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Tester or Measurement (Instrument) Circuits

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Last Updated: November 22, 2021 03:00 PM
Circuits Designed by Dave Johnson, P.E. :
Bad Light Bulb Indicator -  This request came from a Discover Circuits visitor.  He wanted to turn on a LED indicator light whenever a circuit detected a burned out tail/brake light on a car or truck.  The circuit shown below uses a transistor switch, to detect current flowing through a low value resistor. . . Circuit by David A. Johnson P.E.-December, 2006

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
6 Models Available - Call 806-778-8407

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

Barometers -  Note: the above charge monitors are really just toys.  Although fun and interesting, their arbitrary zero limits them to monitoring changing fields and makes them inferior to a mechanical field mill.   __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Barry's magnetic levitation project -  if you hold two permanent magnets close together, you see that one of them will jump strongly toward (or away) from the other.  in 1842, Samuel Earnshaw expressed the perversity of inanimate magnetic objects in his theorem.   __ Designed by Barry Hansen

Batteries charger & PSU-Ideal for digital cameras -  This circuit was created for digital cameras.  it's known the digital cameras have considerable power consumption.  For example my camera Minolta E223 requires.   __ Contact IQ Technologies

Battery automatic power-off has simpler Design -  31-Mar-05 EDN Design Ideas:  Simplified circuit provide as timed battery cut-off to save power Design by Yongping Xia, Navcom Technology, Torrance, CA

Battery Characterizer -  Schematic Only   loads charged nicad and NiMH battery packs and measures milliamp hour capacity. (18f252)  __ Designed by Jon Fick

Battery Current Sensor: Part 1 -  How do simply incorporate constant power throttle __ Designed by Richard Torrens

Battery Desulphation Progress Monitor -  A number of readers have asked how to tell when the Lead-Acid Battery Zapper has done its job and battery desulphation is complete.  in the author’s experience, batteries that are going to respond to this treatment will generally show quite a high peak voltage across the terminals at the beginning of the treatment.  if this__ 

Battery Discharge Monitor -  Here is a battery monitor circuit which disconnects the load when the battery is discharged, preventing a deep discharge which could cause permanent battery damage.  The battery is automatically reconnected when a battery charger or other DC source is connected across the load.  Select a relay which requires less than 100ma coil current and with contacts capable of handling the load and charging __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Battery discharger -  This is a page with a few circuits which may be useful for monitoring the state of your batteries.   __ Designed by Richard Torrens

Battery Equal Charge Indicator -  The circuit below illuminates an LED to indicate unequal charges between two 12 volt lead batteries.  it can be used to verify that two batteries are connected in parallel or isolated since the LED will be off when the voltages are equal within a tollerance, or on if the voltage difference is greater than 100 millivolts.  Three comparators __ Designed by Bill Bowden

Battery Low Voltage Beeper -  This circuit provides an audible and visual low voltage warning for 12V battery powered devices.  idle current: 6ma Low Voltage Warning current: 15ma.   __ Designed by G. Forrest Cook

Battery Monitor also enables constant power boost converter -  11/08/07 EDN Design Ideas:  When powering a microcontroller directly from a battery, it is important to monitor the battery voltage to ensure system integrity Design by Rex Niven, Forty Trout Electronics, Eltham, Victoria, Australia

Battery Monitor Draws 8 µA or Les -  04/13/95 EDN Design Ideas:  The battery monitor in Fig 1 nominally draws 5 µA during normal operation and flashes an alarm indicator when the battery voltage drops below a critical value.  The alarm-state current depends on the desired indicator brightness, but you can easily make the current average less than 500 µA.  This monitor was developed as a change-battery warning Design by Arthur W Du Rea Jr, Science Applications International Corp, Oak Ridge, TN

Battery Monitor Emulates Auto Dashboard -  07/03/97 EDN Design Ideas:   When you use battery-powered scientific-recording equipment, you must know the state of the battery, because an unnoticed battery run-down can lead to loss of data.  Several types of warning indicators are available, but all have their drawbacks.  Moving-coil indicators, test terminals, and digital flags, for example,  Design by TG Barnett and J Millar, University of London, UK

Battery Monitor for 12V Lead-Acid -  This simple circuit makes it posible to monitor the charging process to a higher level.  if you need more information then check out the LM3914 Datasheet. 
Final adjustsments are simple and the only thing needed is a digital voltmeter for the necessary accuracy __ Designed by Jan Hamer

Battery Powered (Li-Ion) Platinum RTD Signal Conditioner with Curvature Correction -  The LT2078 is a micropower dual op amp in 8-pin small outline, standard surface mount package, and LT2079 is a micropower quad op amp offered in the standard 14-pin surface mount package.  Both devices are optimized for single supply operation at 5V.  ±15V specifications are also provided.  __ Linear Technology/Analog Devices App Note, Mar 30, 2010

Battery Powered Lap Top Computer Power Supply -  DN18 Design Notes__ Linear Technology/Analog Devices

Battery Tester for 1.5 & 9V -  Schematic & Notes only, no description included.   __ Designed by Martthew B

Battery Voltage Monitor -  R1 controls the trip-point of the circuit.  adjust it accordingly.  to reverse the logic (have the LED light up when the battery has at least X amount of power,) connect the LED to ground through R4.   __ Designed by Andy Wilson

Battery-Discharge Measurement Circuit -  Battery-life measurement for a portable system is a time-consuming task and many methods used for it do not give reliable results.  Presented here is a circuit using which you can measure...__ Electronics Projects for You

Battery-Level Indicator -  Normally, in mobile phones, the battery level is shown in dot or bar form.  This lets you easily recognise the battery level.  Here we present a circuit that lets you know...__ Electronics Projects for You

Battery-Low Indicator -  Rechargeable batteries should not be discharged below a certain voltage level.  This lower voltage limit depends upon the type of the battery.  This simple circuit can be used for 12V batteries...__ Electronics Projects for You

Battery-Monitor -  A Very Simple circuit and some Variations.  Play with it.  All parts are cheap and should be easily obtained.   __ Designed by G.L. Chemelec

Battery-operated remote-temperature sensor drives 4- to 20-mA current loop -  12/17/04 EDN Design Ideas:  You can remotely measure temperature using a 4- to 20-mA current loop as long as 4000 feet and a battery-powered, white-light LED driver.  You usually configure this equipment to provide a programmable, constant current to an LED from a battery source.  The TPS62300 series of IC s, for example, converts a battery voltage of 2 Design by Scot Lester, Texas Instruments, Dallas, TX

Battery-Status Indicator Uses Two LEDs -  08/12/10 EDN Design Ideas:  Use LED brightness to indicate battery charge.    Design by Abhijeet Deshpande, People’s Education Society Institute of Technology, Bangalore, India

BCD Frequency Meter -  Here is a simple circuit that precisely measures the frequency in BCD format.  The circuit is built around dual comparator LM393 (IC 1) , dual D-type flip-flop CD4013 (IC 2) , binary ripple counter CD4040...__ Electronics Projects for You

BCD readout frequency counter -  This frequency counter isn't the easiest to read, nicest, best frequency counter you can build.  But if all you can find is a few 74HC390 and some ordinary 5mm red LED's, it does the job and is easy and fast to make!  This counter reads 0 - 40MHz to a resolution of 100Hz.  Readout is binary coded decimal (BCD) , with the least significant bits at the top.  The photo at top left shows the counter reading its own internal 2MHz clock. __ Designed by Hans Summers

Beat Balance Metal Detector -  BFO (beat frequency oscillator) metal detectors use two oscillators, each of which produces a radio frequency.  One of these oscillators uses a coil of wire that we call the search loop.  The second oscillator uses a much smaller coil of wire, and is usually inside the control box and is called the reference oscillator.  By adjusting the oscillators so their frequencies are very nearly the same, the difference between them is made audible as a beat note __ Designed by Essex Metal Detectors

Beat Balance Metal Detector (Rev Thomas Scarborough) -  Various embodiments of the BB metal detector have been published, and it has been widely described in the press as a new genre.  instead of using a search and a reference oscillator as with BFO, or Tx and Rx coils as with iB, it uses two transmitters or search oscillators with iB-style coil overlap.  The frequencies of the two oscillators are then mixed in similar fashion to BFO, to produce __ Designed by Andy Collison

Bed Wetting Alert -  Keep the tide out with this effective bed wetting alarm.  You just add some circuitry to Jaycar's "Secret Farter" and make a sensor.__ SiliconChip

Bedwetting Alarm -  Bedwetting is one of the most common childhood problems that can have a significant impact on a child’s health if left unattended.  During the night, the parents would not know if...__ Electronics Projects for You

Bedwetting alarm -  A simple two tone water alarm that is light enough to be worn on the upper arm of a sleeper is described.  it uses two LMC555 CMOS timer chips followed by a complimentary pair of emitter followers to drive an 8 ohm speaker.  Power is supplied by a 9 volt transistor radio battery.  An modification to produce a siren rather than two tone operation is discussed __ Designed by Dick Cappels

Bedwetting/Wet Diaper Alert System -  Bedwetting is one of the most common childhood problems that can have a significant impact on a child’s health if left unattended.  During the night, the parents would not know if the child has urinated and the kid may sleep all night long on a wet bed, or with a wet nappy.  Bedwetting/Wet Nappy alert system provides a very __ Designed by T.K. Hareendran

Beehive scale uses inductive sensing -  EDN Design Ideas:  05/05/2014     A spring scale for measuring honey production senses weight inductively.   This beehive weight scale uses a TI LDC1000EVM inductance processor circuit to measure the weight of a Beehive, by detecting the the change in resonance due to a change in inductance, as the change in weight on the scale occurs.  The processor sensed and measured differences; outputs are sent to a collocated laptop computer via a USB port and displayed by the TI software GUI on the screen.  For this design concept, it was decided to design for a maximum of 160 lbs.   Design by Paul Watson

Beeper to find shorts -  This circuit uses two 741s or equivalent op amp to form a beeper that is used to detect short circuits.  This design offers a way to trace resistance in the milliohm range, right to a short between bridged traces beneath a solder mask.  A1 is configured as a multivibrator.  R1 and C1 determine the frequency of oscillation and __ Contact IQ Technologies

Bench Amplifier -  A small 325mW amplifier with a voltage gain of 200 that can be used as a bench amplifier, signal tracer or used to amplify the output from personal radios, etc.   __ Designed by Andy Collison

Bender senses shocks -  EDN Design Ideas:  05/14/2013    With the aid of a simple mounting system and some soldered-on weights, a piezoelectric “bender” can detect mechanical shocks Design by Don Sherman, Maxim Integrated Products, Sunnyvale, CA

BER Tester Measures Errors in Low-Data-Rate Applications -  12/05/05  EDN Design Ideas:  You don't need an expensive pattern generator to produce a PRBS (pseudorandom-bit-sequence] signal for making elementary BER (bit-error-rate] measurements in low-data-rate continuous-transmission systems Design by Cedric Mélange, Johan Bauwelinck, Jo Pletinckx, and Jan Vandewege, Ghent University, Ghent, Belgium

BFO Metal Detector -  Not the best, but Simple, and Now with a PCB.   __ Designed by G.L. Chemelec

Bias Voltage & Current Senses for Avalanche Photodiodes -  AN92 Avalanche photodiodes, used in laser based fiberoptic systems, require high voltage bias and accurate, wide range current monitoring.  Bias voltage varies from 15V-90V and current ranges from 100nA to 1mA, a 10, 000:1 dynamic range.  This publication presents various 5 volt powered circuits which meet se requirements.  Appended sections detail specific circuit techniques and cover measurement practice.  __ Linear Technology/Analog Devices

Biasing Corrects Position-Sensing Photodiode -  07/07/94  EDN Design Ideas:  An integrator powers the light source in Fig 1's position-sensing circuit, eliminating errors arising from variations in the source's intensity.  This circuit's accuracy is essentially that of the sensor itself, beating designs that use a more complex anal Design by Yishay Netzer, Consultant, Yuvalim, Israel

Bias-voltage & current-senses make avalanche photodiodes work -  03/06/03  EDN Technical Article: Feeding and reading an avalanche photodiode takes a high degree of circuit sophistication.   Design by Jim Williams, EDN's most revered contributor, passed away in June 2011 after a stroke.  He was 63.

Got Designs?
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