Complete List Of Electronics ProjectsAlarm and SecurityDrinking Water AlarmAnti-Theft Security For Car AudiosLuggage Security SystemPower BuzzerInfrared Proximity Detector AlarmGeneral-Purpose AlarmSimple Darkness Activated AlarmModel Railway Short-Circuit BeeperGated AlarmLaser AlarmLow-Cost Low-Intensity AlarmSpeed Alarm For CarsRemote Alarm For Smoke DetectorSimple 6-Input AlarmNight AlertSimple Knock Alarm With Piezo SensorSmoke Alarm Battery Life ExtenderMains Supply Failure AlarmBell AlarmWater Alarm Circuit DiagramMidnight Security LightLow Cost Burglar Alarm For BoatsWater Level AlertTwo-Tone Siren Using One ICFridge Door AlarmBroken Charger Connection AlarmFire Alarm Using ThermistorSafety GuardPowerful Security SirenMini Alarm

AmplifiersSuper Simple 3 Watt Audio Power Amplifier Modular Headphone Amplifier High Power Headphone Amplifier Using BD139-40 Dual Power Amplifier Using TDA7293 MOSFET IC Low Cost 2x20 Watt Stereo Amplifier by TDA2005 AF Amplifier With Digital Volume Control Based On TDA8551 11W Stereo/22W Mono Power Amp Using TDA1519C 5.3W Amplifier With Surround System Balanced Microphone Amplifier Headphone Amplifier Using Discrete Components 22W Stereo Amplifier Using TDA1554

Compact DJ Station 10W Audio Amplifier With Bass-Boost Guitar Amplifier Mini Guitar/Bass Amplifier Playback Amplifier For Cassette Deck 1W BTL Audio Amplifier Very Simple Bench Amplifier Boomer Audio Power Amplifier Using LM4906 Condenser Mic Audio Amplifier 60 Watt Guitar Amplifier 60 Watt Bass Amplifier Mini Portable Guitar Amplifier 22 Watt Car Subwoofer Amplifier Hybrid Headphone Amplifier USB Powered Audio Power Amplifier DC-Coupled Audio Amplifier Simple Hybrid Audio Amplifier Compact High-Performance 12V 20W Stereo Amplifier 36 Watt Audio Power Amplifier Using TDA1562Q Studio Series Stereo Headphone Amplifier 45 Watt Class-B Audio Power Amplifier 60 Watt Audio Power Amplifier 18W + 18W Stereo Hi-Fi Audio Amplifier (TDA2030) A Low Power Wireless Audio Power Amplifier 8 Watt Audio Power Amplifier A High Quality Headphone Amplifier 30 Watt Audio Power Amplifier Pure Class-A Headphone Amplifier Stereo Headphone Amplifier 7 Watt Audio Power Amplifier Portable Headphone Amplifier 25 Watt Audio Amplifier 5 Watt Class-A Audio Amplifier 18watt Audio Amplifier Headphone Amplifier 2Watt Audio Amplifier Portable 9v Headphone Amplifier Speech Amplifier

Audio and MusicOptimized Semiconductor Noise SourceSymmetric Noise SourceUS-Style SirenMulti-Sound For GuitarsGeneral Purpose OscillatorOscillation MonitorPan PotMini Audio Signal GeneratorSounds From The Old WestGuitar ControlCheapskate's Headset AdapterDual Input-Combining Stereo Line Amplifier

Steam WhistleAudio Level Threshold ControlMulti-Melody Generator With Instrumental EffectIR Music Transmitter and ReceiverMulti-tone SirenSound Source Locator Uses PreChampAudible Flasher WarningSurf Simulator Circuit DiagramWhen The Siren Sounds - A Useful CircuitSimple White Noise GeneratorBalanced-Unbalanced Converter For Audio WorkAutomatic Loudness ControlCuckoo Sound GeneratorCricket Chirping GeneratorBells Ring GeneratorMelody Generator4 Channel Portable Audio MixerMusic Generator Schematic Using UM66Laptop Audio-Out SplitterThree Channel Audio MixerDigital Volume ControlStereo to Mono Converter Based on FETThree Channel Audio Splitter

AutomotiveBrake Light Signal ModuleCar Battery SaverCar Boot Lamp Warning (ICM7556)Lambda Probe Readout For Carburetor TuningLights On!Rear Light After Glow (For Bicycles)Car Interior Lights DelayPark-Aid ModificationPark-AidPush-Bike LightSpeed-Limit AlertHeadlight ReminderAutomatic Headlight ReminderAFX Slot Car Lap CounterPetrol Gas Switch For A PajeroCar Reversing Horn With FlasherBicycle Speedometer With Hub DynamoRear Fog Lamp For Vintage CarsCentral Locking InterfaceAutomatic Windshield Washer ControlSimple Headlight RemindersLED Bike LightFog Lamp SwitchFog Lamp SensorFlashing-LED Battery-Status IndicatorMotor Bike Headlight ControllerCar-Bulb Flasher

Battery and ChargersBattery JuicerLi-Ion Battery ChargerLead Acid Battery Charger #1Lead Acid Battery Charger #2Deluxe Charge Rate Limiter for Small Capacity NiCad BatteriesElectric Window/Fence ChargerVersatile Micro-power Battery ProtectorBattery Equality Monitor12 Volt Battery GuardianBattery SaverPC-Powered Battery ChargerA 12V Car Charger For ASUS Eee NotebookSimple Battery Discharger Using Discrete ComponentsBattery Charger Display Using LT1639Battery Switch With Low-Dropout RegulatorMotorcycle Battery MonitorNiCd Battery ChargerFloat Charger For NiMH CellsSimple Battery IsolatorSimple NiCd Battery ChargerNiMH Charger For Up To Six CellsNicad Charger Uses Voltage Cut-OutBattery Desulphation Progress MonitorStorage Battery ExerciserSwitch-less NiCd-NiMH Battery ChargerSolar-Powered High Efficiency Battery ChargerLow-Voltage Cutout For 12V SLA BatteriesBike Battery ChargerSimple Battery Charger - Charges Upto 12 NiCD CellsSolar Battery Protector Prevents excessive DischargeLow Cost Battery Condition Indicator12V Lead Acid Battery DesulphatorHigh-Current Battery DischargerSolar Panel Based Charger And Small LED LampBattery Charger RegulatorLow-Power Car/Bike USB ChargerLithium-Polymer Peak ChargerIn-Car Charger And Switcher For SLA BatteryMobile Phone Travel ChargerNiCd Battery Charger With Reverse Polarity ProtectionNiMh and NiCd Battery ChargerUSB Powered Mobile Phone Battery Charger12 Volt Car Battery ChargerA Friendly Charger for Mobile PhonesLow Cost Universal Battery ChargerMobile Cell phone Battery ChargerMobile Phone and iPod Battery ChargerMobile Phone Battery ChargerDry Cell Battery Charger Using LM741

BoostersStep-Up Booster Powers Eight White LEDsInput Impedance Booster IIInput Impedance Booster10,000x With One TransistorLow-Power Voltage Doubler (Booster)Pump it up: Mp3 BoosterAmpere or Current Booster CircuitBass Booster CircuitAudio Booster

Clock and TimersFlip-Flop Timer Using 4017Three Hour TimerIsolated 1-Hz ClockEgg TimerAlarm Clock With Day SelectorThrifty 2Hz ClockExperimental Pendulum ClockAn Accurate Reaction TimerSwitch Timer For Bathroom LightUp/Down Timer For A Power AntennaPendulum-Controlled ClockMultipurpose Flip-Flop Timer555 Timer With Variable On/Off TimesBuilding A Synchronous ClockLong Delay TimerJogging TimerAmplifier TimerOne second Audible ClockCar Headlights TimerA Tan TimerA Very Useful Timed BeeperA Bedside Lamp Timer

Computer RelatedCD-Rom Drive as Digital-Audio CD PlayerSerial To Parallel ConverterAutomatic Mains DisconnectCase ModdingProcessor Fan ControlIrDA InterfaceHome Network for ADSLHow To Connect Two Computers Using ModemsMonitor Life ExtenderDigital Isolation up to 100MbitsSpeaker-Headphone Switch For ComputersComputer Off SwitchHard Disk SwitchUSB FuseUSB Power Socket With IndicatorUSB Switch For Printers

Laptop ProtectorUSB Operated Home AppliancesUSB Printer Share SwitchUSB Power Injector For External Hard Drives

Filters and OscillatorsBaud Rate GeneratorComparator Based Crystal OscillatorHQ Notch Filter Without Close-Tolerance ComponentsSimple Function GeneratorVery Low Power 32kHz OscillatorVoice Bandwidth Filter

Health and HobbyECG Amplifier By TLC274Railway Points SequencerPulse Rate MonitorPills ReminderQuick Counter For Young ChildrenLED Noughts And CrossesLED Chaser Provides Three Game FunctionsLow-Cost Dual Digital DiceSoldering Iron Tip PreserverGym Agility: A Simple Strategy GameHeart Rate MonitorCall Acknowledged !Model Railway Turnout ControlTranscutaneous Electrical Nerve Stimulator (TENS)Tablet Reminder Uses Watch Module123 Game - All MCU-freeDicing With LED'sCranial Electrotherapy StimulatorPulse Generator And Signal TracerWhistle ResponderSleeping AidDigital Step-Km Counter

Home and GardenRemote-Controlled Fan RegulatorLaser-Guided Door OpenerAutomatic Room Power ControlWater Level Indicator Using 7-Segment DisplayRainwater Storage GaugeCat and Dog RepellerInexpensive Remote Watering SystemYou Have Mail!Whistling KettleDoorbell CascadeGentle BreezeAutomatic Range Hood12V Fan Directly on 220V ACEnvironmentally-friendly Mosquito Repeller

Doorbell MemoryFridge-Door Open AlarmAutomatic Water Tank FillerDigital Remote ThermometerPlant Watering WatcherSalt TasterFridge Door Alarm Schematic 2nd VersionRoom Noise DetectorWater Level AlertHeating System Thermostat

IndicatorsFastest Finger First IndicatorDigital Main Voltage IndicatorMains/Fuse Failure IndicatorModem Off IndicatorLED Bar Off IndicatorSupply Voltage IndicatorFuse MonitorAudio Clipping IndicatorBattery-Charging Indicator For Mains AdaptorTelephone In-Use IndicatorBattery Self Discharge IndicatorTwo-LED Voltage IndicatorBlinker IndicatorYes-No Indicator Has Zero Standby CurrentLow Battery Indicator IILow Battery Indicator IMaximum Minimum Voltage IndicatorClipping Indicator For Audio AmplifiersMains IndicatorEarth Fault IndicatorBlown Fuse IndicatorBattery Indicator For The Caravan110 and 220V AC LED Voltage IndicatorWater Level IndicatorDC or AC Voltage IndicatorBattery Voltage IndicatorPeak IndicatorAudio Indicator Using LM741

IR (Infra-Red)Simple Remote Control TesterSimple Infrared Remote Control ExtenderInfra-Red Sensor/MonitorInfra-red Light Barrier Using 555RC5 RepeaterLight Gate With Counter Using 555 And 4033IR–S/PDIF TransmitterIR–S/PDIF ReceiverIR Remote Control ReceiverInfra-red Receiver

Simple Infrared Control ExtenderDirection Sensitive Light BarrierInfrared Remote Receiver Has Four OutputsRC (Remote Control) SwitchInfrared Remote ExtenderInfrared Fire-Cracker IgniterLong-Range IR TransmitterOn-off Infrared Remote ControlTV MuterIR (Infrared) DetectorBeam-break Detector For Camera Shutter or Flash ControlRemote Operated Home AppliancesWireless On-Off SwitchActive High Pass Filter Using LM741

Inverters and Converters500W Low Cost 12V to 220V InverterUPS For Cordless TelephonesDiscrete Voltage InverterVoltage Inverter Using Switch-Mode Regulator4-Bit Analogue to Digital Converter12V Fluorescent Lamp InverterCheap 12V to 220V InverterInverter For Soldering Iron100W Inverter

Lights and LEDsWhite LED Lamp12 Volt DC Fluorescent Lamp DriverFine Control Super Bright LED PulserBar-Mode Lights SequencerLED–LDR BlinkerMagic LightsPicnic LampHigh-Intensity, Energy-Efficient LED LightSoft Start For Torch - Increases The Life Of Torch BulbsTwo-Position Dimmer220V AC Powered Blinking LEDEL Lamp Driver Using HV832MGVehicle Interior Lighting With Switch-Off DelayLED FlasherReflector For PedestriansMains Powered White LED LampLuxury Car Interior LightMulti-Color LEDAutomatic Light Dimmer6-Channel Running LightLED Lighting For Consumer Unit CupboardLight From Flat BatteriesFlickering Light II30mA LED DimmerBackup Lamp

Dimmer With A MOS-FET1W LED DriverUV Torch LightLED Light PenIrregular FlasherBluish FlasherNovel White LED Torch12V Halogen DimmerAutomotive LED Timing LightEconomical Desk Lamp For CampingEl-Cheapo Fluoro BallastExit Sign With Battery ProtectionStroboscope Uses White LEDsCourtesy Light ExtenderModel Theatre Lighting DimmerUsing AC for LED Christmas LightsLED Lighting For Dual-Filament LampsConstant Current LED DriveAutomatic White-LED Garden LightInteractive Toy Traffic LightsTraffic Lights For Model Cars Or Model RailwaysNeon Flasher Runs From 3V SupplyLED Torch Uses Blocking OscillatorGrand Prix Starting LightsHalogen Lamp Dimmer With Soft StartThrifty LED ProtectorDriver For 20 LEDsMulticolor HD LEDAutomatic Light Controller Using 7806LED Phototherapy UnitUsing LED As A Light SensorSlave Flash TriggerUltra Bright LED LampPortable Lamp FlasherOne Of Nine Sequencer12V DimmerFully Automatic Emergency LightSolar Lamp Using PR4403Slave Flash TriggerPut That Light OutHigh-intensity LED Warning FlasherSmooth FlasherThe Itsy-Bitsy USB LampMidnight Security Light Circuit SchematicIC Controlled Emergency Light With ChargerElectronic Candle Blow OutFlashing-LED Battery-Status IndicatorFading LEDsDancing LEDsBicycle Back Safety LightAutomatic Low-Power Emergency LightTwo Flashing LEDs

Mains Operated LEDAC 220 Volts Flashing LampsBrightness Controller For Small Lamps and LEDsLED or Lamp Pulsar CircuitLED or Lamp FlasherEmergency Light and AlarmTwo-LED Pilot LightFlashing EyesDark Activated LED or Lamp FlasherBattery Powered Night LampCourtesy LightDark Activated Terrace Lamp

MCU - MicrocontrollerPIC Controlled Relay DriverLCD Module in 4-bit ModeAVR DongleUSB-Powered PIC ProgrammerProgramming The Propeller ICContrast Control for LCDsSimple Universal PIC ProgrammerIntelligent Presence SimulatorThe Gentle TouchMultitasking PinsDCF77 Preamplifier

MicrophoneElectronic Ear for Lego RCX ModuleLow-Noise Microphone Amplifier (OP270E)Compressor For Electret MicrophoneSpeech EroderRoom RecorderSpy EarClap Sensitive On-Off RelayHearing AidA Low Cost Hearing AidAmplified Ear

Motor ControlElectronic Motor StarterPWM Dimmer/Motor Speed ControllerStepper Motor GeneratorBipolar Stepper Motor ControlRolling Shutter Motor ControlFan Controller Using Just Two ComponentsReservoir Pump ControllerSolar Hot Water Panel Differential Pump ControllerStepper Motor GeneratorLuminescent GeneratorMotor Turn Stall DetectorTwo Basic Motor Speed ControllersCheap Pump Controller

Efficient Fan Speed ControllerLight-Controlled Pond PumpJunk-box Fan Speed ControllerPump Controller For Solar Hot Water SystemStepper Motor ControllerDC Motor Speed ControllerDiscrete PWM Generator12V Speed Controller/Dimmer

Power (Mains)Non-Contact Power MonitorContact-less AC Mains Voltage DetectorSupply Voltage MonitorElectrical Isolation For I2C BusSimple Electrification UnitMains PulserPower Flip-Flop Using A TriacMains Voltage MonitorMains ManagerMains Slave Switcher IIMains Slave SwitcherMains Frequency MonitorSmart Trailing SocketFuse SaverMini High-Voltage Generator

Power SupplyDual Polarity Unregulated PSU For High-End Audio AmpsHigh Voltage Converter: 90V From 1.5VVery Low Dropout Adjustable Breadboard Power Supply3V Supply SplitterTransformer-less Power SupplyDiscrete Voltage RegulatorSimple Pre-RegulatorDual Power Supply For AmplifiersSwitching Voltage RegulatorLow Power 12V Transformer-less Power SupplyHigh Input Voltage Linear RegulatorATX Power Switch SubstituteCompact Switching Step-Down Converter By MAX639DC/DC Converter From +1.5V To +34VDual Polarity 5 Volt Converter Using LM26859V DC Adapter With Battery Backup3 Volts Car Adapter Using LT1074CTAdjustable 3 Ampere Regulator78xx Voltage Regulators12V Glow Plug ConverterDC Control for TriacsDMM Fuse ProtectorOver-voltage ProtectionFloating 9V Supply For DVM ModulesRS232 Voltage Regulator

555 DC/DC ConverterLow-Power Voltage ReferenceSwitch-Mode Power SupplyLow-Drop 5V RegulatorThrifty Voltage RegulatorUltra Low-Power 5V RegulatorSoft Start For Switching Power SupplyAlarm Power SupplyFast Electronic FuseLogic PSU With Over-Voltage ProtectionPolarity ReverserLead-Acid-Battery Regulator For Solar Panel SystemsFast Voltage-Driven Current SourceVariable PSUReset from Multiple Power SuppliesVoltage Regulator CalculationReverse Polarity Protector7.2V Battery Replacement Power Supply For CamcordersPower Supply For USB Devices5V Power Supply For On-Train Radio CameraNegative Auxiliary VoltageStable Filament SupplyVoltage Levels Control RelaysTriple Power SupplySMPSU With A RelayInductor-less 3-5 Volts ConverterBuck-Boost Voltage ConverterAdjustable Zener Diode3.3 V or 5 V Direct from the Mains100V RegulatorsFully Adjustable Power SupplyBattery Replacement Power SupplySwitch-mode Constant Current SourceUltra Low Drop Linear Voltage RegulatorShort Circuit Protection For Balanced Supply RailsLow-Cost Dual Power SupplyHigh Current Low-Dropout Voltage RegulatorCheap Switch-Mode DC-DC Converter8V DC Power Supply With Over-Voltage ProtectionLow-Loss Step Down ConverterHigh-Voltage Regulator With Short Circuit ProtectionAlternative Halogen Power SupplyQuad Power Supply For Hybrid AmplifierPower MOS-FET Bridge RectifierTransformer-less 5 Volt Power SupplyAdjustable Current Limit For Dual Power SupplyStep-Down Converter ControlleStabilized Power Supply With Short-Circuit IndicationProtection For Voltage RegulatorsSolar Cell Voltage RegulatorLow Voltage Step-Down Converter48V Phantom (Microphone) Power Supply

12V Regulated Inverter Supply9 Volt 2 Ampere DC Power Supply3-30V 3A Adjustable Regulated DC Power SupplyAdjustable 1.3-22V Regulated Power Supply5V Regulated Power Supply1.5 - 35 Volt DC Regulated Power SupplyAmpere or Current BoosterDiscrete Virtual GroundStabilized Regulated Power SupplDual-rail Variable DC Power SupplyDual Opamp Buffered Power SupplyVariable Dc Power Supply

Pulse and FrequencyPulse Generator1kH Synthetic InductorFrequency Doubler1.2GHz VCO With Linear ModulationPulse Frequency ModulatorCMOS Crystal Frequency MultiplierOptical Pulse GeneratorLong-Interval Pulse Generator

RF (Radio)Wire Tracer (Transmitter)Wire Tracer (Receiver)Low Power FM TransmitterSimple RF Detector For 2MOne Transistor Radio10 to 1000 MHz Oscillator0-44dB RF AttenuatorDiode Radio For Low Impedance HeadphonesLongwire Match For SW ReceiversFM Wireless MicrophoneActive Short-Wave AntennaAntenna Tuning Unit (ATU) For 27-MHz CB RadiosSine Wave To TTL ConverterDRM Down-Converter For 455kHz IF ReceiversTuned Radio Frequency (TRF) ReceiverSSB Add-On For AM ReceiversSingle-Chip VHF RF PreampShortwave MonitorAntenna Input & Audio Lineout Adaptor For Portable RadiosRadio Controlled Electronic FlashSimple AM Radio ReceiverActive AntennaOpamp VHF FM TransmitterSimple AM TransmitterSimple Short-Wave TransmitterMedium-Power FM TransmitterThunderstorm PredictorQuality Stereo Wireless Microphone or Audio Link

RelaySolar RelayReducing Relay Power ConsumptionAudio Amplifier Output Relay DelayPushbutton Relay SelectorRelay Coil Energy SaverHandy Time Delay With Relay OutputMomentary Switch Teamed With Latching RelayWater Pump Relay Controller

Sensors and DetectorsAutomatic Heat DetectorTiny Dew SensorTwo-Wire Temperature Sensor Using LM35Sensitive Overload SensorIsolated Fuse Fail IndicatorSpike Detector For OscilloscopesAutomatic Air HumidifierCelsius ThermometerTwo-Wire Temperature SensorInfra-Red Proximity DetectorInfra-Red Level DetectorSimple Moisture DetectorTemporarily Silencing A Smoke DetectorSimple Audio Peak DetectorPseudo Track Occupancy DetectorAcoustic SensorCar Battery Failure DetectorSuper Light SensorSimple BFO Metal LocatorBody Charge DetectorMobile Bug DetectorTemperature-Controlled Soldering IronInvisible Broken Wire DetectorLow Supply Rail DetectionSimple Short-Circuit DetectionSimple One-Wire Touch DetectorSimple Capacitive Touch SensorTemperature-Controlled SwitchCapacitive SensorEnergy Leak DetectorLive Line Detector-Indicator

Speakers and SubwoofersCrowbar Speaker ProtectionCrossover For SubwooferLoudspeaker Protector Monitors Current

SwitchesIR On/Off Switch Using MicrocontrollerSmart Foot SwitchTime Switch

Heat Sensitive SwitchClap SwitchAutomatic Switch For Voltage ConvertersAuto Power OffOn And Off ButtonClap-Controlled SwitchPush Off Push OnMaster/Slave SwitchLow-Voltage Remote Mains SwitchSpeaker-Headphone Switch For ComputersPetrol Gas Switch For A PajeroRC (Remote Control) SwitchMains Slave Switcher IIComputer Off SwitchMains Slave Switcher IElectronic Touch SwitchHard Disk SwitchTemperature Sensitive Switch For Solar CollectorRemote Control Mains SwitchOn Off Touch Switch220V AC Lamp Toggle Switch

Telephone and IntercomLow-Cost Transistorized IntercomDTMF Receiver IC MT8870 TesterCordless Phone Backup2-Line Intercom-Cum-Telephone Line ChangeoverWatch-Dog For TelephonesTelephone Ringer Using Timer ICsTelephone Call Voice ChangerTelephone Line IndicatorTelephone Free IndicatorElectronic Telephone RingerAviation IntercomFull-duplex IntercomTelephone RingerProtection For Telephone Line

Test and MeasurementTransistor TesterMeasuring InductorsHigh Side Current MeasurementsCheap And Cheerful Transistor TesterCable AnalyzerThyristor TesterLiquid-Crystal Display (LCD) TesterInfra-red Remote Control Tester IThree-State Continuity TesterInfra-red Remote Control Tester IIConnection Tester12/24/48 V D.C. Tester

Improved Vibrating Battery Tester4-20mA Current Loop TesterServo Tester Using A 4538Meter Adaptor With Symmetrical InputEl Cheapo Cable TesterFour-Channel Oscilloscope AdaptorPipe DescalerCurve Tracer AdaptorCable Tester Uses Quad LatchFrequency Multiplier For LF MeasurementsCapacitor Leakage Adaptor For DMMInternal Resistance Tester For BatteriesSafe Oscillator For Watch CrystalsSimple Cat.5 Network TesterCheap AC Current MeasurementComputer Data Cable TesterBattery Tester For Deaf and Blind PersonsHyper-Simple Battery Capacity TesterHarmonic Generator With Single OpampIR Remote Control TesterLow Ohms Adaptor For DMM Based On An LM317 RegulatorSwitchable Output Crystal OscillatorSimple Logic ProbeMinimalist OscilloscopeA Very Simple LED TesterCar and Motorcycle BatteryContinuity TesterLED TesterBattery TesterQuick On-Board Junction TesterComponents Voltage TesterSelf-Powered Fast Battery TesterCircuit Board Checker220vAC Operated Remote TesterInfrared Remote Tester III

Tone Control and PreamplifierElectric Guitar PreamplifierUltra-Simple Microphone PreamplifierModular Phono PreamplifierSimple MD Cartridge PreamplifierRIAA Phono PreamplifieBalanced Microphone PreamplifierPreamplifier For SoundcardTen-Band EqualizerTreble Tone ControlAccurate Bass Tone ControlPassive RIAA PreamplifierMultimedia RIAA PreamplifierParaphase Tone ControllerPreamp Stage For Ceramic Phono Cartridge Or Violin PickupsA Balanced Output Board For The Stereo DAC

Modular Preamplifier Switching CenterModular PreamplifierPortable Microphone PreamplifierPhono PreamplifierStereo Preamplifier With Bass Boost

VideoVGA to BNC Adapter (Converter)Video-Out CouplingRGB To Color Difference Converter3-Input Video MUX Cable Driver Using LT1399Video AmplifierVideo Tracer For Trouble-ShootingNTSC-PAL TV Signal IdentifierVideo Isolator

VU MetersSimple VoltmeterLED Volt MeterLinear RF Power MeterESR & Low Resistance Test MeterTV Relative Signal Strength MeterElectronic Torricelli BarometerAudio Power MeterSave Your Ears - A Noise Meter

Miscellaneous

Dimmer Control Voltage Polarity ChangerRMS to DC ConverterFlip-Flop Using CMOS NAND GatesElectronic DieOpamp With HysteresisPWM ModulatorCat And Dog RepellentReset SequencerDiscrete RobotZero Gain Mod For Non-Inverting OpampSimple Under-Voltage Cut-OutSimple Combination LockLogic Probe With SoundRelative Field Strength Meter For A DMMSimple 9-Way Cable IdentifierDual Relay Driver Board

Drinking Water Alarm The working of the circuit is simple.

Timer 555 is wired as an astable multivibrator. The multivibrator will work only when water flows through the water tap and completes the circuit connection. It oscillates at about 1 kHz. The output of the timer at pin 3 is connected to loudspeaker LS1 via capacitor C3. As soon as water starts flowing through the tap, the speaker starts sounding, which indicates resumption of water supply. It remains ‘on’ until you switch off the circuit with switch S1 or remove the sensor from the tap. The circuit works off a 9V battery supply. Assemble the circuit on any general-purpose PCB and house in a suitable cabinet. The water sensor is inserted into the water tap. Connect the lead coming out from the junction of 555 pins 2 and 6 to the body of the water tap. Use on/off switch S1 to power the circuit with the 9V PP3 battery.

This motor starter protects single-phase motors against voltage fluctuations and overloading. Its salient feature is a soft on/off electronic switch for easy operation. The transformer steps down the AC voltage from 230V to 15V. Diodes D1 and D2 rectify the AC voltage to DC. The unregulated power supply is given to the protection circuit. In the protection circuit, transistor T1 is used to protect the motor from over-voltage. The over-voltage setting is done using preset VR1 such that T1 conducts when voltages goes beyond upper limit (say, 260V). When T1 conducts, it switches off T2. Transistor T2 works as the under-voltage protector. The under-voltage setting is done with the help of preset VR2 such that T2 stops conducting when voltage is below lower limit (say, 180V). Zener diodes ZD1 and ZD2 provide base bias to transistors T1 and T2, respectively. Transistors T3 and T4 are connected back to back to form an SCR configuration, which behaves as an ‘on’/‘off’ control.

Switch S1 is used to turn on the pump, while switch S2 is used to turn off the pump. While making over-/under-voltage setting, disconnect C2 temporarily. Capacitor C2 prevents relay chattering due to rapid voltage fluctuations. Regulator IC 7809 gives the 9V regulated supply to soft switch as well as the relay after filtering by capacitor C4. A suitable miniature circuit breaker is used for automatic over-current protection. Green LED (LED1) indicates that the motor is ‘on’ and red LED (LED2) indicates that the power is ‘on’. The motor is connected to the normally-open contact of the relay. When the relay energizes, the motor turns on.