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Freespace Communication Circuits, Page 4
(Light Beam Communication Circuits)
Circuits designed by David Johnson, P.E.
Last Updated on:
Friday, March 23, 2012 08:29 AM
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Dave's FreeSpace (Light Beam) Communication Circuits:
Page 1,
Page 2, Page 3,
Page 4 |
- 5W
FLUORESCENT LAMP INTENSITY MODULATOR
The circuit was designed to experiment with using small fluorescent
lamps as a broad pattern source of modulated light. The circuit hits the
small lamp with narrow 1us pulses at a rate of 10KHz. Each pulse launches
about 10 watts of visible light. The lamp starting method is a bit crude but
the circuit does work.
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- 9v POWERED XENON
PHOTOFLASH Controller
This 9v battery powered circuit is designed for remote control flash
needs. A charge control circuit turns off the high voltage generator when
the photoflash capacitor is fully charged. A neon lamp is included to
indicate when the system is ready to flash.
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- 10MHz TO 20MHz
LASER LIGHT DETECTOR
This circuit was originally designed to detect laser light pulses for an
optical Ethernet communications system. It has good ambient light immunity.
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- 20MHz VCSEL 3mW LASER
TEST CIRCUIT
This circuit takes advantage of some new vertical cavity surface emitting lasers (VCSEL)
that don’t require light output control circuits. The circuit shows how to drive the
device from a single high speed CMOS IC. The circuit can easily be modified to transmit
signals from kilohertz to about 50MHz.
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- 30KHZ LIGHT RECEIVER
AMP
This circuit uses NPN darlington transistor to amplify the signal produced from short
light flashes, as detected by a PIN photo diode. The circuit draws only about
330uA from a 6v battery.
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- 40KHz LASER BURST DETECTOR
This circuit was originally designed to detect weak flashed of laser light bounced
off of a fabric video projection screen. It was used as part of a firearm training
system. It generates a 100mS output pulse whenever it detects a 3ms to 5ms laser burst,
modulated at 40KHz. It is very sensitive and could be modified for long range laser
communications.
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- 40KHZ LED TEST
SIGNAL GENERATOR
This 40KHz crystal controlled oscillator circuit drives an infrared LED with powerful
40ma pulses. The circuit can be used to test optical communications circuits,
designed to receive 40KHz modulated light signals.
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- 40khz Light Detector With
High Ambient Light Immunity
The circuit below was designed to turn on an external 12v relay, whenever it detects
light from a nearby LED light source, modulated at 40KHz to 50KHz. This circuit
was originally designed to operate from a fast moving vehicle. The light transmitter was
positioned at a stationary position, while the matching receiver was mounted on the
vehicle. The circuit has high ambient light immunity and in most cases, can
operate in direct sunlight....
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| Dave's FreeSpace (Light Beam)
Communication Circuits: Page 1,
Page 2, Page 3,
Page 4 |
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