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A Fish Caller - ….(circuit design added 12/08) |
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A Matrix Multi-Tool for the HP 35s Programmable Calculator - Programmable
Calculator Software added 03/09 |
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An SCA Adapter - Subsiduary Communication Authorization. For Advertisement Free
Background Music on FM. This applies to an Additional 67 Khz Modulation on the
standard FM Carrier. It is intended to provide Commerical-Free Background Music
for Stores, Offices and others...(circuit design added 12/08) |
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Aristo Multilog Nr. 970 Simulator - This simulator is based on the impressive
collection of Pickett slide rule simulators by Derek Ross. Derek has given me
permission to use his JavaScript code, which I have enhanced to add the digital
readouts of the scales that you see above. The movable parts of the slide rule are
implemented using the Drag & Drop for Images and Layers library....(added situlator
03/09) |
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Avoiding Doggus Interrupt-Us - Gadget Freak: Planning a romantic evening at home?
Les designed a remote control door opener so you don’t have to manually let Fido out
of his cage. The system consists of a clevis mounted to the shaft of a solenoid and
the door latch of the cage…. (added 2/07) |
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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....(circuit design added 12/08) |
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Bill Bowden: Night Rider - Gadget Freak Case #94: Bill's got a bright idea for how
to safely ride your bike in the dark…. (added 2/07) |
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Bob Solved His Chip Problem - Gadget Freak Case #98, Bob Neidorff's souped-up shop
vac gadget cleans up after wood chip messes even a woodchuck would shun…. (added 2/07) |
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Cat Detector for a Cat or Dog Flap on a door. - This circuit uses one tuned coil
for on the door and just a single wire loop on the animals collar. When the two coils
come close together, it produces a signal that can cause a an LED to light and also
trips a solenoid to unlock the door so it can open. Since all these doors are somewhat
different, I leave ….(circuit design added 3/08) |
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Cat Toy - The PIC12F675 is small in size and low in power. It lends itself to some
really off-beat uses..... (electronic design added 10/06) |
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Cheap Close-up Camera Lens - I often use my digital camera to take photos of some
electronic projects. At times, I need to get in close to capture some details. But,
without some additional optics, my camera just could not maintain focus, as I got
closer to an object. Being a cheap person, I didn’t want to spend money on an
expensive close-up lens... ….(designed by David A. Johnson) |
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Craig Was a Diehard Dashboard DIYer - Gadget Freak: When Craig discovered his
local BMW dealer charges $50 to reset the oil change indicator light on his 1999 BMW
528i, he did what any good engineer would do: He built his own reset tool. The simple,
money-saving tool…. (added 2/07) |
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Craig's Simple Way to Generate a Split Supply - Wall plug transformer low wattage
linear power supplies (hereinafter known as WallWarts) are available cheaply ,as
surplus, from various online electronics component suppliers. Typical price is
$4 to $7 for a 12VDC, 5W part. These make great line isolation and voltage
reduction platforms for all sorts of useful power supplies. A $1 three terminal
regulator and 3 capacitors will make a nice DC power supply... (electronic design
added 6/07) |
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Cricket Chirping Generator - Funny gadget for props and jokes. 5, 12V
Battery operation. (circuit added 6/07) |
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Curve Fitting for the HP 35s Programmable Calculator - Programmable Calculator
Software added 05/10 |
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DCS 400 Multipurpose Connector - This special connector was modified to switch two
cameras (one infra red, 1 ultra violet) on via a tethered blimp from a height of up to
3000 feet (1KM). The transmitter/receiver pair itself can handle up to 5KM, so
more than enough power. System was for Professor Richard Heck, Land Resources
Department, University of Guelph.....(Tony van Roon's electronic schematic / circuit
added 08/09) |
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Dice (nutchip) - A LED dice, bright, unbiased, and spectacular. The display
uses 7 LEDs to simulate the faces of a real dice…. (electronic design added 6/07) |
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Dick Had a Cameo Role in Scream 2 - Gadget Freak Case #102: Give the little
witches and warlocks a real trick when they come clamoring for treats on Halloween
with this doorbell-activated soundtrack. All that's required to build this spooky
sound generator ….(added 2/07) |
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Dick Keeps His Home Fires Burning - Gadget Freak Case #95: Last December it looked
a lot like Christmas at Dick Neubert's home. Try his flicker bulb gadget for that
"home for the holidays" feel.…. (added 2/07) |
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Dick worked the Graveyard Shift - Gadget Freak Case #91: When the local church
needed storm effects for a skit, sound man Dick Neubert found the thunder on the
Internet and added “lightning” with a photoflash strobe. He used an uncommitted output
from the mixing board to trigger the strobe with the sound signal via a simple
interface.…. (added 2/07) |
Egg Timer - This circuit sounds a buzzer after a preset time with P1 using a
common 555 timer IC. Excellent to cook your eggs perfectly. Have fun building or
bread-boarding this circuit and don't hesitate to
experiment on it!...(Tony van Roon's electronic schematic / circuit added 08/09) |
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Electrical Device Harvests Earthworms - A 120vac or 240vac isolation transformer
is used to force earthworms from the ground. (added 7/06) ….(designed by David A.
Johnson) |
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Electro-Etching - An AlternativeCheaper method of Etching PCB'suses much less
Ferric Chloride ….(electronic schematic added 12/08) |
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Electronic Candle Blow Out - LED or bulb switch off with a puff. Funny
gadget, 3V Battery supply (added 2/07) |
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Electronic fish lure - (schematic / circuit added 6/07) |
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Electronic Fuse - Full short-circuit and overcurrent protection is given by this
circuit suitable for workbench applications in technical schools and laboratories
where there is a need to work directly with the mains. … (added 9/07) |
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Electronic Fuse - This is adjustable elctronic fuse that can be used to protect
power supplies from short circuits or can be also used to limit the current usage. It
can be adjusted for currents from 100mA up to 4.3A. ….(design added 11/08) |
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Electronic Fuse for DC Short Circuit Protection - This is an electronic fuse that
protects the load against short circuit. Relays must be choosen with a voltage value
equals to the input voltage. Don't omit using the 100uF capacitor with appropriate
voltage value with respect to the input voltage. If you can't provide, you can use
C106 instead of BRX46. You can adjust the current with using 10K potentiometer. If you
will use the fuse with very high currents, lower the 0R6 5W resistor value (ex. 0R47,
0R33, 0R22 or 0R1). Watt value of the resistor should be increased also. ….(electronic
schematic added 11/08) |
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Electronic I Ching - This circuit is the electronic emulation of the I Ching, a
form of divination originating in China. In the classical form, the response is
obtained by the manipulation of 50 sticks or, more practically, by tossing 3 coins.
The process must be repeated 6 times in order to complete what is called an hexagram.
The various combinations given by the 6 readings are then read with the help of a
book: the I Ching in fact or book of changes, used as a guide for the interpretation
of the results. As the hexagrams look very much like a binary code, ...(added 9/07) |
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Electro-Static Air Filters - This article deals with Principals of a Good
Electrostatic Filter systemPlus Basic Plans. With a Schematic for the HV Static Supply
and I can Now Supply the Trigger Coil for this ….(circuit design added 12/08) |
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Extra long-lasting Dripless Candles - Gadget Freak: A candlelight dinner? Relax
and enjoy the lambent halos and silhouettes. With electronic flame flicker there's no
hurry – the candles never burn down and they won't get wax on your tablecloth. But use
real ones around the hot tub…. (added 2/07) |
Filter Circuit for the Earthworm Seismic Data Acquisition System - The following
design criteria were used to design the Earthworm Filter board. It had to provide low
output impedance, a low-pass filter of at least one pole, preferrably it should use
low power so that no external power would be necessary....(circuit design added
04/05/06) |
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Fish Caller - Fish caller. Your fish's dinner bell!….(Tony van Roon's electronic
schematic / circuit added 08/09) |
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Fogger Smoke Machine - (circuit / schematic design added 2/07) |
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Furby Resurrection - There are several websites documenting the original Furby
circuit board. I decided to replace the original circuit entirely and replace it
with a PIC based controller. The mechanism of the Furby itself was designed
around micro- controllers. It has one motor that runs the eyes,….(electronic
schematic added 08/08/08) |
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Furby reverse-engineered circuit - Through a lot of hard work by people other than
myself, Furby's innner electronics have been fully reverse engineered….(electronic
design added 02/03/04) |
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Hap Tells His Backyard Varmints to Hit the Road - Gadget Freak Case #93: 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…. (added 2/07) |
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Homemade COLDHEAT - My first attempt to build a homemade "ColdHeat" soldering
tool. (7/08/2006) |
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Homemade Corner Cube Reflector Using Glass Mirror Tiles - 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
corner cubes can be molded into plastic for form an array of individual reflectors.
These are often used on bicycles to make them stand out at night. ….(designed by David
A. Johnson) |
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HP 35s Programmable Scientific Calculator - ….gadget added 03/09) |
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Jared's Ride Isn't Fly But the Steering's Perfect - 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…. Gadget Freak / Design News (added
2/07) |
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Ken Put an End to Expensive Front-End Damage - Gadget Freak Case #90: 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..... (added 2/07) |
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Les Wears His Silicon On His Sleeve UPDATED - Gadget Freak Case #73: Looking for
cool way of wowing that special someone on Valentines Day/birthday/whatever? Build her
a flashing heart made from LEDs driven by a programmable microcontroller. Les' gadget
is simple to build and made from easily-obtainable parts. The unique thing about this
design is the LEDs.... (added 2/07) |
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Litter Box - Not every new use of technology requires a microcontroller. This one
uses a 12 volt computer fan from CompUSA, a snap close food box from Walmart, some PVC
pipe from Home Depot, and a large plastic storage container from Big Lots. (electronic
design / schematic added 2/06) |
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Low-Sensitivity Sallen-Key Filter Design with the HP-41C/CV/CX Programmable Calculator
- Programmable Calculator Software added 05/15 |
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Low-Sensitivity Sallen-Key Filter Design with the HP-67 Programmable Calculator -
Programmable Calculator Software added 05/13 |
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Magic Lamp - You have probably seen "magic lamp" circuits in which an ordinary
incandescent bulb is lit by a match. These circuits rely on a hidden temperature or
light sensor and are not particularly interesting. I decided to make a magic
lamp,...(added 7/03) |
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Magnetic gun - When optimally tuned, it will propel a small slug about 1.5 metres
high, or 2.5 metres horizontally. IC1 is a 555 timer in astable mode, sending approx.
10 ms pulses to decade counter IC2. IC2 is continually reset through R3, until pin 15
is taken low through the "Fire" button.... (circuit design added 07/07/07) |
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Make a Potato Battery - The basic experiment is based on the use of a potato, but
many fruits and vegetables work as potential batteries! For the zinc electrode, a
large galvanized nail works well. Nails with a thick, rough zinc texture are
preferable to galvanized nails that are smooth...(project added 6/07) |
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Marshmallow Gun - This device uses a PIC12F629 to create a burst of 30 high
voltage pulses. The PIC activates a 1000 volt N-Chan FET driving a standard
ignition coil. After the ignition, the PIC goes dormant until activated again.
Most of the electronics, including ….(circuit design added 08/08)) |
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Mini efficient coil launcher from disposable camera flash - This is a fun and non-dangeros
project for those people who like to throw projectiles magnetically. It simply works
by placing a ferromagnetic projectile at one end of a coil and pulsing some power in
it. The trick is to switch off power when the projectile is at the middle of the coil,
there are some ways to do it but it isn't important now. The second trick is to
use….(circuit design added 08/08) |
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Modified LED Night Light - The circuit uses the classic series capacitor method to
produce a current limiting LED driver, powered from the AC line. The series
capacitor forms a constant current source and will route the
same amount of current through the parts, even if 3 or 30 LEDs were used in series.
This type of circuit made it much easier to insert 10 series
wired LEDs instead of the three original devices. I also switched from a NPN
darlington driver circuit to a single n-channel FET. This made it easier to select the
right resistor value to turn off the light in the day. I
set the required CdS cell resistance at about 100K, so anything less than that in
resistance should keep the LEDs turned off. I did have to change the
resistor R2 to a 39v zener diode, to limit the peak voltage across the filter
capacitor C1, when the LEDs are turned off during daylight. ….(designed by David A.
Johnson) |
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Momentary High Voltage Arc Circuit - Can be used to Ignite a barbeque or a Gas in
a Potato Gun....(design added 12/08) |
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My New Windmill Design Free Power - A Practical Alternative to help reduce your
Heating Bills....(electronic schematic added 12/08) |
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Nathan Loden: Glidden Special Forces Volunteer - Gadget Freak Case #89: 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)…..
(added 2/07) |
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Nick Has an Illuminating Flashback - Gadget Freak Case #96: Nick Pagazani was
tired of the limited range of his camera's flash, so he developed a slave trigger to
help him brighten up his photos…. (added 2/07) |
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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. I gave this some thought and came up
with the system shown below. It uses a simple plastic foam float attached to a lever
arm, ….(designed by David A. Johnson) |
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Op-Amp Gain & Offset Design with the HP-67 Programmable Calculator - Programmable
Calculator Software added 05/11 |
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Op-Amp Oscillator Design with the HP-67 Programmable Calculator - Programmable
Calculator Software added 05/12 |
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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 that’s needed to get an Orrery in your living room!.....(added
04/04/04) |
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Our Everest Model has a Fireplace! UPDATED - Gadget Freak: 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.….
(added 2/07) |
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Pigeon Scarecrow - I have an area on my roof where a large flock of pigeons like
to roost. Their nesting materials and droppings really make a mess. Often there
is enough junk from them that it clogs my roof gutters. Perhaps one way to scare
them away is with a device mounted on the roof near their favorite roosting spot.
The device.... ….(designed by David A. Johnson) |
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Project Dragon Fish - Gadget Freak Case #97: Joe Peck's exploration of underwater
model rocketry brings him to new heights ... and new depths…. (added 2/07) |
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Resistor Network Solver for the HP-67 Programmable Calculator - Programmable
Calculator Software added 05/14 |
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Salt Water Battery - (electronic circuit added 2/07) |
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Shake to Charge Flashlight - The complete schematic for this device is shown
below. A few things should be pointed out. First, they use some very cheap
1N4001 diodes in the bridge rectifier circuit instead more efficient Schottky diodes.
They also use a small 0.5 Farad cap with a 5.5 volt rating. I noticed that that
this kind of super capacitor was originally designed for maintaining data in memory
chips and has a rather high internal equivalent series resistance. This reduces
the overall efficiency, since the device can’t be charged or discharge very quickly.
Some of the power that should go to the LED will end up being dissipated inside the
capacitor. Better super capacitors do exist. ….(designed by David A. Johnson) |
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Sky Writer - We have seen many projects using a set of LEDs to produce words "in
the air," but none have the feature of an inertia switch to provide registration. One
of the biggest problems with waving a display to produce writing in the air is
maintaining the same position for the letters as it is moved back and forth. If the
words are jumping or shown in reverse, they are difficult to read....(electronic
schematic added 05/08) |
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Talking Fish Hack - These items were sold nationally several years ago. The fish
would sing, open its mouth, turn its head, and flap its tail. After removing the back
panel, all of the existing electronics were removed leaving only the 3 servo motors,
speaker and photocell.….(circuit design added 08/08)) |
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Telephone Voice Changer - Although this kind of voice effect can be obtained by
means of some audio computer programs, a few correspondents required a stand-alone
device, featuring microphone input and line or loudspeaker outputs. This design
fulfills these requirements by means of a variable gain microphone preamplifier built
around IC1A, a variable steep Wien-bridge pass-band filter centered at about 1KHz
provided by IC1B and an audio amplifier chip (IC2) driving the loudspeaker.
….(electronic schematic added 11/08) |
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The Curious Incident of the Dog in the Night UPDATED - 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 …. (added 2/07) |
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The Dripper! (Modified Circuit-works better!) - Scroll down to find circuits.
Just when you get all comfy in bed you hear it.... Drip....Drip....Drip. But when you
stumble into the bathroom to give the faucet a twist, the dripping sound stops. After
a few trips back and forth you venture out without turning on the lights- to "sneak
up" on the drip. The only problem ….(added 03/03/03) |
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The Silicon Wallet - How do you manage your ever-increasing set of password,
secret numbers and personal ID codes? My list is very long: passwords for Internet and
Intranet access at home and office, credit cards and ATM, mobile phone, burglar alarm,
insurance, SSN, tax number, safe lock… To make matters worse, new passwords are being
generated everyday. Apparently, every useful site requires you to register for a
better, customized service. Not surprisingly, problems related to stolen ID, hacked
databases and loss of confidential information are becoming more and more
common....(DESIGN ADDED 06/05) |
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The Ultra-Portable 'MoGo' Laptop Mouse - ….gadget added 03/09) |
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Toy Car Rodent - 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) |
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Toy Organ - Some useful circuits using the LM555 IC. Scroll to find the toy organ
circuit (11/06) |
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TV Remote Control Jammer - Scroll down to find circuits. 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….(added 03/03/03) |
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Ultra-Portable 'MoGo' Laptop Mouse - ….gadget added 03/09) |
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Valentine Heart - 18 LEDs flash at three different rates and you can use these to
create an eye-catching Valentine Heart for that special person! A template for the
heart shape can be downloaded. The circuit is kept simple (and low cost) by using the
4060B IC which is a counter and oscillator (clock) in one package.....Designed by John
Hewes (circuit added 06/07/08) |
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Wave Power Generator Demo System - An inexpensive stepper motor is used as a
voltage generator in this wave generator demo. ….(designed by David A. Johnson) |
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Worm Harvester - 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. ….(designed by David A. Johnson) |
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You Can Get Scrooged Opening a Trap Door - Gadget Freak: Ever try opening an attic
door in the ceiling at the top of the stairs with your hands full of stuff? Try
spelling headache! So Larry installed a 12V motor with a cable shaft in the attic and
attached the cable to the door. Limit switches stop the motor when the door is
fully.... (added 2/07) |
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Yo-Yo Device - At about $1.08 each in small quantities, the PIC12F629 is just
begging to be used in small and strange projects. The original yoyo was equiped with 2
LEDs that lit up when the device was spinning. I decided to add a micro to give
it some extra pazazz.….(circuit design added 08/08) |
