Subject:
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Re: Poor man's Tachometer
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 31 Aug 1999 13:06:06 GMT
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Original-From:
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Laurentino Martins <lmartins@marktest.pt/antispam/>
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Viewed:
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736 times
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At 03:02 31-08-1999 Tuesday , you wrote:
> Laurentino Martins wrote:
>
> > Hello,
> >
> > I'm probably not the first doing this, but since everyone has touch • sensors I decided to improve a bit the usefulness of it.
> > What you see in the gif (it's only 2K) it's a tachometer out of a touch • sensor (CyberMaster) and a technic 8 tooth gear.
> > Note: This is the ideal gear since the tooth are more spaced than the • larger ones.
> >
> > There are two catches in this:
> > 1.
> > You must build it in a way that the gear never touches the touch sensor • body (cyan) but firmly presses down the button with each tooth.
> > What I've done is to create two rings about half the height of a plate
> that are introduced between the cross-axles and keep that distance always
> perfect (not shown).
>
> Would sandwiching a rubber band in place of the 1/2 height rings give you
> enough spacing? A single white band could probably be wrapped around both of
> the cross-axles, and it would keep the Lego-purists happy.
>
> I like your design--it's the most compact one I've seen. The EDGE detection
> gives me an idea. If the 8-tooth gear were replaced by some asymmetric part
> (I can't think of one), could it be used to determine direction as well as
> speed? I
> vaguely recall some hurricane-shaped part--maybe not a Lego one, that might
> work. Even something comma shaped would do the job. Rotating in one
> direction, the "climb" to the edge would be swift and then drop gradually.
> In the other
> direction, it would climb gradually then drop suddenly. Is this workable?
Yes, I had thought of that before.
That should give you 360 degrees of freedom and tell you the direction is turned at any instant, unfortunately the problem is the precision - LEGO is not good to keep the parts tightly integrated (specially under stress) and in this case a hair of distance is enough to change the value to something unwanted.
Second, you would need to perfectly craft that rotating (spiral) part and tune it so it uses the full range of the touch sensor, and not more or less than necessary.
The first problem could be solved with an automatic calibration routine.
The second, is only a matter of persistence. I may give it a try! :-)
Laurentino Martins
[ mailto:lau@mail.telepac.pt ]
[ http://www.terravista.pt/Enseada/2808/ ]
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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