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• AIR TRANSPARENCY MONITOR, XENON FLASH RECEIVER
  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, Page 2
  This is Page 2 of the receiver circuit above.

• AIR TRANSPARENCY MONITOR, XENON FLASH TRANSMITTER
  This is the matching transmitter for the above receiver. The transmitter launches powerful 1000-watt light pulses that last about 20 microseconds.

• FET INPUT HIGH SPEED LIGHT DETECTOR
  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.

• 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

• 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.

• 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.

• LINE POWERED XENON FLASH TRANSMITTER
  This line powered xenon flash circuit drives a small camera type flash tube.  t 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.

• Low Power 40KHz Light Receiver
  Drawing only 100uA, this circuit provides high sensitivity with excellent ambient light immunity.

• 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.