Subject:
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Rotation Sensors - slightly dissapointed...
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 16 Feb 2000 00:50:12 GMT
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Viewed:
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937 times
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Hi,
Last Friday I recieved in the mail the two Rotation Sensors I had ordered
from Shop at Home 8 days earlier from the US (talk about fast delivery! I'm
in Ontario). After hearing everyone tell me how wonderful they are and that
they do not loose count, like my optical drum sensor had done (robot5), I
was excited when they arrived to put them to use.
The first project went without a hitch. I quickly rebuilt my model of the
Netherlands-built KMG Moveit-18 which has had great success overseas. It
worked wonderfully. However, something seemed to be going a bit weird.
The next project was to design a program which would emmulate a vector
drive, that is, to send the gearmotor spinning to a position and hold it
there until the control variable shifts to another integer. So I set up a
basic program running two tasks with a decel. feature that rotates the
motors simultaneously (if required) and holds them at a given position by
correcting for any slew that may occur, and pressed run.
The program ran successfully for about 20 seconds before I noticed motor 1
had shifted out of phase by 22.5 degrees - it had slipped/skipped a count.
"What!" I screamed. I regarded it simply as a fluke... but running more
tests I did discover that the sensors are horribly unpredictable and loose
about 2 counts per minute when rotating continuously... to me, this is
dreadfully unacceptable. I guess now I have to gear them down - less
accuracy if I want to keep my robots quick.
Oh well, I guess I was just wondering if I'm the only one who's discovered
this... the 400 rpm gearmotor shouldn't be doing this.
Iain
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Message has 3 Replies:
 | | Re: Rotation Sensors - slightly dissapointed...
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| (...) Because the LEGO Rotation sensor is a powered type, it might be slightly sensitive to battery voltage. I wonder if you notice the skipping is worse with older batteries. Also, the problem might be aggravated by long wires. Does the skipping (...) (25 years ago, 25-Feb-00, to lugnet.robotics)
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