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Light Beam
Communications Circuits, Page 1
Freespace Circuits: #'sA - KL- MO - Z
Last Updated on:
Monday, October 03, 2011 06:07 PM
Circuits Designed by Dave Johnson, P.E. :
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.
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.
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.
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.
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.
