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Last Updated: December 01, 2017 04:56 AM


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

Circuits Designed by Dave Johnson, P.E. :
Indicate DC Current Flow  -  The circuit below is a simple way to indicate when DC current is flowing through a wire.  The circuit is designed so it will turn on a LED indicator light, whenever the voltage drop across a shunt resistor exceeds about 0.1volts.  The value of the resist . . . Hobby Circuit designed by David Johnson P.E.-October 16, 2005

Indicates Automotive Electrical Voltage  -  When troubleshooting the 12v electrical system of an automobile, it is nice to have a simple voltage indicator tool instead of a voltmeter.  This electronic circuit, hobby circuit is powered by two AA or even two N cells, which will provide enough energy . . . Hobby Circuit designed by David A. Johnson P.E.-July 09, 2006

Knocking rings Doorbell  -  in some apartment buildings and homes, not equipped with a door bell, it may be hard to hear someone knocking on the front door.  The circuit below provides a means to activate a loud beeping sound inside, whenever someone knocks on the door . . . Hobby Circuit designed by David Johnson P.E.-June 14, 2009

Improve Your Batting Average without Steroids -  14-Sep-09 -Design News:   Typical pitching machines make it hard for a batter to prepare a proper swing.  To improve his performance at bat, Nathan Loden created this pitch alert system by attaching an IR LED and sensor to the ball feed mechanism.  When the next ball up is blocking the sensor, the signal is fed into a circuit __ Gadget Freak-Case #148

In at Whatever, Out at 12:00 -  30-Apr-07 -Design News:   John Linstrom likes to listen to his portable tape player while traveling, but it made quick roadkill of the batteries.  The car's 12V system would eliminate the carnage, but the range of voltage at the lighter socket was too wide to power the tape player directly.  This Buck/Boost voltage regulator __ Gadget Freak-Case #101

In-car food & beverage warmer -  This is a very useful device for those who are frequently on the move.  It will keep your tea, coffee or food warm while consuming little power.   __ Designed by © EFY Enterprises Pvt. Ltd.

Indicate DC Current Flow -  The circuit below is a simple way to indicate when DC current is flowing through a wire.  The circuit is designed so it will turn on a LED indicator light, whenever the voltage drop across a shunt resistor exceeds about 0.1volts.  The value of the resist . . . Hobby Circuit designed by David Johnson P.E.-October, 2005

Indicates Automotive Electrical Voltage -  When troubleshooting the 12v electrical system of an automobile, it is nice to have a simple voltage indicator tool instead of a voltmeter.  This electronic circuit, hobby circuit is powered by two AA or even two N cells, which will provide enough energy . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

Intel Joins Robotic Revolution -  11-Jun-14 -Design News:   Elizabeth MontalbanoUntil recently, robots have been largely the milieu of research institutions and niche robotics companies specializing in the field.  But Google's purchase last year of eight robotics companies in six months -- including Boston Dynamics -- shows that even mainstream technology companies are starting __ Video-Gadget Freak

Interactive Beer Pong Table -  13-Apr-11 -Design News:   Since Cameron Hoerig is an engineering student at the University of Cincinnati, the idea of building a typical beer pong table was out of the question.  "I'm an electrical engineering student, so I should have a table that stands out," says Hoerig.  He built an interactive table.  On either end of the __ Gadget Freak-Case #184

Interactive, Arcade-Style Sandbox -  29-Sep-14 -Design News:   Cabe AtwellHuman-Machine Interfaces  (HMIs) are a passion of mine.  I am forever looking for a better way to use the PC that's faster than the old keyboard and mouse.  Capacitive touch screens showed me much is possible.  Kinect, Leap Motion, and a few others tried, but failed to replace the standard.  Sega has __ Video-Gadget Freak

Inverter for Soldering Iron -  Here is a simple but inexpensive inverter for using a small soldering iron  (25W, 35W, etc) in the absence of mains supply.  It uses eight transistors and a few resistors and...__ Electronics Projects for You

IR Remote Control Toggles Appliances -  12-Aug-10 -Design News:   Bill Bowden asked, "Why not use a standard infrared remote control from a TV, DVD player or cable-TV box to control other things?" So, Bill's  project does just that.  His infrared  (IR) receiver decodes the signals from remote controls and uses the data to individually turn on or off __ Gadget Freak-Case # 169

Is the Ring the ‘Worst Product Ever Made?' -  10-Dec-14 -Design News:   Elizabeth MontalbanoKickstarter has become in the last several years a site where both established and potential inventors seek crowd funding for the next great idea in commercial products.  It's also become a place where people with ideas of even questionable commercial viability or quality can be funded, as evidenced __ Gadget Freak

Jared's Ride Isn't Fly, but the Steering's Perfect -  7-Nov-05 -Design News:   So he always stays on course, Jared designed a mechatronic device that simulates perfect steering in an automobile.  The small-scale, single-wheel model determines the speed of wheel rotation from the magnitude of the curve it's traveling.  It works by setting the initial speed of a PIC-controlled dc __ Gadget Freak

Jason Was an Honorary Member of the Captain Nemo Fan Club -  17-Jul-06 -Design News:   Inspired by 20,000 Leagues Under the Sea, Jason built this underwater Remote Operated Vehicle  (ROV) so he, himself, could explore the depths of his bath tub, swimming pool and beyond.  Employing mostly off-the-shelf parts, the ROV is controlled via Visual Basic commands sent over an RS232 serial __ Gadget Freak-Case #87

Jazzy Heart Electronic Jewellery -  Want to be the life of the party? Build the Jazzy Heart LED display!__ SiliconChip

Jerry Had High Ambitions -  22-Nov-04 -Design News:   How high can you go? That's a question that model rocket enthusiast Jerry Baumeister wanted an answer to.  Cheap enough to be used in even "risky" launches, Jerry's battery-powered device features a circuit designed around a Flash microcontroller that performs an analog-to-digital conversion of the __ Gadget Freak

Jogging Timer -  3V Battery powered; Beeps after a fixed minutes delay __ Contact: Flavio Dellepiane, fladello @ tin.it

John Strongly Recommended the Water-Management Option -  8-Sep-03 -Design News:   When a go-kart racer knows the density of dry air entering the engine, he can tune his carburetor's efficiency accordingly and maximize performance.  The problem is weather is always changing.  To avoid any guesswork, John Cashon built an on-board weather station for go-karts.  It monitors three __ Gadget Freak

Kanceruk the Magnificent Strikes Again -  10-Oct-05 -Design News:   As an occasional installer of alarm systems, David covered a lot of ground testing the integrity of the four-conductor cables commonly used as wiring.  Each wire has four conductors and must be checked for shorts and opens.  To cut down on all of the back and forth, he built a simple voltage divider __ Gadget Freak

Ken Put an End to Expensive Front-End Damage -  25-Sep-06 -Design News:   Not satisfied with the low-tech method of suspending a tennis ball from a string, Ken Swanstrom devised a better garage locator device from a laser pointer.  This simple circuit is powered by a 6V dc wall wort, adjusting the output to yield 3V dc as a substitute for battery power.  A CdS cell "looks __ Gadget Freak-Case #90

Key Chain Light -  A key chain with a built-in white LED comes in handy to help you at your front door or search your valuables in the dark.  The intensity of white LED is...__ Electronics Projects for You

KeyCom Helps Keep Everybody in the Same Key -  16-Jul-07 -Design News:   There was dissonance in the church when the pianist and other musicians had to hunt for the key their Music Leader was playing in.  Dick's gadget took the guesswork out of the guitar, the meandering out of the mandolin and the pondering out of the piano.  The Music Leader communicates the key to the __ Gadget Freak-Case #105

Keys Finder -  The ear and mouth of the circuit is a piezoelectric buzzer.  Fizzling in a frequency of 34 KHz produced sound waves that piezoelectric buzzer converts them to an oscillation.  This oscillation passes thought C1 and thought inverters N1N3.  The inverters along with R1 and R2, compose an amplifier with gain 400 !.  The C8 and C9 stabilize and reduce the signal's level.  

KIBO Appeals to Kids' Imagination -  17-Jun-14 -Design News:   Elizabeth MontalbanoThere are an increasing number of toys for helping kids learn by programming and building robots.  Now Boston Device Development and a startup called KinderLab Robotics have entered the fray with a Kickstarter campaign to get kids engaged in robotic programming younger than ever.  The campaign is for __ Gadget Freak

Kick Start Your Harley and Never Open Your Mailbox Again -  2-Sep-16 -Design News:   Rob SpiegelThese gadgets stop your LED Christmas lights from flickering, kick start your Harley, and automate your mailbox. __ Gadget Freak

Kindle Fire HD 6 Teardown -  21-Oct-14 -Design News:   Advertised as the "Most Powerful Tablet Under $100," the Kindle Fire HD 6 was too tempting for the team at iFixit to pass up.  Join us to find out if inexpensive means cheap, irreparable, or just down right economical.  It's teardown time! Click on the Kindle Fire HD 6 to start the slideshow.  Related __ Gadget Freak

Kitchen Circuits -  Do your kids leave the door to the refrigerator open? Or does your celery reach out to keep the door from closing properly when you turn your back? Here's a simple circuit that beeps whenever the door is open for an extended period of time  (which will also put a little pressure on the fridge loiterers in the house)  __ Contact: Charles Wenzel of Wenzel Associates, Inc.

Knock Alarm with timer -  This is a circuit for a knock alarm that uses a piezoelectric plate to detects vibration due to knocking and activates an alarm for about ten seconds __ Electronics Projects for You

Knock Clock -  19-Nov-10 -Design News:   Jake's Clock Will Say Anything Jake Rice can program his desk clock to display anything that comes off his computer.  Rice turned to the ever-popular Arduino platform to create a multi-function clock display that presents time in Arabic numerals  (hh:mm) and in binary  (hh mm ss) , as well as __ Gadget Freak-Case #175

Knocking rings Doorbell -  In some apartment buildings and homes, not equipped with a door bell, it may be hard to hear someone knocking on the front door.  The circuit below provides a means to activate a loud beeping sound inside, whenever someone knocks on the door . . . Hobby Circuit designed by David Johnson P.E.-June, 2009

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