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Gadget Circuits
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Last Updated: October 24, 2017 02:54 PM


Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

Circuits Designed by Dave Johnson, P.E. :

Tester 4-20ma Current LoopThis circuit injects an adjustable current through a wire loop.  Using a digital current meter, the current can be adjusted from near zero to over 24 milliamps . . . Hobby Circuit designed by David A. Johnson P.E.-May, 2012

Touch Alarm for Door KnobI designed this hobby circuit many years ago and it seems be a very popular construction project.  Many companies offer simple alarm devices for personal use in bedrooms or hotel rooms.  A metal chain attached to a box holding the electronics is place . . . Hobby Circuit designed by David Johnson P.E.-May, 2000

Touch Switch controls a 120 VAC loA - DThis is a capacitance based touch on/touch off switch, which can control power to a 200 watt 120vac load . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Use Color Film Negative to Make an Optical FilterThis isn’t an electronic circuit but the file shows the curve for an optical filter made from exposed color film.  The material blocks most visible light but is very transparent to 880nM infrared light.  Kodak 100ASA is exposed to "cool white" fluorescent light for about 5 seconds . . . Hobby Circuit designed by Dave Johnson P.E.-January, 1998

Vertical Lifting Security Gate Power SourceThe circuit that I came up with is shown below.  It uses 5 identical circuits.  Each one is wired in parallel with it assigned 650F super capacitor.  A LM385 provides a 1.2v voltage reference.  A resistor divider measures the voltage across the capacitor and feeds the voltage to a low power, low voltage op amp.  The output of the op amp drives an n-channel FET.  I designed the circuit for a maximum charge current of 600ma.  This would allow the use of a 10 watt solar panel, if needed, in the future.  Each of the five circuits forms a shunt type voltage regulator, limiting the voltage across each capacitor to about 2.6v.. . . Circuit by David Johnson P.E.-November, 2009

Voltage to Frequency Converter + 1us LED Pulse DriverThis circuit receives the signal from the above amplifier and launches powerful 1uS infrared light pulses from a low cost LED that are frequency modulated by the audio information.  The 10KHz center frequency of the pulse stream is low enough so a standard. . . Circuit by David Johnson P.E.-March, 1999

Wave Power Generator Demo SystE - MAn inexpensive stepper motor is used as a voltage generator in this wave generator demo. . . Circuit by Dave Johnson P.E.-March, 2007

Ultimate Universal Remote Control -  19-Aug-2009   Couch potatoes should be particularly interested in Bill Bowden's remote control IR receiver, which allows users to control the power of virtually any electrical appliance  (including those not equipped for remote) using their standard remote control.  It's based on an IR receiver circuit, which is basically a simple toggle switch that features a 48KHz IR receiver module to convert IR signals to 5V digital data representing the particular command sent. So switch a fan or lights on and off, blend up a pitcher of margaritas, pop popcorn and more, all without leaving your couch a euro " possibly ever. __ Gadget Freak-Case 147

Ultra-Portable 'MoGo' Laptop Mouse -  I've wanted an ultra-portable laptop for a long time because lugging a heavy full-sized laptop around on trips was just no fun.  After much research, I had narrowed down the choices to a Toshiba Satellite U200-PT7 or a Lenovo 3000 V100.  They were almost identical __ Designed by Stefan Vorketter

Ultra-Simple Circuit Voltage Probe -  Detects 1.8 to 230 Volts DC or AC Minimum parts counting.  Circuit diagram: Parts: D1 5 or 3mm.  Red LED D2 5 or 3mm.  Green or Yellow LED LP1 220V 6W Filament Lamp Bulb P1 Red Probe P2 Black Probe Device purpose: This circuit is not a novelty, but it __ Designed by Flavio Dellepiane

Ultrasound Detector -  The bat ultrasounds are picked up by the microphone SPKR1 and go through two stages of amplification at Q1 and Q2.  Separately, a tunable  (R12) single frequency is produced by the LM567 oscillator U1.  The LM567 is a tone decoder but here its input is grounded and its voltage controlled oscillator is used as a precision oscillator __ Contact: NJ chapter of the Society for Amateur Scientists

Use Color Film Negative to Make an Optical Filter -  This isn’t an electronic circuit but the file shows the curve for an optical filter made from exposed color film.  The material blocks most visible light but is very transparent to 880nM infrared light.  Kodak 100ASA is exposed to "cool white" fluorescent light for about 5 seconds . . . Hobby Circuit designed by Dave Johnson P.E.-January, 1998

Using old transformers -  There are times when I needed a power transformer with a certain voltage that was not a stock item or if so, it was very expensive.  There is one thing good about not having a lot of money.  It forces you to learn new things and to be a lot more innovative.  Transformers can be a tedious thing to tackle and in many cases it's not worth the trouble to make them when you can just go out and buy them.  But I have found in a few cases some practicality in partially rewinding transformers that I have just found in the junk.  The bigger the transformer that you need to wind the greater there is an advantage to rolling your own.  Why? __ Designed by Jon Tirone, AKA John Fisher

Valentine Heart -  18 LEDs flash at three different rates and you can use these to create an eye-catching Valentine Heart for that special person! A template for the heart shape can be downloaded.  The circuit is kept simple  (and low cost) by using the 4060B IC which is a counter and oscillator  (clock) in one package.  The circuit requires a 9V supply, such as a PP3 battery __ Designed by John Hewes

van Gogh's 'Starry Night' Transformed into Solar-Powered Bike Path -  21-Nov-14 -Design News:   Elizabeth MontalbanoThe Dutch are known for their love of bicycling, and they've also long been early adopters of green-energy and smart-city technologies.  So it seems fitting that a town in which painter Vincent van Gogh once lived has given him a very Dutch-like tribute -- a bike path lit by a special smart paint in __ Gadget Freak

VecAdapt: Use Mega Drive / Genesis Controllers with a Vectrex -  Click one of these links to show an up to date conversion to international currencies using Google Currency Converter:   NZD JPY USD CAD GBP EUR    For other currencies, simply change the selection in the currency box on one of the above linked pages. __ Designed by Kevin Koster

Vending Machine Delivers Every Time -  25-May-10 -Design News:   Reach into your pocket for your last 75 cents, insert the coins into a vending machine and punch B-8.  You watch eagerly as a candy bar drops and catches on part of the machine never making it to the chute.  Ryan Yourishin, William Lindenthal, Nathan Zeleski and Justin Denard have designed a __ Gadget Freak-Case 165

Vertical Lifting Security Gate Power Source -  The circuit that I came up with is shown below.  It uses 5 identical circuits.  Each one is wired in parallel with it assigned 650F super capacitor.  A LM385 provides a 1.2v voltage reference.  A resistor divider measures the voltage across the capacitor and feeds the voltage to a low power, low voltage op amp.  The output of the op amp drives an n-channel FET.  I designed the circuit for a maximum charge current of 600ma.  This would allow the use of a 10 watt solar panel, if needed, in the future.  Each of the five circuits forms a shunt type voltage regulator, limiting the voltage across each capacitor to about 2.6v.. . . Circuit by David Johnson P.E.-November, 2009

Video: BMW's i3 Electric Car Fuels Up With a Home Depot Generator -  17-Sept-2014   Christen Costa Gadget Freak BMW's i3 is an impressive piece of kit.  The frame of the car you have a Gadget Freak project you would like the world to see? Send a brief description of yourgadget and a photo to Executive Editor Jennifer Campbell.  Check out the Best of Gadget Freak-- Volume__ Gadget Freak Video

Video: Pneumatics Power Scary Guy -  02-Nov-11 Design News:   Charles Murray   The Scary Guy is an animatronic figure built by the Scare Factory. Bimba supplied components for electronic controls, air cylinders, valves, fittings, and filters to enable the figure to move its upper body independently. Bimba engineers said the pneumatic bill of materials for the Scary Guy amounted to less than $300. __ Video-Gadget Freak

Voice-Command System Rivals Siri -  25-Jul-14 -Design News:   Cabe AtwellThe Raspberry Pi mini-PC has been used for countless DIY projects since its creation, including 3D printers, drones, a LEGO-based robot, and makeshift DJ soundboard.  Now, two Princeton University students bring us a voice-command system for our homes, based on the simple and affordable Raspberry Pi __ Video-Gadget Freak

Voltage to Frequency Converter + 1us LED Pulse Driver -  This circuit receives the signal from the above amplifier and launches powerful 1uS infrared light pulses from a low cost LED that are frequency modulated by the audio information.  The 10KHz center frequency of the pulse stream is low enough so a standard. . . Circuit by David Johnson P.E.-March, 1999

Warm up to Remote Energy Monitoring -  19-Oct-09 -Design News:   Does Apple's iPhone really have "an application for everything?" Benson Hougland thinks so.  He built his own energy monitor for use in his home.  A programmable automation controller, a power-monitoring I/O module, and two current transformers let him measure current and voltage to provide power-use __ Gadget Freak-Case #151

Washing Machine Flood Alert -  2-Feb-09 -Design News:   The washing machine at Edward Nauman's house kept overflowing and flooding the floor, so he designed a flood sensor to cut the power to the washing machine if the water in the drain rose within 1.5 inches from the top.  The level sensor is mounted in a hole drilled in the drain pipe and the __ Gadget Freak-Case #133

Washing machine flood Gadget -  5-Feb-09 -Design News:   Gadget Freak, Edward Nauman, has created a device that shuts off the washing machine if it starts to flood.  As Nauman says, “It doesn’t spill on ounce of water once it hits the sensor.” And, “It’s pretty simple.” Check our  section for build instructions and a part list. __ Gadget Freak

Wave Power Generator Demo SystE - M -  An inexpensive stepper motor is used as a voltage generator in this wave generator demo. . . Circuit by Dave Johnson P.E.-March, 2007

What Happens When You Combine Arduino and iOS? -  31-Oct-14 -Design News:   The Arduino is great for connecting with hardware but has a limited user interface.  Apple's iOS devices have a great user interface but are limited when connecting with hardware.  I combined an Arduino and iOS using the DTMF audio signals established 50 years ago for touch-tone telephone dialing.  I __ Gadget Freak-Case #267

Whistle Responder -  Beeps when hears your whistle; A gadget suitable for key-holders, games etc __ Contact: Flavio Dellepiane, fladello @ tin.it

Whistling Kettle -  Most electric kettles do not produce a whistle and just switch off when they have boiled.  Fitting a box of electronics directly onto an electric kettle  (or even inside!) to detect when the kettle has boiled is obviously out of the question.  The circuit shown here detects when the kettle switches off, which virtually all kettles do when the water has boiled. __ Designed by Bart Trepak© Elektor

William Noticed a Vibration -  9-Apr-07 -Design News:   Like Jack Godell's coffee in "The China Syndrome," the fluid in William Grill's Seismic Detector reveals subtle vibrations.  The entire detector is built around a laser pointer, a few hobby-type mirrors, a PIN photdiode, regulator and amplifier, enclosed in common PVC tubing and fittings.  This __ Gadget Freak-Case #100

William Played a Mean Game of Go Fish! -  24-Apr-06 -Design News:   Take down the house with this gadget.  William's handheld controller provides the display of a monitored process deviationbut after hours it doubles as a card counter.   (In either case, the algorithm is identical.) It works by adding or subtracting manually-entered "event" counts to a common 8-bit __ Gadget Freak-Case #83

William Saw Light at the End of the Tunnel -  14-Aug-06 -Design News:   Looking to light up the town, model railroad enthusiast William Grill developed this unique and flexible control board for driving lighting for water towers, running and crossing lights, and storefront dress-up lights.  The microcontroller-based application enables the selection of four display __ Gadget Freak-Case #88

Wind Generates Useful Power at Home -  25-Jun-10 -Design News:   Bo Andersson built a wind-powered generator just because he wanted one to use as a foundation for more experiments.  When people said his idea to use a truck "rear end," or differential, to transmit wind power to a generator on the ground wouldn't work, he went ahead and put it on top of a 30-ft __ Gadget Freak-Case #167

Windmill Design Free Power -  A Practical Alternative to help reduce your Heating Bills.   (I wanted to build this as a working unit, but due to health reasons, its not going to happen.)  __ Designed by G.L. Chemelec

Wireless Volume Control -  17-Aug-11 -Design News:   Andrew Morris decided the usual wireless volume controls don’t offer enough functionality, so he created the ultimate volume control that connects between a computer or MP3 player and an amplified speaker system. __ Andrew R. Morris, Gadget Freak-Case #192

Woodstove Temp Monitor and Alert -  28-Mar-11 -Design News:   Paul Westaway wanted to make sure his woodstove didn't exceed the upper limit of temperature and overheat, thus damaging the stove or causing a fire.  He wanted a monitor that could send out an alert if the stove got too hot.  He was surprised he couldn't find a monitor available commercially.  So, __ Gadget Freak-Case #183

World’s Top 20 Electrical Engineering Project Ideas -  Engineers are always in search of projects, and finding meaningful projects makes that search worthwhile. Listed below are some electrical engineering project ideas for such engineers. A lot of them may...__ EFY

Yoga Breathalyzer -  13-Jun-14 -Design News:   The yoga breathalyzer is a breath visualization tool to help you understand and get in touch with your breathing. __ Gadget Freak-Case #256

You Can Get Scrooged Opening a Trap Door -  5-Dec-05 -Design News:   Ever try opening an attic door in the ceiling at the top of the stairs with your hands full of stuff? Try spelling headache! So Larry installed a 12V motor with a cable shaft in the attic and attached the cable to the door.  Limit switches stop the motor when the door is fully open and closed, and a __ Gadget Freak

You Have Mail! -  If your letterbox is some distance from your house, you will find a monitoring device useful to indicate when new post has arrived.  This can take the form of a US-style visible flag; a more modern alternative uses a 433 MHz radio transceiver.  The big advantage of the solution presented here is that is can use an existing two-core bell cable, without requiring any further power source.  The arrival of post is signalled by a blinking LED; for added effect, a digital voice recorder can also be connected which will, at regular intervals, announce the fact that the letterbox needs emptying.  The device is silenced by a reset button. __ Designed by Robert Edlinger© Elektor Electronics Magazine

YoYo enhancement Device -  The original yoyo was equiped with 2 LEDs that lit up when device was spinning.  I decided to add a micro to give it some extra pazazz.  The trick here is to make unit work without a power switch.  The mercury switch is positioned so that it supplies power when unit is spinning.  After about 20 seconds, PIC shuts down in sleep modes,  __ Designed by Luhan Monat-Mesa Arizona

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Gadgets:  #'s - C        D - E        G - L        M - O        P - S        T - Z

 


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