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Electronic Circuits

Also, use the search box at the bottom of the home page.

Audio Circuits

Audio Amplifier Circuits and 1uV/root-Hz noise source
High Fidelity Audio Amplifier (about 7.5 watts into 6 ohms)
Directional Microphone
AGC Dynamic Microphone
Very Low Noise Amplifier
Induction Receiver
White and Pink (1/F) Noise Source
Noisemaking Circuits (police siren and doorbell chime)

Telephone Circuits


Computer Data Logging Circuits


Meter Circuits

Meter/Data Acquisition Amplifier
CD4069 LED Bar Graph - smooth transitions between 5 LEDs.
Measuring RF Voltages with a VOM


Microprocessor Circuits

PicAXE Ionization Chamber
Keyboard Wedgie
Altoids Tin LowFER Transmitter



Water Hammer Seismometer - use a tube of water to detect earthquakes
Live Data from the Lab
Games - the first game show timer was modified for better performance
Noisemaking Circuits (police siren and chime)
Temperature Controlled Ovens
Christmas Tree (or other plant) Moisture Monitor

Kitchen Circuits
Galloping Neons (array of blinking neon lamps)
Deer Repellent (seismic sensor)

Shower Stopper
Gag Circuits: magic lamp, dripper, remote control jammer

Ghost Detector - a changing electric field detector
Readers' Projects

Clock Chips from the past



Two-Transistor Atomic Frequency Standard
CD4069 Atomic Frequency Standard (I know, a little overstated.)
Audio Oscillators
Flip-Flop Flashers, Buzzers, Etc.
Flasher Ideas (LED flasher, silent metronome, low battery indicator, high voltage generator)
Tiny Crystal Oscillator   High-stability gate oscillator uses two, 5-pin SOT packaged devices.
VHF Overtone Crystal Oscillator  A circuit for VHF overtone crystals.

Low Distortion Crystal Oscillator
Ray's Wide Range VCO (Reprint courtesy of RF Design Magazine).


Power Control

Anti-Flicker Circuit for LED Christmas Lights
Magic Lamp (Old idea, new twist.)

Line Powered Flashers (Great for Christmas lights, etc.)
Stepper Motor Experiment
Dome Lamp Dimmer
Emergency Backup Lamp
Battery Saver (Worth the effort!)
Windshield Wiper Delay

Lantern Flasher/Dimmer
Dimmer/ Motor Speed Control


Power Supplies /Regulators

Split Supply for Op-Amps and synthetic ground generators
Mercury Battery Replacement (also see Craig's versions)
Homemade "B" Battery
High Voltage Circuits
Battery Chargers
Power Supplies and Regulators (new low power discrete switcher)
Cockcroft-Walton Diode Voltage Multipliers

Battery Discharge Monitor
Finesse Regulator Noise


Radiation Circuits

PicAXE Ionization Chamber
Frankenstein's Dosimeter
The X-ray Defender detects backscatter X-ray machines.
Radon Detector for the Student includes detailed instructions for a simple ionization chamber.
Radon Accessory for Radiation Detectors
Geiger Tube Simulator
World' Smallest Geiger Counter
Top of Ion Chambers page
My First Experimental Circuit
Large Cookie Tin Ion Chamber
Ion Chamber Bias Supply (Battery Topper)
Experimenter's Chamber
Improved Transistor Circuit
Modify a CDV-715 for High Sensitivity
Polonium Pen
Neon Lamp as Resistor
Nuclear War Detector

Super-Sensitive Ionization Chamber
Components for Ion Chambers

Neon Bulb Quench Experiment
Geiger Counters


"First Web Page of Radio"

Crystal Radio and Amplifiers and simple AM transistor radio circuits. (Also see diode detector info.)
Regenerative Receivers
Reflex Receivers
The Amazing All-Band Receiver
Cellular Phone Helper
Aircraft Receiver
WWV Converter for the Car
Rush Converter for the Car
FM Band Preamplifier
Antennas   Includes longwire, loading coil, active ferrite antenna, active short antenna, vertical.
FM Band Monaural Transmitter
Micropower AM band radio station and wireless "phono oscillator"
The Unfair Radio Transmitter
Superregenerative Air Band Radio
FM Radio Microphone with Internal Loop Antenna

The Bug Duster for cleaning out those pesky bugging devices.
LF Block Converter


RF Circuits

The F.E.D. detects digital RF signals
One Watt Class-C Amplifier
Two Diode Odd-Order Multiplier
Odd-order Diode Multiplier (Reprint courtesy of RF Design Magazine)

Diode Frequency Doublers
Unusual Frequency Dividers
HCMOS Gates Make Frequency Multipliers
Frequency Tripler Using the CA3028
Simple Divide-by-N Using '161s
Ray's RF ID Transponder (Reprint courtesy of RF Design Magazine)
GPS Frequency Standard

Readers' Projects



Test Equipment

Large Inductor Quick Tester (battery topper)
Picoampere Leakage Tester

Transistor Spot Checker
V/I Curve Tracer
Synthetic Isolators - great for checking the SWR of antennas, amplifiers, mixers, etc.
Isolator/Circulator (Reprint courtesy of RF Design Magazine) uses ICs. Here's an external link to a reader's version: http://www.neazoi.com/circulator/index.htm

Curious C-Beeper (Also see the op-amp version down the page.)
Remarkable R-Beeper - by Tom Bruhns
Cheap Computer Data Input and Meter DAQ Amplifier


Video and Optical


VLF/LF Block Converter for the Shortwave Receiver
Altoids Tin LowFER Transmitter
VLF Whistler Reception
SID Seizer
Oddball SID Receiver Experiment (60 kHz)
Schumann Resonance Detector (Area 50)


Weather Related Circuits

New Lightning Detector - especially built for the beginner plus a magnetic antenna version
Sferics (spherics) Detector - a fancy lightning detector
Lightning Detectors (also see the readers' versions) and for testing a Lightning Simulator
Rain Detector
Cloud Charge Monitor
Another One-Transistor Cloud Charge Monitor

Water Hammer Seismometer (weather?)

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.

Special thanks to RF Design for granting permission to reprint a few articles by Ray Page and myself.

Random Pages for the Search Engines to find: Repair Ideas

Note: Many of these projects are appearing on other web sites and books without mention of the source. All of the projects on this website are original work unless I clearly say otherwise. That means I or the clearly identified author sat down with a blank tablet and started from scratch. These projects aren't rocket science but I don't want readers concluding that this site copies from other sources without attribution.

Safety Information and Disclaimer

The information presented on the techlib.com web site is for reference or entertainment purposes only. No claims are made regarding the accuracy or reliability of the information. Circuit ideas and projects are intended for technically trained individuals who are qualified to evaluate their appropriateness and safety. Home-made devices are not reliable and unforeseen consequences may result from their use. Check all local, state, and federal laws regarding the use of home-made devices that transmit or connect to any utility. Do not construct and use illegal wiretaps or recording devices. Do not build bomb triggers or other illegal weapon components. Many circuits use or generate dangerous voltages even when powered by low voltage batteries. Many of the materials used to assemble electronic devices contain dangerous chemicals such as lead. Although the information provided is believed to be original or in the public domain, the devices and suggested uses may violate existing patents. Although practical jokes and gags can be entertaining, the involved parties may feel that they were damaged or that their civil rights were violated. Law enforcement organizations may consider electronic and electro-mechanical components to be paraphernalia for building illegal devices. Electromagnetic energy may cause disease.

That should cover it!

Remember, in our brave new world, consumer products are covered with warning stickers after hordes of lawyers and safety engineers review the design! Your home-made gizmo has no such protection and you are completely responsible for any damage it might cause or be alleged to have caused. Have a nice day ; )

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