- 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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- DC CURRENT INDICATOR #4 December 15, 2008
The circuit below uses some common components to turn on an LED whenever DC current above a certain level is detected. The circuit uses a very popular LM393 dual voltage comparator from National Semiconductor and a common 1N4148 signal diode. The diode acts
as a crude 0.7v voltage reference. Only one of the comparators inside the 8 pin package is used. A pair of resistors across the diode forms a voltage divider, which produce a reference voltage of about 0.015v. ....
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- 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.
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- XENON LAMP FLASH DETECTOR
This circuit uses a small 2.5mm square photo diode in conjunction with a 100mH coil to detect the short light flashes from a xenon lamp. The coil makes the circuit immune to normal room lights. Its 10mv sensitivity can detect light flashes from a range of
over 100 feet. Reflections from a room’s walls and ceiling is usually enough to trigger the circuit. The entire circuit draws only 3 Microamps from a 6 to 9 volt battery.
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