Subject:
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Re: Homebrew rotation sensor idea
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Newsgroups:
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lugnet.robotics
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Date:
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Sun, 21 Nov 1999 21:19:30 GMT
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Viewed:
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589 times
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Excellent idea!
I'd suspect that the relationship would be sinusoidal rather than linear, but
who knows? If it is, it's a sine/cosine generator, too.
Sone LEDs (laser diodes, don't know about others) are polarized in some
specific plane. It is possible to separate the horizontally polarized
component from the vertically polarized component and do things with that. The
plane orientation varies from one laser diode to another. I don't know if it
varies with power output.
Have fun with your upcoming Mindstorms kit. Keep posting things, too.
Dave Paule
(Also a newbie)
_______________________________
> As most of you probably know, if you layer 2 polarized films on top of
> each other, the light transmission through them varies (linearly?) from
> "clear" to opaque as one is turned through 90 degrees with respect to the
> other. I have thoughts (still a bit vague) of making a rotation sensor
> with polarized film and a light sensor (and perhaps a uniform light
> source).
>
> Awkward, perhaps, but depending on the sensitivity of the light sensor
> you use, it seems to me it might provide pretty good resolution, probably
> much better than the 22.5 degress of lego's rotation sensor. You would
> have to track history to know where you were in an absolute sense (the
> pattern inverts every 90 degrees, repeats every 180).
>
> I suspect you could package the whole thing neatly in a few bricks, if
> you used an led light source and made it a powered sensor.
>
> Any thoughts on this? Anyone tried anything similar? Any other uses for
> polarized film you can think of?
>
> Dave Johnson
>
> -------
> Background:
>
> Robotics: Been dabbling for years, and have even won 2 robotics
> competitions. (But don't read too much into that: for the 1987 San
> Francisco Robot Olympics I built a simple line follower but mine was the
> ONLY autonomous entry, and the scoring was slanted heavily in favor of
> autonomy. The second was a lego robotics competition at Alife II put on
> by Fred Martin, and we won - I was working with a partner, Eric Cooper -
> simply because our 'bot completed all three tasks successfully. But the
> robot itself, frankly, was boring, so utilitarian as to be yawningly
> dull. If there would have been scoring for creativity, we'd have been
> near the bottom, there were some truly amazing creations there.)
>
> Electronics: Lots of classes in college, lots of dabbling myself, and for
> the last year have been a real live hardware guy, designing handheld data
> acquisition systems for Palm-based computers.
>
> Mechanics: Deep love of all things mechanical all my life. I was a
> mechanical guy for the ILM creature shop in a former life, but I own no
> machine tools of my own (something I hope to rectify someday: those
> Sherline mills look lovely.)
>
> Computing: Been a programmer since the early 80's in college (FORTH,
> Fortran), but personal computers didn't do anything for me at all until I
> saw a Macintosh for the first time. I've been an avid Mac programmer
> since 1985 (mostly C and C++ the last 8 years or so), and worked at Apple
> for many many years in Developer Support. Also quite a bit of assembly
> language experience, especially on 80xx in college, and on PICs over the
> last year, for work.
>
> Lego: Total Newbie, but I'm hoping that will change quickly.
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Message has 2 Replies:
 | | Re: Homebrew rotation sensor idea
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| I'd also suspect this, having worked at a company that manufactured optical encoders, most of these things are sinusoidal. That is far from a bad thing though. If you build two of these and get them 90 degrees apart so you are seeing both a sine and (...) (25 years ago, 23-Nov-99, to lugnet.robotics)
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Message is in Reply To:
| | Homebrew rotation sensor idea
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| Hi All, New guy here (some background below, if you're interested), been lurking for a week or so, and I'm off to buy my 1st Mindstorms set as soon as Toys 'R Us opens this morning...they have both 1.0 and 1.5 on the shelf, I'll be getting 1.0 after (...) (25 years ago, 21-Nov-99, to lugnet.robotics)
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