Zelda Engagement Ring Box Seals The Deal

September 26, 2012 by Mike Szczys 22 Comments

Congratulations to [John Scancella] and his wife to be. Their recent engagement was aided by one of [John’s] projects. Since [Betsy] is a big fan of Zelda, he thought it would be fun to present the ring with the Zelda music playing in the background. He and a friend combined forces to build what you seen in this image.

The music is played by an Arduino with the help of a wave shield. This is pretty much a one-use item so battery life was never a concern. A magnetic switch was used to detect when the box was opened and start the music playing.

You can see the full-sized images after the break, but we can tell that [John] went with a traditional engagement ring. We’re still waiting to see if 3D printed rings are going to catch on in the geek scene. If you just can’t give her anything but precious metal there’s always the idea of encoding messages on the band itself.

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Hybrid Rocket Engine Uses Acrylic As Fuel

September 26, 2012 by Mike Szczys 33 Comments

We are fascinated by the hybrid rocket engine which [Ben Krasnow] built and tested in his shop. It is actually using a hollow cylinder of acrylic as the fuel, with gaseous oxygen as an oxidizer. We’re already quite familiar with solid rocket propellant, but this hybrid approach is much different.

When a rocket motor using solid propellant is lit it continues to burn until all of the fuel is consumed. That is not the case with this design. The acrylic is actually burning, but if the flow of oxygen is cut off it will go out and can be ignited later. This also opens up the possibility of adjusting thrust by regulating the pressure of the oxygen feed.

[Ben] milled the test rig in his shop. It’s a fat acrylic rod through which he bored a hole. There are two aluminum plates which complete either end of the chamber. The intake has a fitting for a valve which connects to the oxygen tank. There is a nozzle on the outflow end. Check out the video after the break to see a full description. You’ll also get a look at the toll the combustion heat takes on the rig.

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Astounding Papercraft Skills Result In This Working Robot

September 26, 2012 by Mike Szczys 20 Comments

It would have been very hard to believe this is made from paper if we hadn’t seen all the parts being built. As a still image it looks neat, but the speed at which those paper gears turn in the video after the break will certainly leave you slack-jawed. It really is a walking robot made using papercraft (translated).

These are actually being sold as kits, but there’s not much in the way of materials. You’ll get six sheets of paper, some skewers which act as the axles, and a bit of elastic band which stores potential energy when winding-up the model. The genius is in the design, which is printed on those sheets of paper. The build process involves plenty of delicate work. Dozens of cuts lead into hundreds of folds, and that’s before assembly even starts. We’ve never considered building a ship in a bottle, but this might be right up our alley. If you need to give a gift to a tinkerer this should show up high on the idea list.

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Crystal Doorbell Helps Class Up The Joint

September 26, 2012 by Mike Szczys 23 Comments

Even if you live in a dump this quick build will make your doorbell sound high-class. The new rig uses a crystal goblet to alert you of guests at the door. We suppose the room-silencing sound of flatware on a wine glass does make a great attention getter.

For [Tobias] the hardest part of the build was getting his wife to sign off on it. But he says the 1970’s era original was looking pretty shabby, which kind of made his argument for him. It took just two hours to develop and install the replacement. It uses a servo motor with an articulated striker to ping the glass which is hanging inverted between two pegs. The original AC transformer (which are most often 16V) was used to power the Arduino. He built a simple rectifier along with a big smoothing capacitor to make sure the Arduino doesn’t reset when voltage dips. Although it’s not mentioned in his comments, we’d bet the doorbell wire has been rerouted to connect directly to the Arduino, rather than remain patched into the power loop.

Don’t miss the clip after the break to hear how great this thing really does sound.

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Roll Your Own Parabolic Microphone

September 26, 2012 by Mike Szczys 28 Comments

Parabolic microphones are used to listen in from a distance. You see them on the sidelines of NFL football games, but they’re part of the standard issue in detective and spy novels. Now you can build your own parabolic microphone by following this example.

The one component that may be hard to find is the parabolic reflector. You cannot simply use a bowl or other curved object as the precise parabolic shape ensures that sound waves are reflected onto one finite focal point. For this build the reflector was obtained from an eBay seller. But the other parts are scavenged from easy to find sources. The microphone itself is an inexpensive element from Radioshack. It is mounted in the shell from a tweeter speaker, which helps to gather the sound if the element isn’t exactly aligned with the focal point. The setup also needs a preamplification system, which uses many components. Luckily there’s a schematic and other reference material linked in the write up.

You can also build a laser microphone which detects sound waves on a pane of glass.

[Thanks Anonymous]

Machine Offers Cheap Advice – Charges More For Something Profound

September 26, 2012 by Mike Nathan 17 Comments

[Nick Johnson] recently wrote in, sharing a neat project he put together in his spare time.

Our readers are most likely familiar with the ubiquitous “fortune” program that ships with many *nix distros, offering cheeky comments and quotes with the press of a button. [Nick] thought it would be cool to build a fortune telling machine using the app, resulting in the handsome device you see above.

The laser-cut wooden case is home to a Raspberry Pi which does the heavy lifting, a coin acceptor, an LCD screen for displaying the device’s status, along with a SparkFun thermal printer. Upon feeding the machine some money, the user can press the “Advise Me” button, prompting the RaspPi to present a printed fortune from its vast database of sayings. [Nick] took some time to do some rough categorization of the fortune databases, enabling the machine to offer more substantial content as the user inputs more coins.

Check out the video below to see [Nick’s] fortune telling machine in action.

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Pan/Tilt Wheel Trainer Ends Up Being A Different Way To Play Quake

September 25, 2012 by Mike Szczys 17 Comments

This is a special controller that [Gary Scott] built to help train camera operators. The pan and tilt controls on high-end movie cameras use wheels to pan and tilt smoothly. This rig can be built rather inexpensively and used to practice following a subject as you would with a camera. This is where the project takes a turn into familiar territory. [Gary] set up a system so that you can play the game Quake using this controller, with your feet doing the rest.

The pan/tilt controller uses two heads from an old VCR. They are mounted above the guts from an old ball-type mouse. A couple of rubber belts connect the heads to the two mouse bars that are normally rotated by the ball. This gives him control of where the Quake game is looking. But he still needed to be able to move, jump, change weapons. and shoot. So he built a second controller for his feet. It uses a CD and some switches as a joystick, and a set of buttons for the other controls. He actually rigged up solenoids to each of those foot switches to physically press keys on a keyboard. You really must see it for yourself. We’ve embedded his set of videos after the break.

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