Elenco Electronics 202 - Manual (Page 43)

-42-
Project #71
OBJECTIVE: To turn a lamp on and off using light.
Light-controlled Lamp
Project #72
OBJECTIVE: To turn a lamp on and off using the voltage
generated when a motor rotates.
Motor-controlled Lamp
Build the circuit on the left. You will find that the lamp (L2) is on
when neither the slide switch (S1) NOR the press switch (S2) are
on. This is referred to as an NOR gate in electronics and is
important in computer logic.
Example: If neither condition X NOR condition Y are true, then
execute instruction Z.
Project #73
OBJECTIVE: To build a NOR gate.
Light NOR Gate
Cover the unit, turn the slide switch (S1) on, and notice that the lamp (L2) is off
after a few seconds. Place the unit near a light and the lamp turns on. Cover
the photoresistor (RP) and place it near 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).
Use the circuit from project #71. Remove the photoresistor (RP) 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 (L2) 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).