Elenco Snap Circuits® Deluxe Sound & Light Combo - Manual (Page 37)

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Fiber Optics Project 12
Black
Clear
This project is more exciting than it looks. The tone sounds produced
by the strobe IC (U23) are played on the speaker (SP2), even
though there is no electrical connection between them.
The left half the circuit makes a coded light signal, which you see in
the red LED (D1). The right half of the circuit decodes the light signal
and plays it on the speaker. The fiber optic cable is used to transmit
the light signal between the two sides of the circuit. There is no
electrical connection between the left and right halves of the circuit,
only a light connection using fiber optics! If your fiber optic cable was
longer, the two halves of the circuit could be many miles apart.
This circuit is an example of using fiber optic cables for
communication. Fiber optics allows information to be transmitted
across great distances at very high speeds with very low distortion,
by using light.
Build the circuit as shown, turn off the left slide switch (S1), and turn
on the right slide switch. Press keys on the keyboard (U26) to make
sounds and change the light on the color organ (U22). Turn on the
left slide switch to add optical control, and wave your hand over the
photoresistor (RP) to also change the sound and light. For best
effects, place the egg LED attachment on the color organ.
Next, try removing the 1mF capacitor (C7) and see how the sounds
change.
Next, try replacing the photoresistor with the phototransistor (Q4, “+”
on right) and wave your hand over it.
Next, replace the left slide switch with the 500kW adjustable resistor
(RV3). Turn the knob on it while varying the light to the phototransistor.
Build the circuit as shown. Place the clear cable holder on the red LED
(D1) and the black cable holder on the phototransistor (Q4), then place the
fiber optic cable into the holders as far as it will go. For best performance
the cable should stand straight up in the holders, without bending them.
Turn on slide switch (S1) and move the lever on the adjustable resistor (RV)
around. The sound from the speaker (SP2) changes as you move the lever on RV.
See the Sound Project 11
SCC-350_Manual_Part_A.qxp 7/25/14 2:40 PM Page 37