Re: Gyros and Compass Modules

["Dale's" <heinzind@cadvision.com>]

-----Original Message-----
From: protek@shreve.net <protek@shreve.net>
To: personal_submersibles@psubs.org <personal_submersibles@psubs.org>
Date: Wednesday, August 25, 1999 8:37 PM
Subject: Gyros and Compass Modules


>Bill,
>    There are a series of small solid state gyros now available.  All to my
>knowledge are "Rate" gyros.  These output a voltage related to the rate of
>turning for a given axis.  The cheapest that I have come across is from
>Gyration.  They are listed on the Internet as www.gyration.com and have
>specs available.  The problem with rate gyros is that unless you use
>electronic integration, either analog or digital, of the rate to yield
>angle, you can not use them as a compass.  And even if you do integrate
>their outputs they drift to some degree.
>    Your best bet is to purchase a used flux gate compass or get a Vector
>brand compass module made by Precision Navigation form Jameco, Inc.  They
>are also listed on the web and have specs on these modules available.
>Check out Jameco.com The compass must be placed outside the sub where the
>effects of magnetic fields are not going to cause too much error.  House it
>in PVC, aluminum, brass or something that is not magnetic like iron.  These
>modules are about $50, or $100 for the one with gimbles.  You will have to
>use some electronic expertise to connect it to a readout of your own
>design.  Or I think maybe they have a readout module you can purchase.


I'll check out the web site.. I was thinking of a directional gyro,
independant of the magnetic field of the earth.. Airplanes have them, and
when set (ie before you take off) they only drift a couple of degrees an
hour, and that is primarily because of the rotation of the earth.. I figured
that the longest I would be down at one time is about an hour, the
directional gyro would only be out a couple of degrees, and therefore would
be a very good primary navigation source..  I am not sure how far from the
sub you would have to mount a magnetic flux module, to get as accurate a
reading.   I am looking at some airplane wreckers to see if I can find a
price on an electric directional gyro..
The only place I have found so far (and they didnt have any in stock) said
they would run aprox $600.00.. I figure I should be able to locate one for
half that price,  perhaps get a vaccuum driven one, and incorperate it into
the air scrubber system somehow..   Just some ideas....
Bill