Alarms and security related schematics

• Intermittent alarm generator
  
• Burglar alarm
  
• Moisture alarm
  
• Automatic Entry Control System
  
• Fridge door alarm
  
• Ultrasonic remote control & alarm system
  
• Wire loop alarm
  
• Proximity alarm
  
• Electronic lock
  
• Door knob alarm (PDF)
  
• Water seepage alarm (PDF)
  
• Micro-power over temperature alarm (PDF)
  
• Personal silent alarm system
  
• Active IR motion detector
  
• A Basic RF Transmitter for PIR Sensors
  
• PIR motion detector
  
• Simple alarm system
  
• Home security project
  
• 5 Zone alarm circuit
  
• Miniature loop alarm
  
• Novel Buzzer
  
• Gate alarm circuit
  
• Modular Burglar Alarm
  
• Motorcycle alarm
  
• Enhanced 5 Digit Alarm Keypad
  
• Enhanced 4 Digit Alarm Keypad
  
• RF Alarm
  
• Single Zone Alarm
  
• Water Activated Alarm
  
• Water level alarm
  
• Perimeter monitor
  
• Digital combination lock
  
• Alarm control keypad
  
• Almost Ultrasonic Motion Sensor
  
• Touch activated alarm system
  
• Combination Lock (Simple Version)
  
• Combination Lock (PIC16F84)
  
• Low power RFID transponder
  

Audio power amplifier schematics

• 100W Amplifier
  
• 18W Audio amplifier
  
• 25W MOSFET amplifier
  
• Headphone amplifier
  
• Portable headphone amplifier
  
• 2W amplifier
  
• 4W amplifier
  
• 8 watt audio amp
  
• 20W Amplifier
  
• 50W Amplifier
  
• Amplified ear
  
• Two transistor audio amplifier
  
• Personal stereo audio amp
  
• Headphone amplifier
  
• 1.5W Audio amplifier
  
• Low-level audio amp
  
• 10W amplifier
  
• 80W amplifier
  
• LM383 12V Amplifier
  
• 100W Audio amplifier
  
• 100W RMS Amplifier
  
• 2-Channel Power Amplifier
  
• Push-Pull Class A Amp using type 5687 dual triodes
  
• Push-Pull Class A 2A3 Stereo Amp
  
• Single Ended Class A2 SV811-10 Stereo Amp
  
• JLH Headphone Amplifiers
  
• Audio amplifier output relay delay
  
• HeadBanger Headphone Amp
  
• 2W Amplifier
  
• TDA2030 8 Watt amplifier
  
• Headphone distribution amp
  
• Headphone monitor amp
  
• Bi-Directional 2.4 GHz One Watt Amplifier
  
• Bi-Directional 900Mhz One Watt Amplifier
  
• 20 Watt GaAaFET Power on 2.3 GHz
  
• 1 Watt 2.3 GHz RF Amplifier Using a MRF2001
  
• 2.3 GHz Power Amplifiers
  
• 2304 and 3456 MHz Power Amplifiers
  
• 16 Watt amplifier
  
• 8 Watt amplifier
  
• Power amp schematic (PDF)
  
• 20 Watt Class-A Power Amplifier
  
• El-Cheapo - A Really Simple Power Amplifier
  
• Single Chip 50 Watt / 8 Ohm Power Amplifier
  
• Hi-Fi Headphone Amplifier
  
• 100W Guitar Amplifier
  
• Death of Zen (DoZ) - A New Class-A Power Amp
  
• Soft-Start Circuit For Power Amps
  
• Thermo-Fan To Keep Your Amp Cool
  
• Audio Amp Output Power Limiter
  
• 55W (Originally 75W) Power Amplifier
  
• 300W Subwoofer Power Amplifier
  
• 20 Watt / Channel Stereo Power Amplifier
  

Audio preamp circuits

• mu-stage microphone preamp
  
• Solid state microphone preamp
  
• Phono preamp
  
• Masthead preamp
  
• Microphone amplifier
  
• RIAA phono amplifier
  
• Simple microphone preamplifier
  
• Tube microphone preamp
  
• Simple Stereo Electret Microphone Preamplifier
  
• Simple Stereo Electret Microphone Preamplifier
  
• Phono Preamp
  
• Simple microphone preamplifier
  
• ECM Mic preamp
  
• Hi Fi preamp
  
• Balanced microphone preamp
  
• Audio preamp
  
• Electret mic amplifier
  
• Audio preamplifier
  
• Vacuum Tube Microphone Preamp
  
• FET Preamp Cable
  
• Audio preamp
  
• Low impedance microphone amplifier
  
• Hi-Fi Preamplifier
  
• Crown IC-150A Preamplifier (PDF)
  

Automative, car and motorcycle schematics

• Race cart or car datalogger
  
• Analog Tachometer for Gasoline Engines
  
• Headlight On reminder with Light
  
• Flashing High Intensity LED 3rd Brake Light
  
• Car clock
  
• Car message display
  
• Car interval wiper
  
• Safety indicator light
  
• Speed limit alert
  
• Car power supply for MP3 player
  
• Car power supply for MP3 player Mk 2.5
  
• Engine control unit schematics
  
• Portable CD Player Adapter For Car
  
• Car battery charger
  
• Wireless Auto Tachometer
  
• Electronic auto stethoscope
  
• Turn signal alarm
  
• Motorcycle turn-signal system
  
• Cigarette lighter 9V adaptor
  
• PC based EFI programmer
  
• Headlight reminder
  
• Breath Alcohol Tester controlling a car ignition system
  
• Parking sonar
  
• Fuel injector pulse width monitor
  
• BMW R Series Motorcycle Regulator Schematic
  
• 80188XL Engine Tachometer
  
• Simple Car Preamplifier and Artificial Earth
  
• FCD (Fuel Cut Defencer)
  
• Interface between GM's 5 Volt 8192 baud ALDL data stream and a PC serial port
  
• 5301 wideband fuel mixture display
  
• Wide Band Fuel Mixture Display
  
• 3rd brake light
  
• 12V to 9V car coverter
  
• Car Nicad charger
  
• Economy radar detector
  
• Combination lock for car liftgate
  

Data acquisition and data logging schematics

• Datalogger based on 68HC11
  
• Self made data-logger V2.5 (second edition)
  
• Analog input section based on AD9220
  
• uModem 4+4/8 channel A/D board
  
• ADXL202 accelerometer to CV output
  
• Light direction sensor
  
• 12-Bit ADC interface
  
• Digital thermometer
  
• Universal flight controllers / datalogger
  
• Rain detector
  
• Air flow detector
  
• Air flow detector
  
• Strain gauge sensor
  
• ADC0804LCN 8-bit A/D converter
  
• Web-based thermometer project
  
• ADC-x RS232 Interface Schematic (PDF)
  
• Honey Bee counter (PDF)
  
• Capacitance type liquid level measurement (PDF)
  
• Thermostat node schematic
  
• Digital PC Oscilloscope
  
• Ultrasonic Range & Imager
  
• Network of RS485 temperature sensors
  
• Digital compass schematic
  
• Temperature datalogger
  
• Accelerometer Schematic
  
• Serial Port A/D-converter
  
• Centronics port D/A converters and low-pass filter
  
• LCD Thermometer
  
• Wireless Liquid Level Sensing for Restaurant Applications
  
• Ultrasonic range finder circuit
  
• 1-wire barometer
  
• Water-level sensor
  
• Addressable ADC
  
• Wireless weater station
  

Filter schematics

• Voltage Controlled State Variable Filter
  
• Galaxy Noise Filter
  
• RC Notch filter
  
• Low-pass active filter
  
• Filter Circuit for the Earthworm Seismic Data Acquisition System
  
• Active 2nd Order Filters
  
• RC Notch Filter (Twin T)
  
• Multiple Feedback Bandpass Filter
  
• CW filters
  
• Self-tune filter
  
• SSB AF filter
  
• L-Band PHEMT LNA
  
• Helical Resonator Notch Filter
  
• 3KHz low-pass filter plus audio amp (PDF)
  
• Active bandpass filters
  
• Bandpass filters
  
• Narrow band audio bandpass filter
  
• Single-Supply Sallen Key Notch Filter
  
• Single-Supply Twin T Butterworth Low Pass Filter
  
• Inversal notch and bandpass filter
  
• DC Accurate, Active RC Lowpass Filter
  
• Chebyshev Bandpass Filter
  
• Bandpass filters
  
• Chebyshev / Butterworth filters
  
• Biquad Active Bandpass Filter Schematic
  
• "A" Weighting Filter For Audio Measurements
  
• Multiple Feedback Bandpass Filter
  
• 29.85 MHZ bandpass filter schematic
  
• 29.85 MHZ notch filter schematic
  
• LC filter design
  

Games and fun stuff (schematics)

• Visor cradle serial interface
  
• Video ping pong game
  
• Big Mouth
  
• MBC5/CPLD for the GameBoy
  
• GameBoy Camera Parallel Port Interface
  
• Wireless quiz show system
  
• PSX controler to PC MIDI converter
  
• Dreamcast PC serial adapter
  
• GameBoy Cart Programmer
  
• Memory game
  
• 32 Kb x 8 emulator for the GameBoy
  
• Project: NES to Atari 2600 controller interface
  
• Battery Meter for Pinball Machines
  
• Pine Racecar Victory Judge
  
• Interfacing Sony control stick to Empeg
  
• Electronic coin tosser
  
• Electronic craps game
  
• First response monitor
  
• PowerGlove Interface
  
• GameBoy Schematic
  
• GameBoy LCD schematic
  
• GameBoy Power & Cartridge schematic
  
• GameBoy ROM+RAM+MBC1 Cart Schematic
  
• GameBoy MBC1 circuit equivalent
  
• Super GameBoy schematic
  
• Quiz show indicator
  
• Dreamcast interface
  
• Bingo!!! (on your tv)
  
• Slot car TV cronograph
  
• Magic Wand Conjuring Trick
  
• Quiz game circuit
  
• E.S.P. Conjuring Trick
  
• DIT shutterglasses controller
  
• Furby circuit
  
• Archery timer
  
• PIC micro Tetris game
  

Infrared based schematics

• IR detector
  
• USB to infrared adapter
  
• Infrared transmitter for locomotives
  
• IR remote control system for PC
  
• IR Receiver (Amplitude Modulated IR)
  
• IR Transmitter for Audio (Amplitude Modulated IR)
  
• Digibox interface
  
• IR remote control
  
• IR remote control jammer
  
• Long Range Infrared Remote
  
• LCD + IR circuit schematic
  
• Infrared body heat detector
  
• Stereo IR audio receiver
  
• General purpose IR receiver
  
• Wireless IR headphone transmitter
  
• Wireless IR headphone receiver
  
• 40KHz light receiver (PDF)
  
• 40KHz TV-VCR repeater (PDF)
  
• Micro based PIR to IR remote converter
  
• Infrared remote transponder
  
• Build an Infrared night scope
  
• Decoding IR Remote Controls
  
• IR detector
  
• PC IR Remote Control
  
• An Ambient-Light-Ignoring Infrared Active Motion Detector
  
• Infrared Transmitter and Receiver schematic diagrams
  
• Pyroelectric Infrared Sensor
  
• Simple IR transmitter circuit
  
• Simple infra-red detector
  
• Infra Red Switch
  
• IR remote control extender
  
• IR Remote Control Extender Circuit (Mark 2)
  
• IR Remote Control Extender Circuit (Mark 3)
  
• IR Link
  
• IR remote control tester
  
• Infrared repeater
  
• 40khz IR Tester
  
• 555 timer 40khz IR Oscillator
  
• IR detector / emitter
  
• Fire-Stick infrared remote control
  
• Simple infrared remote control
  
• Infrared / Ultrasonic beacon
  
• Implementing Infrared Object Detection
  
• Infrared gate detector
  
• Infrared relay with relay output
  

Laser related power supplies and data transmission

• Laser power supply
  
• Laser transmitter/receiver
  
• Laser harp
  
• Simple laser communicator
  
• LASER listening device
  
• LASER transmitter / receiver
  
• RS-232 Laser Transciever
  
• HeNe laser power supply schematics
  
• Light beam receiver for laser pistols
  
• 12V supply for He-Ne laser
  
• Laser diode transmitter
  
• 20MHz VCSEL 3mW laser test circuit (PDF)
  
• 10MHz to 20MHz laser light detector (PDF)
  
• Micro-power 40KHz burst laser diode driver (PDF)
  
• 40KHz laser burst detector (PDF)
  
• Modulated laser diode tester (PDF)
  
• Laser diode power supply circuits
  
• HeNe laser power supply
  
• Diode Laser Power Supplies
  
• Laser bug circuit
  
• RS-232 Laser Transceiver
  
• Experimental laser data link
  
• Diode Laser Power Supplies
  
• Ar/Kr Ion Laser Power Supply Design
  
• Simple laser communicator
  

LED related schematics

• Variety of LED circuits
  
• Winking LEDs
  
• LED flashing light
  
• LED initials
  
• Color fade
  
• 1.5 Volt LED Flashers
  
• AC Line Powered LEDs
  
• Astable Multivibrator
  
• 9 Second Digital Readout Timer
  
• 9 Second LED Relay Timer
  
• 16 Stage Bi-Directional LED Sequencer, other sequencer and flaser circuits
  
• 10 Stage LED Sequencer
  
• 28 LED Clock Timer
  
• Fading Red Eyes
  
• Two Transistor LED Flasher
  
• 16 Stage Bi-Directional LED Sequencer
  
• Expandable 16 Stage LED Sequencer
  
• LED Photo Sensor Circuit
  
• LED chaser
  
• 7 Segment LED Counter
  
• LED Flasher
  
• LED pulser with audible output
  
• IR Illuminator
  
• Flashing Christmas LED display
  
• ICL7660 LED flasher
  
• 1.5V LED flasher B (PDF)
  
• Low current LED flasher (PDF)
  
• 1.5V LED flasher A (PDF)
  
• Flashing LED advertising badge (PDF)
  
• Flashing LED advertising badge (PDF)
  
• Pulsed LED test circuit (PDF)
  
• Low battery voltage flasher (PDF)
  
• Adjustable flashing LED
  
• PWM white LED drivers
  
• Heart of LEDs
  
• Christmas Star
  
• Christmas tree
  
• LED Counter
  
• PIC16F84 LED chaser
  
• PIC16F84 LED signboard
  
• PIC16F84 LED signboard 2
  
• White LED circuits
  
• LED Mood Light
  
• LED Audio VU Meter
  
• Scrolling LED sign
  
• LM3909 LED flasher
  
• Picxie 2 - 8x8 Animated LED Signboard
  

Lighting schematics

• Garden light switch
  
• DMX lighting and special effects
  
• Microcontroller Multichannel Light Dimmer
  
• Disco style Strobe Light
  
• Varying Brightness AC Lamp
  
• 12 Volt Lamp Dimmer
  
• 120VAC Lamp Chaser Using Solid State Relays
  
• Flashing Neons (NE-51 / NE-2)
  
• Sequencing Neons (NE-51 / NE-2)
  
• Touch Activated Lamp
  
• 220V Flashing lights
  
• Coutesy lamp
  
• Bedside lamp timer
  
• TRIAC light dimmer
  
• 12VDC Fluorescent Lamp Driver
  
• Strobe light
  
• Adjustable Strobe Light
  
• Smart 12V light dimmer (PDF)
  
• Light Sequenced Candelabra
  
• 5W Fluorescent light intensity modulator (PDF)
  
• 1W Fluorescent lamp night light (PDF)
  
• Low-voltage light dimmer
  
• Light chaser
  
• 4-channel dimmer rack
  
• PIC16F873 light controller
  
• Neon desklamp
  
• Electronic night light
  
• Neon lamp dimmer
  
• LED Mood Light
  
• LX-800 Lighting system
  
• Xenon Strobe Light
  
• Lamp flasher/dimmer
  
• Efficient dc lamp dimmer - 74C14
  

Medical and health related schematics

• Snore alarm electronic device
  
• EKG/EEG circuit
  
• Radiation Dosage-Rate Meter
  
• Heartbeat monitor
  
• Cranial Electrotherapy Stimulator
  
• Automated crib lights
  
• Jogging timer
  
• Tan timer
  
• Muscular Bio-stimulator
  
• Pedometer
  
• Heart rate monitor
  
• ECG amplifier
  
• Simple lie detector
  
• Simple lie detector
  
• Heartbeat transducer
  
• ECG Amplifier
  
• EEG preamp, anti alias filter and isolation circuit
  
• Self Contained Electromyograph (EMG)
  
• Cardiac monitor
  
• Galvanic Skin Response (GSR) Schematic
  
• Brain-Wave Machine
  
• Lie detector
  
• Simple lie detector
  
• ECG project page
  
• The ESP SIM (Sound Impairment Monitor)
  
• Respiration system
  

Microcontroller based schematics

• PIC based packet radio encoder (PDF)
  
• RS485-Version of the SAB80C535-Microcontrollerboard
  
• PC IR receiver based on PIC16F84
  
• Record and play fast 1-bit sound on a PIC micro
  
• AT89C2051/4051scanning 7-segment display and keypad
  
• AT89C2051/4051 Driving dot LED
  
• AT89C2051/4051stepper motor interface
  
• AT89C2051/4051connecting dumb terminal
  
• Simple RS232C Level Converter using Transistors
  
• C-52 EVB Robot Controller
  
• Mains clock controller using AT89C2051
  
• AT89C2051/4051 Easy-Downloader
  
• AT89C51/52/55 Easy-Downloader
  
• PIC16F84 programmer
  
• PIC16F84 miniature real-time controller
  
• Isolated RS232 for PIC16F84
  
• PIC16F84 debugging terminal
  
• MiniLOGGER V1.0
  
• Atmel 89C Series Flash Microcontroller Programmer
  
• AT89C2051 real-time controller
  
• PIC12C508 Night-light saver
  
• AT89C2051 Night light saver
  
• Atmel 8051 Flash Based-Microcontroller Programmer
  
• AT89C2051 Digital thermometer and clock
  
• PIC16F84 CW decoder (PDF)
  
• 12C508 Smart Lock
  
• Build a PIC controlled DDS VFO, 0 to 6 MHz
  
• PIC controlled DDS VFO, 0 to 6 MHz
  
• Basic Stamp Lightning Activity Monitor
  
• TCP/IP stack and WWW server in a PIC16F84
  
• PIC16F84 line following robot
  
• PIC16F84 web server
  
• 50 MHz frequency counter, voltage meter & SWR/PWR indicator
  
• Programmer PIC16F84,12C50x and EEPROM 24Cxx
  
• RDS Encoder - digital part
  
• Freign vocabulary recollector
  
• Embedded system to send e-mails (small TCP/IP stack)
  
• Speaking clock using PIC & ISD device
  
• Speaking doorbell using PIC & ISD device
  
• Whistle detector using 8-pin PIC
  
• PIXpand
  
• PIC16F877 to IDE interface
  
• 68HC11 stepper motor control
  
• POCSAG encoder/decoder
  
• Network Time Protocol AVR Clock
  
• DS1820 Temperature Sensor Readout Unit
  
• Talking PIC - based on SP0256
  
• Serial to parallel converter using the AT89C2051
  
• AT89C2051 serial COMs to LED driver
  
• DS1820 Arbiter V2.00 Schematic
  
• PIC18 Schematic
  
• Atmel AVR programmer
  
• Microchip PIC ICSP implementation
  
• 101 AT Keyboard to ASCII Decoder using 68HC705J1A MCU
  
• DTMF tone decoder using Basic Stamp
  
• LCD Serial Terminal
  
• Optical sensor using PIC12C508
  
• A Scenix (and PIC) Programmer
  
• 8088 maximum mode SBC
  
• Long-period watchdog timer
  
• PIC16F84 Range Finder Project
  
• Generate video signals in real-time using a PIC16F84
  
• PIC ICD
  
• PIC Project #1 - RS232 to I2C Interface
  
• Galvanic decoupling of I2C bus
  
• Dual PIC16C84 prototype board
  
• Graphic LCD interface
  
• FSK modem with PIC16C84
  
• Talking YODA project (PIC16C84)
  
• PIC16F84/PIC16F87x-In-System-Programmer
  
• Microcontroller interface for 5KW microwave oven
  
• PIC16F84 Based Morse Code Reader
  
• AVR-Based Serial Port IR Receiver
  
• Interfacing piezo elements to a microcontroller
  
• Speech recognition using HM2007
  
• PIC microcontroller servo motor interface
  
• PIC micro multiple servo motor interface
  
• PIC16F84 countdown timer
  
• PIC16F873 ultrasonic range meter
  
• PIC16F873 Digital clock
  
• PIC16F873 remote display
  
• PIC16F84 stepper motor controller
  
• PICADC - a free, PIC based "intelligent" A/D converter
  
• PIC-Programmer 2
  
• Connecting PIC12C508 8 to 93AA46 serial eprom
  
• GPS LCD Display Project
  
• PIC16F84 LED chaser
  
• AT89C2051 line-follower robot
  
• Night light saver (PIC12C508)
  
• Basic stamp interface circuits
  
• PIC16F84 sound controlled Christmas lights
  
• PIC demo board
  
• PIC LCD and Keypad driver
  
• Programmer for the 68HC705C8 MicroController
  
• 27c801 EPROM Programmer Project
  
• LCD to PIC16C54 schematic
  
• 68HC11 based RDS decoder
  
• Acceleration monitor using ADXL202 and AVR
  
• 40+ MHz 5-digit frequency counter with an AVR 2313
  
• Interfacing DRAM to AT90S8515
  
• Temperature monitor/controller: AVR 2313 / DS1621
  
• PIC16C84 VT-52 Emulator for Linux
  
• Tony Nixons Pocket Programmer (PIC)
  
• 8051 Development System Circuit Board
  
• 8051 Development System Circuit Board
  
• Temperature controlled based on AT89CX051
  
• AFSK 1200 Modem based on PIC16C620
  
• PicCon - Hidden Radio Transmitter Controller
  
• PIC16F84 tone generator
  
• PIC16F84 tone generator (6-Bit)
  
• AVR Beacon Super Keyer
  
• AVR Frequency Counter
  
• AVR Digital Voltmeter
  
• AVR Signal Generator
  
• Ser-Key 10-Key Serial Keypad Encoder
  
• 2-wire LCD interface using PIC16CF84
  
• PIC16F84 Serial I/O-expander with PicBasic
  
• RS 485-RPT Schematic
  
• Connecting LED to PIC Micro I/O pins (PDF)
  
• Microprocessor RS-232 Reset
  
• AT90S8515 experimenter board
  
• A PIC-Based Keyboard Emulator
  
• PIC-based robot
  
• ScanMate audio activated recorded
  
• PIC18F252 bootloader schematics
  
• Remote control encoder/decoder with PIC16C620 & PIC12C508
  
• Electronic door codelock with PIC16F84
  
• Automatic door opener with PIC12C508
  
• Infra/radio remote control transmitter/receiver with PIC
  
• Codelock
  
• Automatic door opener (PIC)
  
• PIC16F876 Datalogger
  
• GPS Repeater
  
• Kodak DC-20 camera interface (PIC12C509)
  
• Kodak DC-20 camera interface (PIC16F84)
  
• Remote control for Raymarine ST4000 Autopilot
  
• PIC programmers for parallel port
  
• Wisp628 ISP Microchip PIC Programmer
  
• Picxie 2 - 8x8 Animated LED Signboard (PIC16F84) Picxie 2 - 8x8 Animated LED Signboard
  
• 10 tricks for interfacing to the PIC16C508
  
• Interfacing the PIC16C508
  
• PIC 5x7 display
  
• Analog to digital conversion notes
  
• Multi-chip programmer
  

Misc audio   

• Pink noise generator
  
• A Schottky-based Saw-to-Tri converter
  
• Saw to triangle converter
  
• Improved saw to triangle converter
  
• Voltage controllable LFO
  
• White noise generator
  
• Low Frequency Sinewave Generators
  
• Horror movies sound effects
  
• Sound amplifier
  
• Temperature sensitive oscillator
  
• Twin-T Audio Sine Wave Oscillator
  
• 1.5V Audio Amplifier
  
• Low Power Op-Amp - Audio Amp (Intercom)
  
• 555 Tone Generator (8 Ohm Speaker)
  
• 3 Transistor Audio Amp (50 milliwatt)
  
• Low Frequency Sinewave Generator
  
• Audio level indicator
  
• Room noise detector
  
• Amplifier timer
  
• Bell ring generator
  
• Amplified ear
  
• Precision audio millivoltmeter
  
• Audio Signal Source
  
• Analog VU meter
  
• Voltage controlled amplifier
  
• Audio graphic equaliser
  
• Intercom preamp
  
• FET audio mixer
  
• Microphone mixer
  
• Tone control
  
• Digital volume control
  
• Sound level meter
  
• CMOS IC audio oscillator
  
• Ultrasound detector
  
• Electronic siren
  
• Two-tone siren
  
• Underwater microphone
  
• Code practice oscillator
  
• Noise generator
  
• Electronic whistle
  
• Very loud beeper (PDF)
  
• Digital noise generator (PDF)
  
• Tone display system
  
• Tube amplifier
  
• Condenser microphone hookup
  
• Phase shifter
  
• Paradoxical Sound Syntheizer
  
• Bias circuits
  
• Audio line isolator
  
• Dynamic microphone to electret microphone input
  
• Line level signal to microphone input adapter
  
• Simple two line output combiner
  
• Electret microphone powering circuits
  
• Use amplifier phono input as line level input
  
• Speaker signals to line level inputs
  
• Spring reverb unit
  
• Sine wave generator
  
• Simple amplifier
  
• 3-Band equalizer
  
• 6-Input mixer
  
• Doorphone intercom
  
• Stereo line driver
  
• Audio notch filer
  
• Peak reading audio level meter
  
• Tone control
  
• Speaker Microphone Circuit
  
• Electronic canary
  
• Electronic siren
  
• NHT subwoofer amp
  
• Voltage Controlled Mixer w/Modulator
  
• Dual Voltage Controlled Oscillator w/Modulator
  
• Dual Voltage Controlled Filter w/Modulator
  
• Stereo Ducker
  
• MS Stereo Decoder
  
• MS Stereo Microphone
  
• RIAA Equalized Stereo Phono Preamp
  
• Tube active crossover
  
• Improved PL tone decoder
  
• Magnetic cartridge amplifier
  
• LM358 preamp
  
• Sound detector
  
• Tone detector
  
• Tone generator
  
• Warbler
  
• Fender Champ Replica
  
• Voltage Controlled Panner
  
• Low Noise Microphone Preamplifier
  
• Bridging Adapter For Power Amplifiers
  
• Simple Surround Sound Decoder
  
• Simplest Ever Amplifier Bridging
  
• Stereo Width Controllers
  
• Power Amplifier Clipping Indicator
  
• Phono Preamps For All
  
• Digital Delay Unit For Surround Sound
  
• Parametric And Sub-Woofer Equaliser
  
• High Quality Sound Mixer
  
• Loudspeaker Protection and Muting
  
• Direct Injection Box for Recording & PA Systems
  
• Minimalist Discrete Hi-Fi Preamp
  
• Signal Detecting Auto Power-On Unit
  
• Load Sensing Automatic Switch
  
• Amplifier thermal protection
  
• Active Sub-Woofer and Controller
  
• Balanced Line Driver & Receiver
  
• VU And PPM Audio Metering
  
• Variable Amplifier Impedance
  
• Linkwitz Cosine Burst Generator
  
• Low Noise Balanced Microphone Preamp
  
• Fast Audio Peak Limiter
  
• Subwoofer Equaliser
  
• Audio output level meter
  
• Stereo compressor
  
• Audio mixer
  

Miscellaneous schematics

• Ultrasonic radar
  
• How to generate a Rotating Field
  
• Chaos generator
  
• Simple BFO metal detector
  
• Electromagnetic Levitator
  
• Build Your Own Digital Setting Circles For Your Astronomical Telescope
  
• PL tone generator (NE567)
  
• Bat detector
  
• Bat detector microphone pre-amplifiers
  
• DGPS receiver
  
• G Strain energy absorber
  
• RDS Encoder
  
• Toggle Switch Debounced Pushbutton
  
• RDS Encoder
  
• Discrete Set/Reset Flip Flop
  
• Monostable Flip Flops (one shot)
  
• Discrete Bistable Flip Flop
  
• Talking Morse Code Practice Computer
  
• Plant watering watcher
  
• Capacitance sensor
  
• Whistle responder
  
• Nocturnal animals whisker
  
• 12V DC electronic door chime
  
• Biasing Op-Amps into Class A
  
• Parasite zapper
  
• Analog computer
  
• BayComm packet modem
  
• Morse monitor
  
• HamComm modem interface
  
• Morse paddle keyer
  
• UV light box
  
• Voice activated tape recorder switch
  
• Random noise generator
  
• Analog pulse counter
  
• Analog opto-isolator
  
• Pulse width modulators (PWM)
  
• Pulse width to voltage converter
  
• Fantastic Atom Expander
  
• Black Light
  
• Computerize Your Room/Home
  
• Flash slave trigger
  
• A Visual CW Zero Beating Aid
  
• A two-way Morse practice set
  
• Magnetic levitation device
  
• Tesla power receiver
  
• Inexpensive APRS Weather Station
  
• Walking robot
  
• Vibrating Pocket Bug Detector
  
• Basic op-amp circuits
  
• Electronic fish lure
  
• Ultrasonic sound receiver
  
• Experimental data transmitter for fiber optics
  
• Experimental fiber optic receiver
  
• Ion detector
  
• Darkness monitor
  
• Electroscope
  
• Simple event counter
  
• Geiger counter
  
• Light detector
  
• Short-circuit beeper
  
• LM 1800 FM stereo decoder
  
• Glitch detector
  
• MAX924 bar-graph level gauge
  
• Ultrasonic generator
  
• Negative ion generator
  
• ELF Monitor
  
• Ion detector
  
• 1uS light pulse descriminator plus F to V converter (PDF)
  
• Broadband 2MHz optical fiber receiver (PDF)
  
• Modulated light received (PDF)
  
• 1uS light pulse receiver plus post amp (MISC)
  
• Broadband 5MHz optical fiber receiver (PDF)
  
• High-speed light receiver (PDF)
  
• Basement doorbell beeper (PDF)
  
• Time to dust indicator (PDF)
  
• Low-power optical interrupter (PDF)
  
• Simple nitrogen spark generator (PDF)
  
• Ultrasonic transducer oscillator circuit
  
• Build logic gates using discrete parts
  
• Jacob's Ladder
  
• Sudden Ionospheric Disturbance (SID) Receiver
  
• A selection of robotics projects
  
• Bat detector (new)
  
• Vat detector (old)
  
• Variety of quick designs
  
• Making a FRED photopopper
  
• Griffith Observatory Tesla Coil
  
• Fogger smoke machine
  
• Dinsmore 1490 digital compass
  
• Geiger counter
  
• Electric field disturbance monitor
  
• Inexpensive seismometer project
  
• Digital dial
  
• Doorbell for the Deaf
  
• Electromagnetic field detector
  
• Insect Repellant
  
• High Quality Intercom
  
• Magnetic Gun.
  
• Metal detector
  
• Static Electricity / Negative Ion Detector
  
• Ultrasonic dog whistle
  
• Popular Electronics Ultrasound Detector
  
• An Inexpensive X-ray Machine
  
• Magnetic levitation circuit
  
• Schmidt Trigger
  
• Digital Call Sign Annunciator
  
• Ultrasonic switch
  
• Sound finding cricket with phase detector
  
• Sound finding cricket
  
• Very basic circuits
  
• Bat detector
  
• FCTS Project
  
• Morse Code Beacon Keyer
  
• Lightning Activated Camera Shutter Trigger
  
• Driving N-channel FETs from TTL
  
• Miniature Self-Powered Autonomous Robot
  
• Electronic Dazer
  
• Morse Code Practice Keyer 1
  
• Morse Code Practice Keyer 2
  
• 741 Light Sensor
  
• Fluid level detector
  
• Full-duplex doorphone
  
• Morse code display
  
• Intercom schematic
  
• Pulse Induction Metal Detector
  
• Scaling ADXL50 accelerometer output
  

Model and remote control schematics

• Snake throat muscle controller
  
• Incline Railway Control Circuit
  
• A Receive Signal Decoder
  
• One ounce rocket ejection timer
  
• LED traffic lights
  
• Two-tone siren
  
• Proportional radio remote control
  
• Alf: The Robotic Matchbox car
  
• Seaplane schematic
  
• Model Rocket with Video Camera
  
• Signal breaking module
  
• PIC based rocket altimeter
  
• Robot with PIC16F84 brain & InfraRed eyes
  
• 0-10V control for RC servos
  
• Autonomous airplane
  
• Multi Rocket Launcher
  
• Model rocket launch controller
  
• Simple flashing light circuit
  
• Simple flashing light circuit
  
• A dual alternating flashing light circuit
  
• Simple flashing light circuit
  
• A dual tandem flashing light circuit powered by a 9 volt battery
  
• Simulate the Gyralite (dual flashing headlights).
  
• Simple train detector using ambient light and a photocell
  
• Simple charge rate monitor
  
• Deluxe charge rate monitor
  
• "CLONEPAC" memory module for Futaba 8UAF/8UAP
  
• Battery pack discharger
  
• Plane locator
  
• Plane locator 2
  
• Battery low voltage alarm
  
• Battery low voltage alarm 2
  
• Ultimate battery low voltage alarm
  
• R/C helicopter camera
  
• Building an RF Remote Control System
  
• Motor walker circuit
  
• Two tone train horn
  
• 27Mhz toy car receiver
  
• 27Mhz toy car transmitter
  
• R/C Emergency locator alarm
  
• Remote switch for radio-control aircraft accessories
  
• Radio Control Battery Backup
  
• Glow Plug driver for model engines
  

Motor and general control schematics

• Bridge head
  
• Light activated relay
  
• Simple 10 Stage Control Box
  
• Simple PWM circuit
  
• H Bridge Motor Control Circuits
  
• Electronic Thermostat Relay Circuit
  
• Interfacing 5 volt CMOS to 12 volt loads
  
• Light Activated Relay
  
• CMOS Toggle Flip Flop With Relay(CD4013)
  
• 555 Timer Monostable Circuit Using Pushbutton
  
• Current loop interface
  
• Switching solenoid driver
  
• Modular relay system
  
• Light/dark detector
  
• Pulse Width Modulation DC Motor Control
  
• Stepper motor controller
  
• Touch switch
  
• Pump controller
  
• 12V Sump Pump Control
  
• Transistor relay driver
  
• Latching relay driver
  
• Relay delay circuit
  
• Touch switch
  
• Low voltage DC motor speed controller
  
• Flashing neon christmas lights
  
• Three input first response monitor
  
• Switch-on delay circuit
  
• Electronic thermostat
  
• LM3911 temperature controller
  
• Programmable light-activated relay
  
• Rolling code 4-channel UHF remote control
  
• Pushbutton one-shot and latch (PDF)
  
• Charge coupled bi-directional power MOSFET relay (PDF)
  
• Finger touch activated switch (PDF)
  
• Machine vibration triggers hour meter (PDF)
  
• Solid state relay (PDF)
  
• Line-powered Xenon flash transmitter (PDF)
  
• 9V Xenon photoflash controller (PDF)
  
• AC switching with TRIAC from TTL
  
• Control 120VAC relay with TTL
  
• Driving a relay with a CPU
  
• Power-line Appliance Controller
  
• DC Motor Constant Speed Control
  
• Simple Switched Servo Driver
  
• Combination-controlled, fully customizable RF remote control
  
• Thermoelectic controller (scriptable thermometer)
  
• Stepper motor positioner
  
• Stepper motor driver
  
• Thermostat
  
• Frequency switch
  
• PIC16F84 RF remote controller
  
• H-Bridge shematic
  
• SN754410 Dual Motor Driver Board
  
• Hot Water Tank Indicator
  
• Temperature monitor
  
• Cold activated switch
  
• Voltage comparator switch
  
• Dark activated switch
  
• DC Push Button Motor Control Circuit
  
• Light detector
  
• DC Motor Reversing Circuit
  
• Sound operated switch
  
• Touch Switches
  
• 6090 digital decoder schematics
  
• Adjustable Voltage motor controller
  
• Serial servo controller
  
• DC Motor-Driver H-Bridge Circuit
  
• PWM Motor Speed Controller / DC Light Dimmer
  
• Constant Temperature Circuit
  
• PWM DC Motor Speed Control
  
• Solenoid starter
  
• CO2 controller for planted tanks
  
• Light activated relay
  
• Delayed shutter control for Kodak DC-20
  
• Gasoline generator automatic throttle controller
  
• Block power switching module
  
• MOSFET H-BRIDGE schematic and theory
  

Music related schematics  

• Drum machine
  
• Simple MIDI-to-CV converter
  
• Sounds effects unit
  
• ETI 603 Sequencer
  
• Synthesizer schematics
  
• Peak-reading meters
  
• Octave screamer
  
• MIDI keyboard circuit
  
• Spring reverb unit
  
• MIDI status indicator
  
• Metronome and pitch generator
  
• Mini metronome
  
• Compact Flash / IDE MP3 Player MKI
  
• Simple colour organ
  
• Guitar fuzz effect
  
• 8 note tune player
  
• Colour (Sound) Organ
  
• Transisor organ
  
• Audible metronome
  
• Visual metronome
  
• Simple line mixer
  
• Simple MIDI tester
  
• ASM-1 Analog Synthesizer Module
  
• MIDI Controller Footpedal
  
• DIY Serial MIDI Interface (80C51/80C31 Version)
  
• Electronic metronome
  
• Sound Effects Generator
  
• Sound Effects Generator 2
  
• Digital Guitar Tuner
  
• Drum tone oscillators
  
• Stereo compressor
  
• Analog MIDI synthesizer
  
• Spring reverb
  
• MIDI to CV interface
  
• Dual phantom power pre-amp
  
• Four channel fuzz box
  
• Theremin controller
  
• Vocal zapper
  
• Guitar Reverb Pedal
  
• Guitar Tremolo Unit
  
• Spring Reverb Unit For Guitar
  
• Ultra Simple Bass Guitar Compressor
  
• Vox AC30 Guitar Amplifier Simulator
  
• Guitar Vibrato Unit
  
• Musical Instrument (Expandable) Graphic Equaliser
  
• Midibox 64
  

PC related schematics

• I2C printer port adaptor
  
• RS232C Level Converter
  
• Isolated Full Duplex RS232C Interface
  
• PC Serial Receiver (57.6K Baud / TTL & CMOS)
  
• PC Serial Port Receiver
  
• Parallel Port Relay Interface
  
• PC based 7-segment rolling display
  
• DB-9 Connector to DB-25 (both RS-232)
  
• Mac Serial Port (RS-422 DIN-8) to RS-232 DB-25
  
• Parallel print capture system
  
• ZX96-Mainboard
  
• Modem Rockwell RCV336/ACF model V1433VQR ext.
  
• Genius Mouse schematics
  
• EEPROM programmer
  
• Macintosh interface for X10 MR26A Wireless Receiver
  
• Sound Card Interface with Tone Keyer
  
• Ericsson phone to PC serial port interface
  
• PC serial port receiver
  
• Parallel port relay interface
  
• ISA 48 I/O digital card
  
• Jupiter card programmer
  
• USB to RS232 Dongle
  
• Parallel (Printer) Port Interface
  
• RS-232 line monitor and loopback cables
  
• The KD2BD Pacsat Modem
  
• A Serial Infrared Remote Controller
  
• PC Serial and Parallel Port Software and Interfaces
  
• Interfacing 16x2 character :LCD to parallel port
  
• RS-232 Protocol Analyser
  
• Radio clock for PC's
  
• Serial to ECP interface
  
• A PC-Based LowFER Frequency Synthesizer
  
• General purpose 48-bit ISA parallel I/O card
  
• 4-channel 8-bit analog-to-digital converter for PC
  
• Printer port ADC
  
• Parallel port ADC based on MAX147
  
• Analog Signal Acquisition for PC Printer Port
  
• More accurate PC/AT clock
  
• Getting power from RS-232 interface
  
• Barcode scanner
  
• PC thermometer
  
• Dive computer interface
  
• Parallel port servo controller
  
• Connect two CD-ROM drives to one soundcard
  
• Headphone driving circuit for soundcards
  
• Get power out of PC parallel port
  
• Null Printer Adapter
  
• PC speaker volume control circuit
  
• How to get power from PC to your circuits
  
• RS-232 surge protection
  
• Simple RS-232 serial port buffer circuit
  
• Get power out of PC RS-232 port
  
• Sound Blaster Microphone Preamplifier
  
• Sega 3D glass interfacing circuits
  
• Convert Atari-style joystick to PC joystick port
  
• Fake Joystick circuit
  
• Using the joystick port as general purpose input
  
• Connect other circuits to PC joystick port
  
• Schematic of a standard PC joystick
  
• Simple PC SmartCard reader
  
• Fax to modem interface
  
• PC interface for point controller
  
• Linux Infra-red Remote Control (LIRC)
  
• Compter microphone
  
• Laptop Computer Serial Port Power Booster
  
• HamComm Interface
  
• Apple II/II+/IIe IDE Drive Interface
  
• Basic Stamp I & PC Relay Controller
  
• CompactFlash to IDE interface
  
• Hi-Fi PC Speaker System
  
• IDE hard-disk interface for Amiga 500
  
• iRDA printer adapter
  
• 160 Baud ALDL Hardware Interface
  
• AT PC Power Supply 1
  
• AT PC Power Supply 2
  
• AT PC Power Supply 3
  
• AT PC Power Supply 4
  
• AT PC Power Supply 5
  
• Digital Signals Decoding Interfaces
  
• 9-pin null modem cable
  
• RS232 - Lowe HF-225 interface
  
• 24-bit parallel port interface with 8255 for Commodore computer
  
• Supply Derives Power From 3-Wire RS-232 Port
  
• 24-line PC digital interface (P