Here’s a camera mount that moves smoothly along a motorized sled. [Bart Dring] created the system and was surprised by it’s popularity, having received several sales requests from photographers. He originally designed the linear bearing system, called the MakerSlide as an inexpensive alternative to other CNC machine solutions. Allowing a computer to map out timed movements for video shots wasn’t on his radar then, but as you can see in the clip after the break, the MakerSlide does an amazing job at it.

The modular track system makes it easy to attach to a base. In this case, a couple of pieces of acrylic let him support both ends of the track on standard camera tripods. [Bart] mentions the knowledge gap between people who work with CNC milling hardware and photographers as an issue in deciding how to control the system. Since photographers aren’t likely to be proficient in EMC2, he designed a control application with an Arduino. It uses a stepper motor controller shield, and does some fancy math to make sure there is smooth acceleration, etc.

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We figured it wouldn’t be long before someone figured out how to remove the ads from the ‘Special Offers’ versions of the Amazon Kindle hardware. There are two things that made this obvious to us, the huge flaw that lets code be easily run as root, and the MP3 tag forming that makes it possible to unlock the device.

[Pat Hartl] knows his way around a *nix shell, so once he gained SSH access to the device he started a search for the ad images that make up the special offers feature. He found them in a few different places, making backups of the files in an alternate location, then removing them with some simple commands. He even rolled the process into a one-click installer like the Jailbreak package. It makes us wonder if Amazon has a way to tell if your device is not longer pulling down content for these offers?

At risk of sounding preachy, Amazon does offer this hardware without ads for a one-time fee. Circumventing the unobtrusive ads may lead to higher hardware prices in the future, and [Pat] mentions that. He pulled off this hack to show the holes in Amazon’s security, and hitting them in the pocketbook is a powerful way to do it.

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You’re out at night and playing a boisterous game of flashlight tag. But how can you tell if you’ve been mortally wounded by your opponents light beam? [Kenyer] solved this problem by building a flashlight tag damage sensor which is worn by each participant. It adds a bit of the high-tech equipment used with laser tag while keeping a low-tech price tag.

The sensor relies on a light dependent resistor to register hits when a flashlight beam passes through the round window. It will only register one hit in a three-second time period. At the end of the game, the total number of hits recorded can be flashed back using an on-board LED to see who is the victor. You can see a demo of this functionality in the clip after the break.

[Kenyer] started with a breadboard prototype using an Arduino as the driver. Obviously the cost of an Arduino for every player is a bit ridiculous. He scaled down the project, running the Arduino code on an ATtiny microcontroller. Read the rest of this entry »

[form], a new user on the Hack a Day forums, was thinking, “what Christmas present i can send a friend, that would be really annoying?” We think he really hit it out of the park with this one. It’s a modified computer speaker that will play “explicit” audio until the power button is pressed 200 times and the light sensor is covered. When this present is unwrapped, the room will fill with sounds not suitable for children, the elderly, or those with heart conditions.

The build is based around an old powered computer speaker. Six Li-ion batteries from an old laptop provide the power, and a very simple circuit pulls sound off an SD card with the help of an ATtiny45.

The schematic for the build looks easy enough, and like a good builder, [form] included the source and HEX files. Sadly (or thankfully), there is no video of the gag gift in action; probably a good thing, because this seems like a great way to lose a friend.

[Nirav] painted this masterpiece by hand… with a little help from a computer. He calls it the semi-automatic paintbrush because you do need to move it over the canvas by hand, but a computer decides when to dispense the ink.

He’s using a piece of hardware we looked at back in September called the InkShield that got a boost from Kickstarter. It’s an Arduino shield that drives an inkjet printer cartridge. The trick is how to know when the cartridge is in position for printing.

The system uses visual processing for that. [Nirav] added an IR led to the cartridge, and uses a camera to extrapolate its position. He actually reused a Python homography module which he had written for use with a projector. That setup was developed as a digital white board, but works just as well for this purpose.

He mentions that results like this won’t be featured in an art museum. But the look is unique, and we’d love to make a set of geeky thank-you notes using the technique.

If you haven’t yet wrapped up your Christmas shopping, you may want to consider building [AlanFromJapan’s] implementation of the ever-classic “Clapper”. With its theme song burned into the brain of anyone old enough to remember the 80s, the clapper was a wonderful device that certainly put the “L” in laziness.

Looking for an excuse to play around with an opamp and microphone [Alan] decided to build his own version of the Clapper based off this similar circuit, which he calls the ClapClap. He built the device using an electret mic that feeds a signal through a small amplifier on the way to the ADC of an ATmega328 microcontroller. The mcu constantly polls the ADC looking for the sound of clapping hands, a solution that works, but isn’t as clean as [Alan] wanted.

He went back to the drawing board, this time building a circuit around an ATtiny2313 microcontroller. Most of the other components remained the same, though the new, smaller design sports some nice PCBs he had made at Seeedstudio. Rather than constantly polling the ADC, this version of the ClapClap looks for peaks in the signal coming from the mic to identify the clapping of hands.

He says that the newer version works great, though he still has a software bug or two that need fixing before he parks himself on the couch for all eternity.

You all know that person.

The one who picks up every present with their name on it, shaking it before busting into their best Carnac the Magnificent impression. Heck, you might even be that person.

[Jason] was thinking about how to combat the gift shaker in his life and put together a simple prank that’s sure to provide him some enjoyment when the shaking and guessing commences.

He bought a premade audio module that stores about 20 seconds of sound, replacing the pushbutton trigger with a pair of wires that can easily make contact when the box is vigorously moved. Everything was carefully mounted in a gift box before being wrapped and set under the tree to surprise the eager gift shaker.

We definitely like the idea, since there are a plethora of ways to customize/enhance [Jason’s] work to fit your specific needs. Whether you go with the kitten/puppy in a box theme, or wire in an incredibly loud alarm, your resident gift inspector will never look at presents the same way again!

Continue reading to see [Jason] explain his gift prank in more detail.

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So you’re really looking for that [Norman Rockwell] Christmas and want to set up your train to encircle the Christmas tree this year. The problem is that all you’ve got is an old LEGO train set and not enough track for it. You can’t just buy some more, because the technology has changed; or can you?

[Chris] was dismayed to find that newer LEGO train sets have gone to battery operation rather than drawing power through metal tracks. The new tracks are plastic, and buying extra segments of the older version is cost prohibitive. He figured out a way to add power conductors to the new track pieces.

It turns out the design of the new tracks matches the old, except they’re all in plastic instead of having metal rails. He bought a plastic add-on set, then picked up some copper foil from the hobby store which is meant for stained-glass work. It’s adhesive backed, and after working out the best way to apply it, he coated the rails with the stuff. As you can see above, the new mates perfectly with the old, and keeps that locomotive chugging along.

If you’ve got copper foil left over after this hack, there’s tons of other uses for it. Perhaps building your own flex sensors is worth a try.