see also:
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Dinsmore Instrument Company
http://dinsmoregroup.com/dico/
has been making digital compass products based on switching Hall technology
for some time. They now have a compass module (1655) based on linear Hall
technology. It has two Hall devices at a 90 degree separation and by reading
the two voltages you should be able to determine the direction of magnetic
north.
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http://www.horizonhobby.com/Description.asp?prod=CMLG180
One cheap ($80 or so) and full-featured gyro (non-heading-hold)
is the CSM ICG180
Questions:
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Direct collimated light into a photocell. Spin the direction the light comes from. (a robot might be able to spin itself occasionally for this, or you could spin a mirror.
Run the output voltage through an ADC and into processor.
If you're doing the spinning mirror, you'll also need a hall effect or slotted disk or something so you know when the mirror is 'dead ahead'.
Have the processor note the orientation of the brightest light heading.
In many environments this is 'good enough' for direction.
For example, outside the brightest light would normally be the sun. The sun is a fixed target during a short activity.
A room with a single, naked light bulb might work as well, if the lamp is in one wall. An overhead bulb would have 'cone of silence' problems.
Anne Ogborn
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