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Tools and measuring electronic circuits

Build your own electronics instrument for testing components and circuits, or temperature measuring device...

1KHz Sinewave Generator

This circuit generates a good 1KHz sinewave using the inverted Wien bridge configuration. Features a variable output, low distortion and low output impedance... [read]

3 Channel Spectrum Analyzer

This 3 channel 15 LED spectrum analyzer is the perfect addition to any audio amp project.... [read]

4 - Channel Digital Logic Analyzer

This is one of the simplest circuit for a PC parallel port based DLA. The Circuit is mainly used to protect the port which is fabricated on the motherboard... [read]

555 stepper pulse generator

The 555 Stepper Pulse Generator kit will help you with the pulse required to drive your favorite DC Servo Motor application.... [read]

Adjustable High-Low Frequency Sine wave generator

This circuit uses the versatile MAX038 function generator. Although in this circuit some of the advanced characteristics of this IC are disabled, you can generate... [read]

Air Flow Detector

This simple circuit uses an incandescent lamp to detect airflow.... [read]

Beat Balance Metal Detector

A Beat Balance Metal Detector made from discrete components. Interesting design.... [read]

Beeper to find short circuits

This circuit uses two 741s or equivalent op amp to form a beeper that is used to detect short circuits.... [read]

Bench Amplifier

This circuit is basically an audio amplifier, but it is placed in this category because it may be used as signal tracer. It is built around simple National... [read]

Capacitance Meter

you will have an instrument capable of measuring all but the largest capacitors used in radio circuits.... [read]

Cellular Phone calling Detector

This circuit was designed to detect when a call is incoming in a cellular phone (even when the calling tone of the device is switched-off) by means of a flashing... [read]

Coil Coupled Operation Metal Detector

One more kind of metal detectors.... [read]

Connection Tester

Simple connection tester built with famous 741 op-amp circuit. Very useful for every electronics workshop.... [read]

Continuity Tester

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... [read]

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... [read]

Decibel Meter

The circuit below responds to sound pressure levels from about 60 to 70 dB. The sound is picked up by an 8 ohm speaker, amplified by a transistor stage and... [read]

Digital Radar Speedometer

It allows us to evaluate the speed of any object moving, especially cars and other vehicles... [read]

Digital 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... [read]

Digital Step-Km Counter

This circuit measures the distance covered during a walk.... [read]

Digital Voltmeter

The ICL7107 is a 3 1/2 digit LED A/D convertor. It contains an internal voltage reference, high isolation analog switches, sequential control logic, and the... [read]

Electromagnetic Field Detector

This circuit is sensitive to low frequency electromagnetic radiation and will detect for example hidden wiring or the field that encompasses a transformer.... [read]

Electromagnetic field detector

This lovely circuit is a real gem! Easy to assemble and more sensitive than many commercial devices available.... [read]

Electronic Stethoscope

Stethoscopes are not only useful for doctors, but home mechanics, exterminators, spying and any number of other uses. Standard stethoscopes provide no amplification... [read]

Field-strength meter

This is a very straightforward circuit. The first stage acts as a crystal receiver.... [read]

Function Generator

Built around a single 8038 waveform generator IC, this circuit produces sine, square or triangle waves from 20Hz to 200kHz in four switched ranges.... [read]

IR Remote Control Modulation Detector

A circuit to extract and measure the modulated carrier of an Infra Red remote control... [read]

IR Remote Control Tester

I have used a photodiode, SFH2030 as an infra red sensor. A MOSFET opamp, CA3140 is used in the differential mode to amplify the pulses of current from the... [read]

Lightning Detector

Here is a VLF receiver tuned to 300 kHz designed to detect the crackle of approaching lightning. A bright lamp flashes in sychrony with the lightning bolts... [read]

Linear Resistance Meter

Most analogue multimeters are capable of measuring resistance over quite a wide range of values, but are rather inconvenient in use due to the reverse reading... [read]

Logic Probe

This circuit is a Logic Probe. It indicates the logic state of the node of any TTL logic circuit. To do that, we have to supply the probe with the same power... [read]

Low Frequency Sinewave Generators

The two circuits below illustrate generating low frequency sinewaves by shifting the phase of the signal through an RC network so that oscillation occurs where... [read]

Low-distortion Audio-range Oscillator

Producing low-distortion sine waves, this oscillator operates over the range 16 to 22000 Hz.... [read]

Metal Detector

A single chip metal detecor with a range of a few inches. This is useful for decting nails or screws in walls and floors, or for locating buried mains cable.... [read]


This device should measure electromagnetic energy, but only the one which human body absorbs.... [read]


This is a variation on the astable multivibrator. Circuit was recently developed to test for N-mosfets(the power kind e.g irf830)... [read]

Oscilloscope testing module

I call this the huntron circuit because a company by that name made a similar device. It is useful for trouble-shooting.... [read]

Picoammeter circuit with 4 ranges

This circuit uses a CA3420 BiMOS op amp to form a picoammeter with 4 ranges. The exceptionally low input current (typically 0.2pA) makes the CA3420 highly... [read]

Pulse-Generator and Signal-Tracer

This simple circuit generates narrow pulses at about 700-800Hz frequency. The pulses, containing harmonics up to the MHz region, can be injected into audio... [read]

Salt Taster

This circuit was designed to detect the approximate percentage of salt contained in a liquid. After careful setting it can be useful to persons needing a quick,... [read]

Self-powered Fast Battery-Tester

This circuit runs a fast battery test without the need of power supply or expensive moving-coil voltmeters. It has two ranges: when SW1 is set as shown in... [read]

Self-powered Sine to Square wave Converter

This circuit is intended to provide good square waves converting a sine wave picked-up from an existing generator. Its major feature consists in the fact that... [read]

Signal Tracer and Injector

A simple test circuit to fault find audio and radio equipment. Can be used to inject a square wave signal, rich in harmonics, or used with headphones as an... [read]

Simple but reliable car battery tester

This circuit uses the popular and easy to find LM3914 IC. This IC is very simple to drive, needs no voltage regulators (it has a built in voltage regulator)... [read]

Simple Lie Detector

Here's a simple lie detector that can be built in a few minutes, but can be incredibly useful when you want to know if someone is really telling you the truth.... [read]

Simple Servo Tester

Tester for servo devices.... [read]

Sine Wave Generator

This oscillator produces sinusoidal wave. It's made around LF351 or TL071CN or TL081CN. A classic Wien Bridge oscillator... [read]

Speech Recorder

The 2 pushbuttons = S1: Start/Pause. S2: Stop/Reset. If you want to play your message, put S3 at Play. Then push S1 to start playing and again to pause. If... [read]

Static Electricity - Negative Ion Detector

This device can detect negative ions in air. It has very few components: one FET, two resistors and battery. You also need multimeter to complete device. This... [read]

Transistor Tester

This simple circuit has helped me out on many occasions. It is able to check transistors, in the circuit, down to 40 ohms across the collector-base or base-emitter... [read]

Triangle-Squarewave Generator

Here is a simple triangle/squarewave generator using a common 1458 dual op-amp that can be used from very low frequencies to about 10 Khz.... [read]

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... [read]

XTal Tester

Tool for XTall testing. This one is MUST HAVE when you work with radio devices, RC toys...... [read]