Project 104
Motor Space Sounds
Project 105
Twist & Blink
Turn it on and wait for any
sounds to stop. Then, spin
the motor (M1) and the
sounds play again.
Do you know why turning
the motor makes the sound
play? Actually, the DC
motor is also a DC
generator and when you
turn it, the motor generates
a voltage that triggers the
sound circuits.
The lamp (L1) is used here
as a 3-snap wire, and will
not light.
This circuit is loud and may bother
other people around you so replace
the speaker (SP2) with the color
LED (D8), (“+” side on top); the
circuit operates in the same manner
but now the color LED flashes
instead of the speaker making
sounds.
Project 106
Light-controlled Lamp
Project 107
Motor-controlled Lamp
Build the circuit to the left. Cover the phototransistor (Q4), turn the slide switch
(S1) on, and notice that the lamp (L1) is off after several seconds. Place the
unit near a light and the lamp turns on. Cover the phototransistor again. The
lamp turns off. The resistance of the phototransistor decreases as the light
increases. The low resistance acts like a wire connecting point C to the positive
(+) side of the battery activating, the music IC (U1).
Use the preceding circuit. Remove the phototransistor (Q4) and connect the
motor (M1) across points A & B. The lamp (L1) lights for a few seconds and
then turns off. Turn the slide switch (S1) on and turn the shaft of the motor and
the lamp will light. As the motor turns, it produces a voltage. This is because
there is a magnet and a coil inside the motor. When the axis turns the magnetic
field will change and generate a small current in the coil and a voltage across
its terminals. The voltage then activates the music IC (U1).
A
B
-45-
1
2
C
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