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Circuits Designed by Dave Johnson, P.E. : |
- ACCEPTABLE
VOLTAGE INDICTOR
I have used this circuit many times in custom test fixtures where a simple go-no go
indication was needed. The circuit can also be used to adjust a particular
voltage be within specific high or low limits. The three LEDs will indicate if
the voltage is high, low or OK. When connected to other converters, such as a
frequency to voltage converter, a current to voltage converter or a power to voltage
meter, it could provide a quick indication of a proper level.
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- BROAD
BAND 2MHz OPTICAL FIBER RECEIVER
If you need more sensitivity than the above circuit this circuit provides about ten
times more gain. It too is designed around an inexpensive plastic optical fiber
detector.
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- BROAD
BAND 5MHz OPTICAL FIBER RECEIVER
This circuit is a simple broad band light detector that uses a very inexpensive IC
and a PIN photodiode that is packaged for use with plastic optical fibers. It has a
bandwidth from 1KHz to over 5MHz. It is great for experimenting with various
modulated light sources.
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- BROAD BAND
50MHz OPTICAL FIBER RECEIVER VERSION A
If the above circuit it still too slow, you can try this circuit. What it lacks in
sensitivity it makes up for in speed. The circuit attaches a plastic fiber optic PIN
photodiode assembly to a small box containing a small 3v battery and a standard BNC
plug. When the box is plugged into to the input of an oscilloscope with a 50-ohm
termination resistor, it can detect light pulse frequencies beyond 100MHz.
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Brownout Voltage Tester
I used this circuit years ago to test AC line powered devices under 95vac line
voltage conditions. It has a rating of 250 watts.
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