Elenco Projects 102-305 - Manual (Page 72)

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Project #296
OBJECTIVE: To show how capacitors can filter out electrical
disturbances.
Place the fan on the motor (M1) and turn off the slide switch (S1).
Press the press switch (S2) and listen to the motor.
As the motor shaft spins around it connects/ disconnects several sets
of electrical contacts. As these contacts are switched, an electrical
disturbance is created, which the speaker converts into sound.
Turn on the slide switch and push the press switch again. The fan spins
just as fast, but the sound is not as loud. Capacitors, like the 470
μ F
capacitor (C5), are often used to filter out undesired electrical
disturbances. If you replace C5 with one of the other capacitors in your
set then the sound will not be changed as much.
Quieting a Motor
Project #297 Transistor Fading Siren
OBJECTIVE: To build a siren that
slowly fades away.
OBJECTIVE: To build a
doorbell that slowly fades away.
Replace the alarm IC (U2) with
the music IC (U1). The circuit
has a doorbell sound that plays
and stops.
Turn on the slide switch (S1), then
press and release the press switch
(S2). You hear a siren that slowly
fades away and eventually goes off.
You can modify this circuit to make
machine gun or ambulance sound
instead like in the other projects. You
can also replace the 10
μ F capacitor
(C3) with the 100 μ F (C4) or 0.1 μ F
(C2) to greatly slow down or speed
up the fading.
Project #298
Fading
Doorbell
!
WARNING: Moving parts. Do not touch the fan or
motor during operation. Do not lean over the motor.