Donald Had a Serious Case of Red Eye

By: 
October 24, 2005

Donald liked to wow people with his PowerPoint presentations. So he developed an easy circuit to modulate an audio signal (CD player) and transmit it over a beam of light (using a laser pointer). The receiver is a simple solar cell with a pre-amp transistor circuit connected to the "line-in" of an audio amplifier. The amplitude-modulated beam of light from the laser pointer produces a varying voltage signal that tracks the audio signal. For added gain, Donald also threw in a pre-amp circuit.

For Donald Marzewski's complete instructions on how to build your own inexpensive laser modulator,

click here

.

Inexpensive Laser Modulator Parts List
Amt Part Description Allied Part #
Modulator:
1 680 ohms Resistor 977-1256
1 200 ohms Resistor 832-0243
1 18 ohms Resistor 296-5526
1 1N4148 Diode 431-0614
1 2N3904 NPN Transistor 431-0406
1 1 muF Capacitor 881-5274
Pre-amp:
1 100K Resistor 296-5610
1 1.2K Resistor 296-5564
1 2N3904 NPN Transistor 431-0406
2 1 muF Capacitor 881-5274
1 1.5V AA battery 774-0200
1 Phono plug 283-0016
Additional parts required: Laser pointer, solar cell. Note: As with all laser light, please exercise proper caution.

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