Elenco Projects 1-101 - Manual (Page 36)

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Project #71
OBJECTIVE: To turn a lamp on and off using light.
Cover the unit, turn the slide switch (S1) on, and notice that the
lamp (L1) is off after a few seconds. Place the unit near a light and
the lamp turns on. Cover the photoresistor (RP) and place it in the
light again. The lamp will not turn on. The resistance of the
photoresistor decreases as the light increases. The low resistance
acts like a wire connecting point C to the positive (+) side of the
battery (B1).
Light-Controlled Lamp
OBJECTIVE: To turn a lamp on and off using the voltage
generated from a photoresistor.
Project #73
Use the circuit from Project #71. Remove the photoresistor (RP) and
connect the whistle chip (WC) across points A & B. Turn the slide switch
(S1) on and clap your hands or talk loud near the whistle chip (WC), the
lamp will light. The whistle chip has a piezocrystal between the two
metal plates. The sound causes the plates to vibrate and produce a
small voltage. The voltage then activates the music IC (U1) and turns
the lamp on.
Project #72
Voice-Controlled Lamp
OBJECTIVE: To turn a lamp on and off using the voltage
generated when a motor rotates.
Use the circuit from Project #72. Remove the whistle chip (WC) and
connect the motor (M1) across points A & B. Turn the slide switch (S1) on
and turn the shaft of the motor and the lamp (L1) 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).
Motor-Controlled Lamp