Elenco LIGHT - Manual (Page 25)

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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 (SP) changes as you move
the lever on RV.
Project 11 Blinking Colors
Build the circuit as shown and turn on
the slide switch (S1). The white and
color LEDs (D6 & D8) are blinking.
Push the press switch (S2). Now the
red LED (D1) is blinking but the white
LED is off.
If you swap the locations of the red
and white LEDs, then the red LED will
be blinking and the white LED will be
off, and pushing the press switch
won’t change anything.
Red light is easier for LEDs to produce than
white light. When the red and white LEDs are
connected in parallel (which happens when S2
is pressed), the red LED will dominate because
it turns on more easily.
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 (SP),
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.