Motorized wheelchair built from LEGO pieces

You’re certainly not going to sneak up on anyone if using this LEGO motorized wheelchair. The high-pitched whine of all those tiny motors sounds like an army of robotic mosquitoes out for blood.

Six of the LEGO Mindstorm bricks are used to drive the motors, with a seventh acting as the master. It’s not pictured above, but there is a joystick on the right hand side which allows the rider to navigate. The master brick monitors the four sensors on that joystick. It then uses a pair of motors to actuate switches monitored by the slave bricks. Each slave has one switch for forward, and another for backward and drives two motors. To get around problems with angular velocities dues to turning, all of the wheels are multidirectional.

The plan is to add Bluetooth control in the near future. The master/slave setup should make that relatively easy as it only affects one of the bricks. The idea is to facilitate Android control to the chair like we’ve seen in other Mindstorm builds.

Don’t miss the demo embedded after the break.

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Quacking egg timer

[Tom] managed to build a geeky, quirky digital timer for the kitchen. Where most would have used a few seven segment displays along with some buttons and called it done, he found a way to make it a lot more fun. The plush addition on top is a yellow ducky with an orange beak. When time runs out the duck will quack, call you back to the kitchen.

As you can see in the video after the break, [Tom's] got his hands full with the family. This project was quick enough for him to fit it in during what dwindling free time he manages to hold onto. He used one of the chips that came with his MSP430 Launchpad. Since this family of processors offer extremely low-power modes when asleep they’re perfect for this type of battery-powered application. As for the duck, it’s a toy that had a couple of watch batteries and a small PCB inside. Some poking around led him to a pad that activates the quacking when grounded.

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MIDI man-in-the-middle hack lets you add pedal to the mix

[Sebastian] has a friend who would like to use a pedal with his MIDI setup, but his keyboard doesn’t support one. Some might interpret that as a sign you need to buy a new keyboard. But [Sebastian] has already done a lot of work with the MIDI protocol. He knew it should be possible to create a MIDI pass-through which adds support for a pedal.

You can see the two MIDI cables connected to the box above. One is the input from the keyboard, the other is the output to the synthesizer. There is also a jack for a pedal input to the left. The chip inside intercepts each packet, rolling in values based from the pedal input and passing on the altered packets to the synthesizer. As you can hear in the video after the break, this works like a charm.

Catch more of [Sebastian's] midi work by following his keyboard sensor replacement projects.

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Zelda engagement ring box seals the deal

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

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

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

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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