Subject:
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controling two motors with only one output?
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Fri, 31 Mar 2000 20:08:14 GMT
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Highlighted:
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(details)
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Hi guys,
I was thinking about multiplexing motors, and it came to
me that it should be easy to control two motors (only
one at a time though) using one output of the RCX.
Below, I describe my general idea, but I would like to
know if you tackle this problem and found better implementation
than mine (as you will see, my idea results in a rather
cumbersome implementation).
If you have, please let me know (pictures appreciated).
The basic idea is that with a double-ratchet, you can control
two different mechanism, depending on the direction of the
motor (see Baum's book for two different sort of double-
acting ratchet).
Therefore, with one output, you could turn lego switches,
so that, depending on the actual (out of 8 possible) position,
your 2 switches will be in the following positions:
switch 1 switch 2
------------ -----------
on-forward off
off on-forward
on-reverse off
off on-reverse
and so on for 4 other positions
If the main motor turn in the reverse direction, it will
activate the other mechanism, which is only a switch
(switch 3) in resting position off.
Therefore, the mechanism is to turn the main motor
forward to select the desire position for the switch 1 and 2,
and then turn switch 3 on by reversing the main motor.
The basic idea is rather straighforward (once ratchet are
understood I mean), but what is difficult is to have
a precise enough device so that the axles for switches 1
and 2 are turned *exactly* by increment of 1 eighth of a turn
each time. Otherwise, after a couple of turns, the mechanism
would be in an unpredictable position (one could use a
rotation sensor, but I want to avoid using RCX ports as much
as possible).
I started building a device along these lines, but the
complexity and the size of it are staggering, so I was
wondering if any of you had made such a thing with a simpler
design. I will post in a near future my own results for
those of you who need a picture (as it is my case).
Denis.
--
Denis Cousineau, Postdoc *****************************
Cognitive psychology * *
Indiana University * Etudiant devant l'eternel *
Psychology Building * *
Bloomington, 47405 *****************************
Office: (812) 856-5217 Fax: (812) 855-1086
E-mail: decousin@indiana.edu http://Prelude.PSY.UMontreal.CA/~cousined
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