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Circuits designed by David Johnson, P.E.
Last Updated on: Thursday, April 07, 2016 02:04 PM

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Sensors / Detectors: Peak Detectors Circuits

AC Peak Detector that is Precise  -  This unique circuit uses a very inexpensive voltage comparator to form a peak detector. The DC voltage produced tracks the positive peak of the input signal.  It works from about ten millivolts to about 10 volts peak to peak.  The maximum frequency is about . . . [Hobby Circuit designed by Dave Johnson P.E.,  02/11/02]


Accurate Low Capacitance Meter  -  The circuit measures the unknown capacitance by applying a clean 20KHz 5v peak to peak triangle signal to the capacitor.  The current routed through the capacitance is sent to a current to voltage converter. The voltage that emerges is therefore a 20KHz square wave signal, whose Amplitude is proportional to the capacitance.  The signalís peak Amplitude is rectified and filtered to produce a DC voltage. . . . [Hobby Circuit designed by Dave Johnson P.E.,  12/12/04]


Audio Activated Switch  -  This circuit will activate a transistor switch when it detects at least 50mv peak to peak of an audio signal.  It could be used to turn on a relay, routing the signal to were it is needed. . . . [Circuit by David A. Johnson P.E.,  07/09/06]


Detector/Switch for Audio Signal  -  For some audio systems it is desirable to have an automatic switch circuit turn on other devices, such as an Amplifier, if an audio signal is detected on one line.  The hobby circuit below will activate a transistor switch when it detects at least 50mv peak to peak of an audio signal.   The switch could be used to turn on a relay, routing the signal to where it is needed.  A single 3v lithium cell will power the electronic circuit for about 5 years . . . [Hobby Circuit designed by David A. Johnson P.E.,  07/09/06]

 

Precision AC Peak Detector  -  This unique circuit uses a very inexpensive voltage comparator to form a peak detector. The DC voltage produced tracks the positive peak of the input signal.  It works from about ten millivolts to about 10 volts peak to peak.  The maximum frequency is about . . . [Circuit by David A. Johnson P.E.,  02/11/02]


Switch detects Audio Signal  -  This circuit will activate a transistor switch when it detects at least 50mv peak to peak of an audio signal.  It could be used to turn on a relay, routing the signal to were it is needed. . . . [Circuit by Dave Johnson P.E.,  07/09/06]

 

 

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