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Subject: 
Re: controling two motors with only one output?
Newsgroups: 
lugnet.robotics.rcx
Date: 
Sat, 1 Apr 2000 22:09:32 GMT
Viewed: 
2158 times
  
Denis Cousineau wrote:

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.

Or you can just build one of the following devices and save allot of time and
effort.

http://www.akasa.bc.ca/tfm/lego_wr.html

See the Motor/Light Block or the (MS)2 Expander

Dean
--
Coin-Op's For Sale!: http://www.akasa.bc.ca/tfm/coin-op.html
Dean's Lego Workshop: http://www.akasa.bc.ca/tfm/lego_wr.html
Vancouver Lego Club: http://www.akasa.bc.ca/vlc



Message has 1 Reply:
  Re: controling two motors with only one output?
 
Indeed, your circuitry is interesting (I'm not sure though it would save time, since soldering can be pretty tedious...). But the challenge here is to make it out of Lego. (and not destroy one piece, by the way...). Denis. (...) Denis Cousineau, (...) (24 years ago, 3-Apr-00, to lugnet.robotics.rcx)

Message is in Reply To:
  controling two motors with only one output?
 
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 (...) (24 years ago, 31-Mar-00, to lugnet.robotics.rcx)  

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