Elenco LIGHT - Manual (Page 61)

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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 fiber optic cable should stand straight
up in the holders, without bending them.Turn on the slide switch
(S1), then push the press switch (S2) several times to send secret
messages between the circuits using Morse Code. If your fiber
optic cable was a lot longer, you could use this circuit to send
messages to your friends in different cities. The speaker is used
to help limit the current through the red LED, and will not make
noise.
If desired, you can swap the locations of the red and white LEDs
(D1 & D6).
Note: If the white LED (D6) does not light or is dim, replace it
with the color LED (D8). The white LED can be brighter and won’t
change colors, but requires higher voltage to activate.
Project 130 Morse Code
Morse Code: The forerunner of today’s telephone system
was the telegraph, which was widely used in the latter half
of the 19th century. It only had two states - on or off (that is,
transmitting or not transmitting), and could not send the
range of frequencies contained in human voices or music.
A code was developed to send information over long
distances using this system and a sequence of dots and
dashes (short or long transmit bursts). It was named Morse
Code after its inventor. It was also used extensively in the
early days of radio communications, though it isn’t in wide
use today. It is sometimes referred to in Hollywood movies,
especially Westerns. Modern fiber optics communications
systems send data across the country using similar coding
systems, but at much higher speeds. MORSE CODE
A . _
B _ . . .
C _ . _ .
D _ . .
E .
F . . _ .
G _ _ .
H . . . .
I . .
J . _ _ _
K _ . _
L . _ . .
M _ _ N _ .
O _ _ _
P . _ _ .
Q _ _ . _
R . _ .
S . . .
T _
U . . _
V . . . _
W . _ _
X _ . . _
Y _ . _ _
Z _ _ . . Period . _ . _ . _
Comma _ _ . . _ _
Question . . _ _ . .
1 . _ _ _ _
2 . . _ _ _
3 . . . _ _
4 . . . . _
5 . . . . .
6 _ . . . .
7 _ _ . . .
8 _ _ _ . .
9 _ _ _ _ .
0 _ _ _ _ _
Project 131 Fiber Shut-Off
Use the preceding circuit but swap the locations of the phototransistor (Q4) and the 100k
Ω
resistor (R5), keep the “+” side of Q4
in the same direction. Now pushing the press switch will turn off the LED in the right half of the circuit.
Black
Clear