PhotoTransistor Based Eye-Tracking

January 3, 2014 by 11 Comments

eyetrack

The applications of eye-tracking devices are endless, which is why we always get excited to see new techniques in measuring the absolute position of the human eye. Cornell students [Michael and John] took on an interesting approach for their final project and designed a phototransistor based eye-tracking system.

We can definitely see the potential of this project, but for their first prototype, the system relies on both eye-tracking and head movement to fully control a mouse pointer. An end-product design was in mind, so the system consists of both a pair of custom 3D printed glasses and a wireless receiver; thus avoiding the need to be tethered to the computer under control . The horizontal position of the mouse pointer is controlled via the infrared eye tracking mechanism, consisting of an Infrared LED positioned above the eye and two phototransistors located on each side of the eye. The measured analog data from the phototransistors determine the eye’s horizontal position. The vertical movement of the mouse pointer is controlled with the help of a 3-axis gyroscope mounted to the glasses. The effectiveness of a simple infrared LED/phototransistor to detect eye movement is impressive, because similar projects we’ve seen have been camera based. We understand how final project deadlines can be, so we hope [Michael and John] continue past the deadline with this one. It would be great to see if the absolute position (horizontal and vertical) of the eye can be tracked entirely with the phototransistor technique.

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Build An Audio Spectrum Analyzer The Analog Way

January 3, 2014 by 18 Comments

bandpass

[Ryan] wanted a spectrum analyzer for his audio equipment. Rather than grab a micro, he did it the analog way. [Ryan] designed  a 10 band audio spectrum analyzer. This means that he needs 10 band-pass filters. As the name implies, a band-pass filter will only allow signals with frequency of a selected band to pass. Signals with frequency above or below the filter’s passband will be attenuated. The band-pass itself is constructed from a high pass and a low pass filter. [Ryan] used simple resistor capacitor (RC) filters to implement his design.

All those discrete components would quickly attenuate [Ryan’s] input signal, so each stage uses two op-amps. The first stage is a buffer for each band. The second op-amp, located after the band-pass filters, is configured as a non-inverting amplifier. These amplifiers boost the individual band signals before they leave the board. [Ryan] even added an “energy filler” mode. In normal mode, the analyzer’s output will exactly follow the input signal. In “energy filler” (AKA peak detect) mode, the output will display the signal peaks,  with a slow decay down to the input signal. The energy filler mode is created by using an n-channel FET to store charge in an electrolytic capacitor.

Have we mentioned that for 10 bands, all this circuitry had to be built 10 times? Not to mention input buffering circuitry. With all this done, [Ryan] still has to build the output portion of the analyzer: 160 blue LEDs and their associated drive circuitry. Going “all analog” may seem crazy in this day and age of high-speed micro controllers and FFTs, but the simple fact is that these circuits work, and work well. The only thing to fear is perf board solder shorts. We think debugging those is half the fun.

3D Printering: Making A Thing In Blender, Part I

January 3, 2014 by 52 Comments

printering

In case you weren’t aware, having a 3D printer is nothing like owning a real-life Star Trek replicator. For one, replicators are usually found on Federation starships and not hype trains. Secondly, the details of how replicated objects are designed in the 24th century is an issue completely left unexplored by TNG, and DS9, and only a minor plot point in a few Voyager episodes. Of the most likely possibilities, though, it appears replicated objects are either initially created by ‘scanning’ them with a teleporter, or commanding the ship’s computer to conjure something out of the hologrid.

No, with your own 3D printer, if you want a unique object you actually have to design it yourself. Without a holodeck. Using your hands to move a mouse and keyboard. Savages.

This series of ‘Making a Thing’ tutorials aims to fix that. With this post, we’re taking a look at Blender, an amazing 3D modeling and animation package.

Because we still haven’t figured out the best way to combine multiple blog posts together as a single resource − we’re working on that, though − here’s the links to the previous “Making a Thing” posts:

This list is sure to grow thanks to your suggestions on what 3D modeling software to feature, but for now let’s make a thing in Blender.

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3D Acoustic Manipulation: Seemingly-Unreal Levitation Using Soundwaves

January 3, 2014 by 33 Comments

Wow. [Yoichi Ochiai], [Takayuki Hoshi] and [Jun Rekimoto] are researchers from the University of Tokyo and the Nagoya Institute of Technology, and they have just learned how to airbend.

Using a series of standing ultrasound waves, it is possible to suspend small particles at the sound pressure nodes. The acoustic axis of the ultrasound beam is parallel to gravity, which also allows the objects to be manipulated along the fixed axis by varying the phase or frequencies of the sound. By adding a second ultrasound beam perpendicular to the first it is possible to localize the pressure node, or focal point, and levitate small objects around a 2D plane.

In their demonstrations they float foam particles, a resistor, an LED, they show off the waves using a piece of dry ice, and even manage to float a small screw.

Sound like crazy talk? Just watch the video.

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Fire At The Geek Group

January 3, 2014 by 121 Comments

Geek Group

The Geek Group, an absurdly large and well stocked hackerspace in Grand Rapids, Michigan caught fire yesterday.

You may recall The Geek Group from their many over-the-top projects that include a quarter shinker, a 200,000 Watt Tesla coil, enough capacitors to kill a demi-god, and a giant robot that crushes TVs. From what TGG has shown on their website and their YouTube, they have an amazing space that could still be the home of quite a few amazing builds.

According to Geek Group head honcho [Chris], the fire was caused by an overheated electric motor. No one was at the space at the time, but the fire was hot enough to crack the exterior brick and melt porcelain insulators in their high voltage lab. To add insult to injury, this was only TGG’s second day of being open to the public.

The folks at The Geek Group are looking for volunteers for their cleanup, so if you’re around the Grand Rapids area and would like to pitch in, head on over around noon today.

A Low Cost Dual Discriminator Module For The Easy-phi Project

January 3, 2014 by 9 Comments

A few months ago I presented you the Easy-phi project, which aims at building a simple, cheap but intelligent rack-based open hardware/software platform for hobbyists. With easy-phi, you simply have a rack to which you add cards (like the one shown above) that perform the functions you want.

Recently my team finished testing our FPGA-based discriminator or “universal input” if you prefer. As easy-phi cards use a well-defined electrical signal to communicate with each other, we needed to make a card that would translate the different kinds of electrical signals from the outside, as well as perform plenty of other functions. It was therefore designed to have a 100MHz input bandwidth with an AC/DC coupled 50 ohm/high impedance input stage (x2) and 4 easy-phi outputs. For this module, we picked the (old) spartan3-an FPGA to perform the different logic functions that may be needed by the final users (high speed counter, OR/XOR/AND, pulse creation,…). Using the cortex-m3 microcontroller present on the board, it may be easily reconfigured at will. All design resources may be found on our Github, and you can always have a look at our official website.

Myst(ery) Box

January 3, 2014 by 7 Comments

Anyone remember the game Myst? Well, [Michael] and his girlfriend have been playing quite a bit of it lately, so for her birthday, he decided to make her something inspired from it.

For those unaware of the classic that is the Myst series, it is a set of games that started back in 1993 where you assume the role of the Stranger who gets to explore other planets (called Ages) to solve various logical and mechanical puzzles.

Anyway, [Michael] got his girlfriend tickets to visit GC319QK (a geocache site requiring diving) — since the gift is a relatively small token, it was logical for [Michael] to make a fancy box for it — and that’s exactly what he did. It’s a peculiar little wooden box with LEDs, a button, a latch, an unplugged wire, different rods and strange looking sensors — and it is a very clever little puzzle.

We could explain to you how it works (with the Arduino, phototransistors and maybe the source code), but instead we think you’ll enjoy watching [Michael’s] video of it.

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