160 Mac Minis, One Rack

December 9, 2012 by Eric Evenchick 128 Comments

[Steve] needed an alternative to the Xserve, since Apple stopped making it. His solution was to stick 160 Mac Minis into a rack. That’s 640 real cores, or 1280 if you count HyperThreading.

First, Steve had to tackle the shelving. Nobody made a 1U shelf to hold four Minis, so [Steve] worked with a vendor to design his own. Once challenge of this was managing the exaust air of each Mini. Plastic inserts were designed to ensure that exaust wasn’t sucked into the intake of an adjancent Mini.

mac-mini An array of 160 computers is going to throw a lot of heat. To provide sufficient airflow, [Steve] built a custom cooling door out of four car radiators fans, connected to a 40A DC motor controller. This was all integrated into the door of the rack.

Another challenge was getting power to all of the Minis. Since this deisgn was for a data center, the Minis would have to draw power from a Power Distribution Unit (PDU). This would have required a lot of PDUs, and a lot of cables. The solution: a one to four Y cable for the Minis. This allows each shelf of four to plug into a single outlet.

The final result is a professional looking rack that can replace a rack of Xserves, and has capacity to be upgraded in the future.

More Fun With Syma 107 Reverse Engineering

December 8, 2012 by Eric Evenchick 4 Comments

[Jim] used a logic analyzer to do some in depth analysis of the Syma 107G helicopter’s IR protocol. We’ve seen work to reverse engineer this protocol in the past, but [Jim] has improved upon it.

Instead of reading the IR output of the controller, [Jim] connected a Saleae Logic directly to the controller’s circuitry. This allowed him to get more accurate timing, which helped him find out some new things about the protocol. He used this to create a detailed explanation of the protocol.

One of the major findings is that the controller used a 3 byte control packet, which contradicts past reverse engineering of the device. There’s also a new explanation of how multiple channels work. This allows multiple helicopters to be flown without the controllers interfering.

The write up is quite detailed, and explains the reverse engineering process. It also provides great information for anyone wanting to hack one of these low cost helicopters. From the details [Jim] worked out, it would be fairly easy to implement the protocol on your own hardware.

[Staci Elaan]’s Awesome Portable Tesla Coils.

December 8, 2012 by Caleb Kraft 45 Comments

We stumbled onto [Staci’s] videos a while ago when we posted this big tesla gun. While it wasn’t the first portable coil we had seen, it was certainly an impressive implementation. In the comments we found [Staci] had already been making these for a while. Hers were big and small, had awesome modulation, and looked freaking cool too.

It also should be pointed out that [Staci] donates her coils to people when she’s done! Let me say that again, she gives them away to groups of people that could use them. That deserves some respect.

Unfortunately, [Staci] didn’t document her builds in great detail at the time. She has added some information recently though. You can read about her first working prototype from 2006, or a slightly more modern one here.

Of course, the real fun is in seeing them work.

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Bird Buggy Soothes A Screeching Parrot

December 8, 2012 by Brian Benchoff 67 Comments

bird

[Andrew] has enjoyed the company of [Pepper] the parrot for more than a decade, but the screeching of a bird in the next room is something you just don’t get used to. [Pepper] gets very lonely some times, and short of having someone carry him around on a shoulder, there’s not much that will calm this parrot down. [Andrew] had the idea of allowing [Pepper] to wander around the house with the help of a mobile platform. Thus was born the Bird Buggy, a parrot-controlled vehicle built just for [Pepper].

The buggy itself is a basic two-wheel drive platform driven with a small beak-compatible joystick mounted just forward of [Pepper]’s perch. With this system, it’s possible for [Pepper] to follow [Andrew] through the house. [Andrew] wanted to make sure [Pepper] couldn’t drive into walls or table legs, so a suite of sensors on the front stops the buggy whenever an object is detected.

One very cool feature of the bird buggy is its ability to drive itself to a recharging station. It does this with the help of a webcam and OpenCV and a pair of markers just behind the charging port. When the Beagleboard on the buggy sees the green and yellow markers for the charging port align, it knows its directly in front of the charging port.

You can see [Pepper] driving his new whip around after the break, along with a very cool demo of the bird buggy docking with its charging port.

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Building A Spectrum Analyzer With Parallel Processing

December 8, 2012 by Brian Benchoff 12 Comments

fft

It’s the end of the semester for [Bruce Land]’s microcontroller design class at Cornell, and the projects coming off the workbench this semester look as awesome as any before. For their final project, [Alexander Wang] and [Bill Jo] designed an audio frequency spectrum analyzer using two microcontrollers in a parallel setup.

This spectrum analyzer takes an audio signal from an iPod, phone, or CD player through a 3.5 mm jack and displays the level for dozens of frequency bands much like an audio visualizer in iTunes or a nice car stereo display. To display these frequency bands, the spectrum analyzer first needs to perform a Fast Fourier Transform on the incoming audio signal. While FFT is extremely fast, the calculations are rather hardware intensive; calculating the frequencies and displaying them on a TV would be a bit much even for the ATMega1284 used in the project.

To graph the audio signal on their small display, [Alexander] and [Bill] broke the build up into two parts – one to do the math on the audio, and another to generate the NTSC video signal for the display.

As seen in the video after the break, the spectrum analyzer works wonderfully, and even though it only functions up to 4kHz, it’s more than enough to see what’s going on in most music.

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Driving A WS2811 RGB LED Pixel

December 7, 2012 by Mike Szczys 46 Comments

[Alan] has been working on driving this WS2811 LED module with an AVR microcontroller. It may look like a standard six-pin RGB LED but it actually contains both an LED module and a microcontroller to drive it. This makes it a very intriguing part. It’s not entirely simple to send commands to the module as the timing must be very precise. But once the communication has happened, the LED will remain the same color and intensity until you tell it otherwise. You can buy them attached to flexible strips, which can be cut down to as few as one module per segment. The one thing we haven’t figure out from our short look at the hardware is how each pixel is addressed. We think the color value cascades down the data line as new values are introduced, but we could be wrong. Feel free to discuss that in the comments.

The project focuses on whether or not it’s even possible to drive one of these pixels with a 16MHz AVR chip. They use single-wire communications at 800 kHz and this really puts a lot of demand on the microcontroller. He does manage to pull it off, but it requires careful crafting in assembly to achieve his timing constraints. You can see a quick clip of the LEDs fading between colors after the break.

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Autonomous Helicopter Works Like A Wii Remote

December 7, 2012 by Mike Szczys 5 Comments

autonomous-ir-helicopter

[Jack Crossfire] took one of those inexpensive indoor helicopters and made it autonomous. He didn’t replace the hardware used for the helicopter, but augmented it and patched into the remote control to make a base station.

The position feedback is provided in much the same way that the Wii remote is used as a pointing device. On the gaming console there is a bar that goes under the TV with two IR LEDs in it. This is monitored by an IR camera in the Wii remote and used to calculate where you’re pointing the thing. [Jack’s] auto-pilot system uses two Logitech webcams with IR filters over the sensors. You can see them mounted on the horizontal bar in the cutout above. The helicopter itself has an IR LED added to it that is always on. The base station follows this beacon by moving the cameras with a pair of servo motors, calculating position and using it when sending commands to the remote control’s PCB.

Don’t miss the demo video of the rig after the break.

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