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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. :

Basement Doorbell BeeperIf you can't hear your doorbell when you are in your basement try this circuit.  This circuit takes advantage of the 24vac power source located near the furnace.  Using a simple current transformer technique, the circuit sounds a beeper whenever the. . . Circuit by David Johnson P.E.-June, 2000

Basement Remote DoorbellThis circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Backpack Is a Wireless, Wearable Charging SystE - M -  7-May-15 -Design News:   Elizabeth MontalbanoBackpacks have long been handy for taking books and other essential items with us when we're on the go.  Now, thanks to a team of Australian researchers, a backpack also lets you carry around with you a complete charging system for all your mobile devices.  A team at the Commonwealth Scientific and __ Gadget Freak

Barometer That Measures Your Height -  July 31, 2009   Here's a weather instrumentthe Dodecahedral Barometerthat can actually determine how tall you are by reading the barometric pressure between your head and your feet.  Mark Thoren notes that his gadget was inspired by the release of some new electronic  products.   __ Gadget Freak-Case 145

Basement Doorbell Beeper -  If you can't hear your doorbell when you are in your basement try this circuit.  This circuit takes advantage of the 24vac power source located near the furnace.  Using a simple current transformer technique, the circuit sounds a beeper whenever the. . . Circuit by David Johnson P.E.-June, 2000

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

Battery Desulfation/Tester -  This circuit helps to Desulfate Lead Acid batteries.   Added Bonus:This Circuit also gives a good indication of the Internal Resistance of the battery __ Designed by G.L. Chemelec

Battery Charger-Constant Current -  a constant current fast charger for high current applications, rc etc.   __ Contact: P. Townshend EduTek Ltd

Battery Conditioner -  keeps unused lead-acid batteries fit and healthy when not in useuses binary counters __ Contact: P. Townshend EduTek Ltd

Beer Tossing Refrigerator -  20-Mar-07 -Design News:   Thanks to John Cornwell, who last year graduated from Duke University, the question of whether or not to get off the couch and grab a beer has become unnecessary to answer.  In fact, with his invention, you donít even have to have anyone at home do it for you or even try to train Fido to fetch you a __ Gadget Freak

Beer Tossing RefrigeratorUpdate -  16-Apr-07 -Design News:   Thornstein Veblen said "invention is the mother of necessity," and that couldn't be more true for John Cornwell's beer tossing refrigerator.  Talk about a great gadget! The press John Cornwell is getting on his refrigerator which will allow you to grab a beer without ever leaving your couch is __ Gadget Freak

Better than a Lazy Susan -  27-Dec-10 -Design News:   Dustyn Roberts' project, Not Lazy Susan, comes from her book, "Making Things Move." In this project Dustyn takes the Lazy Susan concept and turns it into a rotating platform with hidden qualities.  To make things interesting, she uses an infrared  (IR) LED and phototransistor to make the table rotate __ Gadget Freak-Case #177

Bill Had That Weird Sensation He Was Being Watched -  26-Jun-06 -Design News:   Partial to things that go bump in the night, Bill built a circuit that slowly illuminates and fades a pair of red LEDs.  It consists of two op amps, one producing a slow rising and falling voltage  (36V) and the other functioning as a voltage comparator.  In operation, a linear 3V ramping waveform __ Gadget Freak-Case #86

Billiards Ball Counter -  21-Feb-14 -Design News:   I wanted to play a little pool with my brother, but to play call shot, you really need a set of counters to keep track of the number of each of your successes.  My facility has no resources to do this -- neither manual counters nor the familiar beadwork located somewhere above the table.  Electronic __ Gadget Freak-Case #251

Bite Alarm-Pulsed Tone Generator -  produces a pulsed tone with adjustable speed, duration, pitch and volume.   __ Contact: P. Townshend EduTek Ltd

Blinking Arrow -  17 LEDs in four groups bar-mode sequence.  Suitable for shop-windows animation etc __ Contact: Flavio Dellepiane, fladello @ tin.it

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

Boat Lift Controller With Remote -  12-Sep-14 -Design News:   At my lake home, I have a Shore Station boat lift to lift my boat out of the water when it is not in use.  The lift has a manual crank and wheel, which can be quite tedious to operate.  I added a Lift Mate Universal motor from Shoreline Industries to crank the wheel for me.  This type of lift and lift __ Gadget Freak-Case #262

Bob Could Stop On a Dime -  25-Oct-04 -Design News:   Unfortuneately, others could not.  Tired of rear-end repairs, Bob designed an automatic flasher that uses a pressure sensor in the brake line to measure the pressure applied to the brake pedal.  The sensor output controls the rate of a 555 multivibrator chip, which in turn drives a high-power MOSFET __ Gadget Freak

Bob Had a Problem with the Thermal Management -  19-Mar-07 -Design News:   NASA engineer Bob Wilson devised a technological solution for a bureaucratic problem convince building maintenance that his office was frigid in the morning.  By the time anyone responded to a call, the heat was on.  So he programmed a TI MSP430-F2013 microcontroller to record the temperature __ Gadget Freak-Case #99

Bob Solved His Chip ProblE - M -  26-Feb-07 -Design News:   Woodworker Bob Neidorff bought a vacuum to collect the chips and sawdust from his shop equipment, and plumbed it to the vacuum ports on his power tools and to his homemade vacuum hose ports.  But then, he had to turn it on and off every time he used a machine.  That is, until he built this gadget.  A __ Gadget Freak-Case #98

Bob's Apple-Stealing Varmint Was a Nearsighted Nuisance -  6-Oct-03 -Design News:   Tired of marauding wildlife munching on his mums, Bob Forman designed a simple motion detector device that automatically triggers a sprinkler system when unwelcome visitors stray over his property line.  Not only does the dog across the street get an occasional dousing, but also Forman's lawn and __ Gadget Freak

Brake Light Signal Module -  IC1 internal oscillator generates a square wave whose frequency is divided 64 times by the flip-flops contained in the chip in order to obtain about 1 to 4Hz at pin #4: this is the LED Array flashing frequency and can be set to the desired value by means of R3 __ Contact: Flavio Dellepiane, fladello @ tin.it

Breadboard as Hotplate -  A standard 60 mm x 100 mm piece of prototyping strip board    (breadboard) can very simply be used as a 12 V warming plate.  All thatís necessary is to connect the copper tracks in series.  At 12 V the board will pass around 4 A giving a power dissipation of almost 50 wattsmust register on this site __ Designed by Published in Elecktor July/Aug, 2010

Briefcase Alarm -  This miniature alarm unit protects your valuables from theft by sounding an alarm when somebody attempts to pick up your briefcase.  It is a battery-operated gadget that can be hidden in...__ Electronics Projects for You

Broken Charger-Connection Alert -  Detects if a device is not properly connected to its supply.    Suitable for battery chargers, portable appliance supplies etc.   __ Contact: Flavio Dellepiane, fladello @ tin.it

Brr It's Cold in Here -  30-Mar-07 -Design News:   When Bob Wilson, our March 19  couldn't convince building maintenance at his work that his office was frigid in the morning, he devised a solution by programming a TI MSP430-F2013 microcontroller to record the tempearture continuously over several days.  See move about his gadget here__ Gadget Freak

Bryan Had a Feeling He Was Not in Kansas Anymore -  7-Feb-05 -Design News:   After one too many nights lying awake wondering if he had remembered to close the garage door, Bryan decided to reengineer his automatic door opener.  He attached a detector switch to the opener drive rail, which is engaged by the drive shuttle as the door arrives at the fully open position.  He __ Gadget Freak

Build a Hot Wire Cutter -  It's easy to build and lets you cut plastic foam without mess.__ SiliconChip

Build a Solar-Powered Bench, Hear Like a Fly, and Channel Dr. Seuss -  16-Dec-16 -Design News:   Rob SpiegelThe latest batch of s from the Design News archives includes a fly-inspired hearing aid and a homemade game inspired by Dr.  Seuss. __ Gadget Freak

Build the Decision Maker -  Can't make up your mind? Build this simple unit for an emphatic answer when ever indecision strikes.__ SiliconChip

Building Your Own Robot That Writes -  20-May-16 -Design News:   Kerry ErendsonKerry Erendson wanted to create a DIY robot that could write.  The result was InkBot.  Kerry shares the process of designing and building InkBot and shows you how to build your own. __ Gadget Freak

Bus Alert -  11-Nov-10 -Design News:   Bus AlertDash for the Curb When is the bus going to get here? Miles Moody is a busy undergraduate engineering student at the University of Florida.  He takes the bus to school, but the bus schedule is slightly inconsistent.  He hates waiting for it.  The city of Gainesville put GPS devices on their __ Gadget Freak-Case File #174

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