Donald Had a Serious Case of Red Eye
By Design News Staff -- Design News, October 23, 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.
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For Donald Marzewski's complete instructions on how to build your own inexpensive laser modulator,
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| 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 µF Capacitor | 881-5274 |
| Pre-amp: | ||
| 1 | 100K Resistor | 296-5610 |
| 1 | 1.2K Resistor | 296-5564 |
| 1 | 2N3904 NPN Transistor | 431-0406 |
| 2 | 1 µF 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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