Using the Minoru stereo webcam under Linux 
Saturday, January 31, 2009, 04:29 PM - Misc TechnoToys
I just received one these brand new Minoru stereo webcam, which I bought at Amazon from 90 bucks (a steal considering the price of the closest competitor).

Naturally, I'd like to use it under Linux for robot vision, so I was crossing my fingers that one of the webcam drivers on Linux would recognize it.

As soon as I received the camera, I plugged it into my laptop running Ubuntu 8.10 Interpid. There are good news and bads news.

Good news: the device is detected by the uvcvideo driver, and the left and right cameras appear as /dev/video0 and /dev/video1. My video grabbing software was able to grab frames from both camera separately. I tried my own video grabbing test program written in Lush for v4l2.

Now for the bad news: it seems impossible to grab video from the left and right cameras at the same time :-(

It looks like uvcvideo assigns more than half the USB port bandwidth to the first camera, and there is not enough left for the second. I've posted a question about the problem on the uvcvideo developer mailing list. Stay tuned.

UPDATE: Laurent Pinchart, maintainer of the UVC driver is looking into the problem. It looks like the camera reports a higher bandwidth than it needs (at least, that's what how the driver interprets the data). The Minoru people are interested in making their camera work with Linux and are helping out Laurent (sending him a free camera and such).

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Neural Net in JavaScript 
Sunday, January 25, 2009, 11:06 PM - Misc TechnoToys
[via Hack A Day] Shaun Friedle has written a simple neural net code in JavaScript (forward prop only, no learning) and uses it as an OCR engine to break badly designed CAPTCHAs from within the browser. The script is here, and the demo home page here.

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cheap video gear from ChinaVasion 
Sunday, January 25, 2009, 12:10 PM - Misc TechnoToys
China Vasion (not China Vision, oddly enough) has a slew of cheap video gear such as wireless cameras and receivers for $25, and quad-camera systems for $100.

They also have rather unusual widgets, such as this underwater remote camera which comes with an MPEG recorder and costs $250.

The also have this radio-controlled car with a built-in wireless camera and a transmitter-mounted LCD screen. Things like this have been available for some time, but not for $90!

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Fry your retina for $50 
Monday, January 12, 2009, 12:22 AM - Misc TechnoToys
Steve Crandall from Tingilinde pointed me to this 150mW blue laser diode available for $50. An ideal way to fry your retina in the blink of an eye (actually *before* the blink of an eye, and way faster than it).
With proper precaution it might be used to build a CNC laser cutting machine to cut foam (Depron) and such.

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Minoru 3D webcam 
Thursday, October 16, 2008, 04:04 PM - Misc TechnoToys
The Minoru3D Webcam is a stereo webcam soon to be released by its British manufacturer. The website is a single front page with almost no information, beside a few pictures and the address of a marketing company Promotion and Display Technology Ltd. The big questions are the price and the date of availability.

Another British company Nvela, which is sponsored by the Microsoft Research Lab in Cambridge, UK, has produced a stereo webcam called the Hydra, but at 300 pounds ($600) it's way too expensive, and (so far) their SDK is for Windows only. They have been promising versions for Linux and Mac, but since the SDK was developed by Microsoft Research, I wouldn't hold my breath.

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Screwy screw gauge 
Monday, August 25, 2008, 01:54 AM - Misc TechnoToys
Recently, I was looking for 2.0mm wood screws, As it turns out, these little things are horribly difficult to find in the US. So, I tried to look for the closest thing to a 2.0mm wood screw in the US "system".

I stumbled on this Wikipedia page that contains a curve and a table that maps US drill bit gauge numbers to millimeters.

This makes you realize how screwed up the US drill bit system is (like many other US measurement systems I might add).
The curve that maps gauge number to mm is monotonically increasing, but other than that, it has no regularity that I can identify: it's non-linear, non-convex, and it's full of wiggles.

Now for the best part: the gauge scale is unrelated to the gauge scale for screws. However, the scale for screws, at least, is piecewise linear with only two pieces. Naturally, the coefficients aren't anything logical (that would be too much to ask). Since a number zero screw is about 1.5mm, the non-intelligent designers of this devilish systems decided to use a different notation system for smaller screws. Instead of simply using negative numbers (which would have been the least illogical thing to do), they chose to add multiple zeros as the screw gets smaller. They must have thought that simply using negative numbers would confuse the hell out of the average American machinist (then again, they didn't seem to understand the decimal notation to begin with). The formula for converting screw number to diameter is:

mm = 0.03302 x N + 0.1524

For your convenience, here is a table of US screw number to mm:

00000 0.2032
0000 0.5334
000 0.8636
00 1.1938
0 1.524
1 1.8542
2 2.1844
3 2.5146
4 2.8448
5 3.175
6 3.5052
7 3.8354
8 4.1656
9 4.4958
10 4.826

Incidentally, a 2.0mm drill bit is close to a number 47.

How could the US build an industry around this? I'll never figure out....

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Build Furniture from LEGO-like blocks 
Monday, June 16, 2008, 12:28 AM - Misc TechnoToys
This French furniture store sells what looks like oversized LEGO blocks called LunaBlocks, with which one can build furniture. Cool concept.

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Korg USB mini music controllers 
Sunday, June 15, 2008, 06:37 PM - Misc TechnoToys
Korg-Japan has come up with three new USB music controllers that are the same width as a typical laptop: nanoKey (keyboard), nanoPad (drum pads), and nanoKontrol (control knobs).

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Jeff Han's Multi-touch panel at Neiman-Marcus? 
Monday, October 8, 2007, 12:51 AM - Misc TechnoToys
My friend and colleague Jeff Han has been getting a lot of attention in the last year or two with his amazing multi-touch display panel (see various videos here and here, and
his August 2006 TED talks)

Jeff has started a company in New York City called Perceptive Pixel.

The funny thing is that the upscale department store Neiman Marcus is offering Jeff's "online media wall" in the "fantasy" part of its Christmas catalog. The price is "starting at 100,000". If you have to ask.....

There is a nice video on the Neiman Marcus site too.

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EEstor super-duper-ultracapacitor 
Monday, September 10, 2007, 06:31 PM - Misc TechnoToys
Startup company EEstor claims to have produced ultra-capacitors with en energy density of 280 Watt-hour per Kilo. When you realize that your typical LiPo battery is around 140 Wh/kg your interest level goes up a notch. Given that ultra-capacitors can be charged extremely quickly (in seconds), and have a huuuuge maximum current, this might just be the miracle power source, not just for model ariplanes, but also for (full-scale) cars, which is EEstor's main target.

The main limitation of garden-variety ultra-capacitors (the ones you can get from DigiKey) is that they have a very low breakdown voltage (like 3V). The energy per unit mass sucks. It's enough for those e-charger toy airplanes from AirHog with a 10 second running time, but not for R/C planes. Since the energy stored in a capacitor is quadratic with the voltage (1/2.C.V^2) increasing the breakdown voltage can make a big difference. That's apparently what EEstor has done: they were able to raise the breakdown voltage to 1500V....

EEstor doesn't really have a web site, but there was a nice article on them at Technology Review back in January.
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Grand Illusions 
Thursday, March 8, 2007, 02:59 AM - Misc TechnoToys
Grand Illusions is an interesting on-line store that sells various techno-toys, particularly focused on optical illusions and bizarre effects.

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Interstellar Travel: working out the numbers 
Sunday, February 18, 2007, 03:45 PM - Misc TechnoToys
A really nice blog on Physics, Computation and Philosopy called Strange Paths has a long article on interstellar travel. This very detailed article works out the numbers in terms of energy, time (proper and otherwise), velocity, etc. It also has a design for a self-sustaining "ark". An interesting read. The blog also has an extensive list of online and offline books and other resources on mathematics and physics.

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L'Hydroptere: 47 knots in a flying sailboat 
Sunday, January 28, 2007, 11:38 PM - Misc TechnoToys
L'Hydroptere, a radical new sailboat design, has exceeded the speed of 47 knots during its third test this week. Last week-end, l'Hydroptere managed to run one nautical mile at an average of 41.74 knots (a non-official record). The pictures and videos of the Hydroptere flying on its hydrofoils are spectacular.

This the 5th version of the Hydroptere, a concept originally proposed by legendary sailor Eric Tabarly, and developed over the last 15 years by Alain Thebault and his team.

They are hoping to beat the 500 meter speed record (48.7 knots, held by Finian Maynard on a windsurfer), the 1 NM speed record (39.97 knots, also held by Maynard), and to eventually circle the globe in less than 40 days (the current record is 50 days, held by Bruno Peyron).

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ThrustPac: propeller-powered bike 
Friday, January 12, 2007, 11:13 PM - Misc TechnoToys
The ThrustPac is a backpack with a 4-stroke engine powering a ducted fan. The mid-range model features a 1.5HP, 35cc engine, can propel a bike at 40km/h, and costs about $900. The only problem is the loud noise, kinda like flying a 1/4 scale model airplane in the street....

Modern outrunner brushless electric motors are powerful enough to replace those noisy gas engines, and way more quiet. It should be possible to have a decent range with LiPo batteries.

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Secret Life of Machines videos 
Thursday, January 4, 2007, 10:46 PM - Misc TechnoToys
Videos of the British TV documentary series The Secret Life of Machines are available on Google Video. I particularly like the one on the fax machine..
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ISS and Space Shuttle in front of the Sun 
Friday, December 29, 2006, 09:59 AM - Misc TechnoToys
Astrophotographer Thierry Legault took this amazing picture of the International Space Station and the shuttle Atlantis passing in front of the sun. The exposure was so short (1/8000s) that atmospheric disturbances did not have time to blurr the image. You can see all the details of the ISS, and the tail of the space shuttle from 550Km away!

Speaking of astrophotography, here is a list of the top 10 astronomy pictures of 2006, and here is a nice web site with several beautiful pictures of the sky (not necessarily astronomical).

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