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Voltage Detectors / Sensors / Monitors

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Sensors / Detectors -- Main Page
 

Last Updated: October 24, 2017 02:55 PM

Circuits Designed by Dave Johnson, P.E. :

Nine-Volt Battery Voltage Monitor -  This circuit turns on a LED whenever the voltage of a standard 9v battery connected to the circuit drops below 7.2 volts.  it uses a LTC1440 comparator, which also contains a 1.18v reference diode.  in standby mode, the circuit draws only 4uA. . . Circuit by David A. Johnson P.E.-July, 2006

Under/Over Voltage Alarm on AC Line -  Power lines, which deviate much beyond normal voltages can damage expensive electronic equipment.  The circuit below sounds an alarm whenever the line voltage is higher or lower than normal.  I set the alarm limits at about +-15% from standard levels. . . Circuit by Dave Johnson P.E.-March, 2009

Voltage Monitor for a 9v Battery -  Nine voltage batteries are used in a wide variety of electronic devices.  But, you often dont know when it is time to change the battery until the device stops operating.  The hobby circuit below provides a visual indication when the battery needs to be . . . 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:

Mains Voltage Indicator -  This is a circuit for a digital mains voltage indicator that displays main voltage in the form of a LED bar graph with 16 LEDs.  The first LED indicates voltage level at 50 V and the 16th LED shows voltage level for 280 V__ Electronics Projects for You

Maximum Voltage Sorter Uses Analog Multiplexer -  09/29/94 EDN Design Ideas:  The voltage-sorting circuit in Fig 1 continuously finds the maximum of eight input voltages and the corresponding binary address with the aid of two analog multiplexers, IC 1 and IC 2.  The circuit compares each input sequentially with the current maximum voltage and updates the maximum voltage and address when it finds a new maximum __ Circuit Design by Alan L Giles, Tao Systems, Hampton, VA

Microcontroller functions as voltmeter -  10-May-07 EDN Design Ideas:  PIC  microcontroller and FETs enable a four-digit voltmeter __ Circuit Design by Noureddine Benabadji, University of Sciences and Technology, Oran, Algeria

Microcontroller, JFET form low-cost, two-digit millivoltmeter -  06/22/06 EDN Design Ideas:  Software subroutines replace hardware A/D converter __ Circuit Design by Noureddine Benabadji, University of Sciences and Technology, Oran, Algeria

Mini 3 digit display, an inexpensive digital voltmeter -  We build a simple and inexpensive three digit display.  it's a voltmeter module but it has also general purpose digital iO pins.  You could use it as well to read a digital sensor and display the value.  it can be freely programmed, calibrated and even be programmed with a non linear formula.  it's a display where you can define the relation between the measured value and the displayed number.   __ Designed by Guido Socher

Nine-Volt Battery Voltage Monitor -  This circuit turns on a LED whenever the voltage of a standard 9v battery connected to the circuit drops below 7.2 volts.  it uses a LTC1440 comparator, which also contains a 1.18v reference diode.  in standby mode, the circuit draws only 4uA. . . Circuit by David A. Johnson P.E.-July, 2006

Op-Amp Rectifier Signals Input State -  07/21/94 EDN Design Ideas:  The op-amp rectifier in Fig 1 operates from a single supply and provide as a logic output and an LED that indicate the state of the input voltage.  The input-state indications are handy for calibration.  Because the circuit operates from a single supply, the 2.5V reference determines the level around which the circuit rectifies input waveforms __ Circuit Design by Lee E Scaggs, High Country TEK, Nevada City, CA

Philips GM 6012 AF Millivoltmeter manual w/schematic -  vintage television (schematic)  __ Designed by Frank Pocnet

PIC based digital voltmeter (DVM) -  This project will describe how to make a simple digital voltmeter (DVM) using a PIC 16F688 microcontroller.  The range of this DVM is 0-20V, but you can easily increase or decrease the range of input voltage as your requirements after you understand the voltage scaling method described in this project.  The PIC  micro reads the input voltage through one of the 8 analog channels and convert it to a 10-bit digital number using the internal ADC __ Contact Raj Bhatt & Shawon Shahryiar

Powerline Voltmeter -  Heres a rather special voltmeter that will let you measure the AC grid voltage and also see very accurately how it fluctuates around its nominal value.  The voltmeter has a measuring range of around 50 V that you can centre around 220 or 240 V to suit your needs.  must register on this site __ Designed by Published in Elecktor July/Aug, 2010

Precision Audio Millivoltmeter -  Measures10mV to 50Volt RMS in eight ranges Simply connect to your Avo-meter setAT 50A range __ Contact Flavio Dellepiane, fladello @ tin.it

Provides 1.5v, 7a Bus Termination -  09/14/95  EDN Design Ideas:  Some of the newest high-performance processors require a 1.5V bus terminator that can source currents as high as 7A.  This terminator requires a very fast transient response, because the device must react to high peak-current changes that have extremely fa __ Circuit Design by Chester Simpson and Mineo Yamatake, National Semiconductor, Santa Clara, CA

Safely Applies Power to ICs -  11/22/01  EDN Design Ideas:  Supervisory circuits normally monitor a microprocessor's supply voltage, asserting reset to the IC during power-up, power-down, and brownout.  in this way, the circuit ensures that the supply voltage is stable before the microproces __ Circuit Design by Clayton Grantham, National Semiconductor, Tucson, AZ

Scanning Voltmeter with Minimum Mass Wireless Coupler -  ATMega8  A 10 bit scanning voltmeter with a Minimum Mass Wireless Coupler, based on the ATMega8.  Range to the Minimum Mass Base Unit is 10 to 15 cm.  if the voltmeter is battery operated, it can be floated from ground.   __ Designed by Dick Cappels

Serial Voltmeter using the PIC16C71 -  Building a serial voltage meter to measure from 0 to 5 volts DC is actually pretty easy.  Using MeLabs PicBasic, and Microsoft's Visual Basic Version 5 Pro.  You need Visual Basic Pro version because you will have to use Basic's MSComm control.  This control is not available in the Visual Basic 5 "Learning" Edition.  The PIC 16C71 simplifies the task even more by having a built in A/D converter.  Pins 17, 18, 1, 2 are the analog inputs AiN0, AiN1, AiN2, AiN3 respectively.  __ 

Serves as milliohmmeter -  04/15/04 EDN Design Ideas:  When I was recently debugging a design, I discovered that a short circuit existed from a ground plane to a power plane.  I did not have access to a milliohm meter or an equivalent tester for locating this type of short circuit.  So, I logged onto the internet to find an easily constructible milliohm meter __ Circuit Design by AM Hunt, Lancaster Hunt Systems Ltd, Shepperton, UK

Simple Circuit Detects DC Ringing -  08/17/00 EDN Design Ideas:   Ring detection is a common task in telephony-related digital design.  The goal is to sense an ac ringing voltage applied to the telephone line by a central office or PBX (private branch exchange) and then pass an appropriate signal to the C or P __ Circuit Design by Jerzy Chrzaszcz, Warsaw Institute of Technology, Poland

Simple Circuit Detects voltage overrange -  10/10/96 EDN Design Ideas:  Sometimes, a visual indication of whether a sensed voltage is above or below its nominal value can be useful.  Most approaches to overvoltage or undervoltage sensing use two voltage comparators and a resistor divider to form a win __ Circuit Design by Mark Stitt, Burr-Brown, Tucson, AZ

Simple Circuit disconnects load -  02/17/00  EDN Design Ideas:  Placing a load-disconnect circuit on the output of a bootstrapped step-up regulator allows the regulator to start with load currents much higher than would otherwise be possible (Figure 1).  During shutdown, the disconnect completely isolates the battery __ Circuit Design by Larry Suppan

Simple Circuit Disconnects Load From Battery -  03/14/96 EDN Design Ideas:  To prevent battery damage, the circuit in Figure 1 disconnects the load at a predetermined level of load voltage.  This load voltage, VTRiP, is closely proportional to the battery voltage.  R1 and R2 determine the level of VTRiP  that corresponds to voltage of 1.15V at pin 3 of IC 1.  A voltage of 1.15V at pin 3 of IC 1 causes the internal comparator to trip.  Thus, VTRiP=1.15 (R1+R2) /R1 __ Circuit Design by Michael Keagy, Maxim Integrated Products, Sunnyvale, CA

Simple Circuit serves as milliohmmeter -  04/15/04 EDN Design Ideas:  When I was recently debugging a design, I discovered that a short circuit existed from a ground plane to a power plane.  I did not have access to a milliohm meter or an equivalent tester for locating this type of short circuit.  So, I logged onto the internet to find an easily constructible milliohm meter __ Circuit Design by AM Hunt, Lancaster Hunt Systems Ltd, Shepperton, UK

Simples sort out the highest voltage -  11/09/06  EDN Design Ideas:  Greatest-of-three voltage detector drives indicators and external display __ Circuit Design by Ezio Rizzo, Nova SNC, Genoa, Italy, and Vincenzo Pronzato, Felmi SRL, Genoa, Italy

Small Detector Coils with Ferrite Cores for my PI Detectors -  Over the years I have wound and experimented with Hundreds of coils.  Many Varied Sizes and Shape.  Considerably interesting are the Small coils wound on Ferrite cores.   __ Designed by G.L. Chemelec

Solid-State Relay Saves Battery's Life -  09/01/94 EDN Design Ideas:  The circuit in Fig 1 uses a low-resistance p-channel FET, Q4, to disconnect a load from the battery when the battery's voltage drops below a certain value.  After you disconnect the circuit, it remains off until you remove and replace the battery __ Circuit Design by Tom Gay, Siemens, Regensburg, Germany

Standalone Digital Voltmeter Uses a Multichannel ADC -  11/15/12  EDN Design Ideas:  Monitor several different voltages with one instrument.  This Design idea was realized for voltage/current measurement on a four-channel analog voltage source but has wide use in many other applications.  The design is based on the Atmel ATmega8-16AC microcontroller and the MAX1230 12-bit ADC (references 1 and 2).  Although the microcontroller has an internal 10-bit ADC, its more efficient to use an external multichannel ADC than to multiplex more analog channels to the ATmega8-16AC differential ADC inputs __ Circuit Design by Branislav Korenko

Status Indicator Flags Five Discharge States -  01/20/94 EDN Design Ideas:  The circuit actually indicates five conditions of the battery.  A steady glow assures the user that the battery is strong and healthy.  A2-Hz brief flicker off indicates that the battery is starting to show age.  A more insistent, 50%, 5-Hz flashing is a warning to have a spare battery on hand.  A brief flicker __ Circuit Design by Glen Chenier, Fitel Photomatrix, Nepean, ON, Canada

Supervisory IC makes Simple Circuit line Monitor -  03/01/96 EDN Design Ideas:  You can use the MC34161P universal voltage monitor to build a simple ac power-line monitor (a voltage-sensing relay).  in this application (Figure 1) , the mode select pin (pin 7) connects to the internal 2.55V reference (pin 1) , and the IC functions as a positive-voltage window detector.  A small signal transformer provide as total isolation from the power lines and performs a unique role in the circuit.  During the positive half cycles of the line voltage, the transformer functions as a conventional power transformer feeding a 15V power supply through a half-wave rectifier.   __ Circuit Design by Henno Normet, Tavares, FL

Talking Voltmeter -  Ever needed to measure a voltage without taking your eye off something? if so, then this is the project for you!  The Orton Talking Voltmeter takes a voltage measurement in the range 0-5 Volts and then reads it out to you to two decimal places (i.  e.  to 10mV resolution).  The design illustrates the use of the 10 bit ADC in the PIC , as well as pulse width modulation (PWM) for analogue output.  This project also illustrates how to squeeze every last word of program memory out of a PIC !  Sound samples consume almost all of the on-chip flash memory, and even that was after some pretty brutal trimming of the samples and a drop in resolution to seven bits.  Even after all that, the samples are about as brief as you can get without becoming unrecognisable __ Contact Karen's Microprocessor Projects

The Dashboard Digital Voltmeter Project -  This project is heLPFul to anyone who drives an automobile.  I had found this project at the local libary.  in an old publication.  I made it and it worked fine.  Below are the complete text and schematic of the Dashboard Digital Voltmeter.  I re-typed the text and re-drew the schematic.  as the printing from the book was old and faded.  Sit back and read the story why this LED display might just save you from being stranded on the road!  __ Designed by braincambre500 @ yahoo.com

The HOTCHECK: Extended Scale Voltmeter & Battery Tester -  A small and east to build device based on the LM3914 voltage measurement integrated circuit can be used to measure the output voltage of rechqrgeable battery packs.  A built in discharg cir4cuit places a 300mA load on the battery that can be activated by the press of a button.   __ Designed by C. Brent Dane AMA 345702

Under/Over Voltage Alarm on AC Line -  Power lines, which deviate much beyond normal voltages can damage expensive electronic equipment.  The circuit below sounds an alarm whenever the line voltage is higher or lower than normal.  I set the alarm limits at about +-15% from standard levels. . . Circuit by Dave Johnson P.E.-March, 2009

Understanding & selecting RMS voltmeters -  05/11/00  EDN Technical Article: Failing to verify ac-voltmeter accuracy before conducting rms-noise measurements may cause highly misleading results.   __ Circuit Design by Jim Williams and Todd Owen, Jim Williams, EDN's most revered contributor, passed away in June 2011 after a stroke.  He was 63.

Voltage indicator -  The solidstate voltmeter circuit described here indicates the mains voltage with a resolution that is comparable to that of a general-purpose analogue voltmeter.  The status of the mains voltage is available in the form of an LED bar graph__ Electronics Projects for You

Voltage Monitor -  This voltage monitor circuit is based on an Elektor design with a 555 timer IC in the book 302 Circuits, which uses two LEDs (red and green) to indicate whether the voltage is within range.  must register on this site __ Designed by Published in Elecktor July/Aug, 2015

Voltage Monitor -  When the input voltage is 0 the LED glows.  The LED stops glowing when the voltage rises to the level determined by R2.  Reverse + and, pins to reverse operating mode.  To set voltage at which LED goes  __ Contact IQ Technologies

Voltage Monitor for a 9v Battery -  Nine voltage batteries are used in a wide variety of electronic devices.  But, you often dont know when it is time to change the battery until the device stops operating.  The hobby circuit below provides a visual indication when the battery needs to be . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

Voltmeter & AM meter using PIC Microcontroller -  Voltmeter and Ammeter can be easily made using PIC  Microcontroller having ADC (Analog to Digital Converter).  I am using PIC 16F877A and the result is displayed on an LCD Display.  PIC 16F877A is enough if you do this project only for testing purposes.__ 

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Voltage Detectors / Sensors / Monitors:  #'s - C      D - L      M - Z

 


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