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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. :

Night Light from White LEDAs many of you know, I have a pet peeve with poorly made LED night lights.  Often, the light from the LED quickly fades, so within months, the light is useless.  I have posted several versions of modified night lights using higher quality components. . . Circuit by Dave Johnson P.E.-November, 2008

NMH/NiCd 6v Battery TesterI designed this circuit to test rechargeable six volt battery packs under constant current conditions.  As designed, the circuit applies a 10 amp load to the battery pack.  A heat sink must be used on the main power transistor . . . Hobby Circuit designed by David Johnson P.E.-December, 2004

Ocean Wave Power Generator Demo UnitA while back, a Discover Circuits visitor wanted a simply way to demonstrate how electricity could be generated from the up and down movement of ocean waves.  The system was to be part of a science fair project, showing different renewable energy sources . . . Hobby Circuit designed by David Johnson P.E.-January, 2012

One-Watt White LED Night LightAs many of you know, I have a pet peeve with poorly made LED night lights.  Often, the light from the LED quickly fades, so within months, the light is useless.  I have posted several versions of modified night lights using higher quality components.  This circuit is yet another version, which produces much more light than those other designs. . . . Hobby Circuit designed by David Johnson P.E.-November, 2008

Optical Filter using Color Film NegativeThis isnít 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 David Johnson P.E.-January, 1998

Nathan Loden:Glidden Special Forces Volunteer -  4-Sep-06 -Design News:   Looking to paint the town red  (or his buddies at any rate) , Nathan Loden devised this simple device to detect if the paintballs are traveling at a safe speed  (& 300 ft/sec) .  Consisting of sensor circuitry and a microcontroller with a three digit, seven segment display driver, it detects the __ Gadget Freak-Case #89

New Gun Shoots Light Bulb Storms -  5-Nov-07 -Design News:   Here's a gun that can light up an unplugged fluorescent bulb or spark electrical storms in an unplugged incandescent bulbthe same effect as a plaza globe.  Richard Morrow of Cheshire, England, built the Tesla Coil plasma gun using the casing of an inexpensive cordless hand drill.  He uses the __ Gadget Freak-Case #111

New PotatoGun for the French Fryin' Legion -  4-Jun-07 -Design News:   This project is definitely not small potatoesthree barrels loaded with spuds and charged with propane! Two PIC microcontrollers handle the User Interface, Azimuth and Elevation Aiming and Fire Control functions.  Aiming is controlled with a joystick.  The Fire Control subsystem verifies a __  Gadget Freak-Case #103

NFC Ring Opens Many Doors -  7-Oct-13 -Design News:   John McLearNear field communication, a.k.a.  NFC, is at a turning point.  Excitement for wearable technology is at an all-time high with the launch of hotly anticipated products in recent months.  Few, however, have proven practical for the everyday use.  NFC is the gateway technology to more practical wearable __ Gadget Freak

Nick Has an Illuminating Flashback -  8-Jan-07 -Design News:   Photography enthusiast Nick Pagazani was hindered by the range and fixed location of his camera's flash.  Since his camera has no connector for an external flash, he needed a light-activated slave trigger to fire a remote strobe.  It had to ignore the pre-flashes used for red-eye correction and fire __ Gadget Freak-Case #96

Night Light from White LED -  As many of you know, I have a pet peeve with poorly made LED night lights.  Often, the light from the LED quickly fades, so within months, the light is useless.  I have posted several versions of modified night lights using higher quality components. . . Circuit by Dave Johnson P.E.-November, 2008

Night Rider -  20-Nov-06 -Design News:   Bill BowdenTo see and be seen after dark on his bicycle, Bill designed this 40-LED light.  He configured a 555 timer IC to generate a continuous on/off timing cycle to alternately flash two groups of 20 LEDs.  The device operates on four AA batteries, keeping things bright for even the longest night rides.  You __ Gadget Freak-Case 94

Night-Vision Digital Goggle -  At night, on highways, the high-intensity light from the headlight of heavy vehicles blinds oncoming light vehicle drivers  (bike riders and car drivers) for a moment.  This is the main reason...__ Electronics Projects for You

Nintendo Wants to Track Your Sleep and Fatigue -  3-Nov-14 -Design News:   Chris WiltzDuring the company's Q2 investor call last week Nintendo CEO Satoru Iwata announced that the gaming company is developing a sleep-tracking device ó the first of what it plans as a series of quality of life  (QoL) products.  The tracker is being developed in conjunction with ResMed, a medical device __ Gadget Freak

NMH/NiCd 6v Battery Tester -  I designed this circuit to test rechargeable six volt battery packs under constant current conditions.  As designed, the circuit applies a 10 amp load to the battery pack.  A heat sink must be used on the main power transistor . . . Hobby Circuit designed by David Johnson P.E.-December, 2004

Nocturnal Animals Whisker -  A low-rate flashing lamp drives away undesired visitors; Automatic on-off operation __ Contact: Flavio Dellepiane, fladello @ tin.it

Now Witness the Power of These DIY <i>Star Wars</i> Drones -  1-Apr-15 -Design News:   Chris WiltzA maker based in France who goes by the handle Olivier C has been building a series of drones patterned after the famed vehicles of the Star Wars saga.  His most recent project is an Imperial Star Destroyer but he's also completed a TIE Fighter and Millennium Falcon.  Olivier C has detailed his __ Gadget Freak

O, Holy Nerd-Kickstarting the Christmas Decorating -  11-Dec-14 -Design News:   Sylvie BarakKickstarter, the gift that keeps on giving, year round, like an evergreen.  The tech section of the popular crowdfunding site is looking particularly festive of late.  Austin firm Circtistic is looking to get its "hand-crafted" PCB ornaments funded before Christmas day rolls around, with designs __ Gadget Freak

Obey Your Cat's Demands and Build an Automated Food Dispenser -  27-Sep-16 -Design News:   Kerry ErendsonYour cat demands to be fed on time.  With some technical know-how and a 3D printer you can build your own automated cat food dispenser. __ Gadget Freak

Ocean Wave Power Generator Demo Unit -  A while back, a Discover Circuits visitor wanted a simply way to demonstrate how electricity could be generated from the up and down movement of ocean waves.  The system was to be part of a science fair project, showing different renewable energy sources . . . Hobby Circuit designed by David Johnson P.E.-January, 2012

Oculus Rift Dev Kit 2 -- Unleashed -  13-Aug-14 -Design News:   Oculus VR took the world by surprise last year with the Oculus Rift.  This year, it seeks to push the self-created envelope with the Oculus Rift Development Kit 2.  We may not have flying cars, hoverboards, or  (commercial) teleporters, but we do have the latest virtual reality tech.  Join us as we __ Gadget Freak

One-Watt White LED Night Light -  As many of you know, I have a pet peeve with poorly made LED night lights.  Often, the light from the LED quickly fades, so within months, the light is useless.  I have posted several versions of modified night lights using higher quality components.  This circuit is yet another version, which produces much more light than those other designs. . . . Hobby Circuit designed by David Johnson P.E.-November, 2008

Op-Amp Gain & Offset Design with the HP-67 Programmable Calculator -  Programmable Calculator Software

Op-Amp Oscillator Design with the HP-67 Programmable Calculator -  Programmable Calculator Software

Optical Filter using Color Film Negative -  This isnít 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 David Johnson P.E.-January, 1998

Original Two-wire Game Show Timer -  Several Game Show timers included, scroll to find this one.  The game show timer determines which contestant presses their button first by lighting a lamp and ringing a bell and the slower  contestants are locked out.  The circuit is convenient in that only two wires are needed to interconnect the stations and the wires may all go back to the base unit or they may be "daisy-chained" between stations.  There is no electronic limit on the number of stations.  The circuit uses a 24 volt power source and 12 volt lamps when built as shown but the experienced experimenter may scale these voltages along with the zener voltages if desired.  If the SCR triggers when the power is applied or when the reset button is pressed, add a 0.1uF capacitor from anode to cathode.   (A sudden increase in voltage across some SCRs can trigger them, especially if the gate impedance is high.)  __ Contact: Charles Wenzel of Wenzel Associates, Inc.

Orrery -  The Orton Orrery is a mechanically scanned planetary motion simulation that uses flashing LEDs in place of the planets.  In keeping with 18th century Orrery tradition, only the first six planets  (Mercury to Saturn) are present.  A single PIC16F627 is all thatís needed to get an Orrery in your living room!  Electrically, the Orrery is two parts: A rotating assembly consisting of LEDs and PIC, and a motor.  Both are powered separately Ė the spinning part draws power from on-board coin cells and the motor draws power from a small plug-in mains power supply.  The PIC code includes a phase locked loop  (PLL) to maintain synchronisation of the display with motor rotation, thereby avoiding the need for a motor speed controller.   __ Contact: Karen's Microprocessor Projects

Oscilloscope as an Image Viewer -  Cathode ray oscilloscope  (CRO) is a versatile laboratory instrument which is used to display, measure and analyse electrical signals.  It is nothing but a fast x-y plotter that displays an input...__ Electronics Projects for You

Our Everest Model has a Fireplace! -  7-Jul-03 -Design News:   Bruce Field and daughter Ellie are happy campers, thanks to a portable heating/cooling device they built that maintains a constant, comfortable temperature inside their camping tent.  To ensure complete climate control, they equipped a standard room air-conditioner with an electrostatic air filter, __ Gadget Freak

Our Everest Model has a Fireplace! (UPDATED) -  30-Jan-07 -Design News:   Bruce Field and daughter Ellie are happy campers, thanks to a portable heating/cooling device they built that maintains a constant, comfortable temperature inside their camping tent.  To ensure complete climate control, they equipped a standard room air-conditioner with an electrostatic air filter, __ Gadget Freak

Our Fantastic Human-Powered LED Torches -  Sure you've seen LED torches before but not like these.  There are no batteries; you just crank the handle to generate light.__ SiliconChip

Outdoor Garden Solar Lights -  This Outdoor LED Solar Garden Lights project is a hobby circuit of an automatic garden light using a LDR and 6V/5W solar panel.  During day time, the internal rechargeable 6 Volt SLA battery receives charging current from the connected solar panel through polariy protection diode D9 and current limiting resistor R10.  If ambient __ Designed by D Mohankumar

Oxford RobotCar Takes It to Another Level -  26-Apr-13 -Design News:   Cabe AtwellAs engineers, one of our biggest challenges is to lower costs.  Being able to prove concepts with a nice, large budget and having access to sophisticated sensors and mechanisms is great, but ultimately, if humanity, or at least the consumer, is to benefit from our work, we will have to find a way to __ Video-Gadget Freak

Oxygen-Propane Cannon Tests the Big Bang Theory -  25-Jun-07 -Design News:   When Ed Nauman fires his oxygen-propane cannon, anybody within range of the shock wave will definitely see stars.  It's been known to shatter windows 30 ft to the rear! Propane is mixed with oxygen under control of a PIC microcontroller, in a barrel made from a 330 ft 3 nitrogen tank and detonated __ Gadget Freak-Case #104

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

 


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