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40KHz Voltage to Frequency Converter
This circuit was designed to frequency modulate a 40KHz carrier, using human
voice frequencies. A common flip/flop is used at the core of the circuit.
200MHz - 400MHz VOLTAGE controlled OSCILLATOR
If you need a clean emitter coupled logic (ECL) type signal between 200MHz and
400MHz this circuit works fine. It uses four voltage controlled capacitors to
change the frequency.
40KHz Voltage to Frequency
Converter
This circuit was designed to frequency modulate a 40KHz carrier, using human voice
frequencies. A common flip/flop is used at the core of the circuit.
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.
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.
VOLTAGE TO FREQUENCY CONVERTER + 1uS LED PULSE DRIVER
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 my
Handbook of Optical
Through the Air Communications.
Wide Band Zero Cross Detector
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.
