Subject:
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Compass update
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 10 Nov 2000 17:12:44 GMT
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Original-From:
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John Barnes <barnes@sensors*stopspam*.com>
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Viewed:
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558 times
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I have been working away at the compass problem for a while.
(I suppose it's only a problem if the kinds of things you're using
an RCX for involve knowing which way you're pointing ...)
I have built a number of compasses based on both Dinsmore and
Vector modules.
I was recently in touch with the folks at Precision Navigation who
have been extremely helpful (and who make the Vector solid state
compass module) and they had two interesting pieces of information.
1. The current product will run in uncalibrated mode, despite the fact
that the documentation states that calibration is required. The problem
with calibration is that you have to "swing" the compass in "Cal" mode
whereupon it will retain calibration values internally in RAM. Sadly, the
cal data is lost when power is removed. In automobile type applications
where the few hundered micro-amps required to leave it powered don't
matter, this is not a problem. But as Lego sensor, it does, not to mention
having to have "cal" and "operate" buttons etc to perform the function.
I have reworked my Vector based compasses to run in uncalibrated mode
and they seem perfectly fine, good to within about 5% as far as I can tell.
The only downside is the size. You have to build a little board with a PIC
or something to take the serial data from the Vector and convert it to a
current to feed to the RCX and of course the power/signal demux function.
When all is said and done, you end up with a 6 stud on a side cube. I
personally find this large in comparison with other Mindstorms scale
components. Which bring me to ..
2. Precision Navigation are coming out with a smaller device at the beginning
of next year. I hope I am near the top of their list for a couple of devices to
try. Their promise of a 1" x 1" module is perfect for fitting into a 4 x 4 stud
enclosure which is much more in keeping with the scale of things.
I will post more as and when I have more news.
JB
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Message has 1 Reply:
 | | Re: Compass update
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| Hello, Here's a challenge for those of you with Lego cameras and want compass navigation: Point the camera at a compass and process the visual information into directional input. It's a bit more crude, but you can get away with almost any old (...) (24 years ago, 10-Nov-00, to lugnet.robotics)
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