Pictures from Crespiere 2008 
Sunday, September 28, 2008, 10:42 PM - Flying Contraptions
Okay, this comes a bit late, but here are some pics and a movie of the Crespiere Electric R/C meeting which took place in the spring 2008. Crespiere is a get-together of electric R/C airplanes which takes place every year near Paris.



The pictures were taken by Jean-Claude Le Cun.

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Picture and Videos from Inter-Ex 2008 
Sunday, September 28, 2008, 10:01 PM - Flying Contraptions
Inter-Ex, the annual meeting of European builders of unusual miniature flying contraptions took place in Boissy sous Saint Yon, in the south of Paris.

I happened to be in France on business that week-end and attended the Sunday session. I took pictures and movies of the event.

Serge Encaoua of Verti-4 fame was present with his Verti-4. I had a nice chat with him about his design.

Serges flew his Verti-4 in rather turbulent wind, but impressed the crowd with his hover/translation/hover transition, as shown on this video.



The winner of the day was a scale model of White Knight 1 and SpaceShip 1.

Other participants showed a variety of unusual flying contraptions, including a bunch of autogyros, a giant flying daisy flower (by the unequaled Peter Haas), a flying Eiffel tower, a flying squirrel, and a...well, a... how can I say this, a...awww, chucks, just see for yourself. This "thing" didn't fly, but it clearly looked like it was going to fly soon.

The unparalleled Gerard Jumelin brought his Calder-inspired plane, several bird-shaped planes, and "Vague Souvenir", a beautiful translucent blue flying wing shaped like a wave.



Some more videos shot by Stephan Brehm are available here.


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$100 quadrocopter, 20cm diameter 
Sunday, September 28, 2008, 09:19 PM - Flying Contraptions
A $100 micro-quadrocopter, with a diameter of only 20cm is available at ThinkGeek and Hammacher Schlemmer.

It is the lowest cost and smallest quadrocopter I have ever seen. There is a demo video on YouTube. This flying contraption is manufactured by Hong Kong company Alien Tech Ltd.

How can they sell it for so cheap when an InvenSense IDG-300 dual axis accelerometer chip is $35 in quantity? Perhaps they use two LISY300AL from ST Micro, which still cost about $9 in quantity.

Incidentally, ThinkGeek also has an ultra-tiny flying saucer , which they claim is the smallest flying R/C device ever. The good news is that it's $25, the bad news is that you can only control the thrust (you can't actually make it go anywhere, other than by blowing on it).



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Stickduino: A nice addition to the Arduino family 
Saturday, September 27, 2008, 03:54 PM - Electronics
Over the summer I have been playing with a new member of the Arduino family, the Stickduino, and have become quite fond of it.

The Stickdiono's main advantages are: it is very small, it plugs directly into the USB port of a computer, it costs less than $20 assembled, and $4 for the bare circuit board.
Even better, it gives you 8 analog inputs instead of just 6 like the original Arduino. It uses a 16MHz Atmega168 like the Arduino Decimilia.

The only downside is that the pc board USB plug is a little too thin to fit snuggly into a typical USB socket. It doesn't seem to cause any problem with electrical contacts, but it still makes me nervous. I simply glued a piece of thin plastic (cut from an ABS or styrene sheet) underneath the pc board.


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R/C hovering surf board at Hammacher Schlemmer 
Saturday, September 27, 2008, 03:43 PM - Flying Contraptions
Hammacher Schlemmer has yet-another-r/c-toy that is out of the ordinary: a R/C hoverboard. It's a helicopter with two contra-rotating rotors, one in the front, one in the back. It's entirely clear to me how the roll stability is ensured, but unlike with other low-cost R/C toy helis, this one should have good pitch control.
It sells for $90 only at Hammacher Schlemmer, which probably
means that you will find it for $50 in every store in a few months.


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How we Became the United States of France 
Monday, September 22, 2008, 12:33 PM - TechnoPolitics
As a French-American who lived through the French bashing campaign around the start of the Iraq war, I can't help but link to this fun CNN/Time Magazine article: How we Became the United States of France. A rare fun read, in these times of economic and diplomatic disasters (thanks to Patrick for the pointer).

It's almost as funny as Bill Maher's tirade on the French.

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Great Jazz Trio every Tuesday in the Village 
Thursday, September 11, 2008, 11:00 PM - Jazz
There is a delightful small jazz club called "The bar next door" at la Lanterna Caffe, on 129 MacDougal St, just south of Washington Square Village in New York City.

Every Tuesday, they host a fantastic trio, led by tenor sax player Joel Frahm, with bassist Joe Martin, and drummer Bill Campbell.

The trio is totally delightful, if you like post-bop/hard-bop straight-ahead jazz. Joel Frahm is an amazing improviser who can play just about everything with gusto.

I have become somewhat of a regular there over the last few months.

You can get Joel's recording at Amazons MP3 download store.

Joel and Joe have both played with one of my favorite composers/pianists on the NYC jazz scene: David Berkman.


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Arduino Pro: 3.3v 8MHz 
Monday, August 25, 2008, 05:19 PM - Electronics
Sparkfun is offering a new version of the Arduino: the Arduino Pro, which
is lighter, cheaper, and slightly more compact than the Decimilia.
The supply voltage is 3.3v, which makes it compatible with things like gyros and accelerometer sensors. Too bad news is that the clock is only 8MHz, instead of the 16MHz od most other Arduinos.

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UAVP: open source quadrocopter design 
Monday, August 25, 2008, 01:23 PM - Flying Contraptions
The Universal Aerial Video Platform is an open source design for a quadrocopter. The UAVP controller board is based on a PIC microcontroller, and has a number of optional sensors, such as gyros, accelerometers, and altitude sensors.

Several sites in Europe and the US sell the UAVP controller board and associated components. QuadroUFO is a US supplier of parts for DIY Quadrocopters. Most parts that they sell, except for the controller board, can be found from R/C store, such as BP Hobbies, or electronics/robotics suppliers like Sparkfun.

A fully populated controller board with all the sensors is $435. The blank PCB is only $15, but the sensors are expensive.

I'm working on a cheap Arduino-based DIY quadrorotor controller. Stay tuned.....

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Huge Quadrocopter link collection 
Monday, August 25, 2008, 01:12 PM - Flying Contraptions
Quadrocopter building has become an increasingly popular activity in Europe, particularly in Germany.

The MikroKopter Wiki has tons of information (mostly in German), equipment, instructions, and software for quadrocopters.

In particular, it has this huge list of quadrocopters with characteristics, pictures, and links to more details.

Among other things, the site has the schematics and software for a brushless motor speed control, something I have never seen anywhere else.

This other site contains a huge collection of pictures shot at the 2008 Quadrocopter meeting in Germany. There is a bunch of nice-looking QCs there.


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Smartflyer: micro-size quad-rotor flying contraptions 
Monday, August 25, 2008, 12:27 PM - Flying Contraptions
Hartmut Kaak in Germany has produced a series of extremely impressive micro-sized quad-rotor flying contraptions over the last few years. The most impressive aspect is the size of his latest creation, the diminutive Smarty: 15g, and 80mm in length.

TheSmarty uses 4 motors and props cannibalized from a Silverlit X-Twin R/C toy airplane.

Hartmut built his own mixer/stabilizer/controller around an Atmega88 microcontroller and three ADXRS300 solid-state gyros. His software directly produces the PWM signals for the (brushed) motors. More interestingly, he was able to power the whole thing with a single 145mAh LiPo using a MAX1686 voltage pump chip from Maxim (which generates 5V from the LiPo 3.6V).



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Inter-Ex 2008: September 6 and 7 near Paris 
Monday, August 25, 2008, 03:20 AM - Flying Contraptions
The 2008 Inter-Ex will take place September 6 and 7 in Boissy sous Saint Yon, a few kilometers south of Paris.

Inter-Ex is a get-together of creative R/C modeler who design and build unusual flying contraptions. There are pictures of previous editions on the web site.

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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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New Aerobatics video of the Stanford autonomous helicopter 
Saturday, August 23, 2008, 03:48 PM - Flying Contraptions
For several years, my friend and colleague Andrew Ng at Stanford has run an autonomous helicopter project in his lab, with two of his PhD students, Pieter Abbeel and Adam Coates. They have developed new reinforcement learning techniques to automatically learn how to stabilize and control the helicopter. They reached the point where they can pretty much get their heli to perform every aerobatic figure known under the sun. There is a bunch of videos on their website, as well as on their Youtube chanel.



Interesting implementation details: they have no on-board intelligence on the heli. They use a GPS and an IMU with serial outputs directly fed into Xbee Pro modules. The signals are received by a PC on the ground, which remotely controls the heli through the training port of a conventional R/C transmitter.

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VTOL with contra-rotating ducted fan 
Saturday, August 23, 2008, 03:31 PM - Flying Contraptions
There are a few YouTube videos of an interesting VTOL flying contraption that seems to be using contra-rotating propellers, most likely based on a Himax co-axial contra-rotating motor pair from MAXX Products. The plane appears to be very maneuverable (thanks to Bertrand for the pointer).



More videos are available here, here, here, and here.

UPDATE (2008-09-08): Chris Good, the builder of this nice flying contraption, pointed us to his rcgroups forum post describing the construction. The post has several pictures of the innards, and details of the channel mixing. Contrary to what I guessed, Chris used two separate motors (mounted in a push-pull fashion), rather than a co-axial double motor. The motors are geared brushless in-runners.
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"Voyeur" hovering drone with counter-rotating rotors 
Tuesday, July 1, 2008, 12:11 AM - Flying Contraptions
Drone manufacturer Lite Machines Inc. has a video of their latest drone called the Voyeur.

It's a cigar-shaped drone, 686mm in length, 63.5mm in diameter, with two counter-rotating rotors, 762mm in diameter. It seems to be using bushless outrunner electric motors powered by a 3-cell LiPo battery.
The total mass is 1.4kg. The cruising speed is 30 knots and the autonomy 30 minutes.

There is a cool video on YouTube

This must be the same Lite Machines Inc. that got started by producing the first gas-powered micro-helicopter many years ago. It used a Cox 0.8 cubic cm motor and had a really clever mechanical system on the tail rotor to stabilize the yaw. This was a kind a mechanical gyro, before the days of cheap and light solid-state gyros.


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