Elenco Circuit Maker Sound Plus 200 - Manual (Page 49)

Project #102
Turn on the slide switch (S1); the speaker (SP2) will sound and the LED
(D1) will light. Adjust the adjustable resistor (RV) to make different tones.
In an oscillator circuit, changing the values of resistors or capacitors can
vary the output tone or pitch.
Adjustable Tone
Generator
Project #104
Electronic Cicada
Using the circuit from Project #103, replace the photoresistor (RP) back to
the 5.1KW resistor (R3). Place the 0.1mF capacitor (C2) on top of the whistle
chip (WC). Turn the slide switch (S1) on and adjust the adjustable resistor
(RV). The circuit produces the sound of the cicada insect. By placing the
0.1mF capacitor on top of the whistle chip, the circuit oscillates at a lower
frequency. Notice that the LED flashes also at the same frequency.
It is possible to pick resistors and capacitors that will make the pitch higher
than humans can hear. Many animals, however, can hear these tones. For
example, a parakeet can hear tones up to 50,000 cycles per second, but a
human can only hear to 20,000.
Modify the preceding circuit by replacing the 5.1KW (R3) with the
photoresistor (RP). Turn on the slide switch (S1). The speaker (SP2) will
sound and the LED (D1) will light. Move your hand up and down over the
photoresistor (RP) and the frequency changes. Decreasing the light on the
photoresistor increases the resistance and causes the circuit to oscillate at
a lower frequency. Notice that the LED flashes also at the same frequency
as the sound.
By using your finger, see if you can vary the sounds enough to make this
circuit sound like an organ playing.
Project #103
Photosensitive
Electronic Organ
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CM-200_Manual_031914.qxp_CM-200_Manual_031914 4/2/14 12:04 PM Page 49