Subject:
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Re: Dinsmore Compass interface
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 3 Apr 2000 22:08:02 GMT
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Viewed:
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1806 times
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Roger,
I'm interested in your interface, do you have schematics available? Or is this
a package you sell? I've done a good deal of electronics work, so I'm ok with
converting it to a non surface mount device.
I have also just found a compass device for the Palm Pilot from Precision
Navigation (http://www.precisionnavigation.com/palmnavigator3rd.html). I've
been working on communicating between my palm & the RCX with the intention of
adding the palm to the robot as a control device. If this device can be
accessed via some type of API it could be used instead of an additional RCX
sensor. It saves a sensor port also. However, I STILL like the idea of a
compass the RCX can talk to.
-Wes
Roger Hamlett wrote:
>
> In lugnet.robotics, Wes Matchett writes:
> > I've read a lot of discussion about compass sensors ranging over almost two
> > years and as of yet have heard a success story.
> I have a working interface for the RCX. The 'problem' with it, is that it is
> all surface mount, making construction a 'bit of a pig' for anybody who is not
> experienced with this type of construction. It returns 0-96 'round the
> circle', seen as a normal 'light' sensor, and is pretty good. At 'north', it
> will sometimes see 96, and sometimes 0 (depending on which direction you have
> arrived from). The Dinsmore sensor is to my mind 'overdamped' in this
> application, I had to write my code so the unit stops, takes a reading, then
> corrects it's course, rather than working 'on the fly'. You also have to be
> very careful of magnetic interference from the motors...
>
> > I've reached the point I'd like my RCX to be able to accurately do two things:
> > 1) be able to follow a sequence direction/distance commands.
> > 2) be able to go someplace, recording its movement, and be able to retrace • it
> > path.
> >
> > Since the granularity of non-military grade GPS accuracy is expressed in terms
> > of yards .vs. inches - it seems that compass based guidance is the best
> > alternative.
> >
> > I am about to purchase a Dinsmore compass (model 1655) for RCX orientation.
> > Before making the purchase, I'd like to hear from anyone with experience with
> > either of the analog Dinsmore compasses (1525 or 1655).
> >
> > Since they produce an analog voltage in the 0-5v range I'm expecting the
> > interface described by Michael at http://www.alynk.com/usr/gasperi/gpa.htm to
> > work just fine.
> You have to be more complex. The compass returns two voltages, one a sin
> curve, and the other the cosine. The interface has to read both voltages, and
> where they 'cross', and then convert these to generate the 'angle'. I use
> linear interpolation between the crossing points, then a 'look up' table to
> actually do the required conversion - this is done by a PIC12C671, inside the
> actual sensor...
>
> > My hope is that the cost involved will be minimal above the compass - $35, and
> > that the interface is quite simple; simple enough that anyone willing to do a
> > little soldering can build it. If this works, we should have a well priced
> > direction sensor.
> The 'cost' is about right, but as I said, the complexity a little more. I
> could 'rebuild' my unit in non surface mount, without it getting too large (at
> present it fits in a 4*4 'brick', by the height of the Dinsmore sensor (which
> is unfortunately rather tall). I have since been trying other approaches, such
> as very sensitive direct sensors rather than the Dinsmore unit, to try to
> reduce the cost, and size...
>
> Best Wishes
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Message is in Reply To:
 | | Re: Dinsmore Compass interface
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| (...) I have a working interface for the RCX. The 'problem' with it, is that it is all surface mount, making construction a 'bit of a pig' for anybody who is not experienced with this type of construction. It returns 0-96 'round the circle', seen as (...) (25 years ago, 2-Apr-00, to lugnet.robotics)
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