Two Computer Vision Builds From Cornell

December 20, 2012 by 6 Comments

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[Bruce Land], professor at Cornell, is a frequent submitter to our tip line. Usually he sends in a few links every semester from undergraduate electronics courses. Now the fall semester is finally over and it’s time to move on to the more ambitious master’s projects.

First up is a head-mounted eye tracker, [Anil Ram Viswanathan] and [Zelan Xiao] put together a lightweight and low-cost eye tracking project that will record where the user is looking.

The eye tracker hardware is made of two cameras mounted on a helmet. The first camera faces forward, looking at the same thing the user is. The second camera is directed towards the user’s eye. A series of algorithms detect the iris of the user’s eye and overlays the expected gaze position on the output of the first camera. Here’s the design report. PDF, natch.

Next up is a face tracking project implemented on an FPGA. This project started out as a software implementation of a face tracking algorithm in MATLAB. [Thu-Thao Nguyen] translated this MATLAB code to Verilog and eventually got her hardware running on an FPGA dev board. Another design report.

Having a face detection and tracking system running on an FPGA is extremely interesting; the FPGA makes face tracking a very low power and hopefully lower-cost solution, allowing it to be used in portable and consumer devices.

You can check out the videos for these projects after the break.

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Which Way Do Non-polarized Film Capacitors Go? There Is An Answer.

December 19, 2012 by 11 Comments

orienting-non-polarized-film-caps

If you, like us, thought that capacitor orientation only matters for polarized varieties like electrolytic capacitors you should read through this article. [Bruce Trump] looks at why some film capacitors have a stripe printed on one end and why their orientation can matter.

He has an image rolled into his post showing both axial and dipped capacitors with a black stripe printed on one end of the package. This is an indicator of what is going on inside of the component. The end with the line has a conductive foil layer which acts as a shield. But it seems that this shield will do its job better if you do a better job of designing for the capacitor.

The diagram above shows two op-amp circuits, both using a non-polarized capacitor that will affect the circuit if it receives external interference. [Bruce] discusses various aspects of this phenomenon, mentioning that although these careful layouts can be tested in your designs to prove which has more benefits, simulated applications (using SPICE) will perform exactly the same.

Comprehensive Home PCB Fabrication Tutorial

December 19, 2012 by 15 Comments

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From what we’ve seen we’d say [Jianyi Liu] is really good at etching PCBs at home. Now you can learn from his experience. He just published a mammoth guide to fabricating your own PCBs at home. That link goes to his index page which leads to all eight parts of the guide.

He starts off by mentioning that fab house boards are rather inexpensive these days. This will save you a lot of trouble (like acquiring the equipment and raw materials needed to get up and running) but you can’t beat the turnaround time of doing it yourself.

After discussing the particulars about trace width, copper thickness, and a few design considerations he lays out his board and prints the artwork to a sheet of transparency film. A pre-sensitized board is cut to size before a trip through an exposure rig with the film taped onto it. The image above shows him rinsing the board after applying the developer chemical. From here he uses cupric chloride he mixed himself to etch the board. [Jianyi] recommends populating the components before cutting the panel apart — a task which he accomplishes with a hack saw.

Stellarino Brings Wiring-style Coding To The Stellaris Launchpad

December 19, 2012 by 18 Comments

wiring-for-stellaris-launchpad

[Sultan Qasim] wrote in to tell us about the work he’s been doing on the Stellarino library. It’s goal is to break down the coding barriers present for those looking to move from Arduino to ARM. This is accomplished by facilitating Wiring-stlye code for the Stellaris Launchpad ARM development board.

Right off the bat [Sultan] mentions that the interface is Wiring-like, but is not compatible with it. This means you can’t just plop your existing sketches into a C file and get them to work with the addition of a simple include file. But what it does do is provide access to the functions to which seasoned Arduino users have grown accustomed. You can see some examples above, including analogWrite(), digitalRead(), and a simple delay function.

We had a quick look at the library. It uses StellarisWare components which are stored in the ROM of the chip (these are all preceded by ‘ROM_’). The one thing missing is the UARTstudio library which apparently carries a license incompatible with GPL.

Months Of Failure Lead Up To This EL Panel Dimmer That Pulses To The Music

December 19, 2012 by 8 Comments

el-panel-dimmer

Way back in March [Ch00f] took on a for-hire project to make a suit that lights up to the music. He decided to build something based around a pulsating EL panel. He’s put a lot of time and tried of a few different techniques, but he finally has a working EL panel dimmer.

This is a saga we’ve kept our eye on. The fall seems to have been good to him, after a failure using TRIACS he managed to adjust the brightness of some EL wire by messing with the current going to the driver’s oscillator. Standing on the shoulders of that success he designed the board seen above by getting serious about audio signal processing. There’s a microphone on the board which picks up sound which is then processed into a signal responsible for the brightness of the EL panel.

There’s a demo video after the break, but you’ll want to dig into his article to get all the gritty details.

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Sound Reactive Christmas Tree Makes Folks Happy

December 19, 2012 by 4 Comments

This non-traditional Christmas tree in Victoria, British Columbia is bringing people together this holiday season. It boasts over 800 lights that react to sound. You can see the pulsing and color changing that go along with some Tuba carols in the clip after the break.

The art installation was commissioned by the Downtown Victoria Business Association. A great big cherry tree was adorned with strings of individually addressable RGB LED Christmas lights. They are controlled by a system which calculates changes based on onset, energy and frequency analysis of sound picked up by multiple microphones. The effect is delightful and it’s not just musicians getting in on the fun. Passersby can’t seem to help themselves from yelling, clapping, and singing to make the tree sparkle.

Also included in the project is an interactive stop-motion animation film. It’s projected on the side of a building and invites viewers to send a text message to interact with it. A video of this is also found after the jump.

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Reverse Geocache Based On STM32 And GPS Wristwatch

December 19, 2012 by 3 Comments

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[Renaud Schleck] somehow got lucky enough to find a GPS wristwatch in the trash. It had a broken LCD screen so its wouldn’t be of much use on that next hiking trip, but he knew it still had potential. He used the GPS module and a few other parts to build this reverse geocache box.

Reverse geocache is a container that is locked, opening only in a pre-defined geographic location. We’ve seen plenty of these projects around here, like this one that talks, or this one which was given as a Christmas gift. They’re popular projects both because of the unique method of getting at the prize inside, and because it doesn’t take a whole lot of hardware to build one. Once [Renaud] had the GPS module he simply need a user interface, locking mechanism, and a microcontroller to pull it all together.

The interface uses a screen from an old cellphone and one push button. The latching system is a tiny geared motor salvaged from a Laptop optical drive. These, along with the GPS watch board are all monitored by the STM32 microcontroller which he programmed using OpenOCD and the Bus Pirate.

[via Reddit]