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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. :

Radio Tower Lamp Monitor -  The circuit below uses two 3 amp diodes to produce a fairly constant 2 volts whenever current is routed to the tower lamp.  The voltage is used to power a bright LED.  The LED will only turn on when current is actually flowing to the lamp.  With the component values shown, the circuit will work with lamps ranging from 40 to 250 watts. . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Really Loud Output Beeper Circuit -  I you need a real loud beeper, this circuit delivers about 110db (12 inches away) from a 9v battery using a single inexpensive C-MOS IC .  An off-the-shelf piezoelectric beeping device is driven at resonance to insure maximum efficiency.  By changing the control IC to a 74AC14, the same circuit can operate from 3v and 1.5v batteries . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

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:

R/C Plane Locator and Voltage Watch (PPM & PCM) -  The R/C Plane Locator is an audio beacon used to locate r/c aircraft in hard to find places. As many have already experienced, locating a downed plane in a field of tall grass can be very difficult. Or perhaps you don't know if you should be looking up in the trees or down between the bushes. The RCPL will assist you by playing a tri-note beacon and flashing an LED. Listen for the sound and you will have an aid in locating your vehicle. Don't wait until you've lost a plane to build one, by then it's too late. __ Designed by M.J. Pawlowsky

Radar Speedometer -  This circuit is a Digital Radar Speedometer.  it allows us to evaluate the speed of any object moving, especially cars and other vehicles.  The speed is calculated in kilometers per hour (KPH).  its display has three digits.  This radar works with the laser reflexion.  it sends laser radiation to the object and this object reflects the laser radiation to the radar. __ Contact IQ Technologies

Radiator Temperature Indicator -  This radiator temperature indicator can be designed using electronic circuit diagram below.  Temperature indicator consists of two special zener diode, D1 and D2, connected in series to ensure accuracy of 5.96 V Zener voltage at 25 C.  As long as the radiator temperature does not exceed 50 C, thermal indicator will flash a__ 

Radio Spectrum Monitor -  This is an experimental project to analyze radio band in FFT.   __ Designed by The Electronic Lives Manufacturing-presented Chan

Radio Tower Lamp Monitor -  The circuit below uses two 3 amp diodes to produce a fairly constant 2 volts whenever current is routed to the tower lamp.  The voltage is used to power a bright LED.  The LED will only turn on when current is actually flowing to the lamp.  With the component values shown, the circuit will work with lamps ranging from 40 to 250 watts. . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Radio Wave Alarm -  This simple circuit is sure to have the police beating a path to your door, however, it has the added advantage of alerting you to their presence even before their footsteps fall on the doormat.  The circuit transmits on Medium Wave (this is the small problem with the police).  IC 1a, together with a sensor (try a 20cm x 20cm sheet of tin foil) oscillates __ Designed by Rev. Thomas Scarborough

Radon Accessory for Radiation Detectors -  Here's an interesting accessory to the ion chambers above or other radiation detectors that will allow for the indirect detection of radon gas.  Radon is a noble gas and is hard to detect directly; it doesn't react chemically or easily stick to anything and it is usually present in very small amounts.  it has a short half-life of under four days so the concentration in a home is due to a constant replenishment as the gas seeps in from the ground or the structure's building materials.  its decay products are much easier to detect because they readily stick to dust in the air and typically have a short half-life, making them more radioactive.  This accessory draws air through a filter, catching dust laden with the radioactive "daughters" of the radon present in the air.   __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Radon Detector for the Student -  This ionization chamber radon detector is designed to be easy for the student or hobbyist to build and use.  it can form the basis for a variety of experiments for Science Fair competitions, class projects, conversation pieces, or simply satisfying scientific curiosity.  Despite the extreme simplicity, the chamber can detect surprisingly low levels of radon by detecting the radioactive "radon daughters" produced when radon gas decays.  The detector could be used to investigate a variety of scientific questions and demonstrate scientific principles: __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Rain Alarm -  This circuit consumes no current until moisture is detected on the rain plate.  __ 555-Timer

Rain Alarm -  This circuit gives out an alarm when its sensor is wetted by water.  A 555 astable multivibrator is used here which gives a tone of about 1kHz upon detecting water.  The sensor when wetted by water completes the circuit and makes the 555 oscillate at about 1kHz.   __ Designed by Radioland.nt.au

Rain Alarm / Rain Detector -  This rain detector will give you a heads-up the instant it starts to rain, hopefully giving you time to close windows and bring in possessions.  The battery-powered circuit draws virtually no current when the sensor is dry and the current consumption is low when the buzzer is activated so a couple of AA cells will last a long time.  Alternately, a molded power supply with a simple voltage regulator to drop the voltage to 3 volts could be used.  The circuit is basically a handy flasher circuit that operates well on only 3 volts using ordinary silicon transistors.   __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Rain Detector -  This circuit uses a sensor made of a small piece of etched PC board and a simple SCR circuit to detect rain and sound a buzzer.  The SCR could also be used to activate a relay, turn on a lamp, or send a signal to a security system.   __ Designed by Aaron Cake

Rain sound effect Generator -  Agreeable, relaxing effect, helping to fall asleep; Small portable unit, 3V battery powered __ Contact Flavio Dellepiane, fladello @ tin.it

Rainbow LED indicates voltage with color -  7-Dec-04 EDN Design Ideas:  Meters that indicate analog levels via a moving-pointer meter, a numeric display, or a column of LEDs typically occupy considerable panel area and require than a casual glance to read.  An indicator lamp or LED takes little space but indicates only an on or off condition.  However, an unobtrusive LED that changes color as a function of a measured value would enable an observer to easily asse __ Circuit Design by David Prutchi, Impulse Dynamics, Haifa, Israel

Rainwater Storage Gauge -  Not only on ecologically grounds but also economically it makes sense to collect rainwater for use in the garden and increasingly for `grey water` domestic use.  People who take rainwater collection seriously use large underground tanks for storage.  The problem now arises, how can the water level be determined without lifting the tank hatch and peering in?__ Learning Electronics

Random & Psuedo Random Noise Generation -  Actually Add noise to circuits? What? That's the basic idea I had when I started out too.  But over time I have found that noise is useful for testing, linearizing, actually measuring other noise and securing.  There are two basic types of noise sources.  Pseudo generated noise - usually produced by a digital shift register scheme and analog random noise - usually produced by some sort of semiconductor junction.   __ Designed by Steve Hageman

Ratiometric Sensor to Pulse Width, Non-Inverting Response -  The LTC6992 is a silicon oscillator with an easy-to-use analog voltage-controlled pulse width modulation (PWM) capability.  The LTC6992 is part of the TimerBlox family of versatile silicon timing devices.  A single resistor, RSET, programs the LTC6992s internal master oscillator frequency.  The output frequency is determined__ Linear Technology/Analog Devices App Note, Jun 16th 2010

RC Network Eliminates Precision Reference -  08/04/94 EDN Design Ideas:  The circuit in Fig 1 uses a magneto-resistive sensor to detect small magnet displacements without resorting to a precision voltage reference.  A simple RC divider takes the place of the reference, eliminating an expensive component __ Circuit Design by Christophe Basso, European Synchrotron Radiation Facility, Grenoble, France

RC Speed Controller -  fed up of paying 20 for controllers? This 10amp pic version has braking and calibration features.   __ Contact P. Townshend - EduTek Ltd

RCM710 electronic scale, technical manual including schematic -  The RCM710 setup functions and calibration sequences are programmed through the in-built keyboard and display.  Setup and calibration may be disabled by an internal hardware jumper.  __ Airborn Electronics, Australia

RCST -  R/C Servo Tester. This pocket sized device is perfect for checking and testing your servos. it features digital accuracy and convenient features, including a servo exercise mode. __ Designed by T. Black

Read Multiple Switches & a Potentiometer Setting with One Microcontroller Input Pin -  04/22/10 EDN Design Ideas:  Use a single ADC input pin to sense pushbuttons as well as a potentiometer.   __ Circuit Design by Kevin Fodor, Palatine, IL

Really Loud Output Beeper Circuit -  I you need a real loud beeper, this circuit delivers about 110db (12 inches away) from a 9v battery using a single inexpensive C-MOS IC .  An off-the-shelf piezoelectric beeping device is driven at resonance to insure maximum efficiency.  By changing the control IC to a 74AC14, the same circuit can operate from 3v and 1.5v batteries . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

Real-Time Audio Spectrum Analyser on PIC18F4550 -  This project implements a real-time audio spectrum analyser using a PIC 18F4550 8-bit microcontroller from Microchip.  The spectrum frequency analysis is performed by a highly optimised 16-bit Fast Fourier Transformation (FFT) routine coded entirely__ 

Real-Time Audio Spectrum Analyser. Part 2. Firmware -  Schematic and construction The firmware is completely written in C and can be downloaded from the downloads section below.  The firmware is split into 4 parts: ADC Sampling The ADC sampling routine samples the voltage level on RA0 every 50__ 

Real-time Laser Range Finding Vision System -  The author's articles of months past focus on the application of 32-bit high-powered processors to amateur robotics and more recently applying CPLD technologies to the same.  Continuing on this high-tech trend, this article will cover the concepts and implementation of a Real-time Laser Range Finder based on CPLD Processing of NTSC Video for use in small mobile robotics applications. __ Designed by  Kenneth Maxon

Real-world power tests Model FPGAs thermal characteristics -  12-Apr-07 EDN Design Ideas:  Applying forward bias to parasitic diodes smokes out those pesky thermal parameters __ Circuit Design by Jeremy Willden, Ad Hoc Electronics, Pleasant Grove, UT

Reconstruct the Input Current In a Grounded-Impedance Current Sensor -  09/05/12  EDN Design Ideas:  Measure the current into an impedance by reconstruction with current mirrors.   __ Circuit Design by Abhirup Lahiri, New Delhi, India

Recycle precision potentiometers as useful voltage sources -  7-Jun-07 EDN Design Ideas:  A handful of precision op amps and comparators recycles precision potentiometers as handy "volt boxes.   " __ Circuit Design by Mark Thoren, Linear Technology, Milpitas, CA

Reflex Tester -  Testing human reaction speed is not only a fun way of spending time, but also allows the drawing of conclusions, for example on the skills of a momentary driver.  How does the reflex tester works? When the contact closes the power button, the astabil multivibrator that is built with IC 1 produces pulses that are applied to IC 3 __ Designed by Popescu Marian

Refrigerator Door Alarm -  Do your kids leave the door to the refrigerator open? Or does your celery reach out to keep the door from closing properly when you turn your back? Here's a simple circuit that beeps whenever the door is open for an extended period of time (which will also put a little pressure on the fridge loiterers in the house)  __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Regulator Monitors its input voltage -  09/12/97 EDN Design Ideas:  Two- and three-cell portable systems, such as medical sensors, often monitor their battery input to obtain an early warning of a loss of battery voltage.  Typically, this warning is a digital signal that a comparator generates and then sends to the microcontroller.  The circuit in Figure 1 presets one side of a dual linear regulator to generate 2.84V at 100 mA.  The other side operates open loop, as a comparator, to generate the low-battery warning.  both side as are capable of delivering 100- mA output current.  Resistors R1 and R2 determine the low-battery threshold, according to __ Circuit Design by Larry Suppan and Luong Huynh, Maxim Integrated Products, Sunnyvale, CA

Relative Field Strength Meter for a DMM -  Many passive field strength meters have appeared in the past, typically using a 50mA analog meter movement if reasonable sensitivity was to be obtained.  This circuit is similar but has the advantage that it works with the high-impedance load of a digital multimeter, typically switched to the 200mV range.  The sensitivity is adequate for low power equipment like CB radios, cordless phones and model R/C sets (cars, model airplanes, etc) __ Learning Electronics

Relative Humidity Sensor -  This sensor is a capacitive element that changes value with humidity.  By charging the sensor with a fixed current for a fixed time interval, a voltage is developed that is directly proportional to the sensor capacitance value.  __ Linear Technology/Analog Devices App Note, Mar 16th 2010

Relative Humidity Sensor Digitizer-Charge Pump Based -  Hygrometer Digitizer Has 0.3% Accuracy, Although Sensor Must Float Off-Ground.  Humidity Sensor Determines Charge Delivered to A1 integrator During Each Charge Pump Cycle.  Resultant A1 Output Ramp is Reset by Level Triggered C1 via Q1.  Output Frequency, Taken at C1, Varies with Humidity__ Linear Technology/Analog Devices App Note, ,Mar 16th 2011

Relative Humidity Sensor Digitizer-Hetrodyne Based -  Hetrodyne Based Humidity Transducer Digitizer Has Grounded Sensor, 2% Accuracy.  Capacitively Sensed Hygrometer Beats Humidity Dependent Oscillator (C1) Against Stable Oscillator O1.  Difference Frequency is Demodulated by Q1, Converted to Pulse Form at C2.  Counters Scale Output for 0kHz to 1kHz = 0% to 100% Relative Humidity__ Linear Technology/Analog Devices App Note, Mar 16th 2010

Relative Humidity Sensor Digitizer-Time Domain Bridge Based -  Humidity Transducer Digitizer Has Grounded Sensor, 1% Accuracy; Trim Scheme Allows Low Tolerance Sensors.  Clocked Q1A-Q1B Configurations Produce Ramp Outputs.  Q1A Ramp Slope Varies with Humidity Sensor Value, Q1B Ramp Represents Sensors Offset (0% RH does not equal 0pF).  C1, C2 Digitize Ramp Times.  Gate Extracts Time Difference, Presents 0 to 100 Counts Out for 0% to 100% Relative Humidity __ Linear Technology/Analog Devices App Note, Mar 16th 2011

Relative-Humidity Transmitter uses Single Logic IC -  11/08/01  EDN Design Ideas:  The low-cost percentage-relative-humidity radio transmitter in Figure 1 operates in a cold-storage warehouse for vegetable storage at temperatures of 1 to 5C.  it is generally difficult to collect such data from a low-temperature ar __ Circuit Design by Shyam Tiwari, Sensors Technology Ltd, Gwalior, India

Remarkable R-Beeper -  As configured, this continuity beeper emits a tone when the input leads are shorted together.  if a resistance is placed between the leads, the tone's pitch is lowered.  A 1 ohm difference is audible, and the tone stops entirely at around 150 ohms.  There is no tone for semiconductor junctions, even germanium or Schottky.  Short-circuit current is under 1 mA, and open-circuit voltage is about 1.5 volts, so damage to external devices is quite unlikely.   __ Designed by Tom Bruhns

Remote Charging uses Three Wire Sensing -  05/25/95 EDN Design Ideas:  Remote voltage sensing usually uses a four wire sensing System, this System works with three Wires.    __ Circuit Design by D Hayden, Tempo Research, Vista, CA

Remote Control Transmitter -  Although ready-made remote controls are easy to get, with this project we show how to build on at home.  Features are impressive, with 6 radio channels and long battery life.  Complete with PCB layout.   __ Designed by Projects & Ideas from Nutchip.com

Remote control turns battery on & off -  09/12/97 EDN Design Ideas:  The circuit in Figure 1 acts as a latching solid-state relay.  A short application of a magnetic field in the vicinity of S1 toggles the relay on and off.  The relay switches power from a 3V battery at load currents as high as 10 mA.  This remote switch is ideal for battery-powered applications.  in the off state, the circuit draws no current; in the on state, the circuit draws only 100 A.  All the parts are inexpensive and readily available.    __ Circuit Design by Allen Harstine,Integrated Measurement Systems Inc, Beaverton, OR

Remote control using telephone -  Here is a tele-remote circuit which enables switching "on" and "off" of appliances through Telephone lines.  The circuit described here can be used to switch up to nine appliances (corresponding to the digits1 through 9 of DTMF the Telephone key-pad).  The Telephone can be used to switch__ 

Remote CPU/ASIC/FPGA Temperature Sensor -  The LTC2997 is a high-accuracy analog output temperature sensor.  it converts the temperature of an external sensor or its own temperature to an analog voltage output.  A built-in algorithm eliminates errors due to series resistance between the LTC2997 and the sensor diode.  __ Linear Technology/Analog Devices App Note, Jul 7th 2011

Remote digital thermometer sends data over AC power line -  This circuit is a simple oscillator.  it's frequency is in the range 35 kHz - 60 kHz and it' s adjustable.   __ Designed by Ali Alipour.r - alipoor90 @ gmail.com

Remote Digital Thermometer sends data over AC Power line -  This circuit is intended for precision centigrade temperature measurement, with a transmitter section converting to frequency the sensor's output voltage, which is proportional to the measured temperature.  The output frequency bursts are conveyed into the mains supply cables.  The receiver section counts the bursts coming from mains supply and shows the counting on three 7-segment LED displays.  The least significant digit displays tenths of degree and then a 00.0 to 99.9 C range is obtained.  Transmitter-receiver distance can reach hundred meters, provided both units are connected to the mains supply within the control of the same light-meter.   __ Contact Flavio Dellepiane, fladello @ tin.it

Remote Half Bridge Digitizer Platinum RTD with Noise Suppression on Reference -  The LTC2414/LTC2418 are 8-/16-channel (4-/8-differential) micropower 24-bit ΔΣ analog-to-digital converters.  They operate from 2.7V to 5.5V and include an integrated oscillator, 2ppm iNL and 0.2ppm RMS noise.  They use delta-sigma technology and provide single cycle settling time for multiplexed applications.  Through a single __ Linear Technology/Analog Devices App Note, Mar 30th 2010

Remote humidity sensor needs no battery -  04/04/02 EDN Design Ideas:  Using ac-line power sources and batteries for remote humidity sensors is undesirable because these sources can be troublesome if you mount them in inaccessible points, such as smokestacks, cold-storage chambers, or darkrooms, where maintenance is difficult and inconvenient.  Figure 1 shows a simple way to remove the power source from the humidity-sensor circuit __ Circuit Design by Shyam Tiwari, Sensors Technology Private Ltd, Gwalior, India

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


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