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Old Dec 25, 2008, 08:37 AM
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United States, OH, Columbus
Joined Apr 2007
194 Posts
Originally Posted by mmormota
Good find, I don't know any better for an evaluation kit.

I proposed the magnetic sensor because the drift is inherent feature of the piezo gyro's and practically impossible to avoid it. The smm gyro's are better but more expensive, and hard to find smm sensor's in small quantities.
Good point. I think tilt compensated magnetometers deserve to be looked into, the gyro drift problem is (again) quite annoying... A 2 axis one is not quite all that's needed though, to do this properly you need a 3 axis magnetometer. Although I've found that it is possible with only 2 axis using an algorithm in a paper, which estimates the 3rd axis information by knowing the local magnetic inclination.

As with any magnetometer based solution, there is a new problem. If you live in a place with a lot of magnetic inclination, it will potentially limit how far you can pitch up/down. It will be great the lucky bastards living around the equator, not so great in Canada.

Here's a map of magnetic inclination of the world:

For example, in the UK, where I am, I=66 dgrs, meaning the for pitch > ~20dgrs the compass becomes useless even with compensation. What I think will be interesting is to use the magnetometer to correct the gyro when pitch is in a reasonable range, and depend on gyro alone when the magnetometer is in its useless range. If fact I'm going to order that SparkFun board to try is out when I get back to my place in the new year...

This will add another $25 to the cost of the HT... But if it works, at $75, it's still pretty cheap for an almost drift free tracker!
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