New circuits

Simple Field Strength Meter circuitSimple Field Strength Meter
This Field Strength Meter is simple and also quite sensitive. It uses an ordinary digital voltmeter to measure RF signal strength up to a few hundred MHz.

Precision Audio Millivoltmeter circuitPrecision Audio Millivoltmeter
Measures 10mV to 50Volt RMS in eight ranges

Parallel Port Relay Interface circuitParallel Port Relay Interface
Here is an example of controlling a relay from the PC's parallel printer port (LPT1 or LPT2).

PC Serial Port Receiver circuitPC Serial Port Receiver
This circuit was designed to control a 32 channel Christmas light show from the PC serial port.

Connecting Dump Terminal circuitConnecting Dump Terminal
Some applications may not need user display and key interface, dump terminal is an alternative way for program setting, displaying user interfacing command.

Driving Stepper circuitDriving Stepper
M1 is a stepper taken from an old disk drive. There are five pins, i.e., common, coil 1, 2, 3 and 4. Resistance measured between common pin and each coil is about 75 Ohms. Driving current for each coil is then needed about 60mA at +5V supply. A darlington

Analog switch expands I2C interface circuitAnalog switch expands I2C interface
Perhaps the most effective way to gain board space and increase component density is to minimize wiring on the board. A widely used architecture that allows such miniaturization is the I2C bus.

The A/D Easily Allows Many Unusual Applications circuitThe A/D Easily Allows Many Unusual Applications
Two design features of the ADC0801 series of A/D converters provide for easy solutions to many system design problems.

A/D Converters Easily Interface with 70 Series Microprocessors circuitA/D Converters Easily Interface with 70 Series Microprocessors
This application note describes techniques for interfacing parallel I/O and serial I/O 8-bit A/D converters to the INS8070 series of microprocessors. A detailed hardware and software interface example is provided for each type of A/D.

A Tamper-resistant Watt-hour Energy Meter Based On The Ad7751 And Two Current Sensors circuitA Tamper-resistant Watt-hour Energy Meter Based On The Ad7751 And Two Current Sensors
This application note describes a low-cost, high-accuracy watt-hour meter based on the AD7751.

18-bit ADC uses PC's serial port circuit18-bit ADC uses PC's serial port
A PC usually requires a plug-in ADC card to process analog signals. However, with this circuitry, a PC can communicate with an 18-bit ADC through its serial port.

16-bit ADC provides 19-bit resolution circuit16-bit ADC provides 19-bit resolution
Many data-acquisition systems require both high accuracy and a fast acquisition rate. These attributes allow the system to detect small data signals and to group more sensor channels into the same system.

12-Bit Sampling A/D Converter Conserves Power circuit12-Bit Sampling A/D Converter Conserves Power
This application note uses a timer IC (ICL7555), CMOS logic and discrete transistors to automatically control the conversion the MAX190 12-bit SAR analog-to-digital converter (ADC). The delay between conversions can be programed using a resistor. Logic ci

555 Timer as an A/D converter circuit555 Timer as an A/D converter
I had a Basic Stamp project that needed to measure a nominal 12 volt battery, and I wanted a simple solution. This is the simplest I could come up with.

Programmable Bench Power Supply circuitProgrammable Bench Power Supply
Programmable positive and negative power supply.

Tracking Regulated Power Supply circuitTracking Regulated Power Supply
This supply is very suitable for powering an operational amplifier system since positive and negative voltages track.

Triangle-Wave Generator circuitTriangle-Wave Generator
This circuit provides a variable frequency triangular wave whose amplitude is independent of frequency.

Sine Wave Oscillator circuitSine Wave Oscillator
An amplitude-stabilized sine-wave oscillator. This circuit provides high purity sine-wave output down to low frequencies with minimum circuit complexity.

The Full-Wave Rectifier and Averaging Filter circuitThe Full-Wave Rectifier and Averaging Filter
The circuit is the heart of an average reading, rms calibrated AC voltmeter.

The Analog Multiplier circuitThe Analog Multiplier
A simple embodiment of the analog multiplier.

The Reset Stabilized Amplifier circuitThe Reset Stabilized Amplifier
The reset stabilized amplifier is a form of chopper-stabilized amplifier.

Adjustable Voltage References circuitAdjustable Voltage References
Adjustable voltage reference circuits (Positive and Negative).

Precision Current Source circuitPrecision Current Source
Precision Current Sink and Precision Current Source.

Photocell Amplifiers circuitPhotocell Amplifiers
Amplifiers for photoconductive, photodiode and photovoltaic cells.

The Current-to-Voltage Converter circuitThe Current-to-Voltage Converter
The current-to-voltage transducer.

Simple Low-pass Filter circuitSimple Low-pass Filter
This circuit has a 6 dB per octave roll-off after a closed-loop 3 dB point.

Integrator circuitIntegrator
This circuit is essentially a low-pass filter with a frequency response decreasing at 6 dB per octave.

Differentiator circuitDifferentiator
Differentiator and Practical Differentiator.

The Difference Amplifier circuitThe Difference Amplifier
The difference amplifier is the complement of the summing amplifier and allows the subtraction of two voltages or, as a special case, the cancellation of a signal common to the two inputs.

Summing Amplifier circuitSumming Amplifier
The summing amplifier, a special case of the inverting amplifier.

The Unity-Gain Buffer circuitThe Unity-Gain Buffer
The circuit gives the highest input impedance of any operational amplifier circuit.

Non-Inverting Amplifier circuitNon-Inverting Amplifier
The Non-Inverting Amplifier, a high input impedance non-inverting circuit.

The Inverting Amplifier circuitThe Inverting Amplifier
Inverting Amplifier is the basic operational amplifier circuit.

Root Extractor circuitRoot Extractor
Taking the root of a number using log converters is a fairly simple matter. All that is needed is to take the log of a voltage, divide it by, say 1⁄2 for the square root, and then take the antilog.

Computing Circuits circuitComputing Circuits
A circuit which performs both multiplication and division in this fashion.

Servo Preamplifier circuitServo Preamplifier
Saturating Servo Preamplifier with Rate Feedback

Nonlinear Operational Amplifier circuitNonlinear Operational Amplifier
Nonlinear Operational Amplifier with temperature-compensated breakpoints

Positive Peak Detector with Buffered Output circuitPositive Peak Detector with Buffered Output
The peak detector is similar in many respects to the sample-and-hold circuit.

Low Drift Sample and Hold circuit circuitLow Drift Sample and Hold circuit
A sample-and-hold circuit which combines the low input current of FET’s with the low offset voltage of monolithic amplifiers.

A FET Amplifier circuitA FET Amplifier
FET amplifier using a discrete FET pair in conjunction with a monolithic circuit.

More Output Current Swing circuitMore Output Current Swing
High Current Output Buffer with a pair of complementary transistors.

Voltage Comparators circuitVoltage Comparators
Comparator for driving DTL and TTL integrated circuits, Comparator and Lamp Driver.

Level Shifting Amplifier circuitLevel Shifting Amplifier
Level-Shifting Amplifiers: Standard Differential Amplifier and Level-Isolation Amplifier.

Operational-Amplifier Oscillator circuitOperational-Amplifier Oscillator
The free-running multivibrator shown in is an excellent example of an application where one does not normally consider using an Op Amp.

IR Link circuitIR Link
A basic Infra Red Link for audio communication for distances up to 3 meters.

Audio Indicator circuitAudio Indicator
This circuit can be used to remotely monitor a loudspeaker, alarm, or audio source for presence of an audio waveform. It can also be directly connected across loudspeaker terminals used as a peak indicator.

Telephone Bell circuit circuitTelephone Bell circuit
This circuit was floating around on the web apparently untried and since I had recently acquired a school bell I thought I'd give it a try.

40W Magnetic Ballast With Electronic Ignition circuit40W Magnetic Ballast With Electronic Ignition
Here is the schematic of another fluorescent ballast circuit from a lamp I acquired along with the 80W electronic ballast. It actually contains a pair of the circuit in the diagram, one for each bulb.

3-6V Xenon Strobe Light circuit3-6V Xenon Strobe Light
This circuit used to come as a kit from a surplus supplier, but probably isn't available anymore. It shows a few novel concepts such as using a 555 as a pulse width modulator (PWM), and series/parallel camera flash transformers.

14 Watt Compact Fluorescent Electronic Ballast circuit14 Watt Compact Fluorescent Electronic Ballast
This circuit came from a 14 Watt Commercial Electric spiral bulb from Home Depot. In fact, I drew it in that way because it was layed out very well, so much credit should go to Sam Goldwasser.

Ignition Coil Driver circuitIgnition Coil Driver
This is a high energy ignition coil driver circuit capable of running from AA batteries.

Monitor Splitter circuitMonitor Splitter
A Simple Splitter Driving Two (or even more) PC Monitors.

E.S.P. Conjuring Trick circuitE.S.P. Conjuring Trick
A former President of the Magic Circle, three times awarded the International Award for Magic, commented when he saw this trick: "Absolutely incredible!"

Transmit Infrared Signals Through Walls circuitTransmit Infrared Signals Through Walls
How to turn your IR transmitter into an RF transmitter & control stuff throughout your house.

Four channel RF remote control circuitFour channel RF remote control
RF 4 channels remote transmitter and receiver circuits

Simple FM Radio with improved audio gain circuitSimple FM Radio with improved audio gain
Very simple FM Radio circuit using only one transistor.

Simple receiver with microvolt sensitivity circuitSimple receiver with microvolt sensitivity
This receiver costs less than $10 to build, uses commonly available components.

Telephone Audio Interface circuitTelephone Audio Interface
Audio from a telephone line can be obtained using a transformer and capacitor to isolate the line from external equipment.

Telephone In-Use Relay Controller circuitTelephone In-Use Relay Controller
Circuit to close a relay when any phone extension is off-hook.

Telephone In-Use Indicator circuitTelephone In-Use Indicator
Circuit to illuminate an LED when any phone extension is off-hook. LED should illuminate when circuit is off-hook.

Telephone Ring Generator Using Small Power Transformer circuitTelephone Ring Generator Using Small Power Transformer
This ring generator will ring a telephone once every 10 seconds.

Telephone Ring Generator Using Switching Supply circuitTelephone Ring Generator Using Switching Supply
The telephone ring generator shown below generates the needed high voltage from a simple switching mode power supply.

9-pin null modem cable circuit9-pin null modem cable
9-pin to 9-pin female

9-Line Telephone Sharer circuit9-Line Telephone Sharer
This circuit is able to handle nine independent telephones (using a single telephone line pair) located at nine different locations.

Electronics Telephone Talking Circuit circuitElectronics Telephone Talking Circuit
This is the basis of electronics telephone sets.

2 line intercom plus a telephone changeover switch circuit2 line intercom plus a telephone changeover switch
The circuit presented here can be used for connecting two telephones in parallel and also as a 2-line intercom.

Wailing Alarm Siren circuitWailing Alarm Siren
This circuit provides a warbling sound to any alarm circuit.

Christmas Lights Tester circuitChristmas Lights Tester
Simple tester for christmas lights using MC14069.

Car Back-up Alarm circuitCar Back-up Alarm
The circuit diagram of Car Back-up Alarm. It is an older circuit, but still a good circuit today.

Car NiCad Charger circuitCar NiCad Charger
This circuit provides up to 20V output from a regular 13.2V automotive battery, to enable constant current charging of nicad battery packs up to 15 cells at 1.2V.

12V to 9V DC converter circuit12V to 9V DC converter
Simple Car Converter for 12V to 9V.

Power Supply 18V and 1A circuitPower Supply 18V and 1A
This is a classic linear power supply which produces a regulated 18v, rated at about 1 amp.

Audio-video switch circuitAudio-video switch
This is an 8-input x-output audio/video switch module to be controlled from a computer, for example from the parallel port.

AV (Audio/Video) Wireless Transmitter circuitAV (Audio/Video) Wireless Transmitter
This circuit provides you with wireless audio and visual transmission to a TV. The TV acts as a receiver, eliminating the need to buy a separate monitor. You can also hook it up to a VCR or CCD Camera, and even set up a remote CCTV security system!

20 Watt Power Amplifier circuit20 Watt Power Amplifier
Based on TDA2005M. Designed to be used as car Amplifier.

16 Watt Amplifier circuit16 Watt Amplifier
16 Watt Audio Amplifier uses two LM383 IC.

Simple High Quality Preamplifier circuitSimple High Quality Preamplifier
Circuit of simple, high quality preamp. Has all the facilities normally expected.

LED Traffic Lights circuitLED Traffic Lights
The LED traffic Light circuit controls 6 LEDs (red, yellow and green) for both north/south directions and east/west directions.

Photo Electric Street Light circuitPhoto Electric Street Light
Photo Electric Street Light which receives input from a cadmium sulfide photo cell and controls a relay that can be used to switch off and on a street lamp at dawn and dusk.