Re: Source Sealed Potentiometers?


Frnak McKenney wrote:

....

You mentioned the possibility of the platform getting "dunked", which
suggests outdoors: river water, pond water, rainwater. That kind of
exposure to the elements suggests that the platform and its drive
mechanism will need periodic maintenance, and any type of resolver or
encoder that is mechanically connected to that platform or its drive
will need at least as much maintenance (gears need greasing from time
to time <grin>). Given that, will adding mechanical, optical, or magnetic
sensors onto the platform require more?

Rotation speed will be very low, & the rotating assembly is supported
on a bearing, so loading on the gears is pretty low. Most plastic
gears are self-lubricating & maintenance is expected to be little more
than cleaning. Gears in need of maintenance typically start getting a
little noisy but still function for a good while. Optical sensors,
OTOH, tend to fail completely & suddenly - such as from dirt on a
sensor lens or a white reflective surface. Magnetic, I would expect
little trouble from.

I dimly recall that the platform is, what, three inches in diameter?

Yes.

Putting an optical pattern on its uderside would mean... 180 divisions,
so eight binary sensor "bits" to track -- an 180x8 grid, with fairly
closely-spaced "pickups".

Or around the edge, where I have about 0.5" to work with. This is
where I painted my black/white stripes on the 2nd prototype (1/2 black,
1/2 white to tell direction to "home"; narrow white on black to
indicate "home"; stepper to rotate, count/accumulate steps to determine
position) - which worked just fine, except that I'm not 100% satisfied
that it can handle the dirty environment or continue to keep track of
position when/if an external force rotates the turntable.

--snip--
Let us know what you finally come up with. We'll be more than happy to
steal your solution and an use it in our own projects. <grin!>

Sure. You're all more than welcome to it. Whatever "the solution"
ends up being, probably won't be for awhile (it's hobby-related,
subject to the parameters of funding & time that all hobbies must exist
within - nothing planned to ever be sold).

It's too bad someone in Congress didn't sneak an "earmark" onto one of
those last-minute bills for an American Hobby Reaserch and Development
Grant Fund. Maybe next year... <grin?>

They do, & they'll get my vote! Like everybody else, I'm opposed to
all pork-barrel spending except that which directly benefits me! ;-)

Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney ayut minds pring dawt cahm (y'all)
--
The mere formulation of a problem is far more often essential
than its solution, which may be merely a matter of mathematical
or experimental skill. To raise new questions, new possibilities,
to regard old problems from a new angle requires creative
imagination and and marks real advances in science.
-- Albert Einstein
--

I hadn't seen that quote before, but I love it!!

JM

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