate tones for the
blue and green keys, which are played together
at the speaker. The two tones are also control
the color LED. When the tones combine, it is
easier for the color LED to produce green and
blue color.
Project 111
Color Sound (III)
Project 110
Color Sound (II)
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