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Last Updated: June 02, 2021 01:45 PM


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

Circuits Designed by Dave Johnson, P.E. :

Harvest Earthworms with this Electrical Device - When I was a kid my engineer uncle built a circuit similar to the one below.  My cousin and I used it to force earth worms out of the ground to be used for fishing.  It worked like a champ.  Please be careful since there is high voltage at the probe tips . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Homemade Corner Cube Reflector - Corner cubes are optical devices which have a unique property.  Light sent into the front face will be sent back to the source in a parallel path.  As long as light can strike the reflective surfaces the it will always be sent back to the source.  Tiny co . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2006

Honeybee Counter - I designed a circuit similar to this one a long time ago to help a beekeeper count the number of bees going into or out of a hive.  The low power circuit uses a slotted opto-sensor to detect the passing bees.  The circuit advances an electronic counting. . . Circuit by David Johnson P.E.-July, 2000

Gadgets That Fly, Take Fish-Eye Photos & Build Prototypes -  17-Dec-13 -Design News:   Rob SpiegelThis  review looks at a variety of gadgets, including a remote-controlled helicopter that folds into its own controller, a 3D panoramic camera, and a personal 3D printer that sells at the  (relatively) low cost of $1,300. __ Gadget Freak

Gag Bomb Countdown Timer -  18-Jul-14 -Design News:   I created this Hollywood movie-style gag bomb that doubles as an alarm clock and a countdown timer.  This is a fun project that you can build in a day or two.  It is made using an 8051 microcontroller.  The project can be easily done with other microcontrollers or an Arduino, or you can even hack an __ Gadget Freak-Case #259

Galloping Neons -  Here is a line powered array of blinking neons designed for continuous duty.  It would be quite dangerous to power a circuit directly from the power line so some form of isolation is needed.  Since most experimenters will not have 120 volt isolation transformers __ Contact: Charles Wenzel of Wenzel Associates, Inc.

Game Show Timers -  Here is a really simple game show timer designed with the beginner in mind! The power source is an ordinary 12 volt lantern battery or battery pack made up of C or D cells.  The lamps may be ordinary flashlight bulbs; the prototype uses 750 mA Krypton types  (KPR112) with wires soldered directly onto the bulbs.  The control devices __ Contact: Charles Wenzel of Wenzel Associates, Inc.

GameCube Cop Keeps the Peace -  June 15, 2009  Design News:  technology-driven solution.  He created an electronic Time Turner.  The gadget uses a Microchip microcontroller__ Gadget Freak-Case 142

GameCube Cop Keeps the Peace -  15-Jun-09 -Design News:   Three siblings and one GameCube is a recipe for territorial skirmishes.  Many games only support two users.  Jeremy Willden bought his three kids a GameCube for Christmas and quickly discovered parental intervention was critical.  He initially used a kitchen timer, but soon opted for a more technology __ Gadget Freak-Case #142

Gary Knew the Dangers of Eating Uncooked Meat -  1-Dec-03 -Design News:   So now he's grilling up a storm in his backyard, thanks to the table-top sized Tesla Coil he built and refined to extract long, repeatable sparks.  And a lot more goes into this design than plastic pipe and copper wire and tubing.  After much optimization, Gary has been able to routinely achieve 9- __ Gadget Freak

Gary Liked to Pump Up the Volume -  10-Apr-06 -Design News:   Ever turned on your car stereo and BOOM! the woofers unexpectedly jumped out for one filling-loosening bass note? Just great, you've just been diagnosed with turn-on thumpeither due to an amp that never had a muting circuit or one that's failed open circuit.  Either way, OUCH! To fix this problem __ Gadget Freak-Case # 55

Gas Sensors Sniff Out Danger -  15-Jul-10 -Design News:   Natanel Eizenberg decided to build a sensor module that would detect and measure carbon monoxide and methane to help ensure safe environments for his co-workers and family.  But in addition to creating an alarm circuit, Eizenberg added a wireless link that communicates with a nearby PC.  Adding a __ Gadget Freak-Case #168

Gesture Control Coming to a Television Near You -  3-Apr-13 -Design News:   Charles MurrayPressing buttons on your television's remote may one day be passe .  A new technology will enable couch potatoes to change channels, adjust the volume, rewind a movie, browse the Internet, or control myriad other functions with simple physical gestures.  The technology, incorporated into a device __ Gadget Freak

Getting the Internet on His Watch -  23-Feb-04 -Design News:   When he found a bunch of surplus miniature, alphanumeric LED displays, he knew he had the makings of a watch-but how far to go? Adding a barometer, altimeter, and temperature sensor makes it a perfect outdoor accessory.  The coup de grace is the Trippy Bits / four letter word function-random bits __ Gadget Freak

Ghost Detector -  Yes, you read correctly, it's a ghost detector, assuming ghosts exist and, for some reason, have electric charge.  Ok, this is a changing charge detector.  If a ghost disturbs the electric field in the vicinity of this gadget you will see the results on the LEDs.  Don't hold your breath, unless you wish to become a ghost yourself.  There's a pair 'a normal LEDs that display whether the charge at the antenna is changing in a positive or negative direction  (green vs red) .   __ Contact: Lennie Zink

Give My Mascot LIFE! -  18-Apr-05 -Design News:   For Richard Downing's  (and friends) complete instructions on how to build your own robotic mascot, click here .  Watch the video of CAM in action.  Looking to add some monstrous fun to school pep rallies and football games, Richard and three friends working toward engineering degrees at Colorado __ Gadget Freak

Golfers Go Green with Envy -  23-Mar-10 -Design News:   Why putt golf balls into a paper cup when you can have your own variable-terrain putting green? This course designed by Mark Giannasi, Aaron Gaylord, Brody Collins, Thomas Boileau and Maiki Vlahinos offers players three cups and three skill levels.  The most advanced level raises two platforms that __ Gadget Freak-Case #161

Google Glass Moves to the Factory Floor -  16-Sep-14 -Design News:   Charles MurrayFactory floor engineers may soon be able to operate machinery and monitor equipment status simply by tapping their eyeglasses.  At last week's International Manufacturing Technology Show  (IMTS) in Chicago, Beckhoff Automation allowed booth visitors to control the velocity of an industrial robot by __ Video-Gadget Freak

Gordon Dabbled in Backyard Water Sports -  13-Sep-04 -Design News:   Not satisfied with the flow rate he was able to achieve with his Super Soaker, Gordon decided to upgrade to a backyard dunk tank.  By hooking up an off-the-shelf sump pump to a power supply and building in microprocessor control, he can blast a victim with up to 5 gallons of water when the target is __ Gadget Freak

Got Hot Milk? -  5-Sep-05 -Design News:   Raising your kids on "nature's best" milk presents all sorts of logistical issues for a stay-at-home dad.  Even a trip to the grocery store is fraught with peril, as a commercial bottle warmer takes way too long  (15 minutes) with two screaming kids in the car.  Calculating that he needed about 200W __ Gadget Freak

Greg is Chillin' With 50 Cent on His Tricked-Out Keyboard -  18-Jul-05 -Design News:   For Greg Ruhlander's complete instructions on how to build your own computer keyboard with integrated am/fm radio, click here .  Unable to function without his trusty portable am/fm radio at his side-especially while working-Greg hit upon the idea of integrating it directly into his computer's __ Gadget Freak

Ground-Effect Turbulence -  17-May-04 -Design News:   A big fan of the Jetsons, engineer Eddie Edwards has designed a personal electric hovercraft.  Propelled by a lift fan driven by a lithium-ion battery source that runs one hour between charges, he claims his device can achieve a maximum vertical lift of 5 cm, so long as the rider weighs no more than __ Gadget Freak

Guido Had a Strong Aversion to Overbrewed Oolong -  27-Jun-05 -Design News:   For Guido Vollmar's complete instructions on how to build your automatic tea timer, click here .  To view pictures and a schematic diagram of the tea timer, click here .  In search of the perfect cuppa, Guido engineered this simple, battery-operated tea timer with a built-in LED display.  Just fix a __ Gadget Freak

Hack of Egyption Talking Frog Box -  This device 'listens' to a conversations and then interjects words and phrases at inappropriate times.   __ Designed by Luhan Monat-Mesa Arizona

Hack Thanksgiving (Don’t Be a Tech Turkey)! -  27-Nov-14 -Design News:   Sylvie BarakThanksgiving is a time for family.  A time for togetherness.  A time for tech? Yep! Turns out Turkey Day is going digital in all kinds of wonderful ways.  For example, why cook a turkey for hours and hours in an oven when you could just infrared it to crispy perfection in half the time with a __ Gadget Freak

Hack the Spy Ear & Learn to Reverse Engineer a Circuit -  This instructable introduces the venerable Spy Ear in details and my way to reverse engineer a circuit.   __ Designed by Biotele

Hacking the Hot Wheels Radar Gun-Includes of analog front end -  The Hot Wheels Radar Gun is a real radar gun currently  (Feb 2007) available from Walmart and other retailers for about $30  (USD) .  It is a real radar gun, operating at 10.525 GHz capable of clocking cars, people, pets, and toys. __ Designed by Ed Paradis

Hack-Toy Car -  This car measures just 5 1/2 inches in length.  It was sold as a remote control car for $19.95 at Fry's Electronics here in Phoenix.  Powered by 4 AAA batteries, it has a small dc motor and a very interesting steering mechanism.   (08/08/08)  __ Designed by Luhan Monat-Mesa Arizona

Hap Tells His Backyard Varmints to Hit the RoA - D -  6-Nov-06 -Design News:   Tired of torn-up flower beds, Hap took matters into his own hands by combining a sprinkler and wireless driveway alert system.  To allow enough time for the sprinkler valve to open, build pressure, and activate the sprinkler head, he constructed a time-delay unit from an old standby 555 timer.  It __ Gadget Freak-Case #93

Harvest Earthworms with this Electrical Device -  When I was a kid my engineer uncle built a circuit similar to the one below.  My cousin and I used it to force earth worms out of the ground to be used for fishing.  It worked like a champ.  Please be careful since there is high voltage at the probe tips . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Here are 10 Robots You Can Make Yourself -  10-Apr-15 -Design News:   Chris WiltzFrom simple mods to more complex builds, here's a list and instructions for some of our favorite DIY robot projects. __ Gadget Freak

Here's a Jet Engine That Fits in YourGarage -  9-Mar-09 -Design News:   While working on a project for a television program, several-times-over  John Tindall started tinkering with a pulsejet engine.  Pulsejet engines were used by the Germans during WWII.  The technology was left behind by turbofan jets.  But Tindall found the pulsejet well-suited to garage - __ Gadget Freak-Case #136

Home Automation Over Internet -  Hello friends, i am here with another simple but a useful project "Home Automation over internet".  Most of the people thought of controlling home appliances and other things like bulbs tubes and switches etc using an IR remote or a wired things running from your computer to your switch board, but what if you are not at home and suddenly you reminded that you have left something on but you are not sure and you can't even go back __ Designed by Ajay Bhargav ajay_bhargav @ hotmail.com

Homegrown Holiday Lights with Homemade Control -  24-Jan-11 -Design News:   Vince Cappellano wanted to put up some holiday lights that wouldn't cost a fortune but would dance smart.  He did some research with the dream of building a display that would go YouTube viralwithout the familiar disaster of "National Lampoon's Christmas Vacation." He embarked on a system that __ Gadget Freak-Case #179

Homemade COLDHEAT -  My first attempt to build a homemade "ColdHeat" soldering tool.   __ Designed by Jose Pino

Homemade Corner Cube Reflector -  Corner cubes are optical devices which have a unique property.  Light sent into the front face will be sent back to the source in a parallel path.  As long as light can strike the reflective surfaces the it will always be sent back to the source.  Tiny co . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2006

Honeybee Counter -  I designed a circuit similar to this one a long time ago to help a beekeeper count the number of bees going into or out of a hive.  The low power circuit uses a slotted opto-sensor to detect the passing bees.  The circuit advances an electronic counting. . . Circuit by David Johnson P.E.-July, 2000

Hotrod Your Billy Bass -  12-Oct-09 -Design News:   Perhaps you have a "Big Mouth Billy Bass," given to you circa 2001.  If so, its limited repertoire has probably grown stale.  As a  reader it probably crossed your mind to teach your "fish" to sing new songs, such as Monty Python's "Lumberjack Song." Well, you can give Big Mouth Billy __ Gadget Freak-Case #150

Hot-Wire Cutter with Inbuilt Heat Controller -  If you've ever tried to cut polystyrene    (especially!) and polyurethane materials using a saw, razor blade or knife, you'll know that the results are invariably less than satisfactory.  If you are after a clean, precise cut, a hot-wire cutter is the answer.  The hot wire actually melts the material and results in a very neat, very fine cut, without the thousands of bits of foam flakes you normally get.__ SiliconChip

How Many Licks Does it Take to Get to the Center of Google's Nexus 9? -  5-Nov-14 -Design News:   It's a good time for tablet fans.  Apple gave it both barrels last month, with a pair of new iPads -- and today, Google fires back with the Nexus 9 and its newly revised OS, Android 5.0 Lollipop.  It sounds tasty, but how does it tear down? We're about to find out.  Click on the image below and follow __ Gadget Freak

How to Build a 4-Channel Wireless Sensor SystE - M -  11-Jan-17 -Design News:   William GrillDo you have a DIY monitoring project that could use a boost? Here's how to create a 4 channel Wi-Fi sensor system with a 200ft increase in range over most projects you'll find online. __ Gadget Freak

How to Build a Homemade CNC Laser Engraver -  28-Jun-16 -Design News:   A DIY project to help with your DIY projects? This edition of  is going meta with a CNC laser engraver made by Amy Kippen and her team of fellow students at Colorado State University.  The CNC laser engraver consists of a user-controlled laser mounted to the Y axis and an engraving plate __ Gadget Freak

How to Build an Arcade Machine For All Your Favorite Video Games -  5-May-16 -Design News:   Do you long for the days of retro video gaming? Here's how you can turn an old PC into an old-school arcade cabinet with only $100 and a bit of woodwork. __ Gadget Freak

How to Hack an Electronic Trade Show Badge -  29-Mar-16 -Design News:   Are you sick of the same boring badges at every trade show? The ESC 2016 Conference in Boston is featuring an electronic one you can use to play games, control robots, meet new friends, or build your own custom hacks. __ Gadget Freak-Case #278

How to Make Virtual Wall Art and Build a Computer for Your Pet -  25-Jul-16 -Design News:   Rob SpiegelWe continue to move through from the past, getting into devices that solve actual problems as well as devices that put changeable art on your wall..  This collection includes everything from a telescope warmer  (it'll make sense when you read it) to pet cam that let you see how your __ Gadget Freak

How to Make Your Own Apple Watch, a Retro One That Is -  13-Apr-15 -Design News:   Chris WiltzIt won't be long before you'll start seeing the first early adopters of the Apple Watch roaming the streets, which means now's the perfect time to show up that guy with the $10,000 Apple Watch with your own version -- a homemade Apple II Watch.  Instructables user Aleator777 has shared plans for __ Gadget Freak

Hummingbird Makes Coding Easy -  8-Jul-14 -Design News:   Cabe AtwellIf you've ever wanted to learn how to code, here's your chance.  Hummingbird is back with a vengeance as it unveils a new robotics kit that can teach anyone the basic of robotic engineering, even children.  The kit was released on Kickstarter and has surpassed its funding goal of $30,000.  The kit is __ Gadget Freak

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


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