Wishlist - Hardware: Digital compass - Revision history

Drdeath at 14:47, 26 July 2009

2009-07-26T14:47:18Z

2009-04-23T13:10:31Z

‎Hardware parts

2009-04-23T13:09:50Z

‎Hardware parts

2008-10-13T10:28:10Z

‎Uses: link fix

2008-08-19T01:43:15Z

‎Uses

2008-07-29T10:09:29Z

‎One accelerometer

2008-07-29T10:09:05Z

‎One accelerometer

2008-03-17T19:53:41Z

‎Compass

2008-03-17T19:47:32Z

‎Hardware parts

2008-03-17T19:32:07Z

‎Hardware parts

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 The idea is to add a 2 axis or 3 axis magnetometer/compass, this can be an extra sensor, but it also makes sense to replace one of the two planned accelerometers with a compass if the space couldn't be found.
 ==Uses==
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 *The compass sensor isn't nearly as fast as an accelerometer, but that doesn't have to be a big problem, since it is absolute, a relative sensor has to be sampled much faster to get good results. It would be nice if it's at least about 25 Hz, so the motion is fluid.
 *The compass sensor should possibly not be placed very close near antennae, although I don't really know.
 [[Category:Accelerometer]]

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 *[http://www.akm.com/datasheets/ak8973_E-01.pdf AKM 3-Axis Electronic Compass], 4 x 4 x 0.7 mm, I2C interface, 3 axis magnetic sensor, also includes temperature sensor, maximum speed 10-80 Hz? (100 ms per measurement is possible (and draws 0.8 mA), one measurement takes 12.56 ms, so less isn't possible)
 *  [http://www.global.yamaha.com/news/2006/20060726.html Yamaha YAS529 Three-Axis Geomagnetic Sensor IC Chip] (2.0mm x 2.0mm x 1.0mm), I2C compatible. 4mA x 10ms per 3-axis measurement.
-* [http://www.asahi-kasei.co.jp/asahi/en/news/2005/e060322.html] Asahi Kasei Microsystems AK8976A Three-Axis Geomagnetic Sensor + Three-Axis acceleration sensor + 8bit temperature sensor, I2C & SPI, (4.5 mm × 4.5 mm × 1) mm 6.7 mA sensor operation, 460 µA average with measurement at 100 ms intervals
+* [http://www.asahi-kasei.co.jp/asahi/en/news/2005/e060322.html Asahi Kasei Microsystems AK8976A] Three-Axis Geomagnetic Sensor + Three-Axis acceleration sensor + 8bit temperature sensor, I2C & SPI, (4.5 mm × 4.5 mm × 1) mm 6.7 mA sensor operation, 460 µA average with measurement at 100 ms intervals

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 *[http://www.akm.com/datasheets/ak8973_E-01.pdf AKM 3-Axis Electronic Compass], 4 x 4 x 0.7 mm, I2C interface, 3 axis magnetic sensor, also includes temperature sensor, maximum speed 10-80 Hz? (100 ms per measurement is possible (and draws 0.8 mA), one measurement takes 12.56 ms, so less isn't possible)
 *  [http://www.global.yamaha.com/news/2006/20060726.html Yamaha YAS529 Three-Axis Geomagnetic Sensor IC Chip] (2.0mm x 2.0mm x 1.0mm), I2C compatible. 4mA x 10ms per 3-axis measurement.
 A 3 axis magnetic sensor has advantages, the rotation data is also available when holding the device vertical, and the rotation data is 2D instead of just 1D (the third axis can be gotten from the accelerometer). Honneywell's sensor is a bit more integrated, it is able to calculate the heading itself and has a built in calibration mode. With the AKM this must be done in software, which shouldn't be a problem, and leaves space for improvements.

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 ==Uses==
 *Stand alone compass, i.e. useful when GPS perception is low.
-*Orient maps to the terrain, see [[Wishlist:Auto Align Map]]
+*Orient maps to the terrain, see [[Wishlist/Auto_Align_Map]]
 *Show correct direction of GPS coordinates even if the device is rotated or not moving (when moving the direction could be obtained from the GPS movement).
 *Inertial addition to the accelerometers, for this one see below for more information.
 *Robots
 ==Hardware parts==

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 *Show correct direction of GPS coordinates even if the device is rotated or not moving (when moving the direction could be obtained from the GPS movement).
 *Inertial addition to the accelerometers, for this one see below for more information.
 ==Hardware parts==

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 ===One accelerometer===
-With one 3 axis accelerometer (the Wiimote has only one too) you have three inputs. There are 6 degrees of freedom, so it's overdetermined. If you make some assumptions you can sense the following:
+With one 3 axis accelerometer (the Wiimote has only one too) you have three inputs. There are 6 degrees of freedom, so it's underdetermined. If you make some assumptions you can sense the following:
 *When not moving the acceleration is equal to the direction of the up vector, so that can be measured directly. This is for example the case when using the device as steering wheel.
 *When not rotating, accelerations in all directions can be sensed, however some rotation is unavoidable, so you can not really rely on this situation.

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 *Absolute rotation around Z axis, making possible:
 **Map orientation.
 **Shooting/pointing games with real 360 degree vision.
 **Star catalogue, hold your phone as a window to the sky and see the names of constellations and planets. This could of course also be done for mountaintops and other landmarks.

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 *[http://www.ssec.honeywell.com/magnetic/hmc6352.html Honeywell's HMC6352 2-Axis Digital Integrated Compass], 6.5 x 6.5 x 1.5 mm, [[I2C]] interface, 2 axis magnetic sensor, maximum speed 20 Hz
 *[http://www.akm.com/datasheets/ak8973_E-01.pdf AKM 3-Axis Electronic Compass], 4 x 4 x 0.7 mm, I2C interface, 3 axis magnetic sensor, also includes temperature sensor, maximum speed 10-80 Hz? (100 ms per measurement is possible (and draws 0.8 mA), one measurement takes 12.56 ms, so less isn't possible)
+*  [http://www.global.yamaha.com/news/2006/20060726.html Yamaha YAS529 Three-Axis Geomagnetic Sensor IC Chip] (2.0mm x 2.0mm x 1.0mm), I2C compatible. 4ma x 10ms per 3-axis measurement.
 A 3 axis magnetic sensor has advantages, the rotation data is also available when holding the device vertical, and the rotation data is 2D instead of just 1D (the third axis can be gotten from the accelerometer). Honneywell's sensor is a bit more integrated, it is able to calculate the heading itself and has a built in calibration mode. With the AKM this must be done in software, which shouldn't be a problem, and leaves space for improvements.