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Tester or Measurement (Instrument) Circuits

Test Equipment:  #'s - A        B - D        E - G
H - L        M - O        P - S        T - Z


Last Updated: October 24, 2017 02:55 PM
Circuits Designed by Dave Johnson, P.E. :

Control Variable LED Intensity -  The circuit below uses power from four rechargeable AA NiMH
cells to drive 3 white LEDs.  A potentiometer varies the duty cycle of a pulse width modulator circuit to vary the intensity of the LEDs from 0% to 100%.  The beauty of the circuit is that when the . . . Hobby Circuit designed by David A. Johnson P.E.-September, 2009

Convert AC to DC signal with is Full Wave Rectifier -  This is a classic circuit that can accurately convert an AC signal to DC.  Using a LF412 high speed dual op amp, this circuit will rectify any signal up to about 100KHz with a minimum amplitude of about 50mv peak to peak.  At 40KHz the input signal can be . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Cooling Fan Thermostat (12v) -  This circuit will turn on a 12v DC powered cooling fan when the air temperature reaches a certain high temperature and will keep the fan turned on until the temperature drops below a second lower level.  Both the high and low temperatures are both adjustable . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2011

Corona Monitor -  The circuit is powered by +5v and has an on-board voltage regulator as a reference voltage.  The current from a reversed biased photodiode is converted into a voltage using an op amp circuit.  That output voltage is fed to a voltage comparator circuit.  included is an adjustment in the current to voltage converter, to calibrate the installed circuit. . . Circuit by David Johnson P.E.-February, 2010

CT Hour Meter -  Many systems require routine maintenance based on machine operation time.  The circuit below is a simple way to turn on a hour meter whenever AC power is supplied to the machine.  An inexpensive snap-on current transformer from Magnetics inc, is used to . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2010

Current Indicator for Battery Chargers -  This circuit was inspired by a company needing a DC current indicator light which was small enough to be molded into a medium size 28v rechargeable battery assembly.  They specified that they wanted the circuit to turn on the LED indicator light with 500ma or more of battery charge current. . . Circuit by Dave Johnson P.E.-January, 2011

Current Injector -  When you need to measure resistance down to a few micro ohms, this circuit works great.  it is powered from two "C" cell batteries and is designed to inject a well regulated one amp of current into the unknown resistance.  By measuring the voltage drop across the resistor with a digital voltmeter, the resistance value can be accurately measured.  The circuit also is equipped with a low battery monitor.  Published in Popular Electronics, November 1992 - modified on July 11, 2006. . . Circuit by David A. Johnson P.E.-June, 2000

CW & CCW Alternating Motor Driver -  A while back a company needed a motor controller for a custom door latching system.    The system used a small brush motor with a speed reduction gear to both latch and unlatch the door.    When pulsed for about 250ms in the clockwise direction, the motor would unlatch the door . . . Hobby Circuit designed by Dave Johnson P.E.-September, 2010

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Contactless Tachometer on AVR. Part 1. Schematic -  This new contactless tachometer - is the device based on an ATMEGA48 AVR micro controller from Atmel, and is able to measure very high RPMs, as well as very low ones.  it is based on an IR (infra Red) opto-couple to detect shaft rotation.  Principle__ Radio Locman

Continuity buzzer is frugal with power -  04/15/99  EDN Design Ideas:  (contains several designs, scroll to find this one) The continuity detector in Figure 1 is based on W Dijkstra's "Fleapower circuit detects short circuits" (EDN, July 2, 1998, pg 122).  The buzzer indicator allows you to devote full attention to making the connection without having to observe an LED.  The circuit also consumes less power than Dijkstra's circuit.  Power comes from two AA or AAA cells, which last for a period equal to their shelf life.  Current consumption is less than 2.5 mA when the circuit detects continuity and less than 1.7 mA for an open circuit.  Open-circuit voltage is less than 100 mV, and short-circuit current is less than 1 mA.   __ Circuit Design by Hans Krobath, EEC, Nesconset, NY

Continuity Tester -  This circuit will detect low resistances and high resistances to produce a tone from the speaker.  it will detect up to 200k and the circuit automatically turns off when the probes are not used.  __ 555-Timer

Continuity Tester -  This circuit senses only dead shorts on a populated board.  it will not ring through or damage components.  it shuts off when not in use.  it was first published in Electronics magazine, June 21, 1979, page 145 __ Designed by Andrew R. Morris

Continuity Tester -  Among the essentials for circuit design and prototyping is the continuity tester, a simple device which provides an audible indication when a sufficiently low resistance is applied between its input probes.  This version has a feature which automatically turns off the tester after about two minutes, thereby saving the 9 volt battery from inadvertent discharge.  The tester produces a high-pitch tone when less than 10 ohms is placed between the input probes.  The 10 ohm threshold is a convenient value that indicates hard-wired paths, but excludes indications for circuit paths through most components.  in addition, the amount of current presented to the circuit by this __ Designed by Arthur Harrison

Continuity Tester -  Occasionally you need a continuity test between two points in an electronic circuit.  Unfortunately, most continuity testers are prone to "lie".  They don't do that deliberately, but if they see a small resistance, they still tell you that you have continuity.  They just don't know any better __ Designed by Tony van Roon  VA3AVR

Continuity Tester Fits Into Shirt Pocket -  10-Jan-08 EDN Design Ideas:  A pocket-sized continuity tester responds quickly to shorts or opens and is protected against connection to a live circuit __ Circuit Design by Tom Wason, Phoenixville, PA

Continuity Tester Latching -  A continuity tester is a must on every service bench for testing cables, pc-boards, switches, motors, plugs, jacks, relays, and many other kinds of components.  But there are times when a simple continuity test (or your multi-meter) doesn't tell the whole story.  For example, vibration-induced problems in automobile wiring can be extremely difficult to detect because a short or open is not maintained long enough for a non-latching tester to respond __ Designed by Tony van Roon  VA3AVR

Continuity Tester with a Chirping Sound -  Today, theres a party at your home.  And you are busy detecting faults in the decorative lights hanging over the boundaries of your house.  You want to finish the job before...__ Electronics Projects for You

Continuity Tester, Low-Voltage -  Several simple circuits were tried -a lamp, battery and probes still demanded the attention of the eyes; replacing the lamp with a buzzer was more successful but needed some three to four volts and gave no indication of a series semiconductor.   __ Designed by Tony van Roon  VA3AVR

Continuity Tester-essential for Digital projects -  This is another invaluable piece of test equipment for digital work.  it has been designed by us to cater for a particular application servicing digital projects sent in for repair.   __ Designed by Collin Mitchell

Continuity testing, resistor testing, capacitor testing & diode testing -  This is a very useful circuit which can be used for testing electronic component.  Like multimeter one can use this circuit for :- continuity testing, resistor testing, capacitor testing and diode testing.  in this circuit LED glows only when probes L1 and L2 are short-circuited or has a path for the current to flow.  This fact will be used to test components. __ ` Sigmatone

Control Multiple Thermoelectric Coolers -  08/19/99 EDN Design Ideas:  Optoelectronic and other components sometimes use a thermoelectric cooler and a thermistor for temperature control.  A typical thermoelectric cooler __ Circuit Design by Frank Effenberger

Control Variable LED Intensity -  The circuit below uses power from four rechargeable AA NiMH
cells to drive 3 white LEDs.  A potentiometer varies the duty cycle of a pulse width modulator circuit to vary the intensity of the LEDs from 0% to 100%.  The beauty of the circuit is that when the . . . Hobby Circuit designed by David A. Johnson P.E.-September, 2009

Convert AC to DC signal with is Full Wave Rectifier -  This is a classic circuit that can accurately convert an AC signal to DC.  Using a LF412 high speed dual op amp, this circuit will rectify any signal up to about 100KHz with a minimum amplitude of about 50mv peak to peak.  At 40KHz the input signal can be . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Convert any signal to exactly 50% duty cycle -  06/25/13  EDN Design Ideas:  How would you process a variable frequency signal to always maintain a 50% duty-cycle? Here's one way __ Circuit Design by Jim McLucas

Convert voltage to potentiometer-wiper setting -  09/05/02 EDN Design Ideas:  The circuit in Figure 1converts an analog input voltage, ViN, to a proportional wiper setting of a DPP (digitally programmable potentiometer].  The potentiometer's wiper setting, which varies from position 0 through 31, corresponds to the input voltage, which varies from 0 to 1V dc.  The CAT5114, IC 5, is a 32-tap potentiometer with an increment/decrement interface __ Circuit Design by Chuck Wojslaw, Catalyst Semiconductor, Sunnyvale, CA, and Chris Wojslaw, Conexant Systems, Newport Beach, CA

Convert your DMM to a pH meter -  10/17/02 EDN Design Ideas:  it's often necessary to know the acidity of a solution to control a process.  Even inexpensive pH meters can be relatively costly, and many of the inexpensive models have no output that you can readily connect to a computer interface.  A simple solution to this problem is to attach a pH probe to a high-impedance input of an op amp and read the output with a digital voltmeter (Figure 1)  __ Circuit Design by Bill Donofrio, Nu-Products, Cordova, TN

Cooling Fan Thermostat (12v) -  This circuit will turn on a 12v DC powered cooling fan when the air temperature reaches a certain high temperature and will keep the fan turned on until the temperature drops below a second lower level.  Both the high and low temperatures are both adjustable . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2011

Corona Monitor -  The circuit is powered by +5v and has an on-board voltage regulator as a reference voltage.  The current from a reversed biased photodiode is converted into a voltage using an op amp circuit.  That output voltage is fed to a voltage comparator circuit.  included is an adjustment in the current to voltage converter, to calibrate the installed circuit. . . Circuit by David Johnson P.E.-February, 2010

Count Accumulator for Radiation Levels CARL -  The CARL device is an add-on numerical counter that plugs into the headphone jack of 1960s vintage geiger counters such as the Victoreen CDV700 and CDV700-6B.  it should also work with the Lionel ENi/LENI counters, and any other geiger counter that has a headphone output pulse greater than -5V.  Vintage 1960s era geiger counters don't actually count, they use an analog meter with an integrator circuit to give short-term averaged__ G. Forrest Cook

Cranial Electrical Stimulation Unit -  Commercial cranial electrical stimulation (CES) units cost hundreds of dollars but this one is cheap and easy to build.  it is battery-powered, portable and has adjustable current delivery and repetition rate.__ SiliconChip

Cranial Electrotherapy Stimulation (CES) -  IC 1 forms a narrow pulse, 2.5Hz oscillator feeding IC 2.  This chip generates the various timings for the output pulses.  Output is taken at pins 2 & 3 to easily obtain negative going pulses also.  Current output is limited to 600A by R2 and can be regulated from 80 to 600A by means of R3.  The LED flashes every 2 seconds signaling proper operation and can also be used for setting purposes.  it can be omitted together with R4, greatly increasing battery life. __ Designed by  Hack Canada

Cranial Electrotherapy Stimulator -  Current flows through clips placed on the earlobes; Output current adjustable from 80 to 600 microAmperes __ Contact Flavio Dellepiane, fladello @ tin.it

Cricket Monitor -  PIC  Project  This device listens for 'crickets' - little transmitters that bleep out their condition periodically.   __ Designed by Luhan Monat - Mesa Arizona

Crystal heater / temperature stablization (TXCO) -  OK, here is the circuit I used - See image below.   The original National Semiconductor circuit had a 30 K resistor in series with a 400 F cap., both in parallel with the 100 K resistor on the input of the 1st LM324 section.   I found that combo to actually destabilize the operation of the controller for this particular application, so I removed them & changed the 2 F cap in series with the 10 megohm resistor to 5 F.__ Bobengler   NO6B

Crystal Tester -  This circuit enables you to test quartz resonators at the range values from 32kHz to 24MHz.  Confirmation of good state of quartz resonator is done by diode signalling LED and acoustic signal.  Switch S2 enables change of range.   __ Contact IQ Technologies

Crystal Tester to Build -  Please Scroll Down:  Below is the circuit of a simple crystal tester. it switches on a light emitting diode (LED) if the crystal is working. __ Designed by Peter Parker VK3YE

Crystal Tester, #1 -  Transistor Q1, a 2N3563, and its associated components form an oscillator circuit that will oscillate if, and only if, a good crystal is connected to the test clips.  The output from the oscillator is then rectified by the 1N4148 signal diode and filtered by C3, a 100pF capacitor.  The positive voltage developed across the capacitor is applied to the base of Q2, another 2N3563, causing it to conduct.  When that happens, current flows through Led1, causing it to glow.   __ Designed by Tony van Roon  VA3AVR

Crystal Tester, #2 -  Transistor Q1, a 2N3563, and its associated components form an oscillator circuit that will oscillate if, and only if, a good crystal is connected to the test clips.  The output from the oscillator is then rectified by the two 1N4148 signal diodes (1N914 are fine too) and filtered by C1, a 0.01uF ceramic capacitor.   __ Designed by Tony van Roon  VA3AVR

Crystal Tester, #3 -  Your 40- or 80 meter crystal isn't oscillation--what's wrong?is it a wiring error? A solder bridge? A faulty component? Maybe it's the crystal!  A simple circuit that tests whether or not a crystal is good, this is a real chestnut.  First noticed in October 1989 issue of "Popular Electronics Magazine" but the original circuit is credited to Mike Kaufman in Wayne Green's out-of-print book.   __ Designed by Tony van Roon  VA3AVR

CT Hour Meter -  Many systems require routine maintenance based on machine operation time.  The circuit below is a simple way to turn on a hour meter whenever AC power is supplied to the machine.  An inexpensive snap-on current transformer from Magnetics inc, is used to . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2010

Curious C Beeper -  The Curious C-Beeper uses the two-transistor flasher in conjunction with a darlington transistor to make a most unusual capacitance beeper probe.  When a capacitor is touched to the probe, the probe beeps at a frequency that varies with capacitance.  The frequency change __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Current Indicator for Battery Chargers -  This circuit was inspired by a company needing a DC current indicator light which was small enough to be molded into a medium size 28v rechargeable battery assembly.  They specified that they wanted the circuit to turn on the LED indicator light with 500ma or more of battery charge current. . . Circuit by Dave Johnson P.E.-January, 2011

Current Injector -  When you need to measure resistance down to a few micro ohms, this circuit works great.  it is powered from two "C" cell batteries and is designed to inject a well regulated one amp of current into the unknown resistance.  By measuring the voltage drop across the resistor with a digital voltmeter, the resistance value can be accurately measured.  The circuit also is equipped with a low battery monitor.  Published in Popular Electronics, November 1992 - modified on July 11, 2006. . . Circuit by David A. Johnson P.E.-June, 2000

Current loop transmits AC measurement -  01/28/13 - EDN Design Ideas:  Originally published in the Aug 6, 1992, EDN-Design ideas -- Process-control applications use current loops to send information as an analog signal over long distances with high noise immunity.  Using the three-chip circuit in Figure 1, you can measure alternating current or voltage and transmit the results on a 4- to 20-mA current loop.  The circuit accepts a 0- to 10-mV ac RMS input and provide as a 4- to 20-mA output.    __ Circuit Design by Mark Fazio, David Scott, and Boblarke, Analog Devices, Wilmington, MA

Current Monitor compensates for errors -  09/09/10 EDN Design Ideas:  Measure current up to 5A in the presence of 500V common-mode voltage.    __ Circuit Design by Chau Tran and Paul Mullins, Analog Devices, Wilmington, MA

Current Monitor Tracks High DC Currents -  03/01/07  EDN Design Ideas:  Oscillator's output tracks current as it varies inductor's core characteristics __ Circuit Design by Susanne Nell, Breitenfurt, Austria

Current Monitor Uses Hall Sensor -  EDN-Design ideas -- 01/05/12    Use a Hall-effect sensor to measure dc current in the range of 0 to 40A. (Originally published in the March 31, 1987, EDN-Design ideas) The Fig 1 circuit uses a Hall-effect sensor, consisting of an IC that reside as in a small gap in a flux-collector toroid, to measure dc current in the range of 0 to 40A.  You wrap the current-carrying wire through the toroid; the Hall voltage VH is then linearly proportional to the current (i).  The current drain from VB is less than 30 mA. __ Circuit Design by Paul Galluzzi, Dynamics Research Corp, Wilmington, MA

Current Sense Auto Power Switch -  A current sensing switch turns on multiple devices from one master __ Designed by Rod Elliott  ESP

Current Sense Curcuit Collection -  AN105 Sensing and/or controlling current flow is a fundamental requirement in many electronics systems, and the techniques to do so are as diverse as the applications themselves.  This App Note compiles solutions to current sensing problems and organizes the solutions by general application type.  These circuits have been culled from a variety of documents.  __ Linear Technology/Analog Devices

Current Sensor -  High-wattage appliances like electric irons, ovens and heaters result in unnecessary power loss if left 'on' for hours unnoticed.  Here is a circuit that senses the flow of current through the...__ Electronics Projects for You

Current sensor measures 0 to 500A -  09/30/99 EDN Design Ideas:  The simple circuit in Figure 1a can sense both low and high current levels without low sensitivities or loss of accuracy either at the low or the high end of the scale.  The circuit is useful for discerning either low or high currents in noisy environments.  The circuit comprises a current mirror formed by complementary pair Q1 and Q2 and the feedback provided by Q3.  When a current I flows through RS, the voltage at the emitter of Q2 increases.  The voltage at the base of Q3 then increases, which increases the current, iEQ3, through Q3's emitter.   __ Circuit Design by Jose Carrasco, Universidad de Valencia, Department Electronica, Valencia, Spain

Current-Input ADC measures voltages -  EDN Design Ideas:  08/19/1999    A practical realization of a spread-spectrum technique lowers a P's clock-related EMI by approximately 4 dB without the drawbacks associated with  __ Circuit Design by Jim Todsen, Burr-Brown Corp, Tuscon, AZ

Current-sense Amplifier handles high voltages -  11/06/97 EDN Design Ideas:  High-side current-sense amplifiers, such as IC 1 in Figure 1, monitor current from a battery or dc power line in systems for which the ground-return continuity is crucial.  IC 1's 36V maximum operating voltage, however, excludes some applications, including traction-motor batteries and central-exchange power supplies, both of which require operation at voltages exceeding 72V.  The external circuitry in Figure 1 allows IC 1 to monitor current at voltages of 300V and greater.  Q1 and Q2 form a current source whose compliance voltage provide as the high-voltage capability.  IC 1 draws its 100-A supply current from a simple floating power supply comprising C1, C2, avalanche diode D1, and the Q1-Q2 current source.    __ Circuit Design by Andy Fewster, Maxim Integrated Products, Reading, UK

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Test Equipment:  #'s - A        B - D        E - G
H - L        M - O        P - S        T - Z

 


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