Digital Marker Communicates With Touch Screen

October 13, 2012 by Brian Benchoff 27 Comments

In an effort to be more relevant to children that just aren’t impressed with crayons and markers anymore, Crayola released the ColorStudio HD pen. Instead of ink, this pen is filled with electronics that communicate with a tablet to draw different colors in the Crayola ColorStudio app.

[Rob Hemsley] had done some work with capacitive touch screens before, so when he heard the clicking of a tiny relay inside the pen, he automatically knew how it worked. Of course this meant tearing apart the Crayola marker to look at the electronics, but [Rob] also went so far as to replace the microcontroller, allowing you to craft your own ColorStudio HD pen.

The digital Crayola marker communicates with the app by switching a relay on and off very quickly. This completes a circuit between the user’s hand and the touch screen, allowing the tablet to interpret the desired color by measuring how many touches are received per second.

Inside the pen, [Rob] found an RGB LED, a relay, and a PIC microcontroller. Not having any experience with PICs, [Rob] changed out the ‘micro to an ATtiny44 and started writing some firmware with the help of the Arduino IDE.

[Rob]’s updated version functions exactly like the stock version, communicating with the Crayola app by pulsing the relay to indicate the selected color. Even though the Crayola app only has three possible colors, [Rob] says it’s feasible to program the digital pen to send an RGB color value to a tablet, allowing you to choose what color to draw with on the pen.

You can see a video of [Rob]’s updated pen after the break.

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Dry Erase Marker Opens All Hotel Room Doors

October 2, 2012 by Mike Szczys 50 Comments

If you’re carrying around an exposed circuit board and a bunch of wires people are going to notice you. But a dry erase marker won’t turn any heads. And this one holds its own little secret. It acts as a master key for hotel room door locks.

This is really more of a repackaging hack. The exploit is already quite well-known. The Onity brand of key card locks most commonly used in hotels have a power jack on the bottom that doubles as a 1-wire communications port. The first published proof of concept used an Arduino board and a simple adapter to unlock any door in under one second. Now that hardware has been reduced in size so that it fits in the hollow shell of a dry erase marker. Even better, the felt tip has been replaced with the appropriately sized barrel jack. Check out the ultra-fast and inconspicuous use of it after the break. We think using this is no more obvious than actually having the key card.

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Center Pivot Pen Plotter

September 18, 2012 by Mike Szczys 22 Comments

This center pivot pen plotter is an interesting take on the idea, and manages to somewhat simplify the fabrication when compared to a gantry-style built.

Normally we’d see a gantry that travels on two rails, with a print head that moves along its length. Here the gantry is anchored on just one side, with a chain driven system to rotate it along the plotting surface. The print head uses a fine-point felt-tipped marker. It still travels along the arm as you would expect, and can be tilted away from the paper for repositioning.

What was made easier in hardware ends up adding to software complexity. The benefit of a traditional system is that it uses X and Y coordinates to plot a design. The pivot of this mechanism means that as the print head moves further from the center of the machine, the distance between each pixel is magnified. But the clip after the break proves that this issue has been solved.

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Atomic Clapperboard

August 2, 2012 by Mike Szczys 13 Comments

Whether you know it as a clapperboard, a slate, slate board, time slate, or by another name, you probably recognize this staple of movie making. It’s a handy way to help synchronize sound with video, and to keep track of clips when it comes time to edit. But this clapperboard is quite a bit more accurate than most. It’s got an atomic clock source for dead-on accuracy.

The project came from the growing availability of Rubidium clock source modules on eBay. They can be had for under $100 and you’ll enjoy accuracy of 0.1 ppm. [Luddite Tech] grabbed one for himself and included it in this build. As you can see in the clip after the break, the contrast of the eight-digit display is adjustable, and shines brightest when the marker is snapped. We’d guess the cable he connects at the beginning of the demo is used to set the initial time reference. After that the in-built WiFi can be used to push the time markers to a computer.

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