- 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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- 40KHz TV-VCR LIGHT SOURCE REPEATER
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.
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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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- COLOR FILM MAKES OPTICAL FILTER
This isn’t an electronic circuit but the file shows the curve for an optical filter made from exposed color film. The material blocks most visible light but is very transparent to 880nM
infrared light. Kodak 100ASA is exposed to "cool white" fluorescent light for about 5 seconds. Then, the film is developed in the usual way. The color negatives form the filter material
and does a fine job of blocking visible light wavelength and passing the longer near infrared wavelengths. Published in Electronic Design, Dec 2, 1996.
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- Infrared Remote Extender
This electronic hobby circuit is designed to be placed directly in front of a standard TV or VCR remote. The exiting light pulses produced by the electronic 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....
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- MICRO POWER 40KHz BURST LASER DIODE DRIVER
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.
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- OPTICAL RFID TEST CIRCUIT
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.
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- Pigeon Scarecrow
I have an area on my roof where a large flock of pigeons like to roost. Their nesting materials and droppings really make a mess. Often there is enough junk from them that it clogs
my roof gutters. Perhaps one way to scare them away is with a device mounted on the roof near their favorite roosting spot. The device....
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- Reflected Infrared Light Switch
Infrared light reflected off a finger is used to activate this switch circuit.
Drawing only 30uA from a 3v supply, this circuit will detect a human finger with a range of about 1 inch. The sensor uses an inexpensive infrared LED and a matching photo diode.
(added 7/06)
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- Shadow Activated Motion Detector Circuit
There are many ways one can detect nearby human or object motion. This circuit demonstrates one way. It detects motion by noting the changes in the shadow cast by the moving
object. The hobby circuit below works quite well in typical indoor room lighting. I would not recommend its use in direct sunlight. Two small PIN photodiodes positioned about
one inch apart form a shadow detector. With no shadow cast on the devices, both devices produce nearly identical current levels. The current is converted to a voltage with a
load resistor in parallel with the photodiode....
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