Project 39
Spin Sound
Build the circuit shown on the right, but leave the fan off the
motor (M1). When you turn on the slide switch (S1), the music
may play for a short time and then stop. After the music has
stopped, spin the motor with your fingers. The music should play
again for a short time, then stop.
Project 41
Nifty Noises
Build the circuit shown. Turn it on, press the
press switch (S2) several times, and cover the
phototransistor (Q4) several times to hear all the
sound combinations.
Project 40
Loud Spin
Sound
Use the preceding circuit but
replace the 100
W
resistor
with a 3-snap wire. Now the
sound is louder. In this project,
you changed the amount of
current that goes through the
speaker (SP2) and increased
the sound output of the speaker.
Project 42
Loud Nifty
Noises
Use the preceding circuit
but make the sound from
the alarm IC (U2) louder by
replacing the 100
W
resistor
(R1) with the 2.5V lamp
(L1).
Resistors are used
throughout electronics
to limit the amount of
current that flows.
A photoresistor is a light-controlled
variable resistor. The resistance of the
photoresistor
decreases
with
increasing light intensity.
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