Elenco Projects 102-305 - Manual (Page 10)

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Project #104
Spacey Fan
OBJECTIVE: To build a fan
with sound that is activated by
light.
Place the fan onto the motor (M1).
Sounds are heard if light shines on
the photoresistor (RP) OR if you
press the press switch (S2), the fan
may start to spin, but will only get to
high speed if you do BOTH. Try
various combinations of shining light
and holding down the press switch.
Project #106
OBJECTIVE: To show how light is used to turn an alarm.
The alarm will sound, as long as light is present. Slowly cover the
photoresistor (RP), and the volume goes down. If you turn off the
lights, the alarm will stop. The amount of light changes the resistance
of the photoresistor (less light means more resistance). The
photoresistor and transistor (Q2) act like a dimmer switch, adjusting
the voltage applied to the alarm.
This type of circuit is used in alarm systems to detect light. If an
intruder turned on a light or hit the sensor with a flashlight beam, the
alarm would trigger and probably force the intruder to leave.
Light-controlled Alarm
Project #105
Two-Transistor Light Alarm
OBJECTIVE: To compare transistor circuits.
This light alarm circuit uses two
transistors (Q1 & Q2) and both
sets of batteries. Build the circuit
with the jumper connected as
shown, and turn it on. Nothing
happens. Break the jumper
connection and the lamp (L2)
turns on. You could replace the
jumper with a longer wire and
run it across a doorway to signal
an alarm when someone enters.
!
WARNING: Moving parts. Do
not touch the fan or motor during
operation. Do not lean over the
motor.
Visit www.snapcircuits.net or page 74 to learn about Snap Circuits ® upgrade kits, which have more parts and circuits.