Page 145 - 15 Dangerously Mad Projects for the Evil Genius

CHAPTER 10

Laser Voice

Transmitter

signal from a phototransistor. Figure 10-2 shows
PROJECT SIZE: Large the schematic diagram, and Figure 10-3 the

SKILL LEVEL: ★★★✩ stripboard layout.
The project is built on a small piece of
stripboard, and mounted in a plastic project box.
THE EVIL GENIUS LIKES to communicate with his
One hole in the project box allows light from the
friend (also an Evil Genius) who lives in the house
laser or flashlight to enter and fall on a diffuser,
opposite. Radio waves are far too easily
which illuminates the phototransistor. Another hole
intercepted, and Morse code with a flashlight is just lets the sound from the loudspeaker escape.
plain tricky. So, the Evil Genius uses a laser beam
that passes through the glass of his window, across
the road, and through the glass of his friend’s
window, where it hits a receiver so that the friend
can hear what he is saying (see Figure 10-1).

Not being terribly interested in what his friend
has to say in return, he is content to watch her nod,
indicating she has heard the wise words of the Evil
Genius.

One day, the Evil Genius will make another
receiver and transmitter pair so his friend can
respond with something more than just gestures.
The project is comprised of two parts: the
receiver, which amplifies the signal from the laser
and plays it on the speaker; and the transmitter that
modulates the laser beam with the sound wave.

The Receiver

The receiver is the simplest part of the project. It
uses an IC audio amplifier to directly amplify the Figure 10-1 Sound over a laser beam

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