Subject:
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Re: motorized points - beating a dead horse
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 1 Dec 2000 01:06:49 GMT
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Original-From:
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Pete Sevcik <sevcik@SPAMLESSflash.net>
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Viewed:
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903 times
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Steve,
If you are willing to use non-lego parts, there is a reliable solution. You can
build a limit switch that does not use any sensor inputs. You need two
"normally closed" switches, and two diodes. Solder a diode across each switch.
Wire the switches in series with the motor, with diodes pointing in opposite
directions. Arrange the switches to be pressed at each end of your points
mechanical travel. When your points are in the middle, both switches are
closed, and the motor will run in either direction. When a limit is reached,
the switch opens. This stops the motor. The diode across that switch will let
the motor run in the reverse direction.
I have used this method in several projects. It saves a sensor input. A
variation is to use just one switch to identify a "home" position. Control the
excursion away from home by controlling the time the motor is on.
- pete.
sebarile-MOBL wrote:
> Hi All,
> Currently I am attempting to build an automated hump yard. The main problem
> I'm tackling is the RCX controlled motorized points. I've spent 7 hours over
> the last two days trying to build a motorized switch track that will run
> forever with out ripping itself off the base plates and be very *forgiving*
> at the edges of both states, turn or straight. What I mean by forgiving is
> that the motor doesn't burn up or the gears do not get stripped off.
>
> I like really simple and elegant solutions. For instance I would like to be
> CPU switched with no feedback, again forgiving at the edges of both states
> such that the motor can spin for 1.5 secs and not reap havoc. Hanging
> elaborate clutch systems with differentials and angle sensors would not be
> my first choice. Of course beggers can't be choosers.
>
> Yes I have tried a bunch of slip gear configurations and the 2.5N/cm doesn't
> seem to over come the internal detent.
>
> Yes I looked at several designs on the web, I could have missed something.
>
> After at least 10 iterations I am still staring at a desktop full
> of disassembled bricks.
>
> Any ideas? Help?
> SteveB
> PNLTC
--
Pete Sevcik sevcik@flash.net
Techno-stuff Robotics
http://www.flash.net/~sevcik/
Robotics for FUN !
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