Our Experiments with Engine Sound Synthesizer for Electric Airplanes 
Monday, September 14, 2009, 11:55 AM - Flying Contraptions
Back in 2005, my dad Jean-Claude and I set out to build an engine sound generator that could be mounted in an electric model airplane. This would allow scale models to not only look realistic, but also sound realistic, more realistic in fact than gas-powered model airplanes.

Other people have built engine sound generators before, but my dad's idea was to synchronize the pitch of the sound to the speed of the propeller.

After some semi-succesful experimentations with simple eeprom-based circuits, we built a sound synthesizer using a microcontroller module with some custom software. The module was a Tini2138 from New Micros, which has a 60MHz ARM7-TDMI with 512KB or eeprom (plenty of room for sound samples), and a 10-bit DAC.

We succesfully tested out the system in the summer of 2006, but I only got around to writing a page about it just now, though the pics and videos have been available in my gallery since summer 2006.

The system worked quite well, but it's rather bulky and complicated to build for the average hobbyist. We are now developing a new version based on the hugely popular Arduino microcontroller platform. The new system is considerably more simple and lightweight, and will fit into small park-flyers. Stay tuned....
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Flymentor3D: Vision-Based Flight Stabilization for R/C Helicopters and Airplanes 
Thursday, September 10, 2009, 02:21 PM - Flying Contraptions
Chinese manufacturer Shenzen KDS Model Technologies proposes a new type of flight stabilization system for model helicopters and airplanes called the Flymentor3D. Instead of the usual separate gyros, the system uses an all-in-one IMU (not clear if it contains a 3-axis accelerometer or just 3 gyros), and a CCD sensor with a vision system. The CCD camera points down and can detect movements relative to the ground, presumably using some sort of optical flow calculation. The processing involved is similar to what takes place in an optical mouse, and in fact, I suspect they use the same chips.

There is a downloadable manual in PDF for more details (in semi-non-broken English). Unfortunately, no price is given on the KDS website.

The nice thing about vision-based stabilization is that there is no drift, unlike with gyros and low-cost IMUs. The helicopter will stay exactly in the same place with the same heading for as long as you want.
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Air Hogs Switchblade 
Thursday, September 10, 2009, 02:12 PM - Flying Contraptions
Air Hogs will be releasing a new R/C flying contraption in the next few days: the Switchblade. It's bi-motor flying wing with no servo. The pitch is controlled by the motor power, and the yaw by the difference between the powers of the two motors. The unusual thing is that the two half wings can be rotated and clicked in place so as to form a large rotor. The plane can then take off vertically as a helicopter (probably without any meaningful control, except altitude). Once in the air, the two half wings can be unclicked into a regular flying wing configuration and the Switchblade can be flown like a regular plane. One problem seems to be that the plane seems prone to get into steep dives right after the transition from helicopter to flying wing. The absence of an elevator control surface makes if difficult to escape the dives.

Amazon has it for pre-order for $70.

There is a test video on YouTube.

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A week with the Samsung Galaxy i7500 Android phone 
Monday, September 7, 2009, 01:22 AM - Electronics
About a week ago, I got an imported Samsung Galaxy i7500 Android phone from MobileCityOnline.com. This is a $600 unlocked import model built for the European market.
T-Mobile isn't schedule to distribute the phone in the US until later this fall, and I use the phone with AT&T anyway (since I don't get any T-Mobile signal at home).

Problem #1: The main issue with using the Galaxy with AT&T (or any existing Android phone for that matter) is that AT&T uses unconventional frequencies for 3G that are not supported by any Android phone. Hence, using an Android phone with AT&T means being restricted to 2G and Wifi. It sucks, but it sucks less than having no signal at home.

Setting up the phone to work with an AT&T SIM card posed no problem. The Settings->APN entries are as follows:

Name: anything_you_want
APN: wap.cingular
Username: wap@cingulargprs.com
Password: cingular1
MMSC: http://mmsc.cingular.com
MMS Proxy: wireless.cingular.com
MMS port: 80
MCC: 310
MNC: 410

Problem #2: the version of the firmware/software installed on the unlocked Samsung phone is essentially unusable in the US. There is no "Market" app to download software from the Android market, no automatic switching of the screen from portrait to landscape, no access to the accelerometer and magnetometer. Fortunately, the fix is easy: you can flash the latest version of the firmware (H7), and everything will work fine. The procedure is quite simple and described here. You will need a Windoze machine to run the MultiOdin ROM flashing utility.

Thank you kam187 from androidforums for the trick.

The phone is simply fantastic.

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Another foam cutter CNC kit 
Thursday, August 27, 2009, 03:18 AM - Misc TechnoToys
RCFoamCutter has a number of kits of CNC machines for cutting foam costing $400 for a basic kit to about $1300 for a complete kit (including electronics, hot wire power supply and such).

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mbed: ARM7 microcontroller with online toolchain 
Thursday, August 27, 2009, 03:04 AM - Electronics
The mbed microcontroller uses such a cool new concept that one wonders why we haven't seen this before: an online C++ toolchain/development suite. The mbed microcontroller board uses an open design built around a 60MHz NXP LPC2368 ARM7 CPU (datasheet) with 512KB flash, 32KB RAM, USB 2.0, 10/100 ethernet, SD/MMC interface, 2xSPI, 2xI2C, 3xUART, 1xCAN, GPIO, 6xPWM, 6xADCs, and 1xDAC. The library apparently contains simple Arduino-like functions for I/O and such.

It's still in beta at the moment, and the board is supposed to cost about $65 50 UK Pounds, or about $85.

There is a number of articles on the mbed at Elektor, and at Circuit Cellar (PDF).

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Maple: ARM-based Arduino coming soon 
Saturday, August 22, 2009, 12:46 PM - Electronics
The Leaflabs blog has a post about the prototype of a rather appetizing Arduino-like micro-controller board built around an STM32 ARM Cortex-M3 from ST Micro.

The folks at Leaflabs apparently intend to make the board work with the Arduino software suite, and implement an Arduino compatible library. Many of us are drooling at the prospect of an ARM-based, $40 Arduino-quasi-compatible board. It would enable projects that are out of reach of the current Atmega-based Arduino, such as real-time audio processing. It would certainly help that the STM32 has three super-fast 12-bit ADC, as well as two 12-bit DACs! Hello Arduino-based synthesizer modules!

It's not clear which the 3 zillion versions of the STM32 the board uses.

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Audio D-Touch: Tangible musical interface from EPFL 
Thursday, August 20, 2009, 12:24 PM - Music
Enrico Costanza from EPFL sent us a heads-up about the release of his tangible interface system for musical applications called Audio D-Touch. The site includes instructions for building your own d-touch system, as well as downloadable code for Windoze, Mac, and Linux (registration required).

Applications include a drum machine and a sequencer.

More videos are available here.

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Flapping wing micro-UAV from AeroVironment 
Thursday, July 16, 2009, 10:08 PM - Flying Contraptions
AeroVironment has developed a flapping wing micro-UAV under a DARPA-funded project. The prototype made a 20 second radio-controlled flight. There is a video on YouTube, and a short description of the recent milestone.

This is probably the work of micro-RC pioneer Matt Keenon, who works at AeroVironment.

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Stickduino now uses Atmega328 
Wednesday, July 15, 2009, 12:10 AM - Electronics
The new Stickduino Arduino clone as been upgraded with the new Atmega328, so as to match the latest version of the "official" Arduino. The price is still below $20.

Strangely enough, the stickduino website makes no mention of the change!

How do I learned about it then?

Well, I just received a new batch of Stickduinos and tried to program one, but the program wouldn't upload (I kept getting "stk500_recv() programmer is not responding" from avrdude). I started looking on the web for answers, but couldn't find anything. After fiddling for a while, I looked closely at the board, and realized it had an Atmega328. I configured the Arduino IDE for the new Duemilanove Arduino, and everything worked perfectly.

Still, I'm surprised the stickduino people don't mention this anywhere.

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Joel Frahm the Quotemaster 
Thursday, June 11, 2009, 05:32 PM - Jazz
Tenor sax virtuoso Joel Frahm was playing his regular Tuesday-night gig at La Lanterna in NYC this week, accompanied by Bill Campbell at the drums (as usual), and Johannes Weidenmuller at the bass (replacing Joe Martin). Joel is something of a "quotemaster": his solos are often peppered with snippets from all kinds of things from other jazz pieces, classical music, pop music, and just about anything under the sun.

This Tuesday, Joel was in a particularly playful mood, and his high-flying solos brought an unusally rich harvest of detectable/delectable quotes including such things as Peter and the Wolf, Michel Legrand's "Les moulins de mon cur" (Windmills of my mind), and (that's got to be a first) a theme from Star Wars!

Over the last 3 months, photographer Jimmy Katz has come to 8 or 10 of Joel's trio sessions at La Lanterna, equipped with a compact digital multi-track recorder. Each session he recorded has about 3 hours of music. Hopefully, these will soom be distilled and made available.

By ze way, the complete collection of Joel's sessions at Small's are available for on-line listening here.
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Huuuge collection of 3 views 
Saturday, June 6, 2009, 04:09 PM - Flying Contraptions
Bertrand pointed me to this positively gigantic collection of airplane 3 views at rcgroups.

They even have one of my favorites: the obscure the coleoptere.

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Thursday, May 14, 2009, 07:06 PM - Flying Contraptions
There seems to be a renewal of interest in the heretofore abandoned concept of the cyclogyro

The cyclogyro has two rotating sets of "paddles" whose angle of attack is cyclically modified to create lift in the desired direction. The principle is well described by the animation in this Wikipedia article.

There is a YouTube video of a thethered micro-size cyclogyro, which was designed at the National University of Singapore. A detailed description of the design is available here.

A team of Japanese roboticists has apparently revived the concept, using a "pantograph" mechanism to vary the angle of attack (link to IEEE Tans. Mechatronics article),
and a short description with pictures on PhysOrg.

I'm somewhat doubtful of the efficiency of the design, but it looks like a fun thing to build.

There is a number of article on the web that describe 1930's designs for cyclogyros. I am somewhat surprised that none of these designs seem to include an anti-torque system. These paddles are bound to generate a high torque that would make the vehicle pitch up (which is why the cyclogyro on the YouTube video has a propeller in the back).

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Rovio robots play soccer at NYU 
Thursday, May 7, 2009, 11:39 PM - Robotics
This past semester, I have been teaching an undergraduate course Introduction to Robotics. The first series of assignments included programming Arduinos to read sensors and actuate servos and DC motors. The second series included programming a Pololu 3Pi robot to follow a line (using a PID controller), and perform dead reckoning (coming home after following a line to its end).

The last series of homework consisted in getting Rovio robots to play soccer. I feel I should mention this here because the class page showing videos and pictures of the students' soccer-playing Rovios had been mentioned by a number of blogs, including Slashgear and RoboCommunity.

The Rovio robots can be seen as "Wifi webcams on wheels". The goal of the project was to push a tennis ball into a goal. The tennis ball is bright yellow, and the goal posts are red. The rovios are controlled by software running on a laptop which performs the vision and control algorithms. The software is written in our very own Lush language, which is a dialect of Lisp.

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Bill McHenry at La Lanterna 
Wednesday, April 1, 2009, 12:57 AM - Jazz
Tonight at La Lanterna in NYC tenor sax Bill McHenry was sitting in for Joel Frahm, with bassist Joe Martin and drummer Bill Campbell. They played two of Bill McHenry's new compositions "Violetta" and "Lines" which I thought were particularly interesting.

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micRo CNC kit 
Thursday, March 26, 2009, 03:00 AM - Misc TechnoToys
Lumenlab proposes the micRo CNC kit for $500 for a partial kit and $1000 for a complete kit. You can also get a low-end Dell PC to control the CNC machine for $330, pre-configured with Ubuntu.
The total travel dimensions are 34cm x 25cm x 8.9 cm.

[via Makezine blog]

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