Free Electronic Circuits
A collection of electronic circuits and projects to build.

Misc Circuits

- UltraSonic Radar Circuit
- Heating System Thermostat Circuit
- Receiver Battery Low Voltage Alarm Circuit
- 24 Hour Timer Circuit
- XTal Tester Circuit
- On-Off Temperature Control Circuit
- Air Flow Detector Circuit
- Digital Step-Km Counter Circuit
- 6V to 12V Converter Circuit
- AC Current Monitor Circuit
- Beeper to find short circuits Circuit
- Low-distortion Audio-range Oscillator Circuit
- Salt Taster Circuit
- Capacitive Sensor Circuit
- Dual Regulated Power Supply Circuit
- 1KHz Sinewave Generator Circuit
- 12 Volt 30 Amp PSU Circuit
- Seismic detector Circuit
- Telephone In Use Indicator Circuit
- Control Electrical Appliances Using PC Circuit
- 5 to 30 Minute Timer Circuit
- Metal Detector Circuit
- S-video to RCA Circuit
- Photo Timer Circuit Circuit
- Variable DC Power Supply Circuit
- NE555 Basic Monostable Circuit
- Magnetic Gun Circuit
- Function Generator Circuit
- Instrument panel lamp dimmer control Circuit
- Multi Wire Cable Tester Circuit
- Precision Audio Millivoltmeter Circuit
- Amplifier Timer Circuit
- Dome Lamp Dimmer Circuit
- Phoenix Programmer Circuit
- 3 Line Mixer Circuit
- Whistle Responder Circuit
- EPROM adapter for ATMEL 89 Series Flash Microcontroller Programmer Ver 2.0 Circuit
- Linear Resistance Meter Circuit
- Speaker Box Audio Amp Circuit
- High Current Power Supply Circuit
- Precision Receiver Battery Low Voltage Alarm Circuit
- Time Delay Relay Circuit
- FM radio (may be used with PC) Circuit
- Discharger for Receiver Battery Packs Circuit
- Intercommunication (Intercom) Circuit
- Nicad Battery Charger Circuit
- Electronic Canary Circuit
- DC Motor Reversing Circuit Circuit
- Pulse Charger for reviving tired Lead Acid batteries Circuit
- Economy radar detector Circuit
- Ni -Cd Batteries Charger Circuit
- Bedside Lamp Timer Circuit
- Solid State Tesla Coil/High Voltage Generator Circuit
- A small FM transmitter (SMD) Circuit
- Field-strength meter Circuit
- Multi Rocket Launcher Circuit
- PlayPICŽ Circuit
- Voltage Monitor Circuit
- Stereo Preamplifier with Bass-boost Circuit
- The Link "P" - Privacy Link! (Telephone Intercom) Circuit
- Bass-treble tone control circuit Circuit
- Simple Digital Volume Control Circuit
- Portable Mixer Circuit
- Brightness Control for small Lamps Circuit
- Cut Phone Line Detector Circuit
- Motorola Hi-Fi power amplifier Circuit
- Asymmetric Timer Circuit
- Telephone Hold Button Circuit
- Tan Timer Circuit
- Automotive 12V to +-20V converter (for audio amplifier) Circuit
- MILLIGAUSS METER. Circuit
- Cellular Phone calling Detector Circuit
- Gold wafer cards Circuit
- Basic UPS Power Supply Circuit
- Phone Busy Indicator Circuit
- Mains Remote-Alert Circuit
- Precision Metronome and Pitch generator Circuit
- Downed Model Locator Circuit
- The Link A2B+1 (the Link Telephone Intercom - DTMF version) Circuit
- LM317 VARIABLE POWER SUPPLY Circuit
- High And Low Voltage Cut Off With Time Delay Circuit
- Two-wire Lamp Flasher Circuit
- Infra-red Level Detector Circuit
- Digital Stopwatch 0-99sec Circuit
- Regulated 12 Volt Supply Circuit
- Electromagnetic Field Probe with Meter Output Circuit
- Voltage follower with 1G ohm input resistance Circuit
- Car Battery Charger Circuit
- Led display digital Voltmeter Circuit
- Self-powered Sine to Square wave Converter Circuit
- Electronic Locker Circuit
- Auto Heat Limiter for Soldering Iron Circuit
- FET Audio Mixer Circuit
- 20dB VHF Amplifier Circuit
- Simple DC motor PWN speed control Circuit
- Electromagnetic field detector Circuit
- Reverse Bias Oscillator Circuit
- 0-50V 2A Bench power supply Circuit
- Infrared Detector Circuit
- Low Voltage Alarm Circuit
- Fancontrol Circuit
- 24 Second Shot Clock Circuit
- Park Aid Circuit
- Headlights Timer Circuit
- Mini efficient coil launcher from disposable camera flash Circuit
- Automatic Headlight Brightness Switch Circuit
- Phone "Hold" With Music Circuit
- Nostalgic Crystal Radio Circuit
- Telephone Record Control Circuit
- LASER Transmitter/Receiver Circuit
- Infra Red Switch Circuit
- Geomagnetic field detector Circuit
- Touch Switch Circuit
- "SimpleMouse" Smartcardprogrammer Circuit
- Touch Switch Circuit
- Soft Musical Telephone Ringer Circuit
- Transistor Tester Circuit
- Battery-powered Night Lamp Circuit
- Unipolar Stepper Motor Controller Circuit
- Crystal Tester Circuit
- Simple but reliable car battery tester Circuit
- Small Radio Transmitter Circuit
- Field-strength meter Circuit
- Cuckoo sound Generator Circuit
- Deluxe Charge Rate Limiter for Small Capacity NiCad Batteries Circuit
- TTL Power Supply with Crowbar protection Circuit
- Sleeping-Aid Circuit
- 500W low cost 12V to 220V inverter Circuit
- Mosfet TESTER Circuit
- The flashing Heart Circuit
- Downed Model Locator II Circuit
- Jogging Timer Circuit
- Lightning Detector Circuit
- Keys Finder Circuit
- Solid State Power Controller Circuit
- Mini Metronome Circuit
- The Millipede Circuit
- Ponyprog Circuit for AVR & PIC16F84 Circuit
- Picoammeter circuit with 4 ranges Circuit
- Linear FM 50Watt with BLY90 Circuit
- Logic Probe Circuit
- PIC diode tester Circuit
- Muscular Bio-Stimulator Circuit
- 8 Line Intercommunication using 89c51 Circuit
- PWM Motor/Light Controller Circuit
- Triple Stroboscope Circuit
- Transformerless Power Supply Circuit
- 2N3055 Power Amplifier Circuit
- Temperature-controlled Fan Circuit
- 12VDC Fluorescent Lamp Driver Circuit
- 73 MHz Hallogene Lamp Radio-Controlled Circuit
- Fuse Monitor / Alarm Circuit
- Fixed Voltage Power Supply Circuit
- Digital Voltmeter Circuit
- Sound Operated Switch Circuit
- Continuity Tester Circuit
- Electronic Stethoscope Circuit
- iButton electronic lock Circuit
- Batteries charger & PSU - ideal for digital cameras Circuit
- Automatic Loudness Control Circuit
- Repeating Interval Timer Circuit
- Digital Remote Thermometer Circuit
- Time Delay Relay II Circuit
- Rain Detector Circuit
- Inverter Circuit
- The Link 4+0 Internal Intercom Circuit
- Flyback Transformer Driver Circuit
- Live-line Detector Circuit
- Plants Watering Watcher Circuit
- Linear FM 30Watt Circuit
- ATMEL 89 Series Flash Microcontroller Circuit
- ZN414 Portable AM Receiver Circuit
- Digital Volume Control Circuit
- Digital Stopwatch 0-60sec Circuit
- Simple Lie Detector Circuit
- Timed Beeper Circuit
- Ponyprog Circuit for ATMEL'S AVR Circuit
- Telephone line monitor Circuit
- Simple optical switch Circuit
- Producing your own Decrypt Viewing Card Mk2 Circuit
- Stepper Motor Controller Circuit
- Speed-limit Alert Circuit
- Electronic Stethoscope Circuit
- Latching Continuity Tester Circuit
- 5,000W ultra-light, high-power amplifier, without switching-mode power supply Circuit
- Sound Effects Generator 2 Circuit
- Digital Radar Speedometer Circuit
- 3 Channel Spectrum Analyzer Circuit
- Triangle / Squarewave Generator Circuit
- Plant Moisture Meter Circuit
- Funcard Programmer by Diesel Circuit
- Electronics Attenuator Circuit
- Pulse-Generator & Signal-Tracer Circuit
- Self-powered Fast Battery-Tester Circuit
- Voltage Inverter II Circuit
- The Link Telephone Intercom Every Home Should Have One! Circuit
- Room Noise Detector Circuit
- Voice activated switch Circuit
- Oscilloscope testing module (huntron circuit) Circuit
- Capacitance Meter Circuit
- 12 to 120 Volt Inverter Circuit
- Pulse Width Modulation DC Motor Control Circuit
- Medium range transmitter Circuit
- DC Motor Control Circuit Circuit
- Touch Switch II Circuit
- Remote Doorbell Warning Switch Circuit
- 10 Amp 13.8 Volt Power Supply Circuit
- Dual Polarity Power Supply Circuit
- Telephone line monitor Circuit
- Nocturnal Animals Whisker Circuit
- Periodic Timer Circuit
- The Original 2 Phone Link Design Circuit
- Ultra-simple Voltage Probe Circuit
- Economical Pump Controller Circuit
- Adjustable High/Low Frequency Sine wave generator Circuit