6 DoF IMU + Arduino 
Sunday, December 20, 2009, 04:02 PM - Electronics
The DIY Drones store has a very useful piece of hardware: the ArduIMU+ v2. It's an Arduino-compatible board with a 3-axis accelerometer chip and a 3-axis gyro chip with appropriate filters. It also has a connector for a GPS module (with a 4Hz refresh rate). All of this for $100 (plus $90 for the GPS). Very useful.
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Modifying an ESC for digital speed control 
Monday, November 30, 2009, 03:50 PM - Electronics
The tight control loop of quad-rotor helicopters requires very fast response from electronic speed controllers (ESC). Unfortunately, all hobby ESC are PWM controlled, and can't accept pulses at a high rate. This introduces lags in the control loops. Some folks have figured out how to hack commercial hobby ESCs so as to control them with an I2C digital interface. There is a whole thread about this on RC Groups, as well as a PDF file with detailed instructions, and schematics.

The alternative is to buy an I2C compatible ESC from YGE: 60 Euros (about $90) for the 18A YGE-18i, or 70 Euros ($115) for the 30A YGE-30i. Ouch!

Speaking of which, for you ESC DIYers, Fairchild has a 40V, 20A, Dual N & P channel mosfet pair, the FDD8424H (available at Mouser for $0.86).

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Micro heli and 3D-capable plane from e-Flite 
Monday, November 30, 2009, 01:18 PM - Flying Contraptions
e-Flite has come up with two interesting products: the Blade mSR ultra-micro helicopter, and the 4-Site ultra-micro 3D airplane.

The Blade mSR comes in an a "bind-and-fly" version for $150 (requires a separate Spektrum 2.4GHz DSM-compatible transmitter), and an RTF version for $180 (which includes a transmitter). The rotor diameter is 180 mm, and the mass is 28 grams. It uses a 120mAh single-cell LiPo battery.
It's available from Hobby Lobby, and from Red Rocket Hobby.

According to some reviews, the Blade mSR is the first single-rotor (non-coaxial) micro-heli that flies well. Most single-rotor micro helis have a separate motor for the tail rotor. These motors have relatively long reaction times, which makes the heli rather difficult to fly (they will rotate every time you increase or decrease the throttle). The Blade mSR is so tiny that the inertia of its tail rotor is very small, and the reaction time is very short.

The 4-Site Ultra-Micro comes in 2 version: "bind-and-fly" for $170, and "PNP" for $110. A Spektrum DSM-compatible transmitter is required. The wingspan is 386 mm, and the mass is 35.5 grams, with a single-cell 150mAh LiPo battery. e-Flite has other such small planes, but this is the first 3D capable ultra-micro from them. The plane includes a 5-in-1 P board with a 2.4GHz DSM receiver, a brushed speed controler, and two linear servos. Two additional servos for the ailerons are pre-mounted on the plane.
It's also available from Hobby Lobby, and from Red Rocket Hobby.


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Shrediquette: an Arduino-based Tri-copter 
Monday, November 30, 2009, 01:02 PM - Flying Contraptions
The Shrediquette is a tri-rotor helicopter built by William Thielike from Germany. William is a PhD student in biology, who seems to have many talents: micro-controller system design, control, mechanical design, flying contraption construction, as well as film making.

His tricopter is built around an Arduino Pro Mini micro-controller. Oddly, William didn't use the Arduino development tool and C/C++ programming language: he wrote his software in Bascom, a dialect of BASIC.

The yaw control is performed by rotating the tail boom with a servo. This very unlike the more conventional servo-less yaw control of quadcopters, but it's practically unavoidable for tricopters.

Much of the material is available for download, including the schematics, the PC board Eagle files, and the Bascom source code.

An awesome video (below) shows the capabilities of the tricopter.
More videos from William are available on Vimeo.

Tricopter - The Movie... from W. Thielicke on Vimeo.

Thanks to Bertrand for the link.

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eRC Micro P-51 Mustang RTF for $99 
Tuesday, November 3, 2009, 12:05 AM - Flying Contraptions
Hobby Lobby has the eRC Micro P-51 Mustang for $99.00. The diminutive ready-to-fly warbird has a 37 cm wingspan, weighs 30 grams, and comes with a 4-channel 2.4GHz radio. The plane has proportional control for the ailerons, elevator, and throttle. It uses a geared brushed motor.

Apparently, there is no rudder control as with the similarly sized Kyosho Minium Piper Cherokee. But the Minium is $180....

They will be rolling out a spitfire in December.
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David Berkman at Smoke 
Sunday, November 1, 2009, 02:43 PM - Jazz
My favorite jazz composer/pianist on the New-York scene David Berkman was playing at the uptown club Smoke yesterday and Friday with Antonio Hart on the sax, Ted Poor on drums, and Ed Howard on bass. I went to the last set on Saturday and it was awesome. David has a new CD out entitled Live at Smoke (also on Amazon MP3 downloads), with live performances of some of his fantastic pieces from earlier records, like Weird Knack, which appeared on his amazing 2000 CD Communication Theory (though it was mispelled "Weird Knock" on that CD). Interestingly, David post the scores of many of his compositions on his website (though the links seem dead right now).

In fact, I first heard of David Berkman while listening to the WBGO radio station back in 2000. They played a piece from Communication Theory. I was hooked.

David played on Joel Frahm's first two CDs ("Sorry, No Decaf", and "The Navigator"), and composed some of the pieces on these CD (like "Interesting perhaps, but hardly a fascinating rythm"). It would be awesome if David and Joel could record together again. It would also be awesome if David played more often in NYC, particularly downtown.
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ttymidi: serial/usb to MIDI for linux 
Saturday, October 17, 2009, 10:26 PM - Electronics
TTYMIDI is a linux hack to allow any serial or serial/USB device (such as the Arduino) to produce MIDI events compatibel with ALSA in Linux. This makes it easy to turn any Arduino-based hack into a MIDI controller.

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Omer Avital with Joel Frahm and Bill Campbell 
Saturday, October 17, 2009, 09:00 PM - Jazz
This week at the Bar Next Door, Joel Frahm and Bill Campbell were accompanied by bassist Omer Avital (instead of Joe Martin). The second set was particualry energetic, with one of Omer's composition called Flow, which is based on the changes of Giant Steps. I had never heard Joel play giant steps. Pianist/Composer David Berkman says in his book that Joel plays a mean Giant Steps. He is right, despite Joel claim that he hadn't played Giant Steps in while and was a bit rusty.

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Joe Martin's latest album 
Monday, October 12, 2009, 05:25 PM - Jazz
Joe Martin's latest album,'Not By Chance', has been out for about a month now. It features Joe at the Bass, Brad Mehldau on Piano, Chris Potter on Sax, and Marcus Gilmore on Drums. What a nice line-up! Go Joe, go.

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Gadi Lehavi: 13 year-old Jazz piano prodigy 
Monday, October 12, 2009, 12:29 AM - Jazz
Joel Frahm pointed us to a video of this 13 years old Israeli kid, Gadi Lehavi, who has been playing around several NYC Jazz clubs earlier.

His playing is amazing for a boy this age. Actually, it's amazing, Period. He is classically trained, and has been playing Jazz for about a year and a half.

There are more YouTube videos of Gadi here.


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Hydroptere sails at over 100km/h 
Saturday, October 10, 2009, 09:58 PM - Flying Contraptions
On September 4th 2009, L'Hydroptere, a sail-powered hydrofoil beat the speed record for a wind-powered watecraft with an average speed of 51.36 knots over 500 meters. The boat reached peak speeds of 103 km/h. Back in 2008, it briefly reached over 110km/h shortly before it capsized. L'Hydroptere has been in development since the early 90's under the leadership of Alain thebault. This idea was born in the mid 70's following a discussion between a group of aeronautical engineers and French sailing legend Eric Tabarly.

The previous 500 meter record was held by French kitesurfer Alex Caizergues at 50.57 knots.


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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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