Elenco Electronics 202 - Manual (Page 119)

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Project #278
OBJECTIVE: To build a high-frequency oscillator.
Build the circuit and set the adjustable resistor (RV) to the middle
position. Turn on the slide switch (S1) and you hear a high-frequency
sound from the speaker (SP). Move the adjustable resistor slightly to
the left or right and the frequency changes. Quickly rotate the motor’s
(M1) shaft back and forth and the frequency changes.
Motor Tone Generator
Project #279
Motor Tone
Generator (II)
OBJECTIVE: To lower the frequency of
tone by changing the capacitor.
Replace the 0.02 μF (C1) with a 0.1μF (C2).
Now the circuit generates a lower tone.
Project #280
Motor Tone
Generator (III)
OBJECTIVE: To change the tone and
loudness of the generator.
Now replace the motor (M1) with the 1k Ω
resistor (R2). Set the adjustable resistor (RV)
to the middle position and turn the slide
switch (S1) on. The circuit generates a lower
and louder tone than project #279.
Project #281
Motor Tone
Generator (IV)
OBJECTIVE: To use light to change the
tone.
Next replace the 1k Ω resistor (R2) with the
photoresistor (RP). Set the adjustable
resistor (RV) to the middle position and turn
the slide switch (S1) on. Change the tone by
waving your hand over the photoresistor.
Adjust the adjustable resistor to for different
tones.