Free Circuits, Burglar Alarm Schematics, Alarm Power Supply with Battery Back-up, Security Circuits, Fridge Alarms, Temperature Alarms, Battery Powered Alarms, Car Alarm Schematics, Motorcycle Alarm, Hijack Alarm, Electronic Keypads, Electronic and Radio schematics, Power Supply Schematics, Uninterruptible Power Supply, Bench Power Supply, Over-voltage Protection, Current Limiting Power Supply, CMOS Logic, Audio Amplifiers, AM and FM Transmitters and Receivers, RF amplifiers, Infrared Extenders, Infrared Testers, Timer Circuits, 24-Hour Timer, Electronic Student Projects, Electronic School Projects, Design, Theory, Circuit Analysis

Welcome

Below is a guide to the free-to-use circuits from
Circuit Exchange International.
Click on a category.



Alarms & Security Circuits

A wide range of small and not-so-small alarm circuits suitable for domestic and business premises, motorcycles, cars and much more. Some make ideal student projects.
 

Audio Circuits

Amplifiers, Preamplifiers, Tone Controls, Filter, Mixer, Doorphone Intercom, Audio Level Meters and more.
 

Control & Interfacing

Lots of Infra-Red Remote Control Extenders. Change the Channels on Your Satellite Receiver etc. from Your Bedroom. Launch a Model Rocket and more.
 

Music & Special Effects

Build an Electronic Canary, A Metronome, A Sound Effects Generator, An Electronic Siren.
 

Power Supplies & Circuits

Regulated and Unregulated Power Supplies. Transformerless Power Supply. Burglar Alarm Power Supply with Automatic Battery Back-up. Variable Voltage Power Supplies. Bench Power Supply with Output Current Limit. Logic PSU with Over-voltage Protection and more.
 

Radio Circuits

A Range of AM and FM Transmitters and Receivers, RF Preamplifiers, Antennas, Bug Detector, Field Strength Meter, Crystal Controlled Oscillator and more.
 

Switching

Cold Activated Switch, Dark Activated Switch, Light Detector, Motor Control Circuit, Sound Operated Switch, Water Activated Relay, Triac Light Controller and more.
 

Test Gear

Infrared Remote Control Tester, Logic Probe, Sine Wave Generator, Square Wave Oscillator, Crystal Testers, Connection Tester, Function Generator, Metal Detectors and more.
 

Timing Circuits

Basic 555 Monostable, 5 to 30-Minute Timer, A Periodic Timer, An Asymmetric Timer, A 24-Hour Timer, A Pulse Generator.
 

Miscellaneous

A Conjuring Trick. A Magic Wand. A Magnetic Gun. An Insect Repellent. An Ultrasonic Dog Whistle. A Metal Detector. A Doorbell for the Deaf. A Monitor Splitter, LED Torches, a Telephone In Use Indicator and more.
 

Complete Circuit Index

All of the free-to-use circuits currently available from
Circuit Exchange International. New additions are made regularly.
Remember to check the Update page.
 


The Circuit Exchange International Home Page is available in several languages. Along with the schematics, the site covers other aspects of electronics - both theoretical and practical; and there's a simulation section featuring the "TINA" and "Circuit Maker" programs.


Circuit Exchange

Visit the Home Page of Circuit Exchange International
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