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Sensors / Detectors: Peak Detectors
#'s -N     M - Z

Sensors / Detectors -- Main Page


Last Updated: October 09, 2017 03:39 PM

Circuits Designed by Dave Johnson, P.E. :

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.-February, 2002

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.-December, 2004

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.-July, 2006

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.-July, 2006

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
6 Models Available - Call 806-368-7747


Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

A Field Strength Indicator-Analog only -  The circuit is powerd by a single 1.5 volt AA cell.  The current drain is so small, about 60 microamps, I didn't bother with an on-off switch -I just slip a battery in for the day, and hope I remember to remove it when i'm done.  The supply voltage can be increased up to the breakdown voltage of the transistors to increase the sensitivity, but beware - the sensitivty to thermal drift will increase as well.   __ Designed by Dick Cappels

A Low Cost Thermal Peak Detection NiCd Charger -  The electric model aircraft and car industries have produced a bewildering array of field chargers for NIC d motor battery packs.  These range from simple 6 or 7 cell chargers consisting of a resistor and mechanical timer, to more complex chargers with peak detection, cycling, and the ability to handle 36 cell packs __ Designed by Stefan Vorketter

AC Current Probe for Oscilloscope Use -  I needed several current probes when designing the deflection circuits and high voltage supply for a computer display monitor, and the lab in which I was consulting only had one current probe, which I shared with the other four engineers on the project.  We did not really have a budget for test equipment on that project.  Designing the deflection circuit included designing several inductors, a current transformer among them.  it was merely a small diversion to design and put together a couple of simple current probes so I could, for example.  simultaneously watch the base current and the collector current of switching transistors.  The probe described here was designed to be used over the range of several tens of Hz to a couple MHz with currents from a few tens of milliamps to about 10 amps peak-to-peak.  Formulae are give which will allow you to create a design suitable for your own applications.   __ Designed by Dick Cappels

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.-February, 2002

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.-December, 2004

Analog Switch Cuts Peak-Detector Reset Time -  05/25/95 EDN Design Ideas:  The schematic in Fig 1  is a basic configuration for a unity-gain peak detector using the PKD-01FP monolithic peak detector from Analog Devices.  The reset time, tRES, is the time necessary to discharge the hold capacitor CH.  tRES  and the acquisition time tACQ are functions of the IC 's output-current capability.  With CH10 nF, this output-current limitation sets both tRES and tACQ to about 220 �sec __ Circuit Design by Gualtiero Bolognesi, Landis & Gyr, Peschiera Borronmeo, Italy

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.-July, 2006

Audio Peak Reading Meters -  Peak reading meters, popular in Europe for years, are just now coming into greater favor in America, and for good reason.  The main purpose for having a VU meter is obviously to monitor signal levels going to a tape recorder, reverb unit, or some other level-sensitive device, to help optimize the signal to noise ratio of the audio sent to the device.  Too much level will produce distortion, and too little results in the inherent noise of the medium becoming a problem.  Unfortunately, a conventional VU meter responds to the average level of the program material and not to the peaks; yet it is these momentary bursts of higher level that become distorted first.   __ Designed by Ethan Winer-This article first appeared in the April 1981 issue of Recording-engineer/producer magazine.

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.-July, 2006

Digital Lock-In Milliohmmeter -  A milliohmmeter is just the tool for checking trace resistance on a printed circuit board, tracking down shorted traces, and measuring the contact resistance of a switch or connector.  its the kind of tool that would come in real handy occasionally, but not often enough to justify shelling out hundreds of dollars.  Wanting one anyway, I set out to make my own.  it turned out to be not only an exciting project, but a true adventure of discovery as it provided a window into the workings of lock-in amplifiers __ Designed by Dick Cappels

Digital RF Field Strength Indicator -  Useful as a transmitter tune-up meter or an RF sniffer, this is an RF field strength indicator that is loosely based on the Broad Band RF Field Strength Probe, described elsewhere.  it detects RF via a square law detector, basically its a crystal set with gain.  The bias circuit for the detector is significantly modified from the probe to reduce the effects of battery voltage droop during use.   __ Designed by Dick Cappels

Dual-Polarity Peak Detector Operates From Single Supply -  05/12/94 EDN Design Ideas:  The circuit in Fig 1  can detect the peak of either positive or negative inputs, yet it operates from a single supply.  The circuit uses two unity-gain amplifiers to monitor the input signal, one an inverting amplifier and the other a noninverting amplifier.  A typical application is driving a VU meter __ Circuit Design by Chester Simpson, National Semiconductor, Santa Clara, CA

Fast Amplifiers Simplify AC Measurement -  05/09/96 EDN Design Ideas:  The availability of new high-speed amplifiers makes it possible to measure fast-moving ac signals using a simple and inexpensive circuit.  The peak-reading voltage-measurement circuit in __ Circuit Design by Chester Simpson, National Semiconductor, Santa Clara, CA

Fast Audio Peak Limiter -  This peak limiter is simple and very effective.    Uses discrete FET gain control   __ Designed by Rod Elliott  ESP

Field Strength Indicator-Analog only -  The circuit is powerd by a single 1.5 volt AA cell.  The current drain is so small, about 60 microamps, I didn't bother with an on-off switch -I just slip a battery in for the day, and hope I remember to remove it when i'm done.  The supply voltage can be increased up to the breakdown voltage of the transistors to increase the sensitivity, but beware - the sensitivty to thermal drift will increase as well.   __ Designed by Dick Cappels

High-speed peak Detector uses ECL comparator -  09/26/02 EDN Design Ideas:  Professional electronics designers often use peak-detector circuit sin such applications as amplitude measurement, automatic gain control, and data regeneration.  You can build a simple and fast peak detector from a serial diode and a shunt capacitor, but it suffers from serious inaccuracy that stems from the diode's forward-voltage drop __ Circuit Design by Przemyslaw Krehlik and Lukasz Sliwczynski, Institute of Electronics, Krakow, Poland

Inexpensive peak Detector requires few components -  07/07/05  EDN Design Ideas:  All-analog circuit needs no rectifiers __ Circuit Design by Anthony H Smith, Scitech, Bedfordshire, England

Lock-In Milliohmmeter -  A milliohmmeter is just the tool for checking trace resistance on a printed circuit board, tracking down shorted traces, and measuring the contact resistance of a switch or connector.  its the kind of tool that would come in real handy occasionally, but not often enough to justify shelling out hundreds of dollars.  Wanting one anyway, I set out to make my own.  it turned out to be not only an exciting project, but a true adventure of discovery as it provided a window into the workings of lock-in amplifiers __ Designed by Dick Cappels

Low Capacitance Scope Probe Adapter -  An adapter to allow low capacitance probing of high frequency circuits.   __ Designed by Dick Cappels

LTD-Low Cost Telemetering Device -  The ATmega8 microcontroller-based Low-Cost Telemetry Device (LTD) is an efficient telemetry keyer.  The LTD measures the voltage levels of up to four analog channels via its on-chip 10-bit ADC, converts the measurements to numbers, and then sends the data in Morse code to an external transmitter and to an attached RS-232 terminal.  it can be set up either by the RS-232 terminal, in which case, a character string, such as transmitter iD, can can be sent, or it can be set up with only jumpers to ground.  Parts count is very low, in part because the ATMega8's internal clock is used for timing.  Jeff Heidbrier came up with the idea for this project, built the prototype, and colaborated with me on the design of the LTD and this documentation.   __ Designed by Dick Cappels

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Peak Detectors / Sensors:  #'s -N     M - Z

 


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