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Tester or Measurement (Instrument) Circuits

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Last Updated: January 01, 2018 04:02 AM
Circuits Designed by Dave Johnson, P.E. :
Thermostat for 12v Cooling Fan -  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 Johnson P.E.-February, 2011

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:

The "Matchless" Metal Locator  -  it's cheap, its easy to build and it could find a fortune.__ SiliconChip

The "Tenna Dipper" -  Poor mans antenna analyzer, shows resonance of antennas, 80-10 M operation. __ Designed by Steven "Melt Solder" Weber  KD1JV

The Battery Guardian -  Don't get caught with a flat battery; this easy-to-build circuit can cut off the power to a 12V fridge or car stereo system if the battery voltages drops below critical level.__ SiliconChip

The 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 is so steep with capacitance that tiny capacitors may be precisely matched or an exact fixed value may be selected to replace a trimmer in a prototype.  if the user has reasonably moist skin, simply holding one lead of the capacitor to be tested while touching the other lead to the probe is all that is necessary.  The user's body forms the other connection through the beeper's metal case. __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

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 experimenter’s pot-Digital Potentiometer -  The experimenter's pot is a solid state potentiometer using Dallas semiconductor’s DS1869 and National’s LM78L05 two electrolytic capacitor two small push button switch and two optional Molex connector.  this project is very useful especially in finding the right value of resistor in your experiments __ Contact IQ Technologies

The F.E.D. Detects digital RF signals -  The F.E.D. (Frequency Emissions Detector) will, of course, detect anyone's cell phone, so the detector really responds to just about anybody with more than two pennies to rub together.  Most phones occasionally transmit short bursts to the nearest cell tower, even when the phone isn't in use, so a typical 21st century loiterer will eventually set off the detector.  On the other hand, a deer can stare at it for an hour with no effect.  Let's face it, even most burglars emit digital signals these days.  So, in a sense, the F.  E.  D.  is a human detector.  With that in mind, consider using the output to activate a digital camera or video recorder to capture a record of the prowlers.  A recorded barking dog or, one of my favorites, a recording of police radio traffic will scare off most crooks.  Add some hidden flashing red and blue lights to the police chatter and the culprits will actually run away.   __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

The HeartMate Heart Monitor -  Build it and keep tabs on your ticker.  it's just a shot for monitoring your heart rate during exercise, so you dont overdo it.__ SiliconChip

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

The LT6105 Can Monitor the Current of Either Positive or Negative Supplies, Without a Schematic Change. -  Positive or negative current flow is measured by just swapping inputs, -iN connected to most negative side of sense resistor.  +iN is connected to most positive side of sense resistor.  __ Linear Technology/Analog Devices App Note, Jun 29th 2012

The SC480 50W RMS Amplifier Module-Part 1 -  At last! - an amplifier module to replace the venerable ETi-480.it has less distortion, is much quieter, has inbuilt protection and sounds a lot better.__ SiliconChip

The SC480 50W RMS Amplifier Module-Part 2 -  Everything you need to know about putting together this outstanding new power amplifier module (covers both versions).__ SiliconChip

The SID Seizer-monitor SIDs -  The SiD Seizer is a VLF/LF receiver project for monitoring Sudden ionospheric Disturbances, typically caused by solar flares.  This article assume the reader has basic knowledge of the effects of solar flares on the ionosphere. (A web search will yield a wealth of information on SiD reception, including other simple designs, typically employing loop antennas.) Breaking with tradition, the SiD Seizer uses a vertical whip antenna with a tuned amplifier, instead of a tuned loop.  My house and neighborhood have so much magnetic noise that a vertical whip antenna is significantly superior to a loop.   __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

The Simple Circuit man's Spectrum Analyser -  A spectrum analyser is a very useful piece of test equipment to have on your workbench, yet the price tag of commercially avialable analysers places them way outside most hobbyist budgets, even when 2nd hand.  All is not lost - here's a spectrum analyser design you can build yourself that won't break the bank.  The pages linked above describe the construction in detail.  Most photograph insets can be clicked to view a larger high resolution image. __ Designed by Hans Summers

The taming of the slew -  09/25/03  EDN Technical Article: Deriving a slew-rate-measurement approach requires understanding slew rate's relationship to amplifier Dynamics. __ Circuit Design by Jim Williams, EDN's most revered contributor, passed away in June 2011 after a stroke.  He was 63.

The Taming of the Slew -  Linear Technology AN94 __ Designed by Jim Williams - May 1st, 2003

The u-counter, a PIC based programmable frequency meter -  This project proposes a simple frequency reader specifically designed for QRP rigs, also if you may
employ it also as a workbench instrument.  in fact it exhibits several very interesting features, like a maximum working frequency above 40 MHz, a 10 Hz resolution, a low consumption (15 mA) and a very simple assembly.  Moreover it is possible to program an iF value and mode simply by means of two push buttons __ Designed by Francesco Morgantini IK3OIL

The Ultimate Wireless Volume Control -  17-Aug-11 -Design News:   Andrew Morris decided the usual wireless volume controls don’t offer enough functionality, so he created the ultimate volume control that connects between a computer or MP3 player and an amplified speaker system. __ Designed by Andrew R. Morris, Gadget Freak-Case #192

The X-ray Defender -  Detects backscatter X-ray machines - Backscatter X-ray imaging devices have been in the news of late, primarily due to their use in U.  S.  airports and other public facilities.  But, not everyone is aware that the technology is also being deployed in ordinary vans that can image the insides of passing cars and trucks, and even peer into the interior of homes and businesses.  in order to penetrate the exteriors of vehicles and buildings, the x-ray beam is substantially more intense.  in the wrong hands, the beam  __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Thermal Techniques in Measurement & Controlry -  AN5 6 applications utilizing thermally based circuits are detailed.  included are a 50MHz RMS to DC converter, and anemometer, a liquid flow meter and others.  A general discussion of thermodynamic considerations involved in circuitry is also presented.  __ Linear Technology/Analog Devices

Thermal Techniques in Measurement and Control Circuitry -  Linear Technology AN5 __ Designed by Jim Williams - Dec 1st, 1984

Thermally Controlled NiCad Charger -  A voltage controlled current (maximum of 1A) is used to charge a NIC d battery.  The control voltage is derived from the temperature difference between the battery and the ambient air.  The charge current is reduced as the battery heats up.  __ Linear Technology/Analog Devices App Note, Jun 21, 2011

Thermistor Preamp -  (spice design)  __ Designed by Rick 

Thermistor Thermometer: LCD Version -  This is the 2nd version of Thermistor Thermometer Project done by another group of my student.  The 1st version having 4-digit 7-segment LED shows the use of simple display device.  For applications that needs text display, this LCD version is more suitable and easy to adapt for many kinds of measuring devices.   __ Designed by Wichit Sirichote

Thermocouple Interfaces to Serial Port -  11/09/95 EDN Design Ideas:  The circuit in Figure 1 acquires temperature data via an iBM PC serial port using a thermocouple-based sensor.  The sensor is a type-K (chromel-alumel]thermocouple.  When in contact, the dissimilar metals produce a potential difference that is a function of temperature.  Additional thermocouple junctions __ Circuit Design by Daniel Segarra, Sipex Corp  Billerica, MA

Thermocouple Measurement -  Linear Technology AN28 __ Designed by Jim Williams - Feb 1st, 1988

Thermocouple Measurement -  AN28 Considerations for thermocouple-based temperature measurement are discussed.  A tutorial on temperature sensors summarizes performance of various types, establishing a perspective on thermocouples.  Thermocouples are then focused on.  included are sections covering cold-junction compensation, amplifier selection, d__ Linear Technology/Analog Devices

Thermocouple Temperature Measurement System with Amplifier-Based Cold Junction Compensation  -  The EVAL-CN0271-SDPZ contains the circuit to be evaluated, as described in this note, and the SDP-B controller board is used with the CN-0271 evaluation software to capture the data from the EVAL-CN0271-SDPZ circuit board.  Equipment Needed The following equipment is needed:, Bullet text, Getting Started Load the evaluation software by placing the CN-0271 evaluation software CD in the CD drive of the PC.  Using My Computer, locate the drive that contains the evaluation software.  , Functional Block Diagram See Figure 1 of this circuit note for the circuit block diagram and the EVAL-CN0271-SDPZ-SCH-RevA.  pdf file for t__ Analog Devices from the Lab

Thermocouple Temperature Measurement System with Less Than 500 μA Current Drain  -  For this reason, a linearization procedure is implemented in the CN0206-SDP-0 LabViEW software.  The evaluation software then searches the modified look-up table for the thermocouple input voltage, as sampled by the AD7793 System Calibration in addition to linearizing the thermocouple temperature, the evaluation software performs a two-point calibration.  __ Analog Devices from the Lab

Thermocouple Thermometer with Cold Junction Compensation -  The LTC2997 is a high-accuracy analog output temperature sensor. __ Linear Technology/Analog Devices App Note, Jul 7th 2011

Thermoelectric Cooler Temperature Controller for Fiber Optic Lasers -  AN89 Linear Technology This App Note presents circuitry for maintaining 0.01°C temperature control of fiber optic lasers over wide ambient range variations.  The circuitry also features high efficiency power delivery, compact size and low noise.  Detailed descriptions of circuitry and results are given with special emphasis on rmal loop optimization.  An appended__ Linear Technology/Analog Devices

Thermometer & thermostat -  for Room temperatures __ Designed by Richard Torrens

Thermostat -  OK - so I admit is.  This circuit is the same as the last one!  Here is a practical use for the Schmidt trigger.   __ Designed by Richard Torrens

Thermostat  (1N4148) -  Temperature controlled fan with diode temp sensor.  This circuit controls very accurately a fan of any size.  Just adjust the associated resistors for a different type like the R6 resistor of 100 ohm, 2 watt type and you’re all set.  The above circuit diagram is for a small 12 volt fan, the size and type determined by the user. __ Designed by Tonny Von Roon

Thermostat Control for Electric Heaters -  One Advantage of these two units is the Sensor can be placed Away from the heater, therefore sensing the Actual Room temperature, not the direct heat from the heater.  These can also be used in a confined space with a Heat Lamp, to create a Drying Oven  __ Designed by G.L. Chemelec

Thermostat for 12v Cooling Fan -  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 Johnson P.E.-February, 2011

Thermostat for 1KW Space Heater (SCR controlled) -  Below is a thermostat circuit I recently built to control a 1300 watt space heater.  The heater element (not shown) is connected in series with two back to back 16 amp SCRs (not shown) which are controlled with a small pulse transformer.  The pulse transformer has 3 identical windings, two of which are used to supply trigger pulses to the SCRs, and the third winding is connected to a PNP transistor pair that alternately supply pulses to the transformer at the beginning of each AC half cycle.  The trigger pulses are applied to both SCRs near the beginning of each AC half cycle but only one conducts depending on the AC polarity. __ Designed by Bill Bowden

Thermostat Node Schematic -  Circuit Only __ Designed by Ed Cheung

Thermostat with Adjustable Hysteresis -  Switching Circuits:  This small thermostat allows you to select the size of its hysteresis.  You can set both the temperature at which the relay will energize - and the temperature at which the relay will de-energize.  The difference between these two temperatures is the hysteresis.  __ Designed by Ron J.

Thermostat with LED Temperature Display -  I needed to replace two old, unreliable thermostats for controlling the heating and cooling for a large garden shed.  Commercial basic thermostats are available quite cheaply, but some lack the ability to control heavy loads or have the extra features that I require for saving energy when the door is often left open or to indicate temperature being out of range etc.  I like the PIC 18F1320 microcontroller used in my previous project, so decided to use it again in a very similar design to drive three multiplexed LED displays and read the temperature from a Dallas/DS18x20 "1-Wire" sensor.   __ Designed by D. Thorpe, 2006

Thermowell vibration Monitor -  04/14/14 - EDN Design Ideas:  Use Ti's unique inductance - to - digital converter to sense potentially dangerous vibration in thermowell sensors __ Circuit Design by Robert Heider

Throttle Interface for the DC Motor Speed Controller -  Last month, we presented the High-Power Reversible DC Motor Speed Controller.  Here is a companion controller which works with a motorcycle-style throttle control.  it also features a forward/reverse switch to control the motor direction.__ SiliconChip

Tilt Measurement using a Dual Axis Accelerometer  -  Follow the instructions contained in the Readme file for installing and using the evaluation software.  , Functional Block Diagram See Figure 1 of this circuit note for the circuit block diagram, and the file “EVAL-CN0189-SDPZ-SCH-Rev0.  pdf ” for the circuit schematics__ Analog Devices from the Lab

Tilt Sensor Alarm -  Ultra simple circuit of the tilt sensor alarm presented here can be fabricated using readily available inexpensive components.  The circuit is a true transistor based design.  Home made Tilt sensor for this circuit is an ordinary little glass/plastic bottle with two metal needles inserted through its cap, and a small quantity of __ Designed by T.K. Hareendran

Tilt Switch -  The output is LOW at start-up due to the capacitor on pin 4.  When the mercury switch closes, the output goes HiGH and remains HiGH until the reset button is pressed.  This circuit is called a LATCH.  __ 555-Timer

Tilt/Fall Detector Has Staggered Thresholds -  18-Feb-10 EDN Design Ideas:  Comparators and a voltage-divider network let you set threshold levels __ Circuit Design by Marián Stofka, Slovak University of Technology, Bratislava, Slovakia

TiltStick, a Motion sensing Device -  The TiltStick is a small acceleration sensing device in form of a USB stick.  it's using a two axis acceleration sensor to measure acceleration (caused e.g.  by motion and tilt).  The device is emulating a USB joystick and can thus be used in conjunction with any USB equipped host (e.g.  a standard PC or the Nokia N8XX family) without any special drivers.  The TiltStick is the successor of the Tilt Dongle for Palm OS. __ Designed by Till Harbaum <Till @ Harbaum.org>

Time Domain Reflectometer -  Brief description of operation: Pulse source for time domain reflecometry.  Circuit protection: Output is short circuit proof.  Circuit complexity: Simple one IC construction, can be built on small piece of Vero board.  Circuit performance: Works very well with cables from 5 meters to 500 meters (no longer cables tested, should work for up to __ Designed by Tomi Engdahl

Time Domain Reflectometry Generator-PA3DSC -  Schematic only __ Designed by va3iul

Got Designs?
Please eMail
if you want me to link to and/or post your original design Thanks.

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

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