# Tutorial explains the concepts behind an IMU

[Anilm3] wrote in to share the IMU tutorial series he is working on. An Inertial Measurement Unit is most often found in self-balancing robots and quadcopters, providing enough high-speed sensor data to keep up with the effects of gravity.  He previously used some all-in-one IMU devices in school which did most of the work for him. But he wanted to grind down and look at what each sensor spits out and how those measurements are used. The first installment deals with the accelerometer, using its data to calculate pitch and roll. For these demonstrations [Anilm3] is using this ADXL345 sensor board, an Arduino, and some processing sketches for testing.

Whenever working with sensors you need to take noise into consideration. The post shows how to implement a low-pass filter in the code which will help smooth out the readings. The filtered data is then fed to a couple of mostly-painless formulas which calculate the movement of the accelerometer in degrees. The demonstration sketch is mapped to a 3D cube to give you an idea of how accurate the accelerometer is. There’s a little bit of lag which would let a self-balancing robot have a nasty fall. The solution to this issue will be discussed in upcoming parts of the series. The next installment tackles the gyroscope sensor.

# Triangle-grid LED display

[Dearmash] put together this RGB LED display using triangles for each pixel. It’s an interesting deviation from the traditional grid layout. There are two video demos after the break. The first is a plasma-style pattern generated in Processing. The second is a spinning color wheel which would be perfect if synchronized with your Photoshop color spinner.

So the physical build is done, and now [Dearmash] is looking for a purpose for the device (isn’t that always the way it happens?). He mentions that the triangular layout looks cool, but makes text display almost impossible. Does anyone have any ideas on how to make this work? Right off the bat we could see side-scrolling a font similar to the Metallica logo’s M and A. Bu there must be some way to group these pixels together into readable characters. If you always use an upward and downward pointed triangle on the same row as a pixel it makes a parallelogram which would be used to display italicization characters.

# Huge water and light VU meter plus more

This is the senior design project for a group at the University of Vermont. It’s a wet, bubbly, blinky, interactive thing. Each column is a clear tube filled with water, with a string of fully addressable RGB LEDs suspended in the center. In idle mode, the lights scroll through a series of interesting patterns while the water is filled with bubbles to add some depth to the presentation. There is also a VU meter function, as seen here and during the Portal theme song that ends the video demo after the break.

A Teensy++ board is used to address the display. It’s set up to receive serial commands from a Processing script which is responsible for generating the animations. At the top of the frame you can see there’s a Kinect sensor. By standing in the standard post (we think it should be called the Kinect mug shot) the installation will automatically switch over to body control. We could see this thing making its way into a long airplane terminal hallway, following the travelers along their trek from one terminal to the next.

# A one-bit processor

Put on that abstract thinking cap, get out the pen and paper, and spend some time figuring out how this one-bit processor works. [Strawdog] came up with the concept one day during his commute to work (don’t worry, he takes the train… much safer than [Dave Jones’] frightening drive-time podcasts). He sketched it out on paper to make sure he knew where he was going with the project, then collaborated with Legion Labs to implement it in processing as an easier way to visualize its functionality. Since it’s one-bit there’s only room for one instruction. That instruction is a copy, then branch-if instruction. It copies the current bit to one address, and if that bit was one, it branches to a second address.

Going a bit fast for you? We think the description is fairly good, but if you can’t quite put it together from the article’s description, you may want to build this 2-bit paper processor and learn how it works first. It should teach you the basic concepts you need to understand the 1-bit version. As you can see in the image above, there’s also a single-step feature in the processing example that lets you analyze the effects of each instruction during program execution.

# @publictextbox is a Twitter enabled phone booth

In the interests of open communication in shared spaces, [dan] made a public text box that serves as a terminal to the @publictextbox twitter account. We could see something like this being useful in a hackerspace or other hang out to announce to the world the happenings of the resident makers and builders.

The software setup is very simple and can run on just about any old computer you might have lying disused in a corner. The app is built with Processing, and the code is extremely simple and easily modifiable. Even though the case is a lovely cardboard number, the Twitter Box can be dressed up as any imaginable form. We’d love to see a nice TARDIS blue, but we’ll leave that up to [dan].

You can check out the demo of the Twitter phone box after the break. Alternatively, you could re-tweet this post and take part in a load test for the @publictextbox.

# Decorating an Ent for Christmas

These images may look the same, but if you peer closely at the one on the left you’ll notice the eyes staring back at you. It seems animatronic decor is in this year, and we think [Fjord Carver’s] talking Christmas tree is one of the better offerings.

He picked up the diminutive tree at the dollar store, then started added the pieces that put on the show seen after the break. A small strand of battery operated lights, and a bit of garland are traditional. But the Arduino and pair of servo motors are a new holiday tradition. They move parts of the tree to reveal a set of eyes and animate a mouth. He drives the display by sending serial commands from a computer to the Arduino. This way you can script your performances, with flapping jaw, moving eyelids, and blinking lights while the computer supplies the sound.

Is it just us, or does anyone else really want to see this guy singing the Chipmunk’s Christmas Song? Or if that’s a bit too wholesome you could go the more vulgar route.

# Syneseizure makes objects feel loud

Synesthesia is a mix-up in the wiring of the brain where sensory inputs are perceived differently than what ‘normal people’ usually experience. People with synesthesia can have visual input mapped to aural perception in the mind, or driving along a highway where there’s a recent skunk roadkill can smell ‘loud.’ It’s an interesting way of perceiving the world that’s usually inaccessible to most of the population, but the Syneseizure tries to replicate this way of viewing the world.

There’s a bunch of types of synesthesia (Led Zeppelin feels purple, or apples smelling further away than grapes), but [Greg] and his team needed to choose one subtype to reduce the complexity of their project. They chose mapping visual input to touch sensation. This was accomplished by attaching a dozen speakers to the test subject’s face. A webcam recorded where the subject was looking at and with a Processing sketch, the webcam was reduced to a grayscale 4×3 pixel grid. The intensity of the each pixel corresponded to the strength of buzzing in each speaker. All that was left to do is put a mask over the subject and have them walk around.

The Syneseizure was built for Science Hack Day San Francisco and ended up winning the people’s choice award. There’s a bunch of pics and a great write-up on the project website, so be sure to check that out.