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Last Updated: December 01, 2017 05:01 AM

Circuits Designed by Dave Johnson, P.E. :

Remote Doorbell Beeper  -  This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac . . . Circuit by David A. Johnson P.E.-July 11, 2006

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

Rainman John Has a Natural Moisturizer and an Excellent Duck -  15-Mar-04 -Design News:   Seeing lawn spinklers constantly running in the rain, John thought about how silly and wasteful they are.  So he developed a device that monitors the moisture content of the soil and automatically triggers a sprinkler system when required.  The sensor is a pair of electrodes  (based on bicycle spokes __ Gadget Freak

Refrigerator Door Alarm -  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.

Remember-It-All Electronic Etch a Sketch -  September 22, 2008  Design news:  and it's all gone- your great art is lost forever.  Rakesh Reddy has a gadget-based solution- the Remember-It-All Etch A Sketch.  Reddy's gadget captures that otherwise ephemeral art and provides the ability__ Gadget Freak-Case 129

Remember-It-All Electronic Etch a Sketch -  3-Nov-08 -Design News:   One of the frustrations of the Etch A Sketch is its temporary nature.  You put in all that time learning to draw and your little brother  (or spouse) bumps you and it's all goneyour great art is lost forever.  Rakesh Reddy has a gadget-based solutionthe Remember-It-All Etch A Sketch.  Reddy's __ Gadget Freak-Case 129

Remote Control Dog Door Opener -  Gadget Freak: Remote Control Dog Door Opener.    Sometimes you can't teach an old dog new tricks.  Tired of trudging down the stairs to let his dog out of his cage in the middle of the night, Les designed a remote control door opener.  The system.   __ Designed by Gadget Freak

Remote Control Jammer -  Collection of Gag circuits, scroll to find this one.  Do you have an incessant channel hopper that is driving you crazy? Or perhaps you simply want to enforce your own selections.  The TV Remote Control Jammer will do the trick. 

This circuit is a redo of an older design which is not effective on modern remotes.  Modern remote controls are hard to jam but with a little care this circuit will do the job.  The circuit is just a flasher operating at 40 kHz which is the carrier frequency used by common remote controls.  The strong 40 kHz infrared flashing interferes with the signal from the remote.   __ Contact: Charles Wenzel of Wenzel Associates, Inc.

Remote Control Volume -  17-Aug-11 -Design News:   Andrew Morris decided the usual wireless volume controls donít offer enough functionality, so he created the ultimate volume control that connects between a computer or MP3 player and an amplified speaker system __ Designed by Andrew R. Morris, Gadget Freak-Case #192

Remote Doorbell Beeper -  This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac. . . Circuit by David A. Johnson P.E.-July, 2006

Remote Reset Gadget -  This was a trivial, but very useful hack for work.  The code is meant for an 8751, with 24 relays or optocouplers driven off ports 0-2.  Under serial port control, it will blip a selected relay for a half second or so.   __ Designed by Markus Wandel

Remote Telephone Indicator Lights up Ringing Cubicle -  4-Feb-08 -Design News:   You leave your cubicle to get a cup of coffee.  You get a few feet and hear a phone ring.  Is it yours? You dash back and nope, not yours.  You head back for the coffee and hear a phone ring again Alan Vogel has a gadget that solves that aggravating problem.  His Remote Telephone Indicator turns on __ Gadget Freak-Case #115

Remotely Controlling the Room Temperature -  2-Apr-13 -Design News:   Richard A.  Bipes adapted a portable remote so he could adjust his electric space heater without getting up. __ Gadget Freak-Case #236

Resistor Network Solver for the HP-67 Programmable Calculator -  Programmable Calculator Software

RF Remote Control Volume -  17-Aug-11 -Design News:   Andrew Morris decided the usual wireless volume controls donít offer enough functionality, so he created the ultimate volume control that connects between a computer or MP3 player and an amplified speaker system __ Designed by Andrew R. Morris, Gadget Freak-Case #192

Richard and Jen Ace Stochastics -  16-May-05 -Design News:   For Richard Hopkins and Jen Harmel's complete instructions on how to build your own penny slot machine, microcontroller code, and a video of the slot machine in action, click here .  To view the parts list, click here .  Gamblers who play engineering students Richard and Jen's handy desktop slot __ Gadget Freak

Roach Motel-Electronic -  Using a PIC for this device provides a lot of useful functionality.  The timing for the power pulse to the inductor is critical to getting the best Zap from your nine volt battery.  The longer the current is on, the higher the voltage.  Once the inductor reaches saturation, however, you are just waisting power.   __ Designed by Luhan MonatMesa Arizona

Robert Suddenly Realized the Sand Beneath His Feet Was Kitty Litter -  3-Feb-03 -Design News:   All winter long, Robert basks in tropical temperatures right at home in upstate New York-thanks to an ignition timer system he designed for his ancient  (1928) but efficient hot water boiler.  At startup, the timer keeps the ignition on for 90 seconds while the burner comes to temperature.  Tolerant __ Gadget Freak

Robot Hitchhikes Across Canada -  19-Aug-14 -Design News:   Elizabeth MontalbanoIf you see a hitchhiker along the road in Canada this summer, chances are it might not be human.  That's because a robot is thumbing its way across our neighbor to the north as part of a collaborative research project by several Canadian universities.  HitchBOT, as the robot is dubbed, is a __ Video-Gadget Freak

Robotic Hand Teaches Sign Language and 'Rocks on' -  July 13, 2009  Design News:  The Sign Language Emulating Robotic Assistant teaches the deaf to speak and rock__ Gadget Freak-Case 144

Robotic Hand Teaches Sign Language and 'Rocks on' -  13-Jul-09 -Design News:   Here's a robotic hand that teaches sign language, including the international sign for "rock on." J.D.  Ritchey and his fellow mechanical engineering colleagues  (Tim Campbell, Nick Haub and Brian Taylor) from Colorado State University created an acrylic hand to assist in teaching sign language. __ Gadget Freak-Case 144

Rob's Watching His Truck's Diet -  14-May-07 -Design News:   Robert Kwiatkowski designs and deploys data logging systems for Condition Based Maintenance on aircraft carriers.  With gasoline prices soaring, he wanted to improve the fuel efficiency of his thirsty truck.  As a first step, he's doing some data logging via the OBDII port using this simple interface __ Gadget Freak-Case 102

Rocket ControllerGoes Wireless -  23-Jun-11 -Design News:   Here's a wireless way to launch a rocket.  William Grill modified his rocket igniter from an early  submission, Case #124:  Controlling the Rocket Fire.  The earlier model included an igniter "fuse" monitor and single discrete LED display.  William re-tooled with this new __ Gadget Freak-Case #188

Rocket Launch a Conversation -  18-Mar-07 -Design News:   Many of our s , which appear in every issue and on our website, generate a lot of conversation from readers and fellow s alike.  Whether they are offering their thoughts on the latest invention, looking for more information or simply generating conversation, our__ Gadget Freak

Room heating controller -  Tired of mechanical thermostats that overshoot the set point and make you waste expensive energy? Here is a phase-control device that works well and is simple! __ Designed by Manfred Mornhinweg

Roombots Transform Into Reconfigurable Furniture -  23-Jun-14 -Design News:   Ann R.  ThryftRobotic self-assembly techniques range from Harvard's engineered DNA to MIT's macro-scale M-Blocks .  Now the Swiss Ecole Polytechnique Federale de Lausanne  (EPFL) has developed robotic blocks that autonomously self-assemble to form different styles of reconfigurable, adaptive furniture.  Researchers __ Video-Gadget Freak

Roulette Wheel  a 4000 SeriesC-Mos Design. -  Has numbers 1 to 36 plus the 0 and 00, with totally random odds.   __ Designed by G.L. Chemelec

Rudolph Had a Fondness For Eggnog -  13-Dec-04 -Design News:   Why stop at having a shiny red nose when you can have one that blinks, too, and no hangover the next morning? Engineer and amateur-jewelry-maker Jerry created a nifty little holiday stickpin featuring Rudolph the red-nose reindeer.  His low-tech invention involves wiring a low-voltage blinking LED __ Gadget Freak

Ryan Demonstrated the Basics of Torsion Mechanics -  6-Jun-05 -Design News:   For Ryan Shannon and friends' complete instructions on how to build your own electronic version of Twister and associated microcontroller code, click here .  Engineering student Ryan Shannon and friends created a high-tech, interactive version of Twister that tracks the positions of players on any __ Gadget Freak

Ryan Pooh-Poohed Those Low-Carb Diets -  28-Jun-04 -Design News:   To keep his roommates from pilfering his beer reserves, Ryan resolved to build a Fort Knox-like protection device.  The BeerBot waits for a correct activation code and then pours  (drizzles out, actually) beer until a sensor detects the cup is filled.  If the thirsty perpetrator enters the wrong code __ Gadget Freak

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