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Circuits Designed by Dave Johnson, P.E. : |
- LASER/LED
LIGHT OUTPUT INTENSITY METER
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.
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- Laser Light
Detector, 10mhz to 20mhz
This circuit was originally designed to detect laser light pulses for an optical
Ethernet communications system. It has good ambient light immunity.... [Designed by
David A. Johnson]
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- LIGHT
DETECTORS WITH AMIBIENT LIGHT COMPENSATION
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.
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- Light
to Frequency Converter
This circuit uses a CMOS version of the classic 555 timer, to form a light intensity
to frequency converter. A small PIN photo diode is used as the light detector.
The pulses produced are short, so in some applications you may want to stretch them
or feed them through a flip/flop to produce a square wave signal. Although the
circuit shown is designed for a 5v supply, it could operate from almost any voltage
from 3v to 15v.
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- LINE POWERED
XENON FLASH TRANSMITTER
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.
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Low power 100KHz Light Receiver
By starving a high speed logic inverter for current,
this circuit can produce a sensitive 100KHz light receiver circuit, which is immune
to ambient light, but only drawing 100 microamps from a 3 volt supply.
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- PULSED LED
TEST CIRCUIT
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.
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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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