Alarms and security related schematics

• 4 Photo-Detector circuit with delayed release and bipolar output
  
• 5 Zone Alarm Circuit
  
• 5 Zone alarm circuit
  
• 5 Zone Alarm System
  
• Alarm control keypad
  
• Automatic Intruder Alarm
  
• Automatic Intruder Alarm
  
• Build an iButton electronic lock based around a AT91C2051 microcontroller (includes ASM source code)
  
• CMOS single zone intruder alarm
  
• Cold activated switch (frost alarm)
  
• Combination Lock (PIC16F84)
  
• Constructing your own Light Alarm
  
• Digital combination lock
  
• Digital combination lock using pair of CD4013 CMOS chips
  
• Digital Keypad Combination Lock
  
• Door Alarm circuit diagram
  
• Door knob alarm (PDF)
  
• Doorbell for the Deaf
  
• Easy to build tripwire activated alarm
  
• Electronic door codelock (PIC16F84)
  
• Electronic locker digital combination lock circuit diagram
  
• Emergency Light & Alarm
  
• Emergency Light & Alarm
  
• Enhanced 4 Digit Alarm Keypad
  
• Enhanced 4 Digit Alarm Keypad
  
• Enhanced 5 Digit Alarm Keypad
  
• Enhanced 5 Digit Alarm Keypad
  
• Everything-that-moves alarm works by inducing eddy currents in living beings
  
• Fire alarm circuit diagram based on LDR (light-dependent resistor)
  
• Fridge door Alarm
  
• Frost alarm
  
• Gate alarm
  
• Gate alarm circuit
  
• Home security project
  
• iButton electronic lock (Dallas DS1990A)
  
• MC68HC908-based wireless monitoring system is adaptable for use in domestic and industrial settings
  
• Micro-power over temperature alarm (PDF)
  
• Miniature loop alarm
  
• Miniature Loop Alarm
  
• Modular Burglar Alarm
  
• Modular Burglar Alarm
  
• Motorcycle alarm
  
• Multi-zone burglar alarm
  
• Novel Buzzer
  
• Perimeter monitor
  
• Proximity detector (uses human body capacitance)
  
• Proximity detector for humans / living creatures using eddy current detection
  
• Rain alarm / rain detector
  
• Refrigerator door alarm
  
• Refrigerator Door Alarm
  
• RF Alarm
  
• RF Pad - combination-controlled, fully customizable radio frequency remote control
  
• Single Zone Alarm
  
• Single Zone CMOS Alarm
  
• Smartcard controlled relay circuit based around Nutchip microcontroller
  
• Sun - Up Alarm
  
• Touch activated alarm system
  
• Transistor based single zone intruder alarm
  
• Travel Touch Alarm
  
• Ultrasonic radar alarm
  
• Ultrasonic Radar Alarm Circuit Diagram
  
• Ultrasonic remote control & alarm system
  
• Wailing alarm siren
  
• Water Activated Alarm
  
• Water Activated Alarm
  
• Water level alarm
  
• Water Level Indicator with alarm
  
• Water seepage alarm (PDF)
  
• Waterpump Safety Guard for fish pond / fish tank
  
• Wire loop alarm
  
• Wire Loop Alarm using 4001UBE Quad NOR Gate
  
• Wireless alarm system based around Nutchip microcontroller
  

Audio power amplifier schematics

• 10 Watt Audio Amplifier
  
• 10 watt audio power amplifier using discrete transistors (includes PCB layout)
  
• 100W Guitar Amplifier
  
• 100W RMS Amplifier
  
• 13.5 Watt Power Amplifier using a TL081 opamp and TIP125 / TIP120 power transistors
  
• 150W audio amplifier that's cheap to build using TIP142 / TIP147 Darlington power transistors
  
• 16 Watt amplifier
  
• 20 Watt / Channel Stereo Power Amplifier
  
• 20 Watt Audio Power Amplifier
  
• 20 Watt Class-A Power Amplifier
  
• 22 Watt Audio Amplifier
  
• 22 Watt Stereo Amplifier using TDA1554
  
• 22W Audio Amplifier
  
• 25 Watt MOSFET Audio Amplifier using IRF532 / IRF9532 hexfet transistors for output stage
  
• 25W MOSFET audio amplifier
  
• 2W Audio Amplifier using BD139 and BD140 transistors
  
• 300W Subwoofer Power Amplifier
  
• 300W Subwoofer Power Amplifier
  
• 4 channel power amplifier with bi-amping and bridging options
  
• 4W amplifier
  
• 50 Watt Amplifier
  
• 50W Amplifier
  
• 50W audio amplifier using ICL8063
  
• 50W audio power amplifier
  
• 8 Watt amplifier
  
• 8 watt audio amp
  
• Ampliefied speaker, built for MP3 player but can be used with other headphone only devices (PDF)
  
• Amplified ear for surveillance
  
• Amplifier based on LM4780 including a thermal shutdown feature
  
• Audio Amp Output Power Limiter
  
• Audio amplifier output relay delay
  
• Audio amplifier with squelsh-control
  
• Build a good Audio Buffer Amplifier
  
• Class-A/AB Amplifier delivering 100W into a 4 ohm load
  
• Class-C power amplifier
  
• CMoy pocket headphone amplifier
  
• Compact 50W Integrated Amplifier with Meier Headphone Section
  
• Death of Zen (DoZ) - A New Class-A Power Amp
  
• DPA 220 amplifier schematic
  
• DPA 440 amplifier schematic
  
• DPA 880 amplifier schematic
  
• Easy to build DIY 50W amplifier based on ICL8063
  
• El-Cheapo - A Really Simple Power Amplifier
  
• Five Tube Stereo Amplifier
  
• Hammonator Organ to Guitar Amp Conversion (tube amplifier)
  
• HeadBanger Headphone Amp
  
• Headphone amplifier based on 12AX7 tubes
  
• Headphone monitor amp
  
• Headphone practice amplifier
  
• Hi-Fi Headphone Amplifier
  
• High quality exponential VCA
  
• LM380 2.5 watt audio amplifier circuit
  
• Low impedance microphone amplifier
  
• Low Power Audio Amp Experiments
  
• Low power audio amplifier using BC109C along with BD679 and BD680 Darlington pairs
  
• Mini bench amplifier (LM386)
  
• Miniature audio amplifier
  
• Mini-MosFet Audio Amplifier
  
• More Discrete BJT, Low Power AF Amp Experiments
  
• Potpourri of Transistor Audio Amplifier Circuits
  
• Quadraphonic Amplifier based on pair of LM1877 devices
  
• Ruby is an "enhanced" version of the Little Gem battery-powered amplifier (LM386 based design)
  
• Selection of Integrated Circuit Audio Amplifiers
  
• Simple class-D amplifier based on 555 pulse width modulator
  
• Single Chip 50 Watt / 8 Ohm Power Amplifier
  
• Small bench amplifier ideal for testing audio stages in circuits
  
• Soft-Start Circuit For Power Amps
  
• Spatial Distortion Reduction Headphone Amp
  
• Speech Amplifier Box
  
• Stereo audio amplifier based on TDA2822M
  
• Super linear Headphone amplifier
  
• TDA2030 8 Watt amplifier
  
• Thermo-Fan To Keep Your Amp Cool
  
• Tube amplifier
  
• Two 9v battery-powered amps based on the LM386. Schematic and PCB/perfboard layouts.
  
• Two Transistors Audio Amplifier
  
• Voice Amplifier
  

Audio preamp circuits

• Altec 1564A Preamp Power Supply
  
• Altec 428B Microphone Preamplifier schematic
  
• API 321 mic preamp schematic
  
• Audio preamp
  
• Audio preamplifier
  
• Balanced microphone preamp
  
• Basic low frequency preamplifier circuits
  
• Bat detector microphone pre-amplifiers
  
• ECM Mic preamp
  
• Electret mic amplifier
  
• FET Preamp Cable
  
• Hi Fi preamp
  
• Hi-Fi Preamp with remote-control and other advanced features
  
• High quality audio preamplifier (OPA2134)
  
• Intercom preamp
  
• Low impedance microphone amplifier
  
• Masthead preamp
  
• Microphone preamp for portable transceivers
  
• Microphone pre-amp with high emphasis
  
• Neumann U67 microphone preamp power supply
  
• RCA BA-1A two-stage preamp schematic
  
• RCA BA-21A preamplifier schematic
  
• RCA BA-31A preamplifier schematic
  
• Simple microphone preamplifier
  
• Simple microphone preamplifier
  
• Simple transistor preamp - includes a PCB layout
  
• Sound card microphone preamplifier
  
• Ultra-Simple Guitar Preamp
  
• Vacuum Tube Microphone Preamp
  
• Voltage follower with 1G ohm input resistance based on LM11 opamp
  

Automotive, car and motorcycle schematics

• 12V battery level indicator for car batteries
  
• 12V to 9V car coverter
  
• 20 Segment Expanded Scale Voltmeter including a PCB design
  
• 3 Channel, 12 Volt Color Organ for a car
  
• 3rd brake light
  
• 5301 wideband fuel mixture display
  
• 80188XL Engine Tachometer / Race Computer
  
• Adaptive Windscreen Wiper Control
  
• Authentic Looking Knight Rider Led Project
  
• Automatic Headlight Brightness Switch
  
• Automatic headlight brightness switch
  
• BMW R Series Motorcycle Regulator Schematic
  
• Brakelight Flasher
  
• Breakdown safety beacon
  
• Car acceleration meter
  
• Car Alarm Arming Horn Beep Canceller
  
• Car backup / reversing alarm
  
• Car Battery Charger
  
• Car battery charger
  
• Car battery charger circuit
  
• Car Battery Charger, an SCR Design with a 10 Amp rating
  
• Car battery voltage tester using LM3914
  
• Car burglar alarm circuit
  
• Car Door Keypad Using LIN network
  
• Car Nicad charger
  
• Car OBD II J1850 PWM, J1850 VPW, ISO-9141 cables schematic pinout
  
• Car OBDII diagnostic interface cable schematic pinout
  
• Car power supply unit for digital projects, small car PCs etc
  
• Car Timer with Atmel ATiny45 to automatically turn of accessories to prevent flat battery
  
• Combination lock for car liftgate
  
• Common Ground for Older VPW OBD Circuit
  
• Custom USB tyre pressure monitoring system
  
• Economy radar detector
  
• Electronic car ignition circuit
  
• Engine control unit schematics
  
• FCD (Fuel Cut Defencer)
  
• Flashing / pulsing third brake like for cars
  
• Flashing light / emergency beacon for vehicle
  
• Fuel injector pulse width monitor
  
• Grand Cherokee Off-Highway Lights
  
• Headlight flasher
  
• Headlight guard
  
• Headlight reminder
  
• Headlight timer
  
• Hijack alarm
  
• Interface between GM's 5 Volt 8192 baud ALDL data stream and a PC serial port
  
• Interior light extender
  
• KITT (from Knight Rider) Car scanner using incandescant lamps
  
• Large capacitor charge "controllers" (Car Audio)
  
• Low battery cut-off circuit for a car or truck
  
• Motorctcle turning signal system
  
• Motorcycle battery charger
  
• Motorcycle brake light flasher
  
• Motorcycle low battery voltage warning circuit
  
• Opendiag OBD-II Schematics & PCB Layout Opendiag OBD-II Schematics & PCB Layout
  
• Parking aid senses distance to rear of vehicle
  
• Portable CD Player Adapter For Car
  
• Portable CD Player Adapter For Car
  
• Seatbelt reminder circuit
  
• Simple car battery charger
  
• Simple car battery voltage monitor
  
• Simple Car Preamplifier and Artificial Earth
  
• Simple Vehicle Loop Detector (inductive loop for driveway etc)
  
• Speed alert - wireless portable unit
  
• Synchronized multi-spark module (SMSM) for Electronic Ignition Devices (EID)
  
• Third brake light pulser circuit
  
• Two LED trouble light system
  
• Ultrasonic parking sonar electronic circuit diagram using transistors and 4000 series CMOS
  
• Wide Band Fuel Mixture Display
  
• Wiper Speed Control
  
• Wireless Auto Tachometer
  
• Wireless Auto Tachometer
  

Data acquisition (DAQ) and data logging schematics

• 1-Wire Barometer Project
  
• 4 Bit Digitizer / flash ADC using discrete components
  
• 8 Photo-Detector Circuit Board
  
• A PIC Based Temperature Data Logger
  
• Acceleration Sensor Network
  
• Accelerometer Schematic
  
• Accelerometer with microcontroller and display
  
• ADC logger 6ch Measurent and serial port logger with wireless longrange link
  
• Addressable ADC
  
• ADXL202 break-out board
  
• Analog input section based on AD9220
  
• Atmel Mega32 8ch Analog signal measure logger
  
• Capacitance type liquid level measurement (PDF)
  
• Centronics port D/A converters and low-pass filter
  
• Connect a NTC with a wheatstone bridge to a normal AD-Input
  
• Data Acquisition & Logging System Using AT89c51 and Visual Basic
  
• Data Acquisition System using ATmega8
  
• Home Brew Compass Sensor
  
• Honey Bee counter (PDF)
  
• Low cost gyro / accelerometer combo sensor
  
• Making an LM35 temperature recorder (based on PIC12F675) - logs to EEPROM
  
• Making an LM35 temperature recorder (based on PIC12F675) - serial output
  
• Precision Digital Altimeter
  
• Pressure Sensor-Based Altimeter Circuit
  
• Rain detector
  
• Remote digital thermometer sends data over AC power line
  
• Self made data-logger V2.5 (second edition)
  
• Serial Port A/D-converter
  
• Simple Analog to Digital Converter using ADC0808 that displays output using LEDs
  
• Simple device for connecting serial instrument with RS485 or RS232 to the internet
  
• Simple RS422 Converter for Minilogger
  
• Strain gauge sensor interface
  
• Thermostat node schematic
  
• Transducer Amplifiers
  
• Ultrasonic Range Finder & Imager
  
• Ultrasonic range finder circuit
  
• USB datalogger - simple-to-use, long-term measurement solution
  
• Using a 555 Timer as an A/D converter
  
• Voltage follower with 1G ohm input resistance
  
• Water-level sensor
  
• Wind speed logger
  
• Wind speed logger Mk2
  
• Wireless Liquid Level Sensing for Restaurant Applications
  
• Wireless weater station
  
• XL-DIG 3-axis Accelerometer board - 3-axis digital I2C/SPI accelerometer board
  

Filter schematics

• "A" Weighting Filter For Audio Measurements
  
• 136KHz bridged-T notch filter to reduce strength of the German utility station DCF39 on 138.83 kHz
  
• 29.85 MHZ bandpass filter schematic
  
• 29.85 MHZ notch filter schematic
  
• 3KHz low-pass filter plus audio amp (PDF)
  
• 440 Hertz Peaked Low Pass Audio Filter Experiments
  
• 45 to 90Hz hum filter
  
• 'A' Weighting Filter For Audio Measurements
  
• Active bandpass filter with TDA2320A
  
• Active bandpass filters
  
• Bandpass and IF Filter Circuits
  
• Bandpass filters
  
• Biquad Active Bandpass Filter Schematic
  
• Chebyshev / Butterworth filters
  
• Collection of quartz crystal ladder filter circuit diagrams
  
• CW Filters
  
• CW filters
  
• Digital signal processor (DSP) for radio communications
  
• Discrete Component Audio-Frequency RC Filters
  
• Filter Circuit for the Earthworm Seismic Data Acquisition System
  
• Filters for the RadioJove Receiver
  
• Galaxy Noise Filter
  
• LC filter design
  
• Low pass filter for subwoofer
  
• Low-pass active filter
  
• Matching Low Pass Filter for 136kHz transmitter
  
• Multiple Feedback Bandpass Filter
  
• Multiple Feedback Bandpass Filter
  
• Self-tune filter
  
• Self-tuning CW filter
  
• SSB AF filter
  
• SSB AF filter
  
• Variable notch filter with both high and low pass filters
  

Games and fun stuff (electronic schematics)

• 3-up decision maker
  
• Archery timer
  
• Battery Meter for Pinball Machines
  
• Burger Time Arcade Game circuit diagram (PDF)
  
• Coin tosser
  
• Decision maker
  
• Dig Dug Arcade Game (800k ZIP)
  
• DIY shutterglasses controller
  
• Dreamcast interface
  
• Dreamcast PC serial adapter
  
• Dual LED dice (available in kit form)
  
• E.S.P. Conjuring Trick
  
• Electronic Astrologer (decision maker)
  
• Electronic dice
  
• Electronic Nicad glow plug driver
  
• Electronic roulette wheel circuit diagram
  
• Flashing heart
  
• Frogger Arcade Game circuit diagram (PDF)
  
• Furby reverse-engineered circuit
  
• Fuzebox - open source 8-bit game console based on Atmel ATmega644-20PU
  
• Galaga Arcade Game circuit diagram (PDF)
  
• Game Show Timers
  
• Gyrus Arcade Game circuit diagram (PDF)
  
• Hangman game
  
• How to install LED lights to Mini-Z model car (based on PIC12C509)
  
• How to use a SCART TV as a Monitor for MAME arcade game emulator
  
• Interfacing Sony control stick to Empeg
  
• JAM(Just A Minute) Quiz Game Circuit
  
• Judge Dredd pinball locking ring modification
  
• Junior Pacman Arcade Game circuit diagram (PDF)
  
• Ladybug Arcade Game circuit diagram (PDF)
  
• LED Dice implemented with a PIC microprocessor
  
• LED dice project based on 555 timer and CD4017 decade counter
  
• LED dice project including nice veroboard layout (PDF)
  
• LED dice using PIC16F88
  
• LED dice with fast roll
  
• LED dice with slow down tumbling action
  
• LED Zeppelin game of skill and patience
  
• Lego Mindstoms IR Link PIC transceiver
  
• Lego Mindstorms Double Rotation Sensor
  
• Lotto number selector helps you win a fortune
  
• Low-cost bingo game for a TV based on an Atmel microcontoller
  
• Magic Wand Conjuring Trick
  
• Mappy Arcade Game circuit diagram (PDF)
  
• MBC5/CPLD for the GameBoy
  
• Moon Cresta Arcade circuit diagram (PDF)
  
• Mr.Do Arcade Game circuit diagram (PDF)
  
• Multi-User Jeopardy Game (Fastest Finger First)
  
• PacLand Arcade Game circuit diagram (PDF)
  
• Pengo Arcade Game circuit diagram (PDF)
  
• Persistance of vision (POV) toy
  
• PIC10F200-based electronic dice
  
• PIC16F84-based video game system
  
• Pine Racecar Victory Judge
  
• Pine Racecar Victory Judge
  
• Q*Bert Arcade Game circuit diagram (PDF)
  
• Qix Arcade Game circuit diagram (PDF)
  
• Quiz game circuit
  
• Quiz show indicator
  
• Reaction timer using 4013 flip-flop and 4060 12-stage binary ripple counter
  
• Reflex Action Game
  
• Repairing & Upgrading Gottlieb System 80 Pinballs from 1980 to 1989
  
• Scramble Arcade Game circuit diagram (PDF)
  
• Simon Says memory game using a PIC16F84A or PIC16F628 microcontroller
  
• Single LED dice kit circuit diagram
  
• Space invaders game using PIC microcontroller
  
• Spin the device educational project based on PIC12F629 microcontroller
  
• SRX1 (Stephane's Robotic eXperiment 1)
  
• SX28-based color video game system
  
• Tic Tac Toe game based on Microchip PIC16F628 microcontroller
  
• Time Pilot'84 Arcade Game circuit diagram (PDF)
  
• Two player quiz master game
  
• VCR ping pong game
  
• Video ping pong game
  
• Virtual Game System - A game console with a mechanically scanned display
  
• Visor cradle serial interface
  
• Xevious Arcade Game circuit diagram (PDF)
  

Infrared based schematics

• 40khz IR Tester
  
• 40KHz light receiver (PDF)
  
• 40KHz TV-VCR repeater (PDF)
  
• 50MHz Receiver for the IR Detector
  
• 50MHz Transmitter for the IR detector
  
• 555 timer 40khz IR Oscillator
  
• Build an Infrared night scope
  
• Computerized Infrared Remote
  
• Decoding IR Remote Controls
  
• Digibox interface
  
• Direction sensing infrared motion detector using PIR (PDF)
  
• DVD thermometer - display temperature on TV by remotely controlling DVD player by infrared
  
• Fire-Stick infrared remote control
  
• High power infrared remote control to turn off television sets from a distance
  
• Implementing Infrared Object Detection
  
• Improved infrared receiver for PC with status LED
  
• Inexpensive infrared reflectometer
  
• Infa-Red Remote Control
  
• Infra Red Switch
  
• Infra Red wired Repeater circuit to control appliances from a remote location
  
• Infrared / Ultrasonic beacon
  
• Infrared beam barrier / proximity detector
  
• Infrared beam door alarm
  
• Infrared circuits for remote control
  
• Infrared gate (door entry alarm)
  
• Infrared gate for door
  
• Infrared Head Phones
  
• Infrared headphone system (includes transmistter and receiver schematics along with vero layout)
  
• Infrared lamp
  
• Infrared level detector for liquid level detection and proximity detection
  
• Infrared link for 10-BASE-T / 100-BASE-T PC network card
  
• Infrared Motion Detector using a PIR sensor (PDF)
  
• Infrared proximity detector based on Microchip PIC12C508 or PIC12C509
  
• Infrared Proximity Detector based on Vishay TSOP4830
  
• Infrared Receiver Module Schematics
  
• Infrared remote control tester using a SFH2030 photodiode and a CA3140 operational amplifier
  
• Infrared remote transponder
  
• Infrared switch using any infrared remote control
  
• Infrared transmitter for locomotives
  
• IR detector
  
• IR detector
  
• IR detector / emitter
  
• IR illuminator for night-vision tv cameras and scopes
  
• IR Link
  
• IR remote control
  
• IR remote control extender
  
• IR Remote Control Extender Circuit
  
• IR Remote Control Extender Circuit (Mark 2)
  
• IR Remote Control Extender Circuit (Mark 3)
  
• IR Remote Control Jammer
  
• IR remote control tester
  
• IR remote control tester
  
• IR wheel encoder board
  
• iRDA transceiver to extend IR port range up to 15 meters
  
• IR-related ASCII Schematics V1.00
  
• Micro based PIR to IR remote converter
  
• PC IR Remote Control Hardware
  
• Pyroelectric Infrared (PIR) Sensor
  
• Remote control uses an IR receiver chip to receive the IR signal from the remote
  
• Serial port controller infrared transmitter (PIC16F628)
  
• Simple Infa-Red Remote Control
  
• Simple infra-red detector
  
• Simple infrared remote control
  
• Simple IR transmitter circuit
  
• Simple on-off IR photoswitch without use of comparators
  
• Simple Remote control Tester
  
• TV remote control Blocker
  
• Universal Serial Infrared Receiver
  
• Wireless IR headphone receiver
  
• Wireless IR headphone transmitter
  

LASER related power supplies and data transmission

• 20MHz laser light detector (PDF)
  
• 20MHz VCSEL 3mW laser test circuit (PDF)
  
• 40KHz laser burst detector (PDF)
  
• Circuit for temperature stabilisation of laser diodes
  
• Circuit to measure speed of light with nanosecond pulsed 650 nm laser diode
  
• Circuits for biasing and modulating laser diodes
  
• Diode laser electronic circuits for atom optics
  
• Experimental laser data link
  
• Guide to Building a Homemade XY Scanner
  
• Heathkit modulated HeNe laser power supply kit (HK-HI1)
  
• HeNe laser power supply
  
• Home Built Laser Projector
  
• Laser beam alarm system
  
• Laser diode transmitter RF section
  
• Laser high-voltage power supply
  
• Laser light output intensity meter
  
• Laser link communicator project from Electronics Australia magazine
  
• LASER Power Supply
  
• Laser power supply
  
• Laser range finder and reflectivity meter for the MARS-96 international space project (PDF)
  
• Laser Target Finder Sensor
  
• LASER Transmitter/Receiver
  
• Laser transmitter/receiver
  
• LASER Transmitter/Receiver using Pulse Width Modulator (PWM) for 12V / 24V applications
  
• LASER/LED light output intensity meter (PDF)
  
• Low Cost Scanning Laser Rangefinder (PDF)
  
• Low noise PIN diode laser receiver circuit
  
• Micro-Laser range finder
  
• Micro-power 40KHz burst laser diode driver (PDF)
  
• Modulated laser diode tester (PDF)
  
• OPT301 Laser receiver
  
• Rangefinder with Fast Multiple Range Capability
  
• Real-time Laser Range Finding Vision System
  
• RS-232 Laser Transceiver
  
• RS-232 laser transceiver
  
• Simple high current pulsed laser driver using an avalanche transistor
  
• Simple laser communicator
  
• Simple LASER Transmitter/Receiver using HeNe laser tube
  
• Sniper tag laser beam detector
  

LED related schematics

• "Mini-Beacon" miniature programmable LED Flasher that is based around a PIC12F629 microcontroller
  
• "Peggy" - A Light Emitting Pegboard Display
  
• 1.5V LED flasher A (PDF)
  
• 1.5V LED flasher B (PDF)
  
• 10, 8 And 6 Step LED Circuits (CD4017)
  
• 12 Volt Knight Rider LED display
  
• 13 Color LED Rainbow
  
• 13 Color LED Rainbow
  
• 18 LED dimmable LED lamp
  
• 3V LED chaser using 4017
  
• 60 LED Clock
  
• 6V ultra-bright LED chaser using 74HC4017
  
• 7 Segment LED Counter
  
• 7 Segment LED Counter
  
• A "persistence of vision display" (POV display) using LEDs
  
• Adjustable flashing LED
  
• Assorted LED circuits
  
• AVR Color Clock using RGB LEDs
  
• Bedazzler: Do-it-yourself Handheld LED-Incapacitator (non-lethal weapon)
  
• Bicycle LED POV (persistence of vision display) LED display
  
• Bicycle rear flashing LED light
  
• Big 7-segment LED display board with SPI interface
  
• Christmas Star
  
• Christmas tree
  
• Color fade
  
• Colour Shifting For Bi-Colour LED's
  
• Current Regulators For Light Emitting Diodes
  
• Dancing LEDs
  
• Digital Up / Down Counter with 7-segment display
  
• Discrete LED Color Organ
  
• Driving led display matrix from a PIC micro
  
• Fading LEDs
  
• Fantastic Atom Expander
  
• Flashing LED advertising badge (PDF)
  
• Flashing LED advertising badge (PDF)
  
• Fun with LEDs - a variety of LED flahser projects
  
• Giant T-shaped LED matrix display board for financial applications containing 275 8x8 LED modules
  
• Heart of LEDs
  
• High Current Pulsed LED
  
• High Efficiency 12V White LED Driver
  
• High power LED driver using LTC3780
  
• Incandescent LED Circuit
  
• Kitt car scanning LED sequencer
  
• Knight rider scanning LED lights
  
• LED Audio VU Meter
  
• LED Chaser
  
• LED chaser
  
• LED Chaser using 4011 / 4017 CMOS chips
  
• LED color fade
  
• LED dimmer circuit
  
• Led display digital Voltmeter
  
• LED flasher using 4584 hex inverting Schmitt trigger
  
• LED flasher with "Rising and Falling" Brightness
  
• LED Mood Light
  
• LED Mood Light
  
• LED Running Message Display using CD4017 with transistor drivers rather than a CPU
  
• LED Thermometer
  
• LED Voltage Indicator Board
  
• LEDMATRIX, a 80x32 pixel DIY LED matrix display
  
• Little bike light using LEDs
  
• LM3909 replacement using discrete components
  
• Low battery voltage flasher (PDF)
  
• Low current LED flasher (PDF)
  
• Making an Amplified Color Sensor from an LED and an Op Amp
  
• Persistence of Vision Display for Bikes
  
• Pocket Ignignokt LED display
  
• PointLess LED Array - A 8 by 8 array displays something using POV
  
• POV Persistence Of Vision 2 x 32 LED display
  
• Pulsed LED test circuit (PDF)
  
• Regulated Dual White LED Lamp
  
• Robot beacon light display for mounting on top of a robot
  
• Running Message Display
  
• SAA1064 display module project
  
• Schematic and breadboard layout for reversed LED color sensor using an opamp
  
• Scrolling LED sign based on Atmel ATtiny2313 AVR microcontrolle
  
• Selecting of LED projects including a flashing Christmas tree
  
• Seven Component Regulated LED Lamp
  
• Seven Component Regulated LED Lamp
  
• Simplest LED Flasher Circuit using a 2N2222 transistor Simplest LED Flasher Circuit led
  
• Single and Two Cell White LED Drivers Without Inductors
  
• Single cell LED flasher with two-year battery life (LM3909 replacement)
  
• Sky writer - displays 'in air' messages and features inertia switch
  
• Tiny micro-controller driven lightshow using LEDs and a Picaxe 18A (PDF)
  
• Using Common Cathode Or Anode LEDs As Bipolar LEDs
  
• Various LED flashers
  
• Various LM555 LED Blinker Circuits
  
• White LED circuits
  
• White LED Drive Circuit
  

Lighting and light controller schematics

• 12 Volt Strobe, Coil Driven
  
• 1200 Watt Lamp Dimmer Circuit using Q4015LT combination Diac
  
• 12V florescent light inverter
  
• 12V stroboscope
  
• 12VDC Fluorescent Lamp Driver
  
• 12VDC Fluorescent Lamp Driver
  
• 12VDC Fluorescent Lamp Driver
  
• 1W Fluorescent lamp night light (PDF)
  
• 220 Volts Flashing Lamps
  
• 3 Xenone flashing circuits found in flash for disposable cameras
  
• 4-channel dimmer rack
  
• 5W Fluorescent light intensity modulator (PDF)
  
• 6 Channel Auto Reverse Sequential Disco Running Lights
  
• Adjustable Strobe Light
  
• Adjustable Strobe Light
  
• Adjustable Strobe Light
  
• Automated crib light
  
• Automatic Room Lights
  
• Automatic Staircase Light 1
  
• Automatic Staircase Light 2
  
• Battery-powered Night Lamp
  
• Bicycle back Safety Light
  
• Bike Light Flasher
  
• Black Light
  
• Black Light powered by a 6 volt battery
  
• Brightness Control for small Lamps
  
• Christmas lights tester
  
• Circuit for remote lighting controller using a 433MHz AM keyfob transmitter
  
• Courtesy Light
  
• Digitally Addressable DALI Dimming Ballast (PDF)
  
• Dimmable Li-Ion Halogen Bike Light
  
• Diode Type Constant Lighting Circuits
  
• Disco light controller (ZIP file)
  
• DMX lighting and special effects
  
• Easy Xenon DC-DC Converter using LM386
  
• Electronic candle
  
• Electronic night light
  
• Emergency light flasher schematic
  
• Flashing neon christmas lights
  
• Flashy Christmas Lights
  
• Fluorescent Tube "Strip light" Driver
  
• Inverter for fluorescent lights as published in Silicon Chip Magazine February 1991 (PDF)
  
• Lamp flasher/dimmer
  
• LED Mood Light
  
• LEDs or Lamps Sequencer is versatile modular design with no limits on number of lights
  
• Lightning bulb - Create an electrical storm in a light bulb
  
• Low-voltage light dimmer
  
• LX-800 Lighting system
  
• Mini emergency light
  
• Neon desklamp
  
• Neon lamp dimmer
  
• Night light saver using AT89C2051
  
• RHINO8 EL Sequencer
  
• Strobe light
  
• Strobo Disco Light Using Standard Tube Lamp (TL)
  
• TRIAC based lamp dimmer circuit diagram
  
• TRIAC Light Dimmer
  
• TRIAC Light Dimmer
  
• TRIAC light dimmer
  
• Xenon Flash Indicator (XFI)
  
• Xenon Strobe Light
  

Medical and health related schematics

• "TENS" Circuit diagram for muscle stimulation
  
• Brain-Wave Machine
  
• Cardiac monitor
  
• Cranial Electrotherapy Stimulation (CES) circuit diagram
  
• Digital pedometer circuit
  
• ECG amplifier with right leg drive
  
• ECG Measurement and Analysis
  
• EKG/EEG circuit
  
• Electronic Stethoscope
  
• Electronic Stethoscope
  
• Galvanic Skin Response (GSR) Circuit
  
• Heart Rate Monitor (HRM) Receiver Circuit
  
• Heart rate sensor
  
• Heartbeat transducer using infrared LED / detector
  
• Jogging timer
  
• Lie detector
  
• Model 2030 XRAY monitor instruction manual including schematics (PDF)
  
• Muscular Bio-Stimulator
  
• Muscular Bio-Stimulator using 555 timer
  
• OpenEEG open hardware EEG project
  
• Optical Heart Rate Monitor
  
• PC based biofeedback monitor
  
• Portable blood pressure monitor
  
• Positive Feedback Circuit for Isometric Muscle Experiments
  
• Salt taster - detects the amount of salt contained in liquid foods
  
• Simple lie detector
  
• Simple lie detector
  
• Sleeping aid based on electromagnetic-field radiation
  
• Snore alarm electronic device
  
• Stress meter educational project using PIC12F629 microcontroller
  
• Tan timer to prevent sunburn
  
• The ESP SIM (Sound Impairment Monitor)
  
• Tiny EEG interface schematic
  
• Wireless Electrocardiogram Monitor
  

Microcontroller based schematics

• "Singing" Christmas tree based on Microchip PIC16F84
  
• (E)EProm, PIC and GAL Programmer
  
• 10 tricks for interfacing to the PIC16C508
  
• 10 tricks for interfacing to the PIC16C508
  
• 101 AT Keyboard to ASCII Decoder using 68HC705J1A MCU
  
• 128x64 LCD Driver for AT90S2313 (ZIP file)
  
• 2-wire LCD interface using PIC16CF84
  
• 3-wire serial LCD interface for the PIC
  
• 40+ MHz 5-digit frequency counter with an AVR 2313
  
• 4-Channel Timer using Atmel 89C4051 and MAX7219 display driver
  
• 50 MHz frequency counter, voltage meter & SWR/PWR indicator
  
• 6802 Nano computer
  
• 8049 Spy - read the internal ROM contents of a 8048 or 8049 processor
  
• 8051 Development System Circuit Board
  
• 8051 Development System Circuit Board
  
• 8051 Development System Circuit Board
  
• 8051 Development System Circuit Board
  
• 8051 SBC (single board computer)
  
• 8051SBC V1.1
  
• 8088 maximum mode SBC
  
• 80C31 stepper motor controller
  
• 89C2051 microcontroller programmer
  
• 89S52 Project Board
  
• 90S2313 AVR Robot Board
  
• A Real Time Clock IC (DS1307) project using the PIC micro
  
• A Scenix (and PIC) Programmer
  
• Acceleration monitor using ADXL202 and AVR
  
• ADC conversion using ADC0804LCN and 8051
  
• AFSK 1200 Modem based on PIC16C620
  
• 'Almost No Parts' 7-segments 12/24 Hours LED clock with PIC 16F84A or 16F628A
  
• Analog datalogger based on T89C51RD2
  
• Analog to digital (ADC) conversion notes
  
• Arduino based controller interface for servo motors, stepper motors and DC motors
  
• Arduino microcontroller prototyping system
  
• Asynchronous 40-bit TTL CPU
  
• AT89C2051 Digital thermometer and clock
  
• AT89C2051 line-follower robot
  
• AT89C2051 Night light saver
  
• AT89C2051 real-time controller
  
• AT89C2051 serial COMs to LED driver
  
• AT89C2051/4051 Driving dot LED
  
• AT89C2051/4051 Easy-Downloader
  
• AT89C2051/4051connecting dumb terminal
  
• AT89C2051/4051scanning 7-segment display and keypad
  
• AT89C2051/4051stepper motor interface
  
• AT89C51/52/55 Easy-Downloader
  
• AT89Sxx Cheap and Simple Learning Board
  
• AT90S8515 experimenter board
  
• ATmega48 based Nixie Clock
  
• ATmega8 based TNC with GPS and WX support
  
• Atmel 8051 Flash Based-Microcontroller Programmer
  
• Atmel 89 Series Device Programmer
  
• Atmel 89C Series Flash Microcontroller Programmer
  
• Atmel 89C2051 In-Circuit Programmer Schematic
  
• Atmel 89C2051 prototype board
  
• Atmel 90s2313 based TNC
  
• Atmel AT90USB development board
  
• Atmel ATmega128 development board
  
• Atmel ATtiny26 development board
  
• Atmel AVR 90s2313 based POCSAG encoder (ZIP file)
  
• Atmel AVR and 8051 series ISP programmer
  
• Atmel Mega88 Dual Temperatur meter
  
• Atmel Mega88 Temperatur meter, Type K sensor, Heat set and regulator
  
• Atmel Microcontroller based Ultrasonic Ranger
  
• Automatic door opener with PIC12C508
  
• AVR STK200/STK300 ISP Dongle circuit diagram
  
• AVR Thermometer
  
• AVR-Based Serial Port IR Receiver
  
• AVR-Core V1.1 - DIP-like development board for ATmega128 processors (PDF)
  
• AVRlinx V1.1 - Development board for ATmega16, ATmega32 processors with data radio transceiver (PDF)
  
• AVRmini V2.0 - Development board for all AVR processors in 40-pin packages (PDF)
  
• AVRmini V3.1 - Development board supporting all AVR processors in 40-pin and 64-pin packages (PDF)
  
• AVRmini V4.0 - Development board with Ethernet/USB for 40-pin AVR processors (PDF)
  
• AVRmini8 V1.0 - Development board for ATmega8, ATmega44, ATmega88, ATmega168 processors (PDF)
  
• Basic Stamp based altimeter
  
• Build a PIC controlled DDS VFO, 0 to 6 MHz
  
• C-52 EVB Robot Controller
  
• CASIO datalogger system based around Microchip PIC microcontroller
  
• CF/IDE Adapter V1.0 - CompactFlash and IDE interface for your microcontroller
  
• Cheap Ultrasonic Range Finder based on PIC16F877A with a 8MHz crystal
  
• Circuits for interfacing microcontrollers to a wide number of real-word interfaces
  
• Complete Design for Giant 8-foot LCD Counter (Zip file)
  
• Connecting AT90S2313 with LCD display 2x16 char and 4x4 keypad
  
• Connecting LED to PIC Micro I/O pins (PDF)
  
• Cypress PSoC based digital wallet to record secret codes and passwords securely
  
• Darkroom timer using PIC16F84A
  
• Designing a 4-Channel A/D (ADC) converter with the PIC12C671
  
• Digital compass using PIC16F84
  
• Driving high-power loads with a microprocessor
  
• DS1820 Arbiter V2.00 Schematic
  
• Electronic distance meter based on Motorola 68HC908QY4
  
• Electronic irrigation controller based on PIC
  
• Electronic safety lock based on ATtiny26
  
• Ethernet shield for Arduino (Xport)
  
• EZ80 single board computer schematic (Z80)
  
• Fan timer based on Motorola 68HC908QT2
  
• Galvanic decoupling of I2C bus
  
• GPS / Datalogging shield for Arduino microcontroller
  
• GPS LCD Display Project
  
• Hardware Random Number Generator with an SX microcontroller
  
• Homebrew Basic Stamp project
  
• I2C LCD interface
  
• IDE interface to a Microchip PIC16F877 microcontroller
  
• In-Circuit PIC Loader (ISP programmer) over parallel port
  
• Interfacing DRAM to AT90S8515
  
• Interfacing EEPROM to a Basic Stamp
  
• Interfacing the MAX186 8 Channel ADC to the BSII
  
• Interfacing the MAX187 ADC to the BSII to measure voltages
  
• Interfacing the PIC16C508
  
• Isolated RS232 for PIC16F84
  
• JDM programmer
  
• Jupiter card programemr
  
• KD7LMO Micro Beacon (PIC18F252)
  
• LCD clock based on AVR Attiny2313
  
• LCD thermometer using PIC16F871
  
• LCD to PIC16C54 schematic
  
• LED 5x7 display using a PIC microcontroller
  
• Linuxstamp general purpose processor module based on Atmel AT91RM9200
  
• Long-period watchdog timer
  
• Low cost Atmel in-system programmer
  
• Mains clock controller using AT89C2051
  
• Microchip PIC ICD (in-circuit debugger)
  
• Microcontroller sensor and actuator interfaces
  
• Microprocessor RS-232 Reset
  
• Microprocessor using Xilinx FPGA
  
• MiniLOGGER V1.0
  
• MMC to PIC16F876 circuit diagram
  
• Motorola 68HC11 evaluation board
  
• Motorola 68K SBC (single board computer)
  
• MTK-85 8085 Microprocessor Training Kit
  
• Multi PIC Programmer 5 Ver.2
  
• Multi-chip programmer
  
• Multi-chip programmer for Microchip PIC microcontrollers
  
• Multi-chip programmer for PIC microcontrollers
  
• Multipurpose buffered PIC microcontroller development system
  
• Night light saver (PIC12C508)
  
• Nixie clock (PIC16F876)
  
• Parallel AVR programmer
  
• PC to microcontroller communications using power from the PC serial port
  
• PIC 18 programmer (PIC18F458, PIC18F452, PIC18C252, PIC16C745, PIC18F6620, PIC18F6720)
  
• PIC based packet radio encoder (PDF)
  
• PIC demo board
  
• PIC ICD
  
• PIC LCD and Keypad driver
  
• PIC Light Chaser using PIC16C84
  
• PIC micro LED projects
  
• PIC micro multiple servo motor interface
  
• PIC micro programmer
  
• PIC micro to ISA bus interface
  
• PIC microcontroller servo motor interface
  
• PIC Project #1 - RS232 to I2C Interface
  
• PIC Serial LCD project - An RS232 serial LCD interface using a standard HD44780 LCD
  
• PIC sonar (ultrasonic) range finding project with seven segment display using PIC micro
  
• PIC vacuum fluorescent display (VFD) interface
  
• PIC Web Server Schematic
  
• PIC12C508 Night-light saver
  
• PIC12C508 Phase Controller for 2kW heater (ZIP file)
  
• PIC12C509 Gym Timer (ZIP file)
  
• PIC12C509 logic gate replacement for nitrogen filler (ZIP file)
  
• PIC16 DemoKit3 with programmer and displays
  
• PIC16C505 IR / wireless remote control
  
• PIC16F628 controlled FLL (Frequency Locked Loop) VFO for HF (PDF)
  
• PIC16F84 Based Morse Code Reader
  
• PIC16F84 CW decoder (PDF)
  
• PIC16F84 debugging terminal
  
• PIC16F84 LED chaser
  
• PIC16F84 line following robot
  
• PIC16F84 miniature real-time controller
  
• PIC16F84 programmer
  
• PIC16F84 pulse monitor with date/time output (ZIP)
  
• PIC16F84 Serial I/O-expander with PicBasic
  
• PIC16F84 tone generator
  
• PIC16F84 tone generator (6-Bit)
  
• PIC16F84 tone generator with source code
  
• PIC16F84 TRIAC / IGBT brightness phase controller
  
• PIC16F876 Datalogger
  
• PIC16F877 Programmer And Development System
  
• PIC16F877 to IDE interface
  
• PIC18F2550 Project Board
  
• PICADC - a free, PIC based "intelligent" A/D converter
  
• PicCon - Hidden Radio Transmitter Controller
  
• PicoWeb V5.1 (AT90S8515) tiny web server
  
• PIC-Programmer 2
  
• PIC-Programmer 2 for PIC16C84 etc
  
• PIXpand - TI calculator to Playstation memory card interface
  
• POCSAG encoder/decoder (Zip file)
  
• Poor man's analog to digital converter (ADC) using a 2N222 transistor and a few passives (PDF)
  
• Programmer PIC16F84,12C50x and EEPROM 24Cxx
  
• PS/2 keyboard keystroke logger based on Atmel 89C2051
  
• RF remote control based on Basic Stamp
  
• Rotating Sprocket Wheel Generator (PIC16F84)
  
• RS232 interfaced DVM using a PIC12F675 including source code for CCS C Compiler
  
• RS-232 to TTL Translator
  
• RS485-like multi-drop bus with half duplex serial protocol
  
• ScanMate audio activated recorded
  
• Scriptable thermometer / thermometric controller based around a COP8-CCR9-PLC44 microcontroller
  
• Serial LCD controller using a PIC16F628
  
• Serial LCD Controller using Microchip PIC16F628
  
• Serial port I/O interface using AVR microcontroller
  
• Serial to parallel converter using the AT89C2051
  
• Serial-based PIC16F84 Programmer For Windows 95/98/NT/2000/ME/XP
  
• Ser-Key 10-Key Serial Keypad Encoder
  
• Several Atmel AVR programmer circuits
  
• Simple CW Keyer based on Atmel ATtiny 2313
  
• Simple QRSS callsign keyer based on an Atmega AVR programmed in C
  
• Simple RS232C Level Converter using Transistors
  
• Smart card programmer
  
• Solderless Breadboard Arduino Clone for Arduino prototyping
  
• Speech recognition using HM2007
  
• SPI Flash Microcontroller Programmer
  
• SPI2CF, a fast and efficient WLAN interface for the AVR
  
• T89V51CC01 Development board
  
• Tachometer Measures Very Low Frequencies (PIC16F872)
  
• Talking PIC - based on SP0256
  
• TekBots universal device programmer with USB interface
  
• Temperature controlled based on AT89CX051
  
• Temperature monitor/controller: AVR 2313 / DS1621
  
• Tiny 2313 Project Development Board
  
• Tiny Eprom Simulator
  
• Tony Nixons Pocket Programmer (PIC)
  
• Touch senstor based on Atmel AT90S2313
  
• TTL to RS232 adapter using 2N3906 / 2N3904 transistors
  
• Ultra low-cost programmer for AT90S family
  
• Ultrasonic Distance Measurement With the MSP430 (PDF)
  
• Ultrasonic Distance Measurer based on Freescale MC9RS08KA2 (PDF)
  
• USB and GLCD expansion board for 8051 SBC
  
• USBmini V1.0 - Generic USB Full-speed interface board (PDF)
  
• USBtinyISP - AVR programmer & SPI interface project
  
• Using the AT89C4051 as a RTC (real-time clock)
  
• Variety of circuits for RS232 to TTL Signal Conversion
  
• Variety of circuits for TTL to RS232 Signal Conversion
  
• Victoria TAFE programmer (based on AT89C2051)
  
• Wave (Audio) shield for Arduino microcontroller
  
• Wireless communications using a Basic Stamp and low-cost wireless data modules
  
• Wisp628 ISP Microchip PIC Programmer
  
• WLoader - PIC16F877 application loader / bootloader
  

Misc audio (also see Music, Amplifiers, Preamp)

• 1 Watt audio amp using a TDA7052
  
• 12 watt audio amplifier with tone using TDA1020
  
• 3 Channel Spectrum Analyzer
  
• 3-Band audio graphic equalizer
  
• 4 channel audio selector
  
• 5 watt audio amplifier using TDA1010
  
• 6-Input mixer
  
• Active Sub-Woofer and Controller
  
• Actvie speaker based on a dual op-amp (LM833) and TDA2030 power amp
  
• Amplifier thermal protection
  
• An Audio Limiter for NBFM use
  
• An Audio-Noise-Based Voting Circuit
  
• Analog Synth Keyboard Schematic
  
• Assortment of Siren Circuits
  
• Audio DAC3 (SPDIF->Analog Audio)
  
• Audio Detector Circuit
  
• Audio graphic equaliser
  
• Audio Indicator - monitor a loudspeaker, alarm, or audio source for presence of an audio waveform
  
• Audio line isolator
  
• Audio mixer
  
• Audio Signal Source
  
• Audio Speech Processor
  
• Audio VU Meter based on pair of LM324 quad opamps
  
• Automatic Charger for Battery Operated Hi-Fi Preamps
  
• Automatic loudness control
  
• Balanced Line Driver & Receiver
  
• Base / treble control circuit using LM1036N
  
• Bass booster using a TL702 opamp
  
• Bass EQ pre-amp correction for high impedance ceramic crystal pickup
  
• Beat Tracking Strobe
  
• Big Ben sound effects generator
  
• Bridging Adapter For Power Amplifiers
  
• Clack Clack Electronic Bell
  
• CMOS IC 1 kHz Audio Oscillator
  
• Condenser microphone hookup
  
• Cuckoo sound generator
  
• Cuckoo sound Generator
  
• Digital Delay Unit For Surround Sound
  
• Digital noise generator (PDF)
  
• Digital volume control
  
• Digital volume control
  
• Digital Volume Control based around CD4067 CMOS chips
  
• Digital Volume Control using DS1669 Digital Pot IC
  
• Digital Volume Control using DS1669
  
• Direct Injection Box for Recording & PA Systems
  
• Doorphone intercom
  
• Dual Voltage Controlled Oscillator w/Modulator
  
• Dynamic microphone to electret microphone input
  
• Electret microphone powering circuits
  
• Electronic attenuator
  
• Electronic Canary
  
• Electronic canary sound effects
  
• Electronic siren
  
• Envelope generator ADSR
  
• Fast Audio Peak Limiter
  
• FET Audio Mixer
  
• FET audio mixer
  
• Guitar Reverb Effect Version 2
  
• High Quality Sound Mixer
  
• Improved PL tone decoder
  
• ISD4002-120 audio recording circuit
  
• JFET Bass Preamp
  
• Line level signal to microphone input adapter
  
• Linkwitz Cosine Burst Generator
  
• LM358 preamp
  
• Load Sensing Automatic Switch
  
• Loudspeaker Protection and Muting
  
• Low frequency / audio frequency dB output meter
  
• Low Noise Balanced Microphone Preamp
  
• Low Noise Microphone Preamplifier
  
• Magnetic cartridge amplifier
  
• Microphone Mixer
  
• Microphone mixer
  
• Microphone phantom power supply
  
• Minimalist Discrete Hi-Fi Preamp
  
• Minimum Theremin Kit Schematic
  
• Mono To Stereo Synthesizer / Simulator
  
• MS Stereo Decoder
  
• Musical Electronic Bell
  
• Novel buzzer using a relay and transformer
  
• Panner Waveform Generator
  
• Parabolic microphone project circuit (can be used with shotgun directional microphone also)
  
• Paradoxical Sound Syntheizer
  
• Parametric And Sub-Woofer Equaliser
  
• Peak reading audio level meter using CA3140 opamp
  
• Peak-reading meters
  
• Phase shifter
  
• Phono Preamps For All
  
• Police Siren
  
• Power Amplifier Clipping Indicator
  
• Precision Audio Millivoltmeter
  
• RC Audio Oscillator
  
• RDS Encoder
  
• Regulatable audio amplifier using a 741opamp
  
• RIAA Equalized Stereo Phono Preamp
  
• Room noise detector
  
• Room Noise Detector
  
• Signal Detecting Auto Power-On Unit
  
• Simple electronic buzzer
  
• Simple Surround Sound Decoder
  
• Simple two line output combiner
  
• Simplest Ever Amplifier Bridging
  
• Six-channel Mixer and Amplifier
  
• Sound activated relay, V1
  
• Sound activated relay, V2
  
• Sound detector
  
• Sound Level Meter
  
• Sound level meter
  
• Sound operated switch
  
• Sound Pressure Level Meter
  
• Speaker cabinet simulator - professional-quality frequency response in a DIY-friendly circuit
  
• Speaker Microphone Circuit
  
• Speaker signals to line level inputs
  
• Speech recorded using ISD2560
  
• Spring reverb unit
  
• Stereo Audio Isolator
  
• Stereo Audio Isolator
  
• Stereo audio line driver for running audio over long distance cables
  
• Stereo LED VU meter using discrete components (BC547 transistors)
  
• Stereo Width Controllers
  
• Subwoofer Equaliser
  
• Subwoofer Filter, Gainer, Auto Power System
  
• Telephone ring sound simulator using SMT (surface mount technology)
  
• Three channel audio spectrum analyzer
  
• Three channel audio spectrum analyzer
  
• Three-Level Audio Power Indicator
  
• Tone control circuit diagram
  
• Tone control circuit schematic
  
• Tone Control using TDA1524A Tone Control IC
  
• Tone detector circuit diagram
  
• Tone display system
  
• Tone generator circuit diagram
  
• Two Tone Audio Oscillator
  
• Underwater microphone used in a home aquarium to monitor fish sounds
  
• Use amplifier phono input as line level input
  
• Using a speaker as a microphone - impedance matching circuit
  
• Variable Amplifier Impedance
  
• Various tube crossover circuits
  
• Very loud beeper (PDF)
  
• Voice / Audio Record / Playback Circuit
  
• Voice Message Recorder / Player (uses an obsolete voice recorder chip)
  
• Voice Scrambler
  
• Voice-Over Circuit
  
• Voltage controlled amplifier
  
• Voltage Controlled Panner
  
• Voltage Controlled Panner
  
• Voltage Controlled Panner
  
• VU And PPM Audio Metering
  
• Warbler siren circuit diagram
  
• Weird Sound Generator
  

Miscellaneous schematics

• 10 GHz CW Radar based on a X-band Gunnplexer
  
• 12 Volt Toilet Tank Refiller
  
• 1uS light pulse descriminator plus F to V converter (PDF)
  
• 1uS light pulse receiver plus post amp (MISC)
  
• 2D3 Nixie clock schematic using Atmel microcontroller
  
• 6 Pole ElectroMagnet Motor (aka Simple Brushless motor)
  
• 741 Light Sensor
  
• A small collection of quick to build electronic circuit designs
  
• A Two-Way Morse Practice Set
  
• Air flow detector
  
• Air flow detector using an incandescent lamp to detect airflow
  
• Amateur weather station to APRS interface ALWXI-01
  
• Analog computer
  
• Analog opto-isolator
  
• Analog pulse counter
  
• APRS system for GPS tracking
  
• Assorted digital circuits
  
• Aurora Alarm: Automated Detection System for the Northern Lights
  
• Barry's Coilgun Mark I circuit diagrams
  
• Barry's Coilgun Mark II circuit diagrans
  
• Barry's Coilgun Mark III circuit diagrans
  
• Barry's Coilgun Mark IV circuit diagrans
  
• Barry's magnetic levitation project
  
• Basement doorbell beeper (PDF)
  
• Basic Homebuilt Discrete DTL gate circuits (Diode Transistor Logic)
  
• Basic opamp circuits
  
• Bat detector
  
• BayComm packet modem
  
• Beat Balance Metal Detector
  
• Biasing Op-Amps into Class A
  
• Big Ear Stereo Parabolic Microphone
  
• Black Light
  
• Bleeper box for time reference
  
• Broadband 2MHz optical fiber receiver (PDF)
  
• Broadband 5MHz optical fiber receiver (PDF)
  
• Build logic gates using discrete parts
  
• Build your own UFO Bino-Scope unit - upgrade binoculars to become a photosensitive bino-scope
  
• Build Your Own Video-Rate 2-photon Microscope
  
• Building a Hardware Random Bit Generator
  
• Capacitance to Voltage conversion
  
• Capacitive Sensor
  
• Cat or Dog Detector - can be used to control entry on a Cat or Dog Door
  
• Chaos generator
  
• Circuit diagram for Coilgun Pistol Pskov 1100
  
• Circuit diagrams for making logic gates from discrete components
  
• Circuit for driving a liquid crystal (LCD) shutter to simply pass or block light
  
• Circuit for gold wafer card
  
• Circuit for temperature stabilization of a MTP3055E MOSFET
  
• CMOS based electric fence design
  
• CMOS Logic Experiments
  
• Coil Coupled Operation Metal Detector
  
• Color sensor circuit
  
• Computerize Your Room/Home
  
• Count Accumulator for Radiation Levels (CARL)
  
• CW Tone Keyer
  
• Dekatron circuit diagram - device used for dividing by 10 during the valve era
  
• Delayed shutter control for Kodak DC-20
  
• Digg Button Kit
  
• Digital Call Sign Annunciator
  
• Digital Radar Speedometer
  
• Digital Remote Thermometer
  
• Dinsmore 1490 digital compass
  
• DIY 3-axis CNC milling device
  
• DIY Plasma Globe using an automotive ignition coil
  
• DIY Tesla coil - DC Powered with Plasma Output
  
• Doorbell for the Deaf
  
• Driving N-channel FETs from TTL
  
• Easy Morse Code Keyer Circuit
  
• Electric field disturbance monitor
  
• Electromagnetic field detector
  
• Electromagnetic Field Probe with Meter Output using an LF351 opamp
  
• Electronic canary doorbell
  
• Electronic dazer
  
• Electronic inclinometer ("clino"), a surveying device
  
• Fantastic Atom Expander
  
• FCTS Project
  
• FET based metal detector using MPF102 / J310 BF998 FETs
  
• Fish caller circuit
  
• Fluid level detector
  
• FM Morse Code Keyer
  
• Fogger smoke machine controller
  
• Full-duplex doorphone with 3 wires connection
  
• G Strain energy absorber
  
• Garmin Foretrex 101,201, Forerunner 101,201 to Serial DB9 cable schematic pinout
  
• Garmin GPS data interconnect
  
• Geiger counter
  
• Geomagnetic field detector
  
• GoldPic 3 Pulse Induction Metal Detector (has electronic kit available)
  
• GPS receiver support kit
  
• Hacking the Hot Wheels Radar Gun - includes circuit of analog front end
  
• High Quality Intercom
  
• High Speed ISO9141 Interface using Motorola MC33290D ISO driver IC
  
• High voltage stun gun
  
• High voltage zappers
  
• High-speed 75MHz light receiver (PDF)
  
• Home-Built Magnetic Levitator
  
• How to Make a Roomba Serial Interface
  
• Hydrogen Generator, PWM Circuit
  
• Induced voltage sensor delta-peak trigger for coilgun
  
• Induction receiver for tracing wiring behind walls, hearing lightning and other electric discharges
  
• Inexpensive APRS Weather Station
  
• Inexpensive seismometer project
  
• Insect Repellant
  
• Insect Repellant (22KHz audio oscillator)
  
• Intercom schematic
  
• Ion detector
  
• Jacob's Ladder
  
• Jacob's Ladder
  
• Kenwood TH-D7 NMEA GPS bug fix
  
• Laboratory Control System for Cold Atom Experiments
  
• Lazer Tag Equipment Modifications
  
• Lie detector
  
• Light Activated Detector Circuit (LM393/LM555)
  
• Lightning Detector
  
• Lightning detector circuit diagram
  
• LNS Technologies Levitator Kit circuit diagram
  
• Lost keys finder using HCF4069
  
• Low Voltage Alarm
  
• Low-power optical interrupter (PDF)
  
• Magnetic Gun.
  
• Magnetic levitation device
  
• Magnetic levitation project from Electronics Now, February 1996
  
• Magnetic levitation project from Popular Electronics, May 1966
  
• Magnetic levitation project from Popular Electronics, May 1989
  
• Mains Remote-Alert - Remotely operates beeper and/or a LED via mains supply line
  
• Metal detector Mk1 - find hidden treasure at the beach
  
• Metal detector Mk2 - More sophisticated 5 transistor metal detector (BC547, BC557, BC338)
  
• Mini efficient magnetic coil launcher from disposable camera flash
  
• Miniature magnetic gun (rail gun)
  
• Miscellaneous 741 opamp schematics
  
• Miscellaneous Circuits for Idea Purposes
  
• Miscellaneous simple circuits
  
• Mobile APRS / GPS tracking system
  
• Modifications for CDV700 Geiger Counter
  
• Modulated light receiver circuit (PDF)
  
• Monitor output from Motorola Oncore GPS engine in HP Z3801A in GPS Disciplined Oscillator
  
• Morse Code Beacon Keyer
  
• Morse code display
  
• Morse Code Practice Keyer 1
  
• Morse Code Practice Keyer 2
  
• Morse monitor
  
• Morse paddle keyer
  
• Navigator 555A radio direction finder (RDF) circuit diagram
  
• Negative Ion Detector
  
• Negative Ion Generator
  
• Nocturnal Animals Whisker
  
• Nokia 3310 Lcd Thermometer using DS18B20
  
• omentary High Voltage Arc Circuit - can be used to Ignite a barbeque or a Gas in a Potato Gun
  
• Open loop pulse trigger module for coilgun
  
• Optical speed trap to measure the the velocity of the projectile
  
• Optical trigger module for coilgun
  
• PASCO scientific model SF-9211 stroboscope schematic (PDF)
  
• Photo sensor application note showing photodiode and phototransistor circuits
  
• Plant Watering Watcher (moisture meter)
  
• Popular Electronics Ultrasound Detector
  
• Power MOSFET module for coilgun
  
• Powerful stun gun / taser circuit diagram
  
• Project for experimenting with magnetic levitation
  
• Pulse width modulators (PWM)
  
• Pulse width to voltage converter
  
• Rain Detector
  
• Random noise generator
  
• Scaling ADXL50 accelerometer output
  
• Seismic detector interfaces to datalogger
  
• SIM card reader circuit diagram
  
• Simple BFO metal detector using 2N3906 and 2N3904 transistors
  
• Simple DTMF Repeater Controller using PIC16F84
  
• Simple electronic keyer
  
• Simple Frequency Reader for conversion VFOs
  
• Simple Lie Detector
  
• Simple metal detector circuit using BC547
  
• Simple moisture indicator
  
• Simple nitrogen spark generator (PDF)
  
• Single chip metal detecor with a range of a few inches based on CS209A
  
• Solid state tesla coil
  
• Solid State Tesla Coil and Wireless Power
  
• Sony RS-422 ADAT sync cable pinout
  
• Sound finding cricket
  
• Sound finding cricket with phase detector
  
• Spy circuits
  
• Static Electricity / Negative Ion Detector
  
• Stroboscope
  
• Stun gun / taser circuit diagrams
  
• Suddent ionospheric disturbance (SID) receiver
  
• Tesla coil
  
• Tesla coil
  
• Tesla power receiver
  
• Texas Instruments collection of buffer op-amp circuits for ADC
  
• Texas Instruments collection of differential op-amp circuits (PDF)
  
• Three stage induced voltage triggered coilgun
  
• Thyristor fired coilgun circuit diagram
  
• Time to dust indicator - battery powered dust indicator (PDF)
  
• Touch activated switch using CD4011 CMOS NAND gate
  
• Touch switch using transistors
  
• Touch switches
  
• Transresistance photodiode amplifier that behaves as a current-to-voltage converter
  
• Two-component metal detector using a 4093
  
• Two-tone doorbell using 555 timer
  
• u-Blox GPS receiver board
  
• Ultra Low Power LCD Indicator
  
• Ultrasonic dog whistle
  
• Ultrasonic Pest Repeller
  
• UltraSonic Radar
  
• Ultrasonic sonar unit using MAX232 to drive ultrasonic transducer
  
• Ultrasonic sound detector / sniffer
  
• Ultrasonic switch
  
• Ultrasonic transducer oscillator circuit
  
• Ultrasound detector
  
• UV light box
  
• Vareity of circuits for interfacing to/from TTL logic
  
• Very basic circuits
  
• Visible and Infrared Light Detectors
  
• Voice activated switch (VOX) circuit diagram
  
• Voltage Comparator Information And Circuits
  
• Waveform conversion
  
• Weather station with pressure reading, relative humidity, indoor & remote temperature reading
  

Models, remote control toys, robotics

• 0-10V control for RC servos
  
• 27Mhz toy car receiver
  
• 27Mhz toy car transmitter
  
• 5 Second Ramp Generator for Locomotive Sound Card Demonstration
  
• 5 Times Around Circuit
  
• 556 Timer Stall-Motor Switch Machine Drivers
  
• A dual alternating flashing light circuit
  
• A dual tandem flashing light circuit powered by a 9 volt battery
  
• A Receive Signal Decoder
  
• A selection of robotics projects
  
• Across The Track Infrared Detectors
  
• Adding External Meters to DC Throttles
  
• Analog controller for TekBot robot
  
• Angelfire rocket GPS payload
  
• Audible Train Approach Warning Circuit
  
• Automatic - Railway Grade Crossing Circuit (2008 design)
  
• Automatic Railway Grade Crossing Flashers
  
• autopilot: Do it yourself UAV
  
• AVR Line Following Robot
  
• Balancing robot (PDF)
  
• Basic DC controller for model trains (PDF)
  
• Bi-Ped Project 2
  
• Bi-Ped robot project
  
• Block Occupancy Detector For DCC
  
• Build A Roomba Bluetooth Adapter
  
• Building a robot arn using Nitino muscle wire
  
• Building an RF Remote Control System
  
• Charger board for TekBot robot
  
• Circuit diagram for connecting the SRF08/10/235 sonar modules to the BS2p Basic Stamp
  
• Circuit for three axis robot arm based on stepper motors out of 5 1/4" drives
  
• Collection of BEAM robot circuits
  
• Connecting Multiple SRF08 Sonar Modules to a BS2 (Basic Stamp 2)
  
• DCC - Zero Stretching Simulator (LM555)
  
• DCC Circuit Breakers
  
• DCC To DC - Accessory Power Supplies
  
• Deriving power from Lego NXT motor port A
  
• Discharger for Receiver Battery Packs
  
• Downed model locator
  
• Downed model locator Mark 2
  
• Electronic millipede robot
  
• External power supply for Lego NXT
  
• First Across The Line Race Scorer Circuits
  
• Glowplug driver for radio control models
  
• GP2D12 distance sensor
  
• Grade Crossing Bell Ringer (LM555)
  
• Grouped DCC Block Occupancy Detectors
  
• Incline Railway Control Circuit
  
• Launch controller for multiple rockets
  
• LED Out Circuit For Tortoise Switch Machines
  
• Lego compatible, compact rotation sensor
  
• Level crossing for model railways
  
• Locomotive signal braking module
  
• Making a FRED photopopper
  
• Miniature bipedal robot that starts to walk when you clap your hands
  
• Miniature line follower robot
  
• Model Railroad - Infrared Proximity Switch
  
• Model Railroad Odometer Car
  
• Model rocket launch controller
  
• Moderately complex train detector using an infrared LED and an infrared detector
  
• Motor controller board for TekBot robot
  
• Motor walker circuit
  
• Multi Rocket Launcher
  
• Pad launch controller for model rockets
  
• PC Controlled RC Car
  
• PIC-Bot II using Microchip PIC16LF84
  
• Precision Receiver Battery Low Voltage Alarm
  
• Proportional radio remote control
  
• R/C digital camera controller
  
• R/C Emergency locator alarm
  
• R/C helicopter camera
  
• Rail Crossing Diamond Protection Circuit
  
• RC Receiver Battery Low Voltage Alarm
  
• RC Receiver for airplane (35MHz)
  
• RC Servo Controller with preset
  
• RF Modem Robotics Project
  
• Robotic microcontroller board
  
• Roomba robotic vaccum cleaner serial interface
  
• School Bus Signals Circuit
  
• Signal braking module
  
• Signal module for model railways adds a high degree of realism
  
• Simple flashing light circuit
  
• Simple flashing light circuit
  
• Simple flashing light circuit
  
• Simple throttle control ideal for railway shuting yards or a second main track line
  
• Simple Traffic Light Controller
  
• Simple train detector using ambient light and a photocell
  
• Simplest R/C circuit
  
• Simulate the Gyralite (dual flashing headlights).
  
• Slot car TV cronograph displays the lap times of your model cars on a regular TV
  
• Snuf simple autonomous mobile robot
  
• Sonar and PIR Sensor Board for TekBot / general robotics
  
• Tactile whisker for TekBot robot
  
• The Coat Hanger Walker - Simple BEAM robot
  
• Three Terminal Regulator Type Throttle (LM350K)
  
• Timed DC Throttle
  
• Timed Uncoupling Ramp Driver (LM555)
  
• Traffic light controller with 20-output sequencing
  
• Train Mounted Camera Battery Charger
  
• Trooper - miniaturized Scout Walker 2 robot
  
• Turnout Anti-Derail Protection Circuits
  
• Two tone train horn
  
• Various radio control schematics
  
• Various Transistor Throttles Cicuit Schematics
  
• Walking robot
  
• Walking robot (PDF)
  
• Wire guidance sensor
  

Motor and general control schematics

• 12 Volt Differential Temperature Controller
  
• 35KHz Magnetic-Radiation Remote-Control
  
• 4 Digit Keypad Switch
  
• 4-bit receiver for DC motor control
  
• 555 Based Simple Servo Controller
  
• 556 Timer Stall-Motor Switch Machine Drivers
  
• 5A H-bridge motor driver based on TIP122 / TIP127 power transistors
  
• 6090 digital decoder schematics
  
• 9V Xenon photoflash controller (PDF)
  
• A Simple Repeater Fan Controller (PDF)
  
• AC Motor Speed Controller
  
• AC switching with TRIAC from TTL
  
• Assorted relay control circuits
  
• Bipolar stepper motor driver based on 74194 chip
  
• Bridge head
  
• Brushless DC electric motor control by CPLD
  
• Charge coupled bi-directional power MOSFET relay (PDF)
  
• Clap activated remote control
  
• CMOS control voltage for firing Crydom Soft-Start Motor Module
  
• CO2 controller for planted tanks
  
• Constant Temperature Circuit
  
• Constant Temperature Circuit
  
• Control 120VAC relay with TTL
  
• Current loop interface
  
• Dark activated switch
  
• DAS1 - 12 Volt 10 Amp Dark Activated Switch
  
• DC Motor Control Circuit
  
• DC Motor Controller using 74 series chips
  
• DC Motor Driver with L6203
  
• DC Motor Reversing Circuit
  
• DC Motor-Driver H-Bridge Circuit
  
• DC Push Button Motor Control Circuit
  
• Delayed Power Circuit using an SCR
  
• Digital logic controller
  
• DIY Power Pulse Controller
  
• Driving a relay with a CPU
  
• DS1821 programmable thermostat
  
• Dual Stepping motor drivers using UDN2540
  
• Electric heater thermostat
  
• Electronic circuit diagram of cell phone SMS remote control device
  
• Electronic Control for DC Motors Using Discrete Bridge Circuits (PDF)
  
• Fan control based on a TL082 opamp and IRF510 power MOSFET
  
• FAN Thermostat controlled by IR remote controller
  
• Finger touch activated switch (PDF)
  
• GSM SMS javljalnik ALSMS-01 (page in slovenian )SMS remote control project
  
• H Bridge controller for DC motors
  
• H Bridge Motor Control Circuits
  
• H-Bridge Circuit
  
• H-Bridge Motor Driver Using Bipolar Transistors
  
• Heating System Thermostat
  
• High And Low Voltage Cut Off With Time Delay
  
• High and Low Voltage Cutout with delay and Music
  
• High current PWM controller based around a 555 timer
  
• HIGH or LOW Power Switch For Lights or Small Motors
  
• Home Automation Over Internet
  
• Homemade Water Drain Pump controller
  
• Hot Water Tank Level Indicator
  
• How to Make a PWM Circuit without a Microcontroller
  
• LDR light/dark activated relay switch
  
• Light / dark activated relay
  
• Light detector
  
• Light Operated Switch
  
• Light switch using LDR
  
• Light/dark detector
  
• Light/Dark Detector drives a relay
  
• Line-powered Xenon flash transmitter (PDF)
  
• Machine vibration triggers hour meter (PDF)
  
• Micro-step driver - connect a bipolar steppe motor to a PC through the parallel port
  
• Microstepping with PBM3960 and TEA3718
  
• Modular relay system
  
• MOSFET based speed controller uses 9 IRFZ40 power MOSFETS
  
• MOSFET H-BRIDGE schematic and theory
  
• Motor speed controllers
  
• MotorDriver V1.0 - Dual DC Motor Driver Board (LMD18200T based, 55V 3A, 6A peak) - PDF
  
• No-Hum Fan Controller
  
• NPN transistor circuit for relay control (relay driver)
  
• One component stepper motor driver
  
• Optically isolated stepper motor controller
  
• Optically isolated TRIAC driver
  
• Over / Under Voltage Cut-Out
  
• PA fan temperature controlled speed motor speed controller
  
• Pulse width modudulator using 555 timer IC
  
• Pulse Width Modulation DC Motor Control
  
• Pulse Width Modulation DC Motor Controller
  
• Push Button Motor Control Circuits
  
• Pushbutton one-shot and latch (PDF)
  
• PWM DC motor control with SG3525
  
• PWM DC Motor Speed Control
  
• PWM motor controller
  
• PWM Motor Speed Controller / DC Light Dimmer
  
• PWM Motor Speed Controller / DC Light Dimmer
  
• PWM Motor/Light Controller circuit diagrams
  
• Radio Remote Control using DTMF
  
• Relatively simple thermostat circuit diagram
  
• Relay circuit for relay control via an RS232 port
  
• Relay circuit using 74LS573 to driver 5V DC relays
  
• Relay controller based on Microchip PIC16F84 (PDF)
  
• Remote Motor Controller
  
• Rolling code 4-channel UHF remote control
  
• Safe Universal Mains Switching Box
  
• Selection of PWM driver circuits for electric DC motors
  
• Serial servo controller
  
• Several stepper motorol control circuits
  
• Shadow activated (or hand wave) motion detector
  
• Simple 120 VAC motor speed controller based on a TRIAC
  
• Simple keypad operated switch
  
• Simple Servo Controller using 555 Timer
  
• Simple temperature regulated FAN speed controller
  
• Simple Two Speed Contactor DC Motor Controller
  
• Smart switch, short press for on, longer press to turn off
  
• Solenoid starter
  
• Solid state relay (PDF)
  
• Solid-state power controller
  
• Sound operated switch
  
• Stepper motor controller
  
• Stepper motor controller
  
• Stepper Motor Controller using 4027 flip-flop and 4070 XOR gate
  
• Stepper Motor Driver using L298 and L297
  
• Stepper motor driver using PIC12F675
  
• Stepper motor driver using PIC12F675 that offers serial port command interface
  
• Stepper Motor Driver using TEA3718/3717
  
• Stepper motor positioner
  
• Switching solenoid driver
  
• Temperature monitor using 741 opamp
  
• Thermal cooling fan controller
  
• Three electronic circuit diagrams for thermal controllers including linear and PWM control
  
• Time Delay Relay
  
• Time Delay Relay II
  
• Touch switch
  
• Touch switch based on CD4011 flip-flop
  
• Touch Switch using 4011 CMOS NAND Gate IC
  
• Touch Switches
  
• Unipolar stepper motor driver based on 74194 chip
  
• Voice activated switch using MC2830
  
• Voltage comparator switch
  
• Water Detector With Sump/Bilge Pump Controller
  
• Water system controller (PDF)
  
• Wireless RF PWM dual motor controller
  

Music related schematics (also see Audio)

• 2 Note Ribbon Controller
  
• 25-pin PC serial port to MIDI synthesizer interface cable
  
• 3 Channel Color Organ
  
• 8 Note Tune Player
  
• 8 note tune player
  
• 9-pin PC serial port to MIDI synthesizer interface cable
  
• A refined Fuzz Face. Schematic and PCB layout.
  
• Amiga MIDI interface
  
• Ampeg SB-12 Portaflex adapted for use as a bass overdrive stompbox
  
• An ultra-flexible tonestack with clean boost. Schematic, photo, and PCB/perfboard layouts.
  
• Apple Mac to MIDI synthesizer interface cable
  
• Apple Macintosh MIDI interface schematic (basic version)
  
• Apple Macintosh MIDI interface schematic (deluxe version)
  
• B. Blender: Blends an effects chain with the input signal. Works well with bass guitar
  
• Bassline synthesizer/sequencer
  
• Big Muff Pi variant using Bazz Fuss as clipping stage. Schematic and and PCB/perfboard layouts.
  
• Boogie MkI adapted for use as a distortion stompbox
  
• CD4049 based distortion. Schematic, PCB/perfboard layout, and photos.
  
• Closer look at the FET booster based on a vintage Fender 12AX7 input stage.
  
• Colour (Sound) Organ
  
• Colour (Sound) Organ
  
• Compact DJ station
  
• Daisy MP3 player project
  
• Digital Guitar Tuner
  
• Distortion effects using an LM386 audio amplifier IC
  
• DIY Serial MIDI Interface (80C51/80C31 Version)
  
• Drawdio - A very simple musical synthesizer that uses the conductive properties of pencil graphite
  
• Drum percussion sensor schematics
  
• Drum Tone Oscillators
  
• Dual parallel buffered effect loops with blend control. Schematic and perfboard/PCB layouts
  
• Electronic metronome
  
• Faux-phaser circuit with LFO and manual (wah pedal) modes. Schematic and and PCB layout.
  
• Fender Princeton adapted for use as a distortion stompbox
  
• FET overdrive developed as a Tube Screamer alternative. Schematic and perfboard layout.
  
• Guitar Fuzz Effect
  
• Guitar fuzz effect
  
• Guitar Reverb Effect Version 2
  
• Guitar Reverb Pedal
  
• Guitar Reverb Pedal
  
• Guitar Tremolo Unit
  
• Guitar Vibrato Unit
  
• Homebuilt MP3 Player
  
• Improved Silicon Fuzz Face. Schematic, build notes, photo, and PCB/perfboard layouts.
  
• Infinite melody for music synthesizers
  
• Liquidator Tube Phaser/Chorus Effect
  
• Lossless portable digital audio player using the Microchip PIC32
  
• Marshall 100W Super Lead adapted for use as a distortion stompbox. Schematic and PCB layout.
  
• Marshall 18W adapted for use as a distortion stompbox
  
• Matchless DC/30 adapted for use as a distortion stompbox
  
• Metronome Circuit
  
• Microcontroller MIDI interface
  
• MIDI Controller Footpedal
  
• MIDI Drum Machine Analog Input Schematic
  
• MIDI drum machine project
  
• MIDI interface / cable tester
  
• MIDI keyboard circuit diagram
  
• MIDI merger schematic
  
• MIDI Pedalboard Encoder
  
• midi2cv8 to Drum Tone Board Connections
  
• Midibox 64
  
• Miniature metronome
  
• MP3 Player circuit schematic
  
• Mr Smooth is a clean boost to mild overdrive effect
  
• Mr. EQ - a simple, yet potent DIY equalizer
  
• Music player built on microcontroller AT91SAM7S256 with ARM core
  
• Musical Instrument (Expandable) Graphic Equaliser
  
• New clipper circuit diagram (based on TL071 opamp)
  
• Octave screamer
  
• Peppermill overdrive - A simple, transparent overdrive. Schematic and PCB/perfboard layouts.
  
• Portable Mixer with high-quality modular design (9V battery powered)
  
• Portable MP3 music player
  
• Practical MS Decoder Circuit
  
• Real-world MIDI interface platform project including circuit diagram and PCB design files
  
• Schematic of a Rockman-like distortion. Schematic and PCB/perfboard layouts.
  
• Serial MIDI interface
  
• Simple Colour Organ
  
• Simple colour organ
  
• Simple line mixer
  
• Simple metronome using LM1458
  
• Simple MIDI switcher
  
• Simple MIDI tester
  
• Simple open source MP3 player with SD/MMC memory card support
  
• Simple Transistor Organ
  
• Sound Effects Generator
  
• Sound Effects Generator 2
  
• Sound Lab Mini-Synth analog music synthesizer
  
• Spring reverb
  
• Spring reverb unit
  
• Spring Reverb Unit For Guitar
  
• Standard MIDI to MIDI interface cable diagram
  
• Supro 16T adapted for use as a distortion stompbox
  
• The 203 Theremin - A Battery-Operated Version of the Wien-Bridge Theremin
  
• Theremax Theramic Circuit Schematic
  
• Theremin
  
• Theremin controller
  
• Tone Filters for Electronic Organs (PDF)
  
• Transistor organ
  
• Treble Booster/Overdrive including a perf board circuit layout
  
• Tube Screamer-based overdrive. Schematic and PCB/perfboard layouts.
  
• Two channel distortion circuit
  
• Ultra Simple Bass Guitar Compressor
  
• Umble - A distortion stompbox, inspired by Dumble amplifiers. Schematic and PCB/perfboard layouts.
  
• Using the Hot Springs Reverb reverberation unit
  
• Versatile FET booster engine. Schematic and perfboard/PCB layouts.
  
• Vocal zapper
  
• Vox AC-30 Top Boost adapted for use as a distortion stompbox
  
• Wave Multiplier for music synthesizers
  
• Zonk Machine and Treble Booster
  

PC related schematics

• 160 Baud ALDL Hardware Interface
  
• 300/1200 baud BAYCOM MODEM (revision and improved)
  
• 3-axis stepper motor controller for PC parallel port
  
• 7 segment rolling display using PC
  
• 8-way relay interface board for PC parallel printer port
  
• 9-pin null modem cable
  
• A Serial Infrared Remote Controller
  
• Analog Signal Acquisition for PC Printer Port
  
• Apple II/II+/IIe IDE Drive Interface
  
• Assorted computer interface circuits
  
• Basic Stamp I & PC Relay Controller
  
• Bell 202 and CCITT V23 Compatible FSK Modem Circuit
  
• Build your own iRDA SIR Transceiver (Dongle) using MCP2120
  
• Building an Infrared Transmitter for Your PC
  
• CCD linear image sensor to PC parallel interface
  
• Circuit for interfacing a relay / solenoid to a PC based on a 2N7000 FET
  
• Circuits to computerize your room/house
  
• Commodore 64 24-bit parallel port interface with 8255
  
• Computer Controlled Frequency Counter/Logic Probe
  
• Computer microphone
  
• Connect other circuits to PC joystick port
  
• Connect two CD-ROM drives to one soundcard
  
• Convert Atari-style joystick to PC joystick port
  
• Dallas DS1620 based USB Digital Thermometer
  
• DB-9 Connector to DB-25 (both RS-232)
  
• DCF77 receiver to PC RS232 serial port interface
  
• Ericsson phone to PC serial port interface
  
• Ethernet interface for Commodore 64 computer
  
• Extremely simple ADC for the PC (parallel port interface)
  
• Fake Joystick circuit
  
• Fax to modem interface
  
• FM radio for a PIC (uses TDA7000 IC which is now obsolete)
  
• FM radio with PC parallel port interface
  
• Game boy camera PC serial interface
  
• General purpose ISA interface card for PC
  
• Get power out of PC parallel port
  
• Get power out of PC RS-232 port
  
• Getting power from RS-232 interface
  
• GPS receiver (Gamin, Eagle etc) to PC interface cables
  
• HAMCOM & SoundCard MODEM using serial- or soundcard audio
  
• HAMCOM (SSTV, RTTY, FAX...) modem using PC-speaker for TX
  
• HAMCOM (SSTV, RTTY, FAX...) modem using serial audio for TX
  
• Headphone driving circuit for soundcards
  
• Hi-Fi PC Speaker System
  
• Homebuilt RS232 LCD Interface
  
• Homemade Serial to Nokia MBus Interface on a PCB, without using Zener diodes
  
• How to construct Garmin GPS receiver interface cables
  
• How to get power from PC to your circuits
  
• I2C printer port adaptor
  
• i2c-tiny-usb, a simple i2c interface for the usb port
  
• iLINK Interface
  
• Interfacing 16x2 character :LCD to parallel port
  
• Interfacing PC sound card to SSB rig
  
• iRDA interface for motherboard using Vishay TFDS4500
  
• Isolated Full Duplex RS232C Interface
  
• Jasmin floppy disk controller schematics
  
• Laptop Computer Serial Port Power Booster
  
• LCD2LPT with LIRC (LCD to LPT printer port) interface
  
• LCD2USB, cheap open source text LCD interface
  
• Linux Infra-red Remote Control (LIRC)
  
• Mac Serial Port (RS-422 DIN-8) to RS-232 DB-25
  
• Mac to HP48 cable pinout
  
• Machine Independent Parallel Interface
  
• MIDI cable for Sound Blaster cards
  
• More accurate PC/AT clock
  
• MS-DOS EEPROM Programmer
  
• New and Improved Sound Card Packet Interface tested with PSK31 and APRS
  
• Null Printer Adapter
  
• Parallel (Printer) Port Interface
  
• PC based digital thermometer based around a Dallas Semiconductor DS1621
  
• PC based Frequency Meter
  
• PC based thermometer based on Dallas DS1621
  
• PC electrically isolated RS422 interface using SN75176B or MAX485
  
• PC electrically isolated RS485 interface using MAX487 or SN75176B
  
• PC interface for point controller
  
• PC ISA board containing a Z80 microprocessor (coprocessor card)
  
• PC ISA Card Random Number Generator
  
• PC parallel port eight DC power switch cam driver two unipolar stepper motors, lights etc
  
• PC speaker volume control circuit
  
• PC thermometer using PC game (joystick) port
  
• PC-based ISA data acquisition and control board
  
• PG31 GPS RS232 GPS development board
  
• PG31 GPS RS232 USB development board
  
• Pic-Plot GPIB to RS-232 converter
  
• Pic-Plot2 GPIB to USB converter
  
• PTT and soundcard interface for the TM255/455
  
• PTT and/or soundcard interface
  
• Radio clock for PC's
  
• Relay interface add-on board for PC
  
• RFID evaluation kit for PC serial port (PDF)
  
• RS232 - Lowe HF-225 interface
  
• RS232 DB-9 switch to flip between two serial ports
  
• RS-232 line monitor and loopback cables
  
• RS-232 Protocol Analyser
  
• RS232 RS485 USB Converter Board
  
• RS232 serial to USB converter cable circuit schematic
  
• RS-232 surge protection
  
• RS-232 to TTL cable
  
• RS232C Level Converter
  
• Sanyo 20EZ monitor circuit diagram
  
• SB-Bus Drivers Introduction and Circuit Diagrams
  
• Schematic of a standard PC joystick
  
• Sega 3D glasses interface circuit diagrams
  
• Serial port temperature datalogger
  
• Serial servo controller for interfacing hobby servos via RS232 to a PC
  
• Serial to parallel converter - connect a large number of digital outputs to a PC parallel port
  
• Short circuit protected power supply from PC 12V supply
  
• Simple Hankel USB oscilloscope for a PC
  
• Simple music synthesizer for an ATARI
  
• Simple Parallel (Printer) Port Interface
  
• Simple PC SmartCard reader
  
• Simple PC thermometer for serial port but using R/C network for measurement
  
• Simple RS-232 serial port buffer circuit
  
• Simple stepper motor driver for PC parallel port
  
• SmartCard PC Emulator
  
• Sound Blaster Microphone Preamplifier
  
• Stepper motor controller for PC parallel port
  
• SWTP PR-40 Printer Interface Schematics
  
• The Great Z80 Computer Project
  
• The KD2BD Pacsat Modem
  
• Thermal fan control circuit designed for overclocked PCs
  
• TiltStick, a motion sensing device (USB interface to accelerometer)
  
• TM-441 9600bps packet modification
  
• Transceiver to PC interface with a hardware DTMF detector and galvanic isolation (PDF)
  
• Transceiver to PC soundblaster interface for digital operating modes (PSK-31, RTTY, SSTV etc)
  
• USB camera circuit
  
• USB LCD/VFD Controller Hardware
  
• USB to parallel port converter using Cypress CY7C68013A- 56PVXC
  
• Using a PC power supply as a benchtop power supply
  
• Using the joystick port as general purpose input
  
• Various sound card interfacing circuit diagrams
  
• Yaesu FT-897 - PC interface (PDF)
  
• Yaesu VX-7 / VX-7R to PC interface
  
• Z80 Computer
  

PDA / music player interfaces and schematics

• 1.5V iPod Microphone (PDF)
  
• Aladin interface
  
• Apple iPod and iPhone dock pinout
  
• Casio calculator interface schematic
  
• Casio datalogger
  
• Design and build your own iPod docking station
  
• DIY iPhone 3G Charger circuit
  
• DIY iPhone Charger circuit
  
• DIY Microphone Cable for iPod Touch (2nd Gen)
  
• Fitting a JTAG interface to an iPAQ 3600
  
• Interfacing ADXL202 accelerometer to PalmPilot
  
• iPod / USB MP3 charger using MC34063 switchmode regulator
  
• Mass storage and printer interface for the FX-700P calculator
  
• Palm Keyboard interface board
  
• Palm PDA based datalogger
  
• Palm Pilot, Palm III, V, VII, VIIx, Handera interface port pinout
  
• PalmPilot turbo boost guage interface
  
• Portable iPod charger
  
• Serial interface adapter for iPod Linux
  
• SHARP palm-top/hand-held to RS232 serial converter
  
• SHARP palm-top/hand-held to RS232 serial converter
  
• TomTom One V3 connector pinout
  
• USB charger for iPod using 7805 linear regulator
  
• Wireless local network for PalmPilot (large PDF)
  

Photography related electronic circuits

• A home-made light-operated camera trigger using the stamp microprocessor
  
• A simple home-made light-operated camera trigger
  
• AI-1 ("All-in-one") Remote - photographic accessory that you can build
  
• Camera remote control system using Basic Stamp
  
• CamTrig - A home-made light-operated camera trigger
  
• Canon DSLR cable shutter release usin 4N25 for optical isolation
  
• Computer controlled EOS camera shutter trigger
  
• Computer Sound Port Shutter Tester
  
• Computerized Shutter Control of Canon DSLRs
  
• Control your camera (Canon DSLR) with your Palm PDA
  
• Darkroom camera shutter timer
  
• Densitometer & Intervalometer projects
  
• Densitometer & Intervalometer projects including hand-drawn block diagrams only
  
• Digital cameras (AGFA, Olympus) to PC (COM) cable pinout
  
• DIY Intervalometer for a Canon SLR camera
  
• Dual cable (serial + USB) for Nikon Coolpix cameras
  
• Electronic shutter release with ultrasonic remote control
  
• Flash Slave Trigger
  
• Flash slave trigger
  
• Flash Slave Trigger for Digital Camera
  
• High speed flash photography for amateur photographers
  
• High-speed flash photography for amateur photographers (includes several circuit diagrams)
  
• Homebrew Wired Remote for Canon EOS 350D Camera
  
• How to Build Your Own Light Meter (PDF)
  
• Infrared remote control with intervalometer function for Nikon cameras
  
• IR Remote Control for Nikon cameras, standard version
  
• Kodak DC-20 camera interface (PIC12C509)
  
• Kodak DC-20 camera interface (PIC16F84)
  
• kShutter: Simple remote shutter for Nikon Coolpix camera
  
• kShutter2: Advanced remote shutter for Nikon Coolpix cameras
  
• Large collection of strobe / photoflash circuit diagrams
  
• Lightning Activated Camera Shutter Trigger
  
• Lightning activated camera shutter trigger
  
• Lightning Activated Camera Shutter Trigger
  
• Making your own RS-60E3 Remote Control for Canon EOS cameras
  
• Nikon Coolpix 950 / 990 / 995 Flash-adapter
  
• Nikon IR-Remote Control based on Atmel ATtiny13
  
• Nikon programmable memote / intervalometer
  
• Programmable Hi Speed Flash & Camera Trigger
  
• Programmable Optical Slave Flash Trigger for Digital Cameras using PIC12F675
  
• Remote shutter (or 'cable release') for SLR and DSLR cameras
  
• Sea & Sea TTL (Motormarine II, SX-1000) Flash Interface (underwater photography flash)
  
• Serial cable for Casio QV-200 digital camera
  
• Simple sound syncronizer / sound activated shutter trigger for amateur photography
  
• Slave flash trigger
  
• Slave Flash Trigger Circuit
  
• Slave flash trigger with counting logic (Silicon Chip Mazine article)
  
• Stop Action 3D-Photography using an audio flash trigger
  
• Timelapse photography with the Canon 10D using a 555 timer based circuit
  
• Universal Exposure Timer and Event Counter
  
• Universal sound and optical slave flash trigger
  

Power supplies and control schematics

• +9V *and* -9V from one battery
  
• 0-14 volt, 0-2 amp current limited variable power supply regulator
  
• 12 Vdc - 120 Vac Inverter Schematic
  
• 12 volt battery monitor
  
• 12 Volt Gel Cell Charger
  
• 12 volt power supply
  
• 12 Volt Switching Power Supply circuit diagram and PCB layout
  
• 12V 30A power supply
  
• 12V Lead-Acid Battery Monitor using LM3914
  
• 12V to 120V Inverter
  
• 12V, 4-AA Cell Differential Temperature Charger
  
• 13.8V 30-40A Power Supply (PDF)
  
• 1A Variable Regulated Power Supply
  
• 200 Watt Modified PC Power Supply 13.5 Volt 14 Amp
  
• 3rd harmonic distortion meter for measuring the quality of AC supply
  
• 5 volt power supply
  
• 500W low cost 12V to 220V inverter
  
• 6V to 12V Converter
  
• 6V to 12V Converter
  
• AC Power Meter
  
• Active Power Zener
  
• Adjustable power supply using LM317
  
• Adjustable Voltage Regulator using a 7805 or other fixed linear voltage regulator instead on LM317
  
• Advanced High Voltage PSU circuit
  
• Alkaline battery charger
  
• Alternative power source for Magellan GPS receivers
  
• Amplified zener regulator
  
• Assorted power source and control circuits
  
• Automatic 12V Lead Acid Battery Charger
  
• Automatic 9V NiCad battery charger
  
• Back And Forth - Bidirectional Bipolar Stepper Motor Driver
  
• Basic 78xx series regulator mains power supply circuit diagram
  
• Basic Power Supply
  
• Basic Solid State Relays
  
• Basic UPS Power Supply
  
• Battery Characterizer
  
• Battery charge for 12V SLA batteries
  
• Battery Charger Ideas
  
• Battery Charger, Current and Voltage Regulated for Sealed Lead Acid batteries
  
• Battery Low Voltage Beeper
  
• Battery Low Voltage Beeper
  
• Battery voltage monitor
  
• Bench power supply
  
• Breadboard supply - very low dropout adjustable power supply
  
• Build A 10 Amp 13.8 Volt Power Supply
  
• Build a breadboard power module for integrated circuits
  
• Build A High Performance Voltage Regulator From Discrete Components
  
• Build A Simple Rechargeable CMOS Battery
  
• Car Ignition Coil Driver from 110V AC
  
• Car Ignition Coil Driver from 12V DC - Can be used as an electric fence
  
• Charge Monitor for 12V lead acid battery
  
• Charger for gel lead acid batteries
  
• Cockcroft-Walton voltage multipliers (PDF)
  
• Compressor-mate power protection for refrigerators, freezers and air conditioners
  
• Controller for hybrid (photovoltaic- wind turbine and diesel engine) power plant
  
• Current booster for 78nn series voltage regulators
  
• DC to AC inverter using a 555 timer
  
• DC Voltage and Current Source
  
• Dual (postive and negative) 12V power supply
  
• Dual Polarity Power Supply
  
• Dual Polarity Power Supply
  
• Dual power supply
  
• Dual regulated power supply
  
• Dynamo Current and Voltage Regulator
  
• Easy power supply
  
• Efficient unipolar stepper motor driver (only uses power when it makes a step)
  
• Expanded Scale Battery Volt Meter
  
• Expanded Scale Battery Volt Meter
  
• Fast NiMH / NiCd Battery charger
  
• Filtering PC bus POWER
  
• Fixed Voltage Power Supply
  
• Fixed Voltage Power Supply
  
• Flyback transformer driver
  
• Fuse blown indicator
  
• Fuse monitor / alarm
  
• Generating -5VDC from +5VDC
  
• Gyrator circuit
  
• High Current Power Supply
  
• High Current Power Supply
  
• High current regulated power supply
  
• High Side Current Monitors (LM358, Zetex - ZXCT-1009)
  
• High voltage DC generator
  
• High Voltage High Current Power Supply
  
• High Voltage High Current Power Supply
  
• High-Voltage Pulse Generator
  
• HV supply: 12VDC in, 12KV out
  
• Inverter, 12 volt unit, MOSFET design
  
• Inverter, A 12 volt unit, Very Basic type
  
• Lead acid battery charger with float
  
• Lead/acid battery charger
  
• Lead-Acid Battery Monitor
  
• LED battery voltage monitor. A fuel gage for your gel cell battery.
  
• Lithium Battery Rejuvinator
  
• LM311 Thermostat circuit diagrams
  
• LM317 Regulator Circuit
  
• LM3914 battery monitor
  
• Low Battery Voltage Cutout Circuits
  
• Low Power LED Voltmeter
  
• Low Power LED Voltmeter
  
• Low Voltage Alarm for batteries and other volatile DC power sources
  
• Low-dropout 12V regulator (LM324)
  
• Machine power loss beepter (PDF)
  
• Multiple voltage power supply
  
• N.O. Magnetic Reed Switch ON /OFF Circuit (SCR equivalent)
  
• Nagative voltage generation using 555 timer
  
• Negative Supply from single positive Supply using 555 timer
  
• Negative voltage generator
  
• Nicad battery charger
  
• Nicad battery charger
  
• NiCad Discharger for Tx & Rx Packs
  
• NiCd Cell Charger
  
• Nine Volt Battery Eliminator
  
• One 9V battery gives +18, +25, +33V
  
• Power reminder beeper (PDF)
  
• Power supply provides +5VDC regulated, +10VDC unregulated and 7.5VAC
  
• Preselect Twin Coil Switch Machine Circuit
  
• Pulse Charger for reviving tired Lead Acid batteries
  
• PWM DC Motor Speed Control
  
• PWM Motor Speed Controller / DC Light Dimmer
  
• PWM Motor/Light Controller
  
• PWM Motor/Light Controller
  
• PWM Motor/Light Controller variants
  
• Regulated 12V supply
  
• Regulated Power Supply Circuits
  
• Simple +5V power supply circuit
  
• Simple Capacitance Multiplier Power Supply For Class-A Amplifiers
  
• Simple constant current source
  
• Simple DC Adapter Power Supply
  
• Simple NiCad battery charger using LM317
  
• Simple power supply
  
• Simple switching power supply
  
• Simple switching power supply (mains operated)
  
• Simple switching regulator (experimental)
  
• Simple voltage booster based on Linear Technologies LT1372, includes PCB design
  
• Single to 3-phase power conversion
  
• Small battery-powered USB charger including circuit diagram and PCB layout
  
• Snowmobile GPS power adapter
  
• Solid state relay circuit
  
• Solid State Tesla Coil/High Voltage Generator
  
• Team digital - SCR16 - Twin Coil Switch Machine Adapter
  
• Temperature Controlled Nicad Charger
  
• Temperature Controlled NICD Charger
  
• Tesla coil / HV generator
  
• Transformer Secondary Voltage Reduction
  
• Transformerless Power Supply
  
• Transformerless Power Supply
  
• TTL power supply with crowbar protection
  
• Turn an ordinary wall wart / plug-pack into a regulated device
  
• Unplugged power cord alarm
  
• Unregulated power supply
  
• USB charger
  
• Using Pass Transistors Beef Up Voltage Regulator current output
  
• Valve power supply
  
• Variable Dual Lab Power Supply
  
• Variable power supply
  
• Voltage and current regulated power supply
  
• Voltage converter
  
• Voltage doubler
  
• Voltage Inverter
  
• Voltage Inverter
  
• Voltage inverter
  
• Voltage Inverter using 555 Timer
  
• Voltage Inverter using LM380 audio amplifier IC
  
• Voltage Monitor using UA741 operational amplifier
  
• Voltage monitor with LED indicator
  

Radio-frequency schematics (also see Transmitters)

• 1 Watt 2.3 GHz RF Amplifier Using a MRF2001
  
• 1.5 W RF Power Amplifier type class-C
  
• 10 meter (28MHz) band RF amplifier
  
• 10 MHz WWV Receiver
  
• 10.7MHz FM detector
  
• 10W HF linear amplifier
  
• 136 kHz direct conversion receiver
  
• 14MHz SSB 10mW Transceiver
  
• 15M CW Transceiver Design
  
• 160m mini portable End Fed Half Wave Tuner - MkII
  
• 175KHz inductive pulse receiver (PDF)
  
• 18 dB LT1253 DDS Amplifier
  
• 2.3 GHz Power Amplifiers
  
• 20 Meter CW Transceiver
  
• 20 meters CW QRP Transceiver (PDF)
  
• 20 Watt GaAaFET Power on 2.3 GHz
  
• 200-400 MHz voltage controlled oscillator (PDF)
  
• 20dB VHF Amplifier
  
• 222 MHz Transverter
  
• 23 dB Bipolar DDS Amplifier
  
• 2304 and 3456 MHz Power Amplifiers
  
• 27MHz transmitter
  
• 2M - 20M transverter
  
• 2m (144MHz) Dual Gate FET Low Noise Amplifier
  
• 2N2222 40 Meter CW/DSB Transceiver
  
• 30 Meter, Discrete Component CW Transceiver Built Manhattan-style
  
• 30 W Digital Wattmeter for RF (0-500MHz)
  
• 30 watt FM linear amplifier
  
• 300 baud RF modem circuit schematic
  
• 30M Direct Conversion Receiver Project
  
• 30M PSK31 Transceiver
  
• 3W HF QRP linear amplifier
  
• 4 channel 433MHz remote control transmitter / receiver based on SM5162 and SM5172 chips
  
• 40 Meter Band Direct Conversion experimental receiver
  
• 40 Meter Popcorn Superhet Receiver
  
• 40 Segment LED S-Meter
  
• 40 to 6 Meter "No Tune" Transverter
  
• 40m band direct conversion receiver
  
• 42 Mc Band to 88 Mc Band (retrofit converter) Project
  
• 450-2000KHz AM receiver (ZN414)
  
• 455 Khz MF to AF converter used for DRM reception in a Yaesu FRG-100 receiver
  
• 45-860MHz Radio receiver based on UV916-tuner
  
• 49MHz walkie-talkie
  
• 5 tubes SSB QRP Transceiver for 20m Ham band
  
• 5 watt, 80 meter QRP CW Transceiver
  
• 50 MHz Receiver based on MC3372
  
• 500mW HF linear amplifier
  
• 500W HF linear amplifier
  
• 50MHz converter project based on a NE602/SA602/NE612
  
• 50MHz RF Power Amplifier using BFG97
  
• 56K RF Modem
  
• 6 Meter SSB transceiver
  
• 60-120MHz FM receiver with AFC
  
• 60W Linear amplifier using IRF840 power MOSFET
  
• 60W RF linear amplifier using IRF840
  
• 6m SSB & CW QRP transceiver
  
• 73MHz remote controller hallogen light
  
• 75 Meter QRP SSB Transceiver
  
• 78-80 MHz Superfast Scanner using a DDS (direct digital sythesizer)
  
• 7MHz SSB Transceiver
  
• 80 Meter CW ARDF receiver
  
• 80 meter direct conversion receiver
  
• 80m band direct conversion receiver
  
• 80m SSB & CW QRP superhet transceiver
  
• A compact L-match ATU for portable use
  
• A Multimode Phasing Exciter for 1 to 500 MHz from ARRL (PDF)
  
• Active antenna 1 to 20dB, 1-30 MHz range
  
• Active Antenna AA-7 HF/VHF/UHF, 3-3000MHz
  
• Active Antenna Experiments
  
• Active Antenna for AM-FM-SW
  
• Advanced VHF power meter (PDF)
  
• Aircraft Radio Communications Receiver
  
• AM BCB radio receiver
  
• AM receiver circuit diagram
  
• AM receiver for aircraft communications
  
• AM Short Wave Broadcast Receiver circuit diagram
  
• AM to FM conveter
  
• AM/FM/SW active antenna
  
• AM-Receiver for Aircraft communication (118.250MHz)
  
• An end-fed antenna, L-match coupler and resistive bridge for HF
  
• An Inexpensive Tone Encoder
  
• Assorted RF circuits
  
• Audible S-Meter
  
• Aviation band receiver
  
• Basic 10GHz / 24GHz gunplexer / gunn diode control circuit (PDF)
  
• Basic RF oscillator
  
• Basic Vox Circuit
  
• Bi-Directional 2.4 GHz One Watt Amplifier
  
• Bi-Directional 900Mhz One Watt Amplifier
  
• Bipolar transistor RF mixer
  
• Bootstrapping a Phase Locked Loop for Better Performance
  
• Broadcast-Band RF Amplifier
  
• Bug detector / countersurveillance monitor
  
• Bug detector with beep using 7413 or 74LS13
  
• Build a COS Detector to detect the presence of a carrier on a receiver
  
• Build a good GaAs FET preamp for 2 meters, 222MHz or 440MHz
  
• Car radio tunes the amateur bands
  
• Cascode 7 Experimental Receiver
  
• Cascode Hybrid-Based WWV Receiver for 5 MHz
  
• CB (27MHz citizens band) 2.5W transmitter
  
• CB (27MHz citizens band) receiver
  
• Class B series modulator
  
• Class E Power Amplifier Design (136KHz operating frequency)
  
• CMOS RF PLL sythesizer
  
• Compact 20 - A 14 MHz Direct Conversion Receiver
  
• Convert 2m VHF FM PMR transceiver Motorola Radius M110 into an amateur radio
  
• Converter to Hear Amateurs on your FM Radio
  
• Converter to yune six metres on your two metre receiver
  
• COR Carrier Delay timer / Hang Timer
  
• Crystal Radio
  
• Crystal radio circuits including diode performance comparison
  
• DC40 - 40M Direct Conversion receiver
  
• Deluxe Direct Conversion Reciever
  
• Demodulator Schematic/Design using Gilbert Cell Mixer
  
• Digitally tuned radio board to create an embedded FM radio controlled by a Mega128
  
• Direct Crystal radio receiver examples
  
• Direction finder system
  
• Dopler RDF (radio direction finder) circuit
  
• Electroluminescent Receiver Kit includes circuit diagram
  
• Electronic Eavesdropping Devices Detector
  
• Electronic Eavesdropping Devices Detector (bug detector)
  
• Experimental DSB/CW QRP rig for 20 and 40 meter bands (PDF)
  
• External antenna for the GPS-38, Magellan 2000, or Eagle Explorer GPS receivers
  
• FM radio active antenna
  
• Four channel RF remote control
  
• Four Channel Wireless Transmitter and Receiver using RF modules (PDF)
  
• Galvanic isolated CAT & audio interface for amateur radio
  
• Generic VHF power amplifier
  
• GPS jammer
  
• Harmonic oscillator
  
• HF 10 watt amplifier for 18MHz using a 2SC1969/2SC1944 transistor
  
• HF/6M Antenna Tuner Preselector and Antenna Switcher
  
• HF/VHF mini portable antenna tuner
  
• HF/VHF portable antenna tuner
  
• High quality AM through your FM stereo
  
• High-Performance Direct-Conversion Receivers from ARRL (PDF)
  
• High-Performance, Single-Signal Direct-Conversion Receivers for ARRL (PDF)
  
• Homebrew 20m CW Transceiver
  
• Homebrew 30m CW Transceiver
  
• Homebrew 40m CW Transceiver
  
• Homebrew 6m DSB Transceiver
  
• Homebrew 6m SSB/CW Transceiver
  
• How to Build a 300MHz AM, RF Remote Control System
  
• ICOM CI-V interface with RS232 RTS to PTT
  
• Improved AM-Receiver for Aircraft communication
  
• Improved CMOS RF PLL sythesizer
  
• Improved FM Stereo Modulator
  
• inexpensive high speed microwave data link using an Alpha Gunnplexer for 10 Mbps data rate
  
• Junk Box NDB Low Pass Filter
  
• K8IQY's Original 2N2/40 CW Transceiver Rig
  
• Kenwood TR-7950 manual & schematics (PDF)
  
• KL 400 RF linear amplifier
  
• LF to HF Converter
  
• Linear FM 50 watt amplifier with BLY90
  
• Linear FM 50Watt with BLY90
  
• Low Frequency Circulator/Isolator Uses No Ferrite or Magnet (PDF)
  
• Low Power RF ID Transponder (PDF)
  
• MC13136 based narrow band receiver
  
• Medium Frequency TRF Receiver
  
• MF and HF Receive Antenna Splitter
  
• Morse Code Beacon Keyer
  
• Multiplier Generates Odd Harmonics (PDF)
  
• MW Enhanced Crystal Receiver using 741 IC
  
• MW/SW Radio receiver
  
• Novel crystal set requires no antenna, earth
  
• One transistor FM receiver
  
• One transistor regenerative receiver
  
• One Watt 2.45 GHz Linear Amplifier using RF Micro Devices RF2126
  
• One watt class-C RF amplifier (PDF)
  
• Op Amp Radio
  
• Op-amp based radio receiver
  
• Op-Amp Radio
  
• Phase Locking and Tuning
  
• Phase-Locking ULNs for Optimum Performance
  
• Phasing SSB exciter
  
• PLL synthesized FM radio that can decode DTMF
  
• Pocket sized 20m (30m) CW QRP transceiver
  
• Popcorn Direct Conversion Main Frame
  
• PSK Transceiver - Unique transceiver design does not use a SSB transmitter
  
• Q-multiplier
  
• QRP - Circuits for measuring RF Voltage, RF Current, RF Power, SWR
  
• QRP Antenna Tuner
  
• R2T2 Haywire Home Station
  
• Radio Wave Alarm
  
• Receive Loop Preamplifier for LF reception
  
• Receiver based on NE602
  
• Receiver building blocks
  
• Regenerative receiver for the AM broadcast band using two transistors
  
• Regenerative Short Wave Radio
  
• Regenerative shortwave receiver
  
• RF Actuated Keying Monitor
  
• RF front-end for triple conversion GPS receiver (PDF)
  
• RF Isolator Uses Differential Amplifiers
  
• RF noise bridge for HF
  
• RF Power Amplifier Module using Toshiba S-AV10H
  
• RF Power meter / dummy load
  
• RF preamp circuit diagrams
  
• RF Sniffer under 0.5MHz to above 500MHz
  
• RTTY terminal unit
  
• RX3302 receiver module schematic
  
• SA602, SA612 RF Mixer
  
• SCA Adapter - listen to advertisement free background music on FM broadcast radio
  
• SCA Subcarrier Demodulator for FM broadcast stations
  
• Send Morse on your VHF Rig
  
• Sensitive LW/MW/SW Shortwave general coverage receiver
  
• Simple 40 meters CW QRP Transceiver (PDF)
  
• Simple CW identifier for a FM repeater (PDF)
  
• Simple Dual Band SSB Transceiver (20/40 meters)
  
• Simple RIT circuit based on a 2N7000 FET
  
• Simple wireless radio data link
  
• Smooth Tone Clickless CW Sidetone Generator
  
• Some experiments with active or voltage probe antennas (VPA)
  
• SOP direct conversion receiver
  
• SOP receiver (PDF)
  
• SSB linear amplifier made from a bunch of 2N2218 transistors
  
• SSB Receiver / Exciter and Linear amp
  
• Stacked Torroid VFO Experiments 2008
  
• Subcarrier adapter to listen to hidden subcarrier signals on FM radio
  
• Super 80 ultra-simple SSB receiver for 3.5 MHz a basic superhet
  
• Super improved AM-Receiver for Aircraft
  
• Super Scanner 45-860MHz with 0.01Hz stepsize
  
• Superior TV-tuner receiver 45-860MHz in 2500Hz step
  
• Superregenerative 27MHz receiver
  
• SW30+ 30 Meter CW Transceiver
  
• Switching Diode Frequency Doublers (PDF)
  
• SWR bridge covering HF to VHF
  
• Synthesized HF receiver
  
• TBA120 narrowband FM receiver
  
• TDA7000 receiver
  
• The MRX-40 Mini Receiver (PDF)
  
• TR1001 868.35 MHz Hybrid transceiver schematic
  
• Two Diode Odd-Order Multiplier
  
• Two Transistor Reflex Radio
  
• TX Module Combiners (copied from commercial circuits)
  
• UHF Preamplifier covers 450MHz - 800MHz based on MPSH10 / BF180 / BCY90
  
• Universal USB digimode interface supports CAT (Yaesu), CI/V (Icom) and RS-232 (Kenwood) units (PDF)
  
• USB / CAT (CI-V) adapter tested with FT-8900, FTB-9800, VX-7R, VX-7, FT-817 and IC- 706MkIIG
  
• Variable Bandwidth CW Filter
  
• Variety of receiver converter projects
  
• VFO from 2001 ARRL Handbook, page 14.20
  
• VFO from 2001 ARRL Handbook, page 17.74
  
• VHF 6 Meterband RF amplifier
  
• VHF receiver converterer
  
• VLF radio receiver schematic
  
• VLF Upconverter for Shortwave Receiver
  
• Wave Bubble - A design for a self-tuning portable RF jammer
  
• Wave Bubble self-tuning portable RF jammer
  
• Wee Willy 75 Meter DSB Transceiver Project
  
• Wideband SWR meter
  
• Wideband VHF/UHF/SHF 22dB RF preamp with MAR-6 or MAR-8 (MSA-0885)
  
• WLW 500KW Transmitter Schematic
  
• Yaesu band decoder schematic
  
• Yaesu FT-736R doppler compensation
  
• ZN414 receivers
  

Solar-power schematics

• 12 Volt 20 Amp Solar Charge Controller
  
• 1381 solar engine
  
• AA Battery Solar Charger
  
• AA battery solar charger
  
• Buck Mode Switching Regulator for Solar Applications
  
• Build a DIY solar iPod charger
  
• Converter that enables long cable wiring for pyranometer
  
• LED7 solar tracker
  
• Measure solar radiation on an Ubuntu Server
  
• Photovoltaic Solar Battery Regulator and Load Controller
  
• Portable solar battery charger
  
• Remote Solar LED light
  
• SCC2 10 Amp Solar Charge Controller
  
• SCC2 10 Amp Solar Charge Controller
  
• Self Powered Solar Box Furnace
  
• Sensor Electronic Tracker with H-Bridge Drive
  
• Sensor Electronic Tracker with Simple Solar Charge Controller
  
• Shunt-mode Solar/Wind Charge Controller
  
• Solar cell battery charger circuit diagram
  
• Solar cell Nicad charger using Maxim MAX639
  
• Solar charge controller
  
• Solar Charged LED Flashlight
  
• Solar energy meter
  
• Solar Panel Charge Controller / Low Voltage Disconnect Circuit
  
• Solar Panel Charge Controller / Low Voltage Disconnect Circuit
  
• Solar Panel Charge Controller / Low Voltage Disconnect Circuit (SPC1)
  
• Solar Panel Current Meter
  
• Solar Panel Current Meter
  
• Solar Powered Night Light
  
• Solar Powered Reading Lamp
  
• Solar robots
  
• Solar switching regulator as published in Silicon Chip Magazine January 1994 Part 1/2 (PDF)
  
• Solar switching regulator as published in Silicon Chip Magazine January 1994 Part 2/2 (PDF)
  
• Solar Tracker
  
• Solar tracker
  
• Solar tracking control system
  
• SPC2 6 Amp Solar Power Center
  
• SPC2 6 Amp Solar Power Center
  
• SPC3 9 Amp in / 10 Amp out Solar Power Center
  
• Zener-based solar engine
  

Telephone and intercom related schematics

• 1-line telephone status indicator powered from a 3V battery (PDF)
  
• 4-line telephone status indicator that is polarity independent (PDF)
  
• 8-line intercom system using 89C51 microcontroller
  
• 900MHz cordless phone bug
  
• Assorted telephone circuits (ring generator, in-use indicator, audio interface)
  
• Audio Visual Indicator for Telephones
  
• Caller ID decoder (requied Postscript file viewer and/or Ordcad schematic capture)
  
• Cellular Phone calling Detector
  
• Cellular Phone calling Detector
  
• Cellular Phone calling Detector
  
• Cellular Phone calling detector (detects RF field)
  
• Cordless phone backup power source using LM317L
  
• Cut phone line detector
  
• Cut Phone Line Detector
  
• Cut Phone Line Detector
  
• Cut Phone Line Detector
  
• Cut telephone line detector
  
• Detecting a telephone ring signal
  
• Digisound ring modulator
  
• Digital/Standard Phone Line Tester
  
• DSL / ADSL phone line filter
  
• FM Telephone Bug
  
• FM Telephone Bug
  
• FM Telephone Bug
  
• FM telephone line bug transmitter (88MHz to 94MHz)
  
• Greek telecard reader
  
• High Quality Intercom using LM380 amplifier IC
  
• Hold function for Telephone
  
• Home made PBX / PABX
  
• Incoming call indicator (ZIP file)
  
• Infinity bug for remote telephone surveillance
  
• Isolated Telephone Interface
  
• Isolated Telephone Interface (phone tap) for tape recorder, PC sound card etc
  
• Line in use indicator that handles two independent phone lines (PDF)
  
• Low cost intercom using transistors
  
• Off line Telephone tester
  
• Phone "Hold" With Music
  
• Phone Broadcaster / telehone bugging device circuit diagram
  
• Phone Busy Indicator
  
• Phone Busy Indicator
  
• Phone Busy Indicator
  
• Phone In Use Indicator circuit diagram
  
• Phone in-use (manually activated)
  
• Phone In-Use Light
  
• Phone line in use indicator
  
• Phone line indicator
  
• Phone line to audio interface
  
• Phone Off-Hook Indicator using CD4049 hex inverter
  
• 'phone rang' indicator light
  
• Phone ring circuit schematic using a piezo buzzer for sound output
  
• Phone to audio interface for SSI202 input
  
• Phone-In-Use indicator
  
• Remote Telephone Bell Ringer
  
• Ringing Phone Light Flasher
  
• Ringing Phone Light Flasher
  
• Ringing Phone Light Flasher using optocoupler and relay
  
• Simple alarm with telephone dialler interface
  
• Simple circuit to connect telephone equipment to audio mixer
  
• Simple intercom
  
• Simple Phone Tap
  
• Simple Phone Tap Circuit
  
• Simple Phone Tap circuit diagram
  
• Simple Skype VoIP analog adapter
  
• Simple speakerphone
  
• Simple telephone line tap for intercepting telephone calls
  
• Smart Phone light
  
• Soft Musical Telephone Ringer
  
• Soft musical telephone ringer
  
• Talking phone dial monitor (PDF)
  
• Taxi phone automatic dialler
  
• Telephone amplifier
  
• Telephone amplifier
  
• Telephone auto-dialler (useful for an alarm dialler)
  
• Telephone Hold Button
  
• Telephone Hold Button
  
• Telephone Hold Button circuit
  
• Telephone in use light
  
• Telephone Line Filter / Protector
  
• Telephone Line Monitor
  
• Telephone line monitor
  
• Telephone line monitor
  
• Telephone line simulator
  
• Telephone music on hold interface
  
• Telephone privacy adapter
  
• Telephone Record Control using 2N4360, 2N2222 and 2N2102
  
• Telephone Recorder
  
• Telephone Recorder
  
• Telephone recorder to record phone conversations automatically
  
• Telephone ringing circuits
  
• The 89C51 PABX
  
• The Link 4+0 - Internal Intercom (Doesn't offer external line access)
  
• The Link A2B+1 (the Link Telephone Intercom - DTMF version)
  
• The Original 2 Phone Intercom Link Design
  
• Universal telephone hold
  
• Use old telephones as an intercom
  
• Wireless Telephone Bug
  

Test equipment circuit diagrams

• 10Hz - 100KHz D.D.S. Function Generator
  
• 2.5 GHz Frequency counter
  
• -20 dB Couplers for use with a with a spectrum analyzer or other sensitive detector
  
• -20 dBm, 14.060 MHz Precision Signal Source
  
• 220V live wire-in-wall scanner
  
• 250MHz RF Generator with 1kHz display resolution
  
• 3 in one tester (audio, tone generator, diode/circuit tester)
  
• 555 go / no-go tester
  
• 555 Timer IC Tester
  
• 5Hz to 500KHz frequency meter
  
• AD9850 DDS daughterboard
  
• Audible Logic Probe based on LM339 operational amplifier
  
• Audio Millivoltmeter
  
• Audio Test Oscillator
  
• Automatic heat limiter for soldering iron
  
• Battery Tester for 1.5 and 9V
  
• BCD readout frequency counter
  
• Beeper to find short circuits
  
• Beeper to find short circuits (continuity tester)
  
• Build an inexpensive Hall effect Gaussmeter
  
• Capacitance meter
  
• Capacitance meter - precision meter for small capacitors
  
• Capacitance meter that connects to multimeter
  
• Connection tester for checking solder joints and other connections
  
• Conrad Electronics MM3610D multimeter cable pinout
  
• Contactless Mains Voltage Indicator
  
• Contactless Mains Voltage Indicator
  
• Continuity tester
  
• Continuity tester
  
• Continuity tester 2
  
• Continuity Tester based on 4 x 2N3904 and 1 x 2N3905 transistors
  
• Continuity tester using transistors
  
• Crystal tester
  
• Crystal tester that covers a range of 32kHz to 24MHz
  
• DCC Ammeter using ZXCT1009 current monitor
  
• DDS from 1-60 MHz with built-in amplifier and variable output level using Analog Devices AD9851
  
• Design for a slightly more expensive Gaussmeter
  
• Digital SWR / Power Meter
  
• Digital voltmeter (DVM)
  
• Digital Voltmeter using ICL7107
  
• Digital Wattmeter, measures from nanowatts to kilowatts using AD8307, PIC16F876, LCD Display
  
• Dip Oscillator for HF
  
• Distortion Analyser
  
• Elecraft XG2 receiver test oscillator (PDF)
  
• Electric field & leakage detector
  
• Electronic Circuit for Crystal Parameter Measurement
  
• EMF field probe (electromagnetic field probe) covering up to 100kHz
  
• ESR Meter
  
• Exclusive 2.5 GHz Frequency Counter with Blue 2x16 LCD display
  
• Field Strength Meter (FSM) covers 2Mhz - 1Ghz with peak reception at 3-200Mhz
  
• Field strength meter for the 137 kHz band
  
• Fixed Frequency "Tuner Dipper"
  
• Fluke 8010 / 8012 Interface
  
• Frequency and capacitance meter
  
• Frequency Counter / Timer / Logic Tester
  
• Frequency counter measures to 2.5 GHz and offers LCD display
  
• Full Featured Transistor Tester
  
• Function generator based on 8038PCD function generator IC
  
• Function generator based upon 8038 waveform generator IC
  
• Grid dip meter
  
• Ground Fault Indicator
  
• Heathkit signal generator user manual and circuit diagram
  
• High Impedance Voltmeter
  
• High Resistance Voltmeter
  
• Homebrew signal generator tunable from 3 to 30 Mhz
  
• Improved DCC Ammeter (2009) using Zetex ZXCT1009 current monitor
  
• In-circuit electrolytic capacitor checker
  
• In-circuit electrolytic capacitor tester
  
• Inductive meter adapter to measure inductance using a frequency counter
  
• Latching Continuity Tester to help find intermittent faults, has quite a few innovative features
  
• Latching continuity tester using 4093
  
• LC meter with LCD display for readout
  
• LCD Frequency Counter
  
• LCD frequency counter (PIC16F84)
  
• Led display digital Voltmeter using ICL7107
  
• Line Output / Flyback transformer tester
  
• Linear Resistance Meter
  
• Linear Resistance Meter
  
• Linear scale analog watt meter / RF power meter
  
• Live line detector
  
• Logic probe
  
• Logic probe
  
• Logic probe based on CMOS 4001 chip
  
• Logic probe with 7-segment display based on 74LS00 and 74LS47
  
• Logic probe with pulser
  
• Low Power Antenna Analyzer and ATU Tuning Aid
  
• Low-Cost Phase Noise Measurement
  
• Microphone Circuit Test Oscillator
  
• Mini DDS (direct digital synthesizer) using an Analog Devices AD9832 (12MHz maximum frequency)
  
• Mini tester: Handles continuity testing, resistor testing, capacitor testing and diode testing
  
• Miniscope - simple all-valve 1-inch CRT oscilloscope
  
• MOSFET tester for N-type MOSFET transistors
  
• MOSFET transistor tester
  
• Multi wire cable tester that handles up to eight conductors
  
• Opamp Design and Test Board
  
• Optical ballistic chronograph for measuring projectile velocity
  
• Oscillopscope triggering circuit for recording long transients at fast sweep speeds (PDF)
  
• Oscilloscope testing module (huntron circuit)
  
• Oscilloscope testing module (Huntron circuit) that shows Lissajous patterns
  
• Panel Mounting Radio Frequency Counter
  
• PCB VSWR bridge
  
• Philips SB-6668 frequency counter upgrade
  
• PIC based frequency counter
  
• PIC logic probe with pulser
  
• PIC16F84 based diode tester
  
• Picoammeter circuit schematic with 4 ranges using CA3420
  
• Pink Noise Generator for Audio Testing
  
• Poor man's frequency counter
  
• Precision audio millivoltmeter
  
• Precision Frequency Marker
  
• Precision VXO for Crystal Characterization & Matching
  
• Pulse Reading Logic Probe
  
• Pulse Reading Logic Probe
  
• Quickie servo tester for testing servo motors (based on Atmel AT90S2343)
  
• RCM710 electronic scale, technical manual including schematic
  
• Resistor decade box
  
• Return Loss Bridge
  
• RF field strength meter
  
• RF Power Meter for the QRP measures up to 25 watts
  
• Schematics and C code for a 0-5V PIC LCD volt meter
  
• Schematics and C code for a PIC frequency counter operating up to about 50 MHz (7 segment)
  
• Schematics and C code for a PIC frequency counter operating up to about 50 MHz (LCD)
  
• Self Oscillating Amplifier for Distortion Testing
  
• Self-powered Fast Battery-Tester - Tests 1.5 to 15 Volt cells
  
• Sensor to display, built with thermistor, 12-bit ADC, 89S52 and LED display
  
• Service monitor / deviation meter circuit
  
• Servo Motor Test Circuit (LM555)
  
• Signal Tracer and Injector
  
• Simple diagnostic tool for use on repeaters in the field
  
• Simple electronic S meter
  
• Simple Frequency Counter
  
• Simple Ground Loss bridge for Ground Loss Measurement at LF
  
• Simple Inductance Meter
  
• Simple light sensor adapter for oscilloscope
  
• Simple Ph Meter
  
• Simple polarity detector
  
• Simple Polarity Tester
  
• Simple test equipment to build
  
• Single chip digital voltmeter using ICL7129
  
• Sound pressure level meter
  
• Spectrum analyzer Mk 1
  
• Spectrum analyzer Mk 2
  
• Square wave oscillator (555) for test applications
  
• Stereo Test Tone Generator
  
• Stereo Test Tone Generator
  
• SWR Bridge 1 to 1000 Mhz (1GHz)
  
• TDR cable reflection tester (Time Domain Reflectometer)
  
• TDS/PPM Meter for measuring of the amount of salts in a solution
  
• The u-counter, a PIC based programmable frequency meter (PDF)
  
• Thermistor Thermometer: LCD version
  
• Time Domain Reflectometer (TDR)
  
• TinyScope - simple all-valve 1-inch CRT oscilloscope
  
• Transistor tester and signal injector
  
• Transistor tester using 555 timer and 4027
  
• Triple Stroboscope
  
• True RMS Watt Meter
  
• TTL pulse counter/logic probe
  
• TTL Pulse Reading Logic Probe
  
• TXTVb - 70cm ATV Test Generator (PDF)
  
• UHF signal generator
  
• Ultra-simple Voltage Probe
  
• Ultra-simple voltage probe
  
• Universal frequency counter & voltage meter
  
• UTP Cable Tester
  
• VCR Tuner Based RF Spectrum Analyzer Schematic
  
• VHF signal generator
  
• Wire tracer
  
• Wireless Frequency counter
  
• XTal Tester for testing quartz crystals based on a pair of BC550C PNP transistors
  
• Z80 controlled Viscometer project
  
• Zener diode tester based on a 555 timer