Subject:
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Re: Motor mis-match.
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 15 Jan 2001 04:18:53 GMT
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Viewed:
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682 times
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Thank you! I'm glad to see someone has taken a semi-scientific
approach to the whole question. I have one correction/comment to make
though:
It's doubtful that the Lego motors will heat up significantly enough
to affect their operating speed. There is a more likely cause - the
batteries. All batteries exhibit a recovery effect (there is a
technical name for this, but I've forgotten it) by which an unloaded
battery will appear to regain some of it's lost charge. This applies
to both rechargable and non-rechargable batteries. This effect can
most dramatically be seen by using a pen-light flashlight and some
batteries with 1 foot and 4 toes in the grave. Turn the flashlight on
and watch as the lamp dies. Switch it off and wait a few seconds. Turn
the light on again and behold the (temporary) ressurection. The closer
the are to being totally, completely, 110%, fliat-lined dead, the
shorter and less intense this recovery will be. This does, however,
apply equally well to "good" batteries, it's just that using dead ones
in a high-current load like a flashlight is more dramatic. Switching a
Lego motor on for a few seconds will drain the batteries somewhat.
Disconnecting them to change motors will allow them to recover a
little bit and probably accounts for why the next "cold" motor seems
to run faster than the last "warm" motor. The other question here is
whether the motor outputs are regulated, and how tightly. I don't know
how the RCX is designed in terms of its motor outputs, but, given that
motors don't generally require pinpoint voltage regulation, I can't
see that Lego would go to too much trouble and expense in this area.
The sensors and the MPU I can see, but not the motors.
...and YES we do NEED stepper motors.....
Matthias Jetleb
VA3-MWJ
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Message is in Reply To:
 | | Motor mis-match.
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| I was having a boring evening - so I decided to test some theories about Lego motors - and at the risk of seeming pedantic - here are my findings: Several times, people on this list have asked why their robots don't drive in a straight line - the (...) (24 years ago, 15-Jan-01, to lugnet.robotics)
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