First step towards cheapo IMU.

[billyzelsnack]

I've been wanting to build an IMU using rc heli gyros for quite some time now. I finally got around to starting on the project. Here's the first results of getting data from the gyro.

phpBB [media]

It was easier than I thought. Currently all it is doing is taking the gyro pulse width and passing it to the servo, but that does mean the gyro data is making it into the uC!

The next step is to try using a crystal instead of a resonator and see if I can get rid of some of the jitter.

[billyzelsnack]

http://www.nintendo.com/whatsnew/detail ... hEO9zBvyPH

It's an add-on to the Wii to make it more precise. I really am hoping that is a 3-axis gyro. If that's the case it will dramatically decrease the cost of making an IMU.

[billyzelsnack]

In line with my previous post..

http://motusgames.com/

This is supposed to be for the PC. From stuff I've read around it looks like it'll have accelerometers, gyros, and magnetometers. All for under $100 supposedly. Should even be pretty precise since the same guys make golf swing trackers.

I've sent a mail asking about a devkit, but I've not heard back yet.

[Nathan Monson]

It's an add-on to the Wii to make it more precise. I really am hoping that is a 3-axis gyro. If that's the case it will dramatically decrease the cost of making an IMU.

The MotionPlus module uses the Invensense IDG-600 2-axis gyroscope with an on-board analog to digital converter. The interface is 4 wires -- I2C data/clock (400KHz) and +3.3V/GND.

At $30, the MotionPlus will be the cheapest MEMS gyroscope for sale at qty 1. The Invensense parts are very good. The Bioloid IMU uses the IDG-300, a lower dynamic range version of the IDG-600.

Nobody knows the ADC resolution yet, but if it is 10+ bits this will be a useful part for robotics applications.

- Nathan

[billyzelsnack]

Sounds good. Kinda disappointing that it's not a triple axis in there. Where did you find this detailed at btw?

[Nathan Monson]

Sounds good. Kinda disappointing that it's not a triple axis in there. Where did you find this detailed at btw?

Invensense put out a press release:
http://www.google.com/search?q=motionplus+idg-600

The 400KHz I2C interface used by Wiimote peripherals was reverse engineered a while back. The $30 is quoted all over, although I don't know the source.

For a year, I've been hoping somebody would release an inexpensive IDG breakout board with a digital interface. I didn't expect Nintendo to do it!

- Nathan

[limor]

maybe not 30$ but certainly a large variety of cheap gyros here:
http://www.sparkfun.com/commerce/categories.php?c=85

and outside US :
http://robosavvy.com/store/

[billyzelsnack]

You can see the MotionPlus in action here..

http://kotaku.com/5025688/wii-sports-2- ... icing-info

At the end they play a sword fighting game that shows that drift really is not that big of a problem with it. Though maybe the way the game works masks it.

[JonHylands]

At the end they play a sword fighting game that shows that drift really is not that big of a problem with it. Though maybe the way the game works masks it.

If you watch carefully, you can see that they reset (for drift) the wiimote before every match by pointing it at a very specific part of the screen and clicking the A button.

- Jon

[billyzelsnack]

Yeah I noticed the reset. It still is impressive that it still is not drifting enough to ruin the game over the course of a match. They are swinging that thing around quite a bit and fast.

[billyzelsnack]

I've not seen these IMU guys before..

www.motionnode.com

$1000 with 3 accel / 3 gyro / 3 magno / USB

[limor]

I've not seen these IMU guys before..

www.motionnode.com

$1000 with 3 accel / 3 gyro / 3 magno / USB

stick this 5DOF board and this compass module onto a USB Arduino or a Bitwhacker and you have a similar solution for under $220

[billyzelsnack]

Yeah. Those items tempt me all the time.

I just mentioned this because this is the cheapest I've seen a full on commercial IMU for.

[billyzelsnack]

ooh.. Look at this..

A 3-axis accel + 3-axis magnetometer.

http://www.sparkfun.com/commerce/produc ... ts_id=8806

[JonHylands]

ooh.. Look at this..

A 3-axis accel + 3-axis magnetometer.

http://www.sparkfun.com/commerce/produc ... ts_id=8806

Yeah, I just ordered one... Looking forward to seeing how well it works...

- Jon