|
Light Beam Receiver for Laser Pistols: |
|
SINGLE IC FORMS SENSITIVE MODULATED LIGHT RECEIVER
(15) (4069rvr1)
The circuit uses a very inexpensive C-MOS IC that is
connected to a small photodiode. Using an unique
inductive feedback network, the circuit provides high
sensitivity under high ambient light conditions. It is a
great circuit when you want to extend the range of an
optical remote control transmitter. |
|
|
|
40KHz LIGHT RECEIVER IS IMMUNE TO AMBIENT LIGHT
(16) (40krvr1)
If you want even more sensitivity than the above
circuit, try this design. When used with a one
centimeter square photodiode, you can achieve a range of
several hundred feet with a standard TV or VCR remote
control module. |
|
1uS LIGHT PULSE RECEIVER PLUS POST AMP (27)
(500krvr3)
This circuit is designed to detect very weak light
pulses lasting 1uS. It uses a tuned LC feedback network
to provide high sensitivity while giving high ambient
light immunity. A post voltage amplifier is included
with a gain of about X20. The circuit is described in
more detail in the
receiver section of Dave Johnson's
Handbook of Optical Through the Air Communications.
(this link is off-site) |
|
1uS LIGHT PULSE DISCRIMINATOR PLUS F TO V CONVERTER
(28) (1usdes1)
This circuit is designed to detect the narrow 1uS pulses
produced by the above amplifier circuit. The clean logic
type pulses produced by the discriminator are then sent
to a frequency to voltage converter. The circuit is
designed to process a pulse frequency of 10KHz that is
frequency modulated by voice audio signals. The circuit
is described in more detail in the
of Dave Johnson's
Handbook of Optical Through the Air Communications. |
|
VOLTAGE TO FREQUENCY CONVERTER + 1uS LED PULSE DRIVER
(34) (voicex2)
This circuit receives the signal from the above
amplifier and launches powerful 1uS infrared light
pulses from a low cost LED that are frequency modulated
by the audio information. The 10KHz center frequency of
the pulse stream is low enough so a standard infrared
LED can emit ten times more light than conventional long
pulse techniques. The circuit is described in more
detail in the
transmitter section of Dave Johnson's
Handbook of Optical Through the Air Communications.
(this link is off-site) |
|
40KHz TV-VCR LIGHT SOURCE REPEATER (35) (40kvcr)
This circuit is designed to be placed directly in front
of a standard TV or VCR remote. The exiting light pulses
produced by the circuit match the pulses from the remote
but are about 10 times more powerful. Using the device,
the remote can operate a TV or VCR over three times the
normal distance. |
|
MICRO POWER 40KHz BURST LASER DIODE DRIVER (36)
(40klrl)
Some laser tag or simulated combat games can use this
circuit to send short bursts of modulated laser light at
the opponent's vest, equipped with a matching light
receiver. The circuit operates from three 1.5v cells
(4.5v) that should provide enough energy for about
200,000 shots. |
|
9v POWERED XENON PHOTOFLASH CONTROLLER (42) (xenflsl)
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. |
|
SIMPLE NITROGEN SPARK GENERATOR (43) (spark4)
Nitrogen or air sparks are very powerful light sources
that produce flashes that last only a few nanoseconds.
This line powered circuit generates a continuous series
of very small sparks across electrodes with a 0.05 inch
gap. |
|
LINE POWERED XENON FLASH TRANSMITTER (44) (xen2xtr)
This line powered xenon flash circuit drives a small
camera type flash tube. It has an optical isolator to
allow the flash to be safely triggered from some remote
device. A flash rate of 2Hz is possible with the
circuit. |
|
20MHz VCSEL 3mW LASER TEST CIRCUIT (58) (20mhzlsr)
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. |
|
40KHz MODULATED LIGHT DETECTOR (59) (40krvr2)
This circuit uses a unique cascode amplifier circuit to
convert the current from a PIN photo diode to a current
without any feedback network. It is very stable and very
sensitive. The circuit shown has the potential for a
conversion factor of 10 volts per microwatt at 900nm. I
included a simple JFET post-amplifier with a gain of
about 20. |
|
40KHz LASER BURST DETECTOR (60) (40krvr3)
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. |
|
10MHz TO 20MHz LASER LIGHT DETECTOR (61) (20mrvr2)
This circuit was originally designed to detect laser
light pulses for an optical Ethernet communications
system. It has good ambient light immunity. |
|
PULSED LED TEST CIRCUIT (63) (testled)
This circuit is designed to test visible and infrared
LEDs in pulsed mode operations. It can drive the LED
with peak currents in excess of 10 amps. A light
detector nearby can monitor the response time and
intensity of the LED under test. |
|
FET INPUT HIGH SPEED LIGHT DETECTOR (69) (fetamp0)
This circuit is yet another design that converts current
from a PIN photo diode to a voltage. It has a bandwidth
that extends beyond 50MHz. |
|
AIR TRANSPARENCY MONITOR, XENON FLASH RECEIVER (70)
(airmon0)
I designed this circuit many years ago to monitor the
quality of a mile long column of air for future optical
communications experiments. The transmitter system
(circuit 72 below) uses a powerful xenon flash in
conjunction with a large 12 inch fresnel lens at the
transmitter end and a matching 12 inch lens with a PIN
photo diode at the receiver. The receiver system was
connected to a weather station and a computer to collect
the changes in intensity of the light flashes under
different weather conditions. It has the potential for a
30+ mile range. I have also used this system to conduct
cloud bounce experiments. |
|
AIR TRANSPARENCY MONITOR, XENON FLASH RECEIVER (71)
(airmon1)
This is page two of the receiver circuit above. |
|
AIR TRANSPARENCY MONITOR, XENON FLASH TRANSMITTER
(72) (airmon2)
This is the matching transmitter for the above receiver.
The transmitter launches powerful 1000-watt light pulses
that last about 20 microseconds.
5W FLUORESCENT LAMP INTENSITY MODULATOR (75)
(5wlamp)
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.
LASER/LED LIGHT OUTPUT INTENSITY METER (80) (laserpwr)
This circuit uses a large 1cm X 1cm silicon PIN photo
diode and a transimpedance amplifier to measure the
light power output of infrared and visible LEDs and
laser diodes. It can be modified to produce almost any
milliwatts to volts scale factor. It can be connected to
either a multi-meter or an oscilloscope.
|
|
LIGHT DETECTORS WITH AMIBIENT LIGHT COMPENSATION
(83) (40krvr4)
These circuits were taken from a few application notes
on infrared remote control devices. They use a current
compensation method to separate the modulated light
pulses from ambient light. They appear to have limited
bandwidth and may only work at the 30KHz to 50KHz
frequencies often used by TV and VCR remotes. I have not
yet tested the circuits. |
|
OPTICAL RFID TEST CIRCUIT (87) (opiddemo)
I designed this test the concept of using light
techniques to send identification data instead of RF. A
more detailed discussion on this scheme can be found in
the Imagineered new products section. |
|
WIDE BAND ZERO CROSS DETECTOR (109) (zerocross1)
This circuit was designed to convert a low amplitude
40KHz signal into a clean square wave signal. It will
work with inputs as small as 5mv peak to peak or as
large as 3 volts peak to peak. The input frequency can
range from a few kilohertz to about 150KHz. |
|
40KHZ LED TEST SIGNAL GENERATOR (111) (40khzref2)
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. |
|
XENON LAMP FLASH DETECTOR (112) (xenonflsdet1)
This circuit uses a small 2.5mm square photo diode in
conjunction with a 100mH coil to detect the short light
flashes from a xenon lamp. The coil makes the circuit
immune to normal room lights. Its 10mv sensitivity can
detect light flashes from a range of over 100 feet.
Reflections from a room’s walls and ceiling is usually
enough to trigger the circuit. The entire circuit draws
only 3 microamps from a 6 to 9 volt battery. |
|
30KHZ LIGHT RECEIVER AMP (121) (30khzamp1)
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. |
|
40KHZ LIGHT RECEIVER AMP
(122) (40khzamp1)
This circuit is similar to number 121 but provides more
gain and operates up to 40KHz. However it draws more
power supply current. |
