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Table Of Contents
01
Alarms and security related schematics
02
Audio filter schematics
03
Audio power amplifier schematics
04
Audio preamp circuits
05
Automative, car and motorcycle schematics
06
Data acquisition and data logging schematics
07
Games and fun stuff (schematics)
08
Infrared based schematics
09
Laser related power supplies and data transmission
10
LED related schematics
11
Lighting schematics
12
Medical and health related schematics
13
Microcontroller based schematics
14
Misc audio (also see Music, Amplifiers, Preamp)
15
Miscellaneous schematics
16
Model and remote control schematics
17
Motor and general control schematics
18
Music related schematics (also see Audio)
19
PC related schematics
20
PDA interfaces and related schematics
21
Power supplies and control schematics
22
Radio-frequency schematics (also see Transmitters)
23
Solar-powered schematics
24
Telephone and intercom related schematics
25
Test equipment schematics
26
Timing, oscillators etc. (schematics)
27
Transmitter schematics (also see RF)
28
Video related schematics
Alarms and security related schematics
- Intermittent alarm generator
- Burglar alarm
- Moisture alarm
- Fridge door alarm
- Ultrasonic remote control & alarm system
- Door knob alarm (PDF)
- Water seepage alarm (PDF)
- Micro-power over temperature alarm (PDF)
- Personal silent alarm system
- 5 Zone alarm circuit
- Miniature loop alarm
- Gate alarm circuit
- Perimeter monitor
- Digital combination lock
- Touch activated alarm system
Audio filter schematics
- Active 2nd Order Filters
- RC Notch Filter (Twin T)
- 3KHz low-pass filter plus audio amp (PDF)
- “A” Weighting Filter For Audio Measurements
- Multiple Feedback Bandpass Filter
Audio power amplifier schematics
- 100W Amplifier
- 18W Audio amplifier
- 25W MOSFET amplifier
- Headphone amplifier
- Portable headphone amplifier
- 2W amplifier
- 8 watt audio amp
- 20W Amplifier
- 50W 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
- Audio amplifier output relay delay
- HeadBanger Headphone Amp
- 2W Amplifier
- TDA2030 8 Watt amplifier
- 16 Watt amplifier
- 8 Watt amplifier
- 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
- Phono preamp
- Simple microphone preamplifier
- Phono Preamp
- Simple microphone preamplifier
- ECM Mic preamp
- Hi Fi preamp
- Electret mic amplifier
- Audio preamplifier
- Audio preamp
- Low impedance microphone amplifier
Automative, car and motorcycle schematics
- 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
- Portable CD Player Adapter For Car
- Car battery charger
- Wireless Auto Tachometer
- Headlight reminder
- Breath Alcohol Tester controlling a car ignition system
- Parking sonar
- Simple Car Preamplifier and Artificial Earth
- Interface between GM’s 5 Volt 8192 baud ALDL data stream and a PC serial port
- 3rd brake light
- 12V to 9V car coverter
- Car Nicad charger
- Economy radar detector
Data acquisition and data logging schematics
- TempSentry temperature sensor technical info and schematics
- Datalogger based on 68HC11
- Analog input section based on AD9220
- Light direction sensor
- 12-Bit ADC interface
- Digital thermometer
- Compost temperature and moisture monitor
- Rain detector
- Web-based thermometer project
- Honey Bee counter (PDF)
- Capacitance type liquid level measurement (PDF)
- Digital PC Oscilloscope
- Serial Port A/D-converter
- Centronics port D/A converters and low-pass filter
- Water-level sensor
Games and fun stuff (schematics)
- Big Mouth
- GameBoy Camera Parallel Port Interface
- PSX controler to PC MIDI converter
- GameBoy Cart Programmer
- Memory game
- Project: NES to Atari 2600 controller interface
- Pine Racecar Victory Judge
- 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
- Bingo!!! (on your tv)
- Slot car TV cronograph
- DIT shutterglasses controller
Infrared based schematics
- IR remote control system for PC
- IR Receiver (Amplitude Modulated IR)
- IR Transmitter for Audio (Amplitude Modulated IR)
- Universal IR-Remote Lamp Controller
- IR remote control
- 40KHz light receiver (PDF)
- 40KHz TV-VCR repeater (PDF)
- 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
- IR Ranging
- Pyroelectric Infrared Sensor
- Simple IR transmitter circuit
- Simple infra-red detector
- IR remote control extender
- IR remote control tester
- Infrared repeater
- 40khz IR Tester
- 555 timer 40khz IR Oscillator
- IR detector / emitter
- 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
- 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)
- Experimental laser data link
LED related schematics
- Winking LEDs
- LED flashing light
- LED initials
- 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
- 1.5V LED flasher B (PDF)
- Low current LED flasher (PDF)
- 1.5V LED flasher A (PDF)
- Flashing LED advertising badge (PDF)
- Pulsed LED test circuit (PDF)
- Low battery voltage flasher (PDF)
- Adjustable flashing LED
- LED Mood Light
- LED Audio VU Meter
- LM3909 LED flasher
- Picxie 2 - 8x8 Animated LED Signboard
Lighting schematics
- 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
- 5W Fluorescent light intensity modulator (PDF)
- 1W Fluorescent lamp night light (PDF)
- Electronic night light
- LED Mood Light
- LX-800 Lighting system
- Xenon Strobe Light
- Lamp flasher/dimmer
- PWM light bulb regulator
Medical and health related schematics
- Radiation Dosage-Rate Meter
- Heartbeat monitor
- Cranial Electrotherapy Stimulator
- Automated crib lights
- Joigging timer
- Tan timer
- Muscular Bio-stimulator
- Pedometer
- Simple lie detector
- The ESP SIM (Sound Impairment Monitor)
Microcontroller based schematics
- Z80 core #1- Z80 CPU and memory (PDF)
- Z80 core #2- Z80 CTC and SIO
- Z80 core #3- RS-232 drivers for the SIO
- RS485-Version of the SAB80C535-Microcontrollerboard
- PC IR receiver based on PIC16F84
- 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
- 12C508 Smart Lock
- Build a PIC controlled DDS VFO, 0 to 6 MHz
- PIC controlled DDS VFO, 0 to 6 MHz
- TCP/IP stack and WWW server in a PIC16F84
- PIC16F84 line following robot
- 50 MHz frequency counter, voltage meter & SWR/PWR indicator
- Embedded controller based on MC68HC11F1
- 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
- PIC16F84 mechanically scanned clock
- 68HC11 stepper motor control
- Serial to parallel converter using the AT89C2051
- AT89C2051 serial COMs to LED driver
- 101 AT Keyboard to ASCII Decoder using 68HC705J1A MCU
- DTMF tone decoder using Basic Stamp
- A Scenix (and PIC) Programmer
- Long-period watchdog timer
- PIC16F84 Range Finder Project
- Generate video signals in real-time using a PIC16F84
- PIC Project #1 - RS232 to I2C Interface
- Dual PIC16C84 prototype board
- Talking YODA project (PIC16C84)
- PIC16F84/PIC16F87x-In-System-Programmer
- Microcontroller interface for 5KW microwave oven
- PIC16F84 Based Morse Code Reader
- Interfacing piezo elements to a microcontroller
- PICADC - a free, PIC based “intelligent” A/D converter
- AT89C2051 line-follower robot
- PIC16F84 sound controlled Christmas lights
- Convenient PIC module
- Spread spectrum transceiver controlled by PIC
- 68HC11 based RDS decoder
- PIC16C84 VT-52 Emulator for Linux
- Temperature controlled based on AT89CX051
- 2-wire LCD interface using PIC16CF84
- PIC16F84 Serial I/O-expander with PicBasic
- PIC R/C Servo Controller
- Microprocessor RS-232 Reset
- A PIC-Based Keyboard Emulator
- ScanMate audio activated recorded
- 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
- http://www.vekoll.vein.hu/~jap/electronic/codelock.html
- Automatic door opener (PIC)
- Picxie 2 - 8x8 Animated LED Signboard (PIC16F84) Picxie 2 - 8x8 Animated LED Signboard
- PIC-FC1 Frequency Counter
- 10 tricks for interfacing to the PIC16C508
- Interfacing the PIC16C508
- PIC 5x7 display
- Analog to digital conversion notes
- Multi-chip programmer
Misc audio (also see Music, Amplifiers, Preamp)
- A Schottky-based Saw-to-Tri converter
- Saw to triangle converter
- Improved saw to triangle converter
- Voltage controllable LFO
- White noise generator
- Horror movies sound effects
- Sound amplifier
- Temperature sensitive oscillator
- Old-fashioned siren effect
- Simple VOX circuit
- 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
- A Stereo Digital Volume Control based on the CS3310
- Voice record/playback using ISD 1000A
- Audio Graphic Equaliser
- 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
- Very loud beeper (PDF)
- Digital noise generator (PDF)
- Condenser microphone hookup
- Phase shifter
- Paradoxical Sound Syntheizer
- 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
- 3-Band equalizer
- 6-Input mixer
- Doorphone intercom
- Stereo line driver
- Audio notch filer
- Peak reading audio level meter
- Tone control
- Electronic canary
- Improved PL tone decoder
- Magnetic cartridge amplifier
- LM358 preamp
- Sound detector
- Tone detector
- Tone generator
- Warbler
- 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
Miscellaneous schematics
- Chaos generator
- Simple BFO metal detector
- Electromagnetic Levitator
- Build Your Own Digital Setting Circles For Your Astronomical Telescope
- Electric field disturbance monitor
- Discrete Set/Reset Flip Flop
- Monostable Flip Flops (one shot)
- Discrete Bistable Flip Flop
- Plant watering watcher
- Capacitance sensor
- Whistle responder
- Nocturnal animals whisker
- 12V DC electronic door chime
- Random noise generator
- Hardware random bit 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
- Tesla power receiver
- Basic op-amp circuits
- Supervisory Control And Data Aquisition project (for Home Automation and Security)
- 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
- Variety of quick designs
- Fogger smoke machine
- Electric field disturbance monitor
- Dual comparator forms temperature-compensated proximity detector
- Electromagnetic field detector
- Ultrasonic dog whistle
- An Inexpensive X-ray Machine
- Magnetic levitation circuit
- Ultrasonic switch
- Very basic circuits
- Bat detector
- FCTS Project
- Morse Code Beacon Keyer
- Lightning Activated Camera Shutter Trigger
- Electronic Dazer
- Morse Code Practice Keyer 1
- Morse Code Practice Keyer 2
- 741 Light Sensor
- Fluid level detector
- Full-duplex doorphone
- Scaling ADXL50 accelerometer output
Model and remote control schematics
- R/C Receiver <-> Joystick Port Interface for Flight Simulators
- LED traffic lights
- Two-tone siren
- HEXBOT robot
- Alf: The Robotic Matchbox car
- A Low Cost Thermal Peak Detection Charger
- A Miniature High-Rate Speed Control with Brake
- An On/Off Motor Control with Brake
- 0-10V control for RC servos
- 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
- Building an RF Remote Control System
- Two tone train horn
- Radio Control Battery Backup
- Glow Plug driver for model engines
Motor and general control schematics
- 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
- 12V Sump Pump 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
- Combination-controlled, fully customizable RF remote control
- Thermoelectic controller (scriptable thermometer)
- Stepper motor positioner
- SN754410 Dual Motor Driver Board
- Temperature monitor
- Cold activated switch
- Voltage comparator switch
- Dark activated switch
- DC Push Button Motor Control Circuit
- Light detector
- Sound operated switch
- Touch Switches
- Detect fan failure with a single transistor
- http://www.rentron.com/SerialServo.htm
- Constant Temperature Circuit
- PWM DC Motor Speed Control
- Solenoid starter
- CO2 controller for planted tanks
- Light activated relay
Music related schematics (also see Audio)
- Drum machine
- Simple MIDI-to-CV converter
- Sounds effects unit
- ETI 603 Sequencer
- Synthesizer schematics
- Peak-reading meters
- Octave screamer
- Optical Theremin - electronic musical instrument
- Spring reverb unit
- Metronome and pitch generator
- Mini metronome
- 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
- Electronic metronome
- 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
- D.C. Mixer for music synthesizers
PC related schematics
- I2C printer port adaptor
- RS232C Level Converter
- Isolated Full Duplex RS232C Interface
- ISA 8-bit output card
- PC based 7-segment rolling display
- Parallel print capture system
- Modem Rockwell RCV336/ACF model V1433VQR ext.
- Genius Mouse schematics
- PC serial port receiver
- Parallel port relay interface
- ISA 48 I/O digital card
- Parallel (Printer) Port Interface
- RS-232 line monitor and loopback cables
- A Serial Infrared Remote Controller
- Interfacing 16x2 character :LCD to parallel port
- 8254 Timer and Counter Board
- 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
- 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
- DC-DC Power Supply from car 12V battery to PC motherboard
- Linux Infra-red Remote Control (LIRC)
- Compter microphone
- Laptop Computer Serial Port Power Booster
- HamComm Interface
- Hi-Fi PC Speaker System
- IDE hard-disk interface for Amiga 500
- Parallel port ADC/DAC
- Parallel port ADC using ADC0804
- High speed 20MSPS ADC interface
- 9-pin null modem cable
- 24-bit parallel port interface with 8255 for Commodore computer
- 24-line PC digital interface (PDF)
- SPDIF-interface to AudioPCI
PDA interfaces and related schematics
Power supplies and control schematics
- Power supply provides +5VDC regulated, +10VDC unregulated and 7.5VAC
- Basic increase in DC voltage
- Power Tool Torque Control
- Generating Negative 5 Volts from 9 Volt Battery
- LED Battery Condition Indicator
- LM317 Variable Voltage Regulator
- LM317 Regulator With Pass Transistor
- High Current Regulated Power Supply
- Simple Variable Voltage Source
- Variable 3 - 24 Volt / 3 Amp Power Supply
- 2 watt switching power supply
- Variable Voltage and Current Power Supply
- Low Power DC to DC Converter
- Constant Current Battery Charger
- Variable DC power supply
- Using the 78xx Series Voltage Regulators
- 6V to 12V Converter
- Tesla coil / HV generator
- 12VDC To 120VAC Inverter
- High Current Power Supply
- Dual Polarity Power Supply
- High Voltage High Current Power Supply
- Transformerless Power Supply
- Fixed Voltage Power Supply
- Voltage Inverter
- Voltage Inverter
- 1A Variable Regulated Power Supply
- Negative voltage generator
- 12V battery capacity tester
- NE555 Low Voltage Battery Disconnect Circuit
- Power reminder beeper (PDF)
- Unplugged power cord alarm
- Machine power loss beepter (PDF)
- HV supply: 12VDC in, 12KV out
- Generating -5VDC from +5VDC
- Filtering PC bus POWER
- Bidirectionall power inverter
- Adjustable power supply using LM317
- Simple +5V power supply circuit
- 12V 30A power supply
- Dual regulated power supply
- Fuse blown indicator
- Gyrator circuit
- Variable power supply
- Nicad battery charger
- Regulated 12V supply
- Unregulated power supply
- 12 volt battery monitor
- 12 volt power supply
- 5 volt power supply
- Battery voltage monitor
- LM3914 battery monitor
- Multiple voltage power supply
- Voltage doubler
- Voltage inverter
- PWM Motor Speed Controller / DC Light Dimmer
- PWM Motor/Light Controller
- Low Power LED Voltmeter
- PWM Motor/Light Controller
- PWM Motor/Light Controller variants
- Low Power LED Voltmeter
- Temperature Controlled NICD Charger
- Simple Capacitance Multiplier Power Supply For Class-A Amplifiers
- Simple DC Adapter Power Supply
- Variable Dual Lab Power Supply
- Charger for gel lead acid batteries
- 12V to 120VAC inverter
- Nicad Battery Discharger/Capacity Indicator
Radio-frequency schematics (also see Transmitters)
- CW RECEIVER 40/80 meter CW receiver
- TRF AM Receiver circuit
- Receiver building blocks
- Crystal radio
- Automatic message sender for CB
- RF Sensing relay driver
- Vibrating pocket bug detector
- 2MHz RF Oscillator
- 50-150MHz Overtone Oscillator
- Simple Op-Amp Radio
- NASA TURFTS - TDRSS User RF Test Set
- HF Linear RF power amplifier
- 100W HF Linear AMP
- 3W FM Transmitter
- Crystal radio
- Op-Amp Radio
- Car radio tunes the Amateur Bands
- Crystal set that requires no antenna
- 80m Direct Conversion Receiver
- A compact L-match ATU for portable use
- Morse Adaptor for your VHF/UHF FM rig
- An end-fed antenna, L-match coupler and resistive bridge for HF
- AM Broadcast Band Regenerative Receiver
- 50 MHz to 146 MHz Converter
- Hear Amateurs on your Shortwave Radio!
- Compact 20 14 MHz direct conversion receiver
- Hear Amateurs on your FM Radio!
- RF actuated CW monitor
- LF to HF Converter
- Super 80 ultra-simple SSB receiver for 3.5 MHz
- The MRX-40 Mini Receiver
- Phase Shift Radio Direction Finder
- Bug detector
- 175KHz inductive pulse receiver (PDF)
- 200-400 MHz voltage controlled oscillator
- Icom CT-17 Logging & Control Interface Level Converter
- AM/FM/SW active antenna
- RF Sniffer <.5 to >500 MHz
- Frequency Synthesizer
- Four Channel Wireless Transmitter and Receiver
- Wireless event receiver
- Talking receiver
- Wireless motion detector
- 418MHz Control RX/TX
- 2N2222 40 Meter CW/DSB Transceiver
- AM receiver
- Field strength meter
- MW preamplifier
- Simple field strength meter
- 4 band double-tuned preselector
- ZN414 AM receiver
- ZN414 shortwave receiver
- Phased lock loop schematic
- SOP direct conversion receiver
- Simple UHF dummy load
- Receiver
- 30m direct conversion receiver
- Popcorn direct conversion receiver
- 40m direct conversion receiver
- 80m direct conversion receiver
- R-399-A Communications Receiver
- 136 kHz direct conversion receiver
- How to Build a 300MHz AM, RF Remote Control System
- RF Modem Robotics Project
- Smooth Tone Clickless CW Sidetone Generator
- Variety of receiver converter projects
- One transistor FM receiver
- 42 Mc Band to 88 Mc Band (retrofit converter) Project
- 50MHz Assistant (Preamp & Power Amp.)
- Bug detector
- Basic RF oscillator
- Superregenerative 27MHz receiver
- Radio Control Electric Switch
- 56K RF Modem
- 80M ARDF direction finder
Solar-powered schematics
- AA battery solar charger
- Solar Panel Charge Controller / Low Voltage Disconnect Circuit
- Solar Panel Current Meter
- Solar Charged LED Flashlight
- AA battery solar charger
- Solar Panel Charge Controller / Low Voltage Disconnect Circuit
- Solar Panel Current Meter
- Solar cell Nicad charger
Telephone and intercom related schematics
- Phone in use circuit
- Digisound ring modulator
- Incoming call indicator
- Telephone Ring Generator Using 60Hz Power Transformer
- Telephone Ring Generator Using Switching Power Supply
- Telephone In-Use LED Indicator
- Telephone In-Use Relay Circuit
- Telephone Audio Interface
- Ringing Phone Light Flasher
- Phone Busy Indicator
- FM Telephone Bug
- Cut Phone Line Detector
- Simple Phone Tap
- Telephone Hold Button
- Telephone Recorder
- 1-line telephone status indicator (PDF)
- Line in use indicator (PDF)
- 4-line telephone status indicator (PDF)
- Caller ID decoder
- Telephone in use light
- Detecting a telephone RING
- Phone In-Use Light
- Phone to audio interface
- Phone Off-Hook Indicator
- ‘phone rang’ indicator light
- Phone Line to Audio
- Phone in-use
- Telephone Line Monitor
- Use old phones as an intercom
- Phone-In-Use indicator
- Hold function for Telephone
- Digital/Standard Phone Line Tester
- Universal telephone hold
- Talking phone dial monitor
- Telephone line simulator
- Telephone privacy adapter
- Telephone ringing circuits
- Simple circuit to connect telephone equipment to audio mixer
- Cut phone line detector
Test equipment schematics
- Tri-Waveform Generator
- JFET crystal testing oscillator
- ESR Meter
- Line Output / Flyback transformer tester
- AC Line Current Detector
- Triangle and Squarewave Generator
- Voltage probe
- Live line detector
- Electric field & leakage detector
- Simple polarity detector
- RCM710 Electronic Scale
- 3 - 12 MHz Signal Generator
- Some simple test equipment to build
- RF Power Meter for the QRPer
- Dip Oscillator for HF
- Two Tone Audio Oscillator (use for SSB tests)
- Simple pH meter
- Temperature compensated pH meter
- pH meter with calibration
- LASER/LED light output intensity meter (PDF)
- Frequency and capacitance meter
- Simple light sensor adapter for oscilloscope
- Time Domain Reflectometer (TDR)
- EMF field probe
- Function generator
- Logic probe
- Zener diode tester
- Signal tracer & injector
- Pulse Reading Logic Probe
- Pink Noise Generator for Audio Testing
- Audio Millivoltmeter
- Audio Test Oscillator
- Full Featured Transistor Tester
- Opamp Design and Test Board
- Microphone Circuit Test Oscillator
- Distortion Analyser
- Self Oscillating Amplifier for Distortion Testing
- Build a Magnetic Field Immunity Tester
- 555 Timer IC Tester
- 555 go / no-go tester
- 12V Lead-Acid Battery Monitor
- Continuity tester 2
- Continuity tester
- Logic probe
- 220V wiring detector
- In-circuit electrolytic tester
- PIC logic probe with pulser
Timing, oscillators etc. (schematics)
- Staircase wave generator
- 1 Second Time Base From Crystal Osc.
- Power-On Time Delay Relay Circuit
- Low Voltage , High Current Time Delay Circuit
- Power-Off Time Delay Relay Circuit
- Generating a Delayed Pulse With a dual 555 Timer
- 1KHz Sinewave generator
- Timed beeper
- Weign Bridge generator
- Time Delay Relay
- Time Delay Relay
- Wide-swing Variable Crystal Oscillator
- Circuit that momentarily closes a pair of contacts at long intervals
- Line powered 60Hz clock generator (PDF)
- Micro-power pulse generator (PDF)
- Darkroom camera shutter timer
- Divide by 1.5 counter (PFD)
- High-output square wave generator (PDF)
- D Flip-flot one-shot circuits (PDF)
- Clock divider
- Clock doubler
- CMOS oscillator
- Crystal 32.768KHz CMOS Oscillator
- Crystal oscillator
- Cheap 40KHz clock
- Stable 40KHz clock
- ‘Rounding Off’ a square wave
- Switch debounce using 555
- Square wave to sine wave converter
- Micropower pulse generator (PDF)
- Push Button Switch Debouncer
- Square wave oscillator
- Clock generator
- 555 Timer Tutorial + Circuits
Transmitter schematics (also see RF)
- Portable 40W CW transmitter
- Spark-gap transmitter
- Wireless microphone
- A 3m (100 MHz) small bug
- Basic FM Transmitter
- Micro Power AM Broadcast Transmitter
- FM Beacon Transmitter (88-108 MHz)
- FM transmitter
- Two Valve 40m CW Transmitter
- Frequency agile 80m CW QRP transmitter
- 80 metre DSB transmitter
- One Valve CW transmitter
- 175KHz inductive pulse transmitter (PDF)
- Small Radio Transmitter
- FM Telephone Transmitter
- Micropower Event Transmitter
- FM transmitter
- 4 transistor transmitter
- FM transmitter
- Op-amp based FM transmitter
- Miniature FM transmitter
- Sensitive FM transmitter
- Simple RF transmitter
- 1.5 volt tracking transmitter
- Tracking transmitter
- Micro Power FM Broadcasting Circuits
- Low Power FM Transmitter
- 30-Meter QRP Transmitter for Morse Code
- Miniature FM Transmitter #1
- Miniature FM Transmitter #2
- Miniature FM Transmitter #3
- Light sensing RF transmitter
- Micro-Spy with FETs
- Micro-Spy with USW
- Micro-Spy with TTL
Video related schematics
- Audio / video distribution amplifier
- Driver for multiple VGA monitors
- Closed-Caption Decoder
- PIC-Tock video clock
- Video signal amplifier
- MC1374 based TV transmitter
- TV transmitter
- Simple TV transmitter
- Video signal edge enhancement
- Video amplifier
- Digital volt meter with video output
- Video switcher (PDF)
- Video switcher
- TV/Radio antenna cable galvanic isolator
- S-video to composite video adapter
- VGA converter for video projectors and fixed frequency monitors
- VGA to TV converter
- VGA to PAL and NTSC converter
- Do-it-Yourself VGA ro PPrPb Cable
- Many video amplifier circuits includiing transmission over UTP (PDF)
- Mark II video digitiser
- Video digitiser
- Audio-video switch
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